Sputters and dies when hot!

OUFan22 · Oct 12, 2005

My '94 GT is giving me problems. It runs fine when it is cold. When I drive in stop-and-go traffic it will start sputtering as if there is bad gas in the tank and then it dies. It also does the same thing when the engine is hot and I have to stop somewhere and then start it again and go. When it starts sputtering I will try to get the RPM's up but the engine won't rev and it bogs and dies again, especially if I try to drive it bogs and dies again. Usually if I let it cool for 30 minutes to an hour it is runs OK.

Any suggestions?

mo_dingo · Oct 12, 2005

This same thing happened to me when I blew a HG. Check to make sure your don't have any coolant in your oil first.

Have you ran the codes? Do that second. Does the EGR operate when you goose the throttle? Does it seem stuck open?

You also might want to check your plugs/wires/cap/rotor.

The pip in the dizzy doesn't like heat, and it may be on it's way out. So you might want to check that out too.

If you don't know how to do any of the above, do a search.
Scott

OUFan22 · Oct 12, 2005

I talked to a guy who is a Ford mechanic and he said it might be a head gasket. But he said that it would sputter all the time if that was the problem. I was thinking it might be the O2 sensors.

I haven't pulled any codes. What is a "pip in the dizzy"?

1994Vib.RedGT · Oct 12, 2005

I have this same damn problem, I too would like to know what it is

OUFan22 · Oct 12, 2005

Someone said that I need to replace the TFI module on the distributor. Does this sound familiar to anyone? Just looking for verification. Thanks.

BlownFiveLiter · Oct 12, 2005

Unplug your mass air sensor (while the engine is off), and take it for a spin. Sounds exactly like mine, when it went bad.

Chythar · Oct 12, 2005

OUFan22 said:
I talked to a guy who is a Ford mechanic and he said it might be a head gasket. But he said that it would sputter all the time if that was the problem. I was thinking it might be the O2 sensors.

I haven't pulled any codes. What is a "pip in the dizzy"?

Sorry, we talk about this stuff so often that we forget not everyone knows the abbreviations. "Dizzy" is short for distributor. The PIP is also called the stator, it tells the computer at what point in the rotation the distributor is. The computer uses that to set up spark advance and other things like that. If the PIP is going out, the computer doesn't know if cylinder 1 is about to fire, or its firing cylinder 4 now, etc. So, it's going to mess up the fuel flow and timing and the car's gonna run like crap.

Unfortunately, the PIP is inside the distributor. You need to remove the gear at the bottom of the distributor to disassemble it and change the PIP inside. some people find it easier to just replace the distributor, which comes with a new PIP.

As for the TFI module on the distributor, that's for the 93 and newer Mustangs. The TFI module for 94-95 is on the passenger side, under the air intake hose and right next to the strut tower. It looks like a heat sink, with metal fins sticking out of it. It's also important to the computer for fuel injector timing and such, and can also cause your problem. Short of some heavy-duty electrical testing, you're better off replacing them one at a time.

Do you have a buddy that has a 94-95 GT or Cobra? You can borrow his TFI and/or distributor, and see if either one solves the problem. I'd suggest trying the TFI first; it's easier to swap out.

doobsstang · Oct 12, 2005

I am having the same problem...ran codes and I am getting 172: HEGO indicates Cylinder Bank #1 is "lean", and Code 542: sonething about Fuel pump, ECA something motor to ground. Sorry forgot the exact words for the last code...lol, sorry...I am not sure what it is...cleaned MAF, checked fuel pressure...injectors are probably dirty but I do not think it is just the injectors. If you figure this out let me know...

DFG 5OH · Oct 12, 2005

timing.

Chythar · Oct 12, 2005

doobsstang said:
I am having the same problem...ran codes and I am getting 172: HEGO indicates Cylinder Bank #1 is "lean", and Code 542: sonething about Fuel pump, ECA something motor to ground. Sorry forgot the exact words for the last code...lol, sorry...I am not sure what it is...cleaned MAF, checked fuel pressure...injectoras are probably dirty but I do not think it is just the injectors. If you figure this out let me know...

Code 542: "Fuel pump open, bad ground or always on". Here's a good URL for codes:

http://www.troublecodes.net/Ford/

It soulds like your fuel pump isn't working right, and likely isn't providing enough fuel pressure. Not enough fuel pressure, and the engine will run lean. Only getting code 172 (without 171, which is the same error on the other side of the engine), tells me you're just barely running lean.

First thing, check your fuel pressure. You can get testing kits at your local parts store. With the vacuum hose off the fuel pressure regulator, you should be getting about 38psi with the engine idling. If it's much lower (like 35 or so), then the pump is likely going bad. I'd suggest replacing the fuel pressure regulator at the same time, just to make sure the whole system is working well.

doobsstang · Oct 12, 2005

Ok, I got the fuel pressure tested today and it was about 30-32psi...I thought this was ok...I checked it right off the fuel rail...so this is too low? New fuel pump and reg...?

HISSIN50 · Oct 12, 2005

I did not read every word here so apologies if I am redundant. When it dies, you should check for spark. If you dont have spark, check injector pulsing (with a noid light). If you have injector pulsing but no spark, the PIP is ok - look at the TFI, coil, etc.

If the spark and injector firing are both missing, look at the PIP (Profile Ignition Pick-up).

Do be sure you have decent fuel pressure too. WHen pumps are on the outs, the diaphram often gets weak. This weak diaphram stops pumping adequately when the pump gets hot (rubber gets flimsy). Once cooled off, it comes back.

Good luck with it.

Chythar · Oct 12, 2005

doobsstang said:
Ok, I got the fuel pressure tested today and it was about 30-32psi...I thought this was ok...I checked it right off the fuel rail...so this is too low? New fuel pump and reg...?

Definitely too low. Stock pressure is 38psi, and the fuel pump is supposed to push about 50-60 psi. Normally, I would suggest replacing the fuel pressure regulator first, because it's the cheapest and the most likely culprit. But with the fuel pump error code, it's more likely to be the fuel pump pushing just 30psi.

HISSIN50 · Oct 12, 2005

Chythar said:
Definitely too low. Stock pressure is 38psi, and the fuel pump is supposed to push about 50-60 psi. Normally, I would suggest replacing the fuel pressure regulator first, because it's the cheapest and the most likely culprit. But with the fuel pump error code, it's more likely to be the fuel pump pushing just 30psi.

I will respectfully disagree. Spec is ~30 PSI+ (most see 32-33) at idle with the vac line attached (assuming a cam which allows a decent vacuum signal). Then at WOT, pressure is 38-39 PSI.

I assumed he just tossed a gauge on the Schrader valve (without disconnecting the vac line) to get an idea. And 30 PSI is fine.

I have never seen a stock system push 50-60 PSI - the FPR does not allow this.

doobsstang · Oct 12, 2005

He took the vacuum line off and it read 36-38psi...Is this ok, and if there is nothing wrong with the fiuel pump why does it still throw me a fuel pump code and tell me it is running lean in cyl bank #1...could this possibly be just dirty injectors?

Edit: He revved the engine and the fuel pressure didnt move...is this normal or a symptom of a problem?

Chythar · Oct 12, 2005

HISSIN50 said:
I will respectfully disagree. Spec is ~30 PSI+ (most see 32-33) at idle with the vac line attached (assuming a cam which allows a decent vacuum signal). Then at WOT, pressure is 38-39 PSI.

I assumed he just tossed a gauge on the Schrader valve (without disconnecting the vac line) to get an idea. And 30 PSI is fine.

I have never seen a stock system push 50-60 PSI - the FPR does not allow this.

Respect? Wow....

I did mention earlier he should check with the vac line off, but should've said it again. Good to know what the psi should be with the vac line on.

The 50-60psi referred to an earlier post today to what the fuel pump was putting out on its own, before the fpr dropped it to 38. And I was wrong, the poster said it's about 90psi. As opposed to the Walbro pumps putting out 190psi, etc.

Chythar · Oct 12, 2005

doobsstang said:
He took the vacuum line off and it read 36-38psi...Is this ok, and if there is nothing wrong with the fiuel pump why does it still throw me a fuel pump code and tell me it is running lean in cyl bank #1...could this possibly be just dirty injectors?

Edit: He revved the engine and the fuel pressure didnt move...is this normal or a symptom of a problem?

With the vacuum line off, the fuel pressure will not move. It's driven by the vacuum provided by that specific hose.

It's possible that there's just a short to the fuel pump, like a frayed wire. Dirty fuel injectors can also cause this problem, if they're not adding as much fuel as they're supposed to. The fuel pump code should really be solved first. Anyone have suggestions for testing the fuel pump?

mo_dingo · Oct 12, 2005

If you disconnect the vacuum line to the FPR, and the pressure doesn't go to 38-39, then there is a problem. Either 1 your fuel pump is bad, or 2 your FPR is bad.
Scott

SeventyMach1 · Oct 12, 2005

Chythar said:
Respect? Wow....

I did mention earlier he should check with the vac line off, but should've said it again. Good to know what the psi should be with the vac line on.

The 50-60psi referred to an earlier post today to what the fuel pump was putting out on its own, before the fpr dropped it to 38. And I was wrong, the poster said it's about 90psi. As opposed to the Walbro pumps putting out 190psi, etc.

When you see a Walbro 190 ..... I think that would be 190 lpr .... not 190 psi. That is rediculously high. Too high for a diesel, lol.

HISSIN50 · Oct 12, 2005

Justin is right about the pump nomenclature - it is LPH.

If the pump was at fault due to lack of pressure, it very often spits out that both banks are lean, not one or the other. Pinging at WOT is an obvious sign.

The SN's use the FPM and CCRM to pass voltage to the pump. Probing with a meter is the way to find the issue.

Since this is all recursively cobbled up on this thread:

When the FPR vac line is attached, as it is when you drive, the FP is controlled via manifold vacuum.

When we disconnect the vac line at the FPR, this simulates WOT. SO the pressure should not appreciably change when the vac line is off, no matter what anyone does with the throttle. The reading might dip for a second if you whack the throttle open, but it should quickly return to 38-39 PSI (or whatever an AFPR is set at).

Once again, if seeing 30+ PSI with the vac line attached and 38-39 PSI at WOT (in real time or simulated with the vac line disco'd), that is fine.

If one believes the fuel system is jacked, one can carefully(!) use a fuel crimp tool on the return line. If pressure goes up with the line crimped, the FPR is suspect. If pressure stays low with the line crimped, that suggests the pump is weak.

If one thinks they have dirty injectors, a cylinder balance test will help rule that out. If it passes, then there is no appreciable cylinder drop from any cylinder and they are all squirting or not squirting equally. If a cylinder fails the CBT, the puter can retest up to two more times using different criteria to see if the injector(s) is/are passable.

Good luck.

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