EFI Tuning the 5.0 Windsor

[skullandbones]

This is my first hot rod with a EFI system. I've done multiple carbs mostly and to say they can be a PITA is an understatement. However, at least, you feel like you can tune the engine. With the Ford EFI system, there isn't a lot you can do past the basic timing. I have not been concentrating on the engine tune much as I have other "fish to fry" so to speak. But now I'm focusing on what I can do until I can change the computer or get outside help at a dyno shop. I'm checking them out. Got two recommendations last night. I've had a hard time telling if I have the basic timing right. I can't get the marks clear enough and the angle to see the timing is awkward. So I ordered a timing strip that is supposed to help. Once I verify that my timing is at about 13 degrees, I will feel better about that. I finally got to check my fuel rails (stock) with a proper gauge and found that before start the pressure is 40 psi. After start, it varies between 38.5 and 39. My idle is not steady so that could be the variation from the change in manifold pressure. The only thing I haven't checked is the coil which is also a stock one.

My plan is to go to an after market computer but that is after tires and a couple of other major purchases so I need to get this thing running cleanly. Right now it is stumbling at about 4 to 4.5K rpms. It also will have a slight miss intermittently at various speeds but not continuous. When I first got it running, I let it loose to see what it would do and it wound up to 6K so fast it surprised me. However, it has developed this stumble so now it does not perform as it did. The timing has been fiddled with some but I thought I had it right. That's why the timing stripe. The car runs good most of the time and starts every time so it's kind of difficult for me to understand. I guess I should get the wide band A/R sensor installed as that will be a requirement for the aftermarket chip and it's not that expensive. But still don't know if the limitations of the stock system will make the A/R sensor not that useful until the other computer stuff is added.

If I can get the stutter or stumble or whatever you call it out, I think I would be happy for a while at least. This little problem is actually keeping me alive so I can't complain too much.

Thanks for any help you can suggest.

WEK.

[Jeff Kleiner]

Let's start by confirming that you understand that the timing has to be set with the SPOUT removed. Next set TPS voltage at idle to .95 +/- .02. Your fuel pressure at idle is good but you need to see what it's doing under load when the stumble occurs. If you don't have enough hose on your fuel pressure gauge extend it it so that you can run it out through the back of the hood and tape it to the windshield where you can see it while driving---do you observe a drop when the stumble occurs?

Let us know.

Jeff

[Dan Babb]

Are you checking the fuel pressure with the vac line disconnected? You set it with no line connected...then you put the line back on for driving.

Generally speaking, with more throttle, your vac reading drops...the regulator senses that and will increase fuel pressure a bit to supply more fuel when you need it.

Also, has everything been setup properly so your computer knows you have 24lb injectors? You can't just plug upgraded meters and injectors in without things being setup properly.

[Mike N]

For your combination 4 to 4.5 K is going to be in the highest cylinder pressure range (peak torque). Does the miss / stumble continue above 4.5K?. Did you check plugs / plug gaps? Could also be a weak mixture but I'm guessing spark.

[skullandbones]

I checked plugs first and there are no deposits and the electrode is tan. It looks like the picture of a perfectly burning plug that you see on the trouble shooting sites. Also, check gap. It was good. As far as pushing it past that point, I have pretty much given up on trying to work thru that stumble. I did "pedal" the throttle a little once and it did rev up to around 5.5 K rpms but I'm a little nervous about taking it there with this issue.

I did forget to disconnect the fuel regulator line to the manifold so I will need to do that at idle. But I have to have the regulator vacuum connected when checking for the stumble, correct? I have set up the engine with a new Summit EFI harness and also matched 24 lb injectors and MAF. The EGR has been deleted. I will have to get the pressure gauge again and tape it to the windscreen and have a ride along partner to do the readings for me. I don't think I can give enough attention to all necessary aspect of this test, by myself. I'm curious to see if the fuel rail pressure actually goes above 40 when loading the engine. I don't know how much pressure drop would be significant if it goes in that direction. It's going to be Thursday before I can get someone to help me with that.

So tasks are check basic timing without spout (have been doing that all along). The timing has been tweeked a couple of times so it may be off though. We already did the TPS procedure. So I will check the fuel rail pressure while driving and then if that doesn't show something I will remove the cold air tube, clean the throttle body and recheck the TPS position once more. Don't like fooling with the EFI lines especially with a device hooked up to the Schrader valve but I do have a new Halon extinguisher so I think we are prepared to experiment. Thanks, Jeff, Mike, and Dan for your input. I will get back to you at the end of the week.

WEK.

[Mike N]

What EEC (computer) do you have? What color TFI module. There are two, black or grey. I vaguely remember there being a problem with mis-matching the TFI to the EEC that causes issues at and above 4500 rpm. Read this http://www.google.com/url?sa=t&rct=j...74035653,d.b2U

[skullandbones]

It looks like I may have the wrong TFI module on my engine. I had three engines: the crate engine, the donor 92 GT, and another parts engine from a 95 GT. There were two distributors from the two GT donors but I don't remember which belonged to which. I am using the EEC-IV computer from the 92 GT. I picked the best distributor for my engine based on look and feel of the bearings and circuitry. I used the other distributor as a pre-oiler. So I took the grey TFI off of that one and stored it. I have the black TFI installed on my engine now. I vaguely remember reading something about the TFI incompatibility but did not pay any attention to it obviously! I believe the computer gets the timing signal at the wrong time due to the incompatibility so it would always be wrong no matter how good the basic time is set. I need some of that dielectric grease or whatever lub they use between the TFI and distributor housing so I will ask the rep to pull out a TFI for a 92 GT. That should be interesting. I will get back to that article to see if it says there. This would be a great solution if that's what it is. The engine has never run like I would have expected but has run reliably most of the time with a miss here and there. I guess the computer is getting "mixed signals". I will let you know when I find out for sure.

Thank you,

WEK.

[rich grsc]

Not dielectric grease, heat sink paste.

[skullandbones]

Thanks. That makes sense to protect the electronic module.

[skullandbones]

I found this explanation on one of the forums. It's a little clearer, at least, to me.

Gray or Black? "Pattern Failures in the modules; driveability & no - start problems.
Most technicians who deal with Ford driveability and no-start problems have become very familiar with the Thick Film Ignition (TFI) system. Ford started using the six-pin TFI module with the EEC-IV computer system in 1983, and for years it remained basically unchanged. The early TFI system, which Ford calls the "Push Start" TFI system, uses a gray TFI module. Originally, the module was mounted on the distributor.
In the late '80s Ford began to relocate it away from the distributor on some vehicles to provide better protection from the effects of engine heat, but system operation remained the same. It uses a Hall effect pickup (stator) in the distributor, which generates a battery voltage, 50% duty cycle square wave, called the PIP signal, to the EEC-U PCM and the TFI module. The PCM processes this signal and sends out another battery voltage, 50% duty cycle square wave, called the SPOUT signal, to the TFI module. As long as the TFI module is receiving a SPOUT signal, it will fire the coil at the rising edge of that signal (except during engine cranking, when SPOUT is ignored) and the vehicle will run with the amount of timing advance commanded by the computer.


In the early '90s, Ford began using a different TFI system on certain vehicles--the Computer Controlled Dwell (CCD) TFI system. The TFI module on CCD TFI is always black in color.
There are a few major differences between the two systems. As the name implies, with the CCD system, the computer controls primary dwell. The CCD TFI module still ungrounds (fires) the coil at the rising edge of the SPOUT signal, but now the falling edge of the SPOUT signal (which had no meaning to the Push Start TFI module) is used by the CCD TFI module to ground the coil. The PIP signal remains the same 50% duty cycle square wave, but SPOUT signal duty cycle varies according to how much dwell is desired by the computer.
Another major difference between the two systems is the IDM circuit. Pin #4 on the CCD TFI module, which was the start circuit input on the Push Start TFI module, is now the IDM signal, sent directly from the TFL module to pin #4 on the EEC-IV computer. This signal is still a filtered (low voltage) version of the ignition primary waveform, but is filtered internally in the TFI module rather than through an external resistor. There isn't any start circuit input to the CCD TFI module; the module infers engine cranking from a low rpm input from the PIP signal.
Since these two TFI systems are so significantly different, yet so similar in appearance, parts application problems will inevitably occur. A gray Push Start TFI module will plug right into a CCD system, and vice versa. To make matters worse, parts books are often incorrect on TFI module applications!

With the incorrect TFI module installed, the vehicle will run, but driveability and MIL (malfunction indicator lamp) problems will result. For instance, if a gray Push Start TFI module is installed in a CCD system, the computer will not be able to control ignition dwell, and the MIL will illuminate with memory codes for the IDM circuit set, as the gray TFL module is incapable of generating an IDM signal to the computer. If a black CCD TFI module is installed in a Push Start system, dwell will remain fixed, since the SPOUT signal duty cycle never changes.


Source: by David S in Motor Service, June, 2001 via web.archive.org

miesk5 NOTE; use BLACK modules in 1994-1996 Broncos

Mike: your recollection was correct as the above verifies. I hope this is exactly what is causing the "stumble". If so, I will be happy with the engine the way it is for a while.

Note: easier when you know what you are looking for!!!

Thank you,

WEK.

[skullandbones]

The two identical shaped ICMs are very different in operation. Lesson learned. Changed out black for gray. Gray is the correct ICM for the 92 EEC-IV.

I'll do a test run in the AM.

Thanks, WEK.

[skullandbones]

I'm pleased to report that my "stumble is missing" now (pun). But seriously: the engine revs through the 4.5 range up to 5.5K rpms without any hesitation or misfire now. I had my fingers crossed that it would be that good but you know that doesn't always happen. After reading the two different accounts of the technology, I'm surprised the engine has been doing as well as it has with the wrong module. I still have a random misfire occasionally but not like before and not as frequent.

Next step is to install the jumper circuit across my cutoff switch to save the ECU memory for drivability. I think Jeff mentioned this a while back but I've just gotten to it and hope that will provide for a little more consistent operation since the computer should be able to store the tweeks it makes from driving session to driving session. We will see. So right now I am experiencing a little surge in the idle, a random misfire in the engine at various speeds and rpms but not at one spot like before and not very frequently. I didn't drive for more than 15 minutes today so I will need to do some longer sessions to help the computer out. Also, with the small timing changes we've made, I need to verify the basic timing again. I have decided on a new computer that requires a wide band O2 sensor so I think I will purchase the O2 sensor first and begin to use it to monitor my progress with the timing, fuel rail pressure, etc. I was not sure if the computer I'm looking at would support the data from any O2 sensor but the vendor said it will work with any of them. Sure do appreciate the support I get on this forum.

Thanks,

WEK.

[rich grsc]

I know that most people will disagree, but the EEC-IV computer from the 92 GT is not a self learning system. The memory stores the fault and diagnostic codes. I turn mine off frequently, and never notice anything different on restart.

[skullandbones]

I know that most people will disagree, but the EEC-IV computer from the 92 GT is not a self learning system. The memory stores the fault and diagnostic codes. I turn mine off frequently, and never notice anything different on restart.

Rich: Is the 94 and after self learning? I have read about the differences from PCM to PCM but didn't know that the 92 didn't do that function. I believe you can have the 94 and later ones reflashed but don't quote me on that. Not being able to reflash the 92 PCM was a disappointment. The advent of the MegaSquirt PiMP at least gives me hope again. It's sort of the light at the end of the tunnel. WEK.

[rich grsc]

You can run a piggyback chip on the Fox body computers.

[Mike N]

Bill the EEC does not tune but does correct for stoichometric air fuel ratio based on the feedback it sees from the O2 sensors during closed loop operation, mainly cruise. Google "EEC KAMREF" to learn more.

[skullandbones]

I know that most people will disagree, but the EEC-IV computer from the 92 GT is not a self learning system. The memory stores the fault and diagnostic codes. I turn mine off frequently, and never notice anything different on restart.

OK my memory isn't that great anymore but I did remember somewhere where it said that there was adaptive learning on the Fox body Mustangs. So I went to my library and found a book I haven't read in a while, "Ford Fuel Injection and Electronic Engine Control" (author: Charles O. Probst). It appears he believes the EEC-IV does have it. He calls it "Adaptive Control" (pg 45) but also refers to it as adaptive learning. He also says if you want the idle of the car to be smooth, you have to keep a circuit similar to what I mentioned to maintain that memory from drive to drive. Otherwise the computer has to learn all over from scratch. When I first opened the book, pg 106 came up and KAM or Keep Alive Memory has a small section. It states that codes are stored but also what they call "adaptive corrections". I know I wasn't contemplating that mod without some reason. I think Jeff K. posted a pic of a similar fuse holder at the time I was inquiring about the subject. Anyway, I know the computer will not learn better performance habits (open loop) but it does appear to learn some drivability characteristics in the "closed loop". Since I'm still having some idle issues, I have to consider this as a possible way to improve the situation. I will do the mod to be safe.

I had another thought related to the computer type. Are the later model (post Fox body) PCMs better in the sense that you could have them reflashed. Don't want to do the piggy back thing. I would consider doing this as an interim step to my final goal but it would have to plug in to the existing harness. If it involved changing the TFI module again, that would be OK. I was thinking in terms of a Cobra computer that had a high performance tune. Don't know if it is possible. Does anyone know?

Thanks,

WEK.

[skullandbones]

One thing I have not taken into consideration is the stock TFI distributor related to timing advance. I don't know if I need to increase the mechanical advance for this as I have checked to see what it's set at from the factory. I think basic timing around 12 degrees is OK and if total timing should be 36 I have seen in several places, I should have a mechanical advance of 24 degrees. There are calibrated plates that are marked 11L, 12L, 13L that represent half of the advance for those items. If I have a 12L then it should be OK. The other aspect is when the timing comes in. Has changed that to bring the total timing in at a different time than stock for performance purposes?

Thank you,

WEK.

[Jeff Kleiner]

There is no mechanical or vacuum advance incorporated into the Ford TFI distributor; the computer controls timing. Set the base timing with the SPOUT pulled, reinstall it and the ECU does the rest.

Jeff

[skullandbones]

Hi Jeff,

I was talking with a friend yesterday while doing something else on my car and he told me this. He had EFI at one time and then he changed to carb. I assumed we were talking about the EFI setup as we had just been discussing my "wrong module" installation. I guess he had changed gears and was talking about his most recent setup. So I was thinking it had some mechanical advance in it. After checking my pre-oiler distributor today, I can see there is not much inside the distributor except the timing trigger wheel. Thanks for straightening me out. As Forrest would say, "one less thing!". But on the other side of the coin is it's one less thing to give you some control in tuning this engine with EFI. I find it a little frustrating but after my drive yesterday, it is a little better. It's just not quite as good as I expect yet.

Thank you,

WEK.

[skullandbones]

After my trip into the eastern mountains of AZ, I have still got a problem with the engine loosing power intermittently. I have scoured Mustang forums and found tens of accounts of the same symptoms as I am having but no real solution that is "black and white". It can range from loose baffles in the tank to coil voltage, distributor, injectors, vacuum leaks. I when around 600 miles on the trip during which off and on the engine would sputter and change exhaust note to what sounds like a real misfire. The plugs do not indicate that from the way they are burning (tan with no deposits). So my next step is to change fuel pumps to one that has the correct capacity for my upgraded engine. I know that what I have done is considered "mild" compared to most but it is enough to be significant. So I'm following Ford Racing calculations which recommend a much larger capacity pump from the 88 ltr/hr stock unit. I believe the actual capacity I need is between the popular sizes but in the 120 ltr/hr range. This is my first attempt to really solve the stumbling issue without throwing new parts at the problem as this would be an expected upgrade anyway. I haven't given it high priority since the engine does run acceptably for most of the time when I driving but I guess I have been pushing it harder and this could be part of the problem. If not, I would have done it anyway to get the numbers to make sense. If I get a 155 ltr/hr unit, that should be plenty of pump as that will support over 440 hp. Next I will change the fuel rails and begin researching the pressure regulator to see if that needs adjustment. Even though I think this is an electronic problem, I still have to do the fuel supply upgrades. Both components of the EFI are necessary to make a performance engine work well. It will be interesting to see if this makes a difference. WEK.

[OCCPete]

I highly recommend getting a chip burned on the dyno to get your setup right. I was having a lot of the same problems with my 351W and they all went away after getting a custom chip burned. The chip, programming, and dyno time was about $300 total and got me an increase of 50hp. Well worth it.

[skullandbones]

Pete,

Was that very long ago when you got the chip burned? I haven't gotten estimates even in the same ball park. That's why I'm eventually going to a MegaSquirt PiMP but don't want to do it twice. I have to change the pump anyway but I'm thinking you're right about it being a computer issue.

Thanks for the suggestion,

WEK.

[OCCPete]

About 2 years ago.

[skullandbones]

It might be better to discuss the MAF issue I may or may not be having here. I spoke with a dyno guy about my intermittent stumbling and lack of power a couple of days ago. He agreed that if I was going to upgrade to a larger capacity fuel pump, it would not hurt and might help eliminate a possible variable in the equation. However, his main suggestion sort of surprised me. He said to trash the Summit MAF which is matched to the 24 lb injectors I got. He said I should use a C&L housing with either the 19 or 24 lb calibration tube and use my stock 92GT electronics on the new housing. I have heard many different opinions about this but I may do it since it makes sense that the electronics would be more compatible with the ECU since they was designed together. I will do that as a second step in this process if the pump does not help at all with the misfire or whatever you want to call it. I was on a 550 to 600 mile trip and experienced this issue many times off and on. I usually had the power but sometimes I had to gear down one gear to pull as strong as it would have in that higher gear (5th to 4th or 4th to 3rd). The exhaust note was distinctly changed when it was experiencing the issue and when it went back into power mode like it was normal again the exhaust sound was smoother. It wasn't gradual either. It was like and on/off switch. So the new pump is my first step that was a planned upgrade even without the issue.

I also saw an interesting diagram in another thread regarding the HO firing order. Mine is the correct firing order but I will change the orientation of my wires per this diagram to reduce the misfire chances of my engine.

Thanks,

WEK.

[DaleG]

Next step is to install the jumper circuit across my cutoff switch to save the ECU memory for drivability.

A 15 amp fuse is shown; I think you want a 5 or 6 amp. Better yet, get a 6 amp self-resetting circuit breaker to fit in that fuse holder.

Cheers, Dale

[skullandbones]

hi Dale,

I had forgotten about that pic but when I pulled it, I was expecting someone to say something. I didn't have another fuse on hand at the time so I used that one. I did load it with a 5 amper when I installed it. Guess what. I was fooling around in the dash area and accidently hit the horn button while the battery cut off switch was in the off position. Just like you guys have said, it blew. Oh well. I will get one of those automatic resetting breakers when I can find it. I'm so glad people actually look so close for details. It can save you some time or it may actually save injury or death in some extreme conditions. Thanks, WEK.

[CHOTIS BILL]

With the miss coming and going it sounds like when I had one clogged fuel injector. It was like flipping a switch. I used some fuel injector cleaner in the gas tank and that fixed my problem.


Bill Lomenick

[DaleG]

hi Dale,

I had forgotten about that pic but when I pulled it, I was expecting someone to say something. I didn't have another fuse on hand at the time so I used that one. I did load it with a 5 amper when I installed it. Guess what. I was fooling around in the dash area and accidently hit the horn button while the battery cut off switch was in the off position. Just like you guys have said, it blew. Oh well. I will get one of those automatic resetting breakers when I can find it. I'm so glad people actually look so close for details. It can save you some time or it may actually save injury or death in some extreme conditions. Thanks, WEK.

Here: http://www.summitracing.com/parts/bss-ucb6/overview/

Type I - Automatic Reset

Type I circuit breakers automatically reset after opening. If the fault or overcurrent condition still exists, the breaker will continue to cycle between ON and OFF positions until the overcurrent problem is corrected. These devices are sometimes called "cycling breakers." Type I/Automatic Reset circuit breakers do not address, or correct, overcurrent or fault conditions. They only react by cycling OFF and ON. Any overcurrent or fault condition that causes a Type I circuit breaker to operate should be corrected as soon as possible. Continued vehicle operation with an overcurrent or fault condition (causing the Type I circuit breaker to cycle) is NOT recommended.

[skullandbones]

Thanks Dale for the heads up on that part. I wish the timing had been different. I just made an order to Summit but I'll get it on the next one.

WEK.

[HookedonFord]

WEK,

I was reading the part about your MAF and noticed you have a cold air system. Before you change the MAF, one free suggestion would be to "clock the maf". Basically, try rotating it (e.g. 3,6,9, and 12 o'clock positions) to get the meter in the best position to receive even air flow, minimizing air bursts/turbulence.

Jim

[skullandbones]

I'll put that on my to do list, Jim. It looks like I'm going to have to unmounts the MAF anyway to prepare for exchanging it with another one if it comes to that but this will give the one I have an opportunity to run better with the different orientations. The C&L housings are not supposed to be affected by the orientation but the Summit one I have doesn't say that. The laundry list is growing! BTW: I've taken extreme care to allow the air flow to be constant, that is, flowing in as well as out in a non turbulent way according to the experts for cold air induction. However, it would not surprise me at all if something as simple as orientation would make a difference. I would take that and admit that I was wrong if a freeby fixed the problem. Thanks again, WEK.

[HookedonFord]

WEK, if you search corral.net, C&L's have the orientation problem as well and I think C&L recommends to using the stock air box to help prevent the problem. Honestly, i don't think you would be buying yourself much going to C&L, just my opinion after owning /using three of them. I even have small shield in the front of my Cobra oval air filter to keep the open hood scoop burst air off my Mass-Flo sensor.

[frankeeski]

The other thing you may want to check on is whether you have a screen installed before the MAF. Chris over at Pro-M made sure to ask whether I was using a stock airbox or a cold air style intake. He explained that without the screen in the air steam that turbulent air could really mess with the MAF. The screen helps straighten the air going into the MAF. Here is a picture of the Pro-M unit I got. Notice the screen in the picture.

BTW, my MAF setup is for sale, I'm going with the Stinger PiMP System and no longer need it.

[skullandbones]

Yes, I do have that screen on mine. I would like to get the present setup running as good as it is capable of running before I do any more major changes but the Stinger PiMP system is on my radar screen. Unfortunately, it's down the priority list with Wilwood brakes for the front ahead of it. That will be nice to get rid of the MAF. I think the Stinger system only uses a wide band O2 sensor and your manifold pressure. The only downside is the $900 price tag. Really that's not bad compared to some systems. That is also including the O2 gauge/sensor. Right now I'm going to change out that fuel pump and see how it runs.

Thanks for the info on the specific components. It's not always the way you think it is even when the company advertises it to have a certain attribute.

WEK.

[CraigS]

To throw a little Lexus experience in here re; fuel pump. A small pump, by itself is only going to cause a problem under hard acceleration, IF the pump can not, at that time, keep up w/ the engines fuel needs. If you were doing some full throttle acceleration and had a problem I could se a pump as a cause. OTOH, as soon as you went back to a more normal driving mode the problem would go away as the pump would quickly catch up to the engine's requirements.(Some Lexus models had a two speed pump controlled by the ecu and a relay. When the relay went bad the car had only a low speed pump. It took a lot of troubleshooting to discover the problem because it only happened under conditions that were pretty much illegal to duplicate on the street) I am adding this comment so you don't waste $ and time on a new pump expecting it to cure this intermittent problem. If you also discover an intake sock problem or some other related fuel system problem, then it may pay off. But your problem does not sound like it is fuel supply related to me.

[Jeff Kleiner]

Craig (& Bill),
That's pretty much what I was saying in post #5 of this thread:

http://thefactoryfiveforum.com/showt...l-line-Systems

Some troubleshooting needs to be performed before throwing parts at it. Bill, we're just trying to help ya' find the problem methodically and in the process maybe keep you from spending money needlessly while chasing geese.

Good luck,
Jeff

[skullandbones]

I know how we claim we help spend other people's money on their project which is true many times. However, your help also saves a lot of wasted coin like in this situation. I was planning to change the pump as part of the upgrading of the engine. One day it's going to have more cubes and more HP so it makes sense to go to the 255 l/hr. So it will be done and would have been done eventually anyway. If it helps at some level, then I'll take it but not expecting it to be the root cause either. Thank you again,

WEK.

[Carlos C]

WEK:

A couple more cents thrown in for good measure. First, what EFI harness are you using? I think I saw it somewhere that it came from Summit Racing. Is that right?
Secondly, did the injectors, transmission, and computer come from the same car? I see that you're using Summit's MAF sensor.

Ok, so here are a few more things for your list:
1. With these computers, everything has to match, including the transmission, as the computers are pre-programmed for specific hardware at the factory. That's why the Ron Francis harness comes with a plug to choose for auto or manual tranny.
2. If you're in fact using the donor's EFI harness, I can tell you first hand that a nicked wire can wreck havoc on the whole system. My engine would not start; heck, it wouldn't even turn over. But none of the electrical test would show a fault, even though there was a slight ground somewhere. This brings me to...
3. Check all your electrical grounds. This is VERY important. In your case, concentrate on the fuel pump and it's relay, EFI harness, and any other custom related components to your issue. Make sure that the attaching points are tight, and free of paint, powder coat, or rust. It wouldn't matter if you have a 255 ltr/hr pump, if you have a ground issue, you'll get the performance of an 88 ltr/hr.
4. Check your O2 sensors; one may have gone bad. Unless you have installed a "Check Engine" light, there's no readibly way to tell. You'll either have to hook up a code scanner to the ECM port, or take the sensors out, and test them with a sensor tester and an open flame. You can buy either of these electronic devices from your local auto parts stores.

Good luck.

Carlos

[frankeeski]

Bill, Two more things. First is the Summit Racing MAF, you do know it is made by Pro-M don't you? Did you have it calibrated for cold air? That is another thing Chris told me, he said unless you are running the stock airbox and tube the MAF must be calibrated for cold air.

Second is, I thought I read somewhere you are using a 94 style intake with a 92 harness. Is that correct? If so the 94 throttle body may not be compatible with the 92 harness. Just thinking out loud.