Revisiting an old issue with my 5.0 (never able to figure it out)

[mic_lx]

Hey everyone. I'm trying to revisit a really OLD issue that I have with my 5.0 GT.

I have almost 12 years with my car and in all this time I have never been able to determine why sometimes it's running rich and basically dies. Here are the symptoms:

If I leave the car idling for several minutes (5 to 10 or more minutes) with the AC on, then if put it in 1st and go try driving, my car will either stumble and just die or will run really sluggish.
If the car doesn't die, I can put it in neutral again and give it some gas. Then I can see that black smoke will come out from the exhaust. It will do this until it "clears" everything out and will start running ok again.
If the car dies, then I will have to leave it still for 3 t 5 minutes and start it up again. Trying to start up the car before that time frame will result in just cranking and the engine will not start up.
Now, I said that this behavior will happen when having the car idling with the AC on, it will do this same thing with the AC off, but it will take more time to do it than with the AC on.

When I bought the car 12 years ago it already had the EGR disabled (valve is still there, but the tube to the header is welded) and air pump removed.

After getting the car I installed an original 94-95 Cobra upper and lower intake and a BBK cold air intake and a Fluidyne radiator. The car already a MSD coil and ignition box. I don't know if the ECU has/had ever been modified or anything.
It had original E7TE heads and original exhaust manifolds.

I have replaced the following:
Fuel pressure regulator.
Fuel pump (whole assembly).
PCV valve.
Both O2 sensors.
TPS.
IAC.
Cap and Rotor.
Spark plugs and wires
MSD box has been removed due to failure, OEM ignition is now working fine.
Replaced E7TE heads with GT40P heads, GT40P specific headers, E303 cam, new water pump.

Even after replacing all this, the issue is still there. Now, all this was replaced through the years, so the behavior has been the same before and after all this changes.

The ECU has never given any other codes for this issue. It has given me codes when the TPS, IAC and O2 sensors have failed and also the permanent code for the EGR not working.

I have always been suspicious that by not having the EGR in working order it's making this behavior to happen.
I know not having EGR does not benefit in anything and actually gas mileage is horrible and at some point I was trying to make the EGR work again to see things improve.

Anyone has any other ideas on what else I can check or do??

 

[96blak54]

This may seem like dumd questions, but im only clarifying. You never stated anything about the injectors or the style of fuel pressure regulator, so do we assume they are like stock? Yellow injectors and non adjustable fuel pressure regulator? And that the fuel regulator vac line is is good?

 

[mic_lx]

This may seem like dumd questions, but im only clarifying. You never stated anything about the injectors or the style of fuel pressure regulator, so do we assume they are like stock? Yellow injectors and non adjustable fuel pressure regulator? And that the fuel regulator vac line is is good?

Yeah, they are stock. Fuel regulator is non adjustable, vaccum line is ok. All injectors are yellow (connector) and never been replaced.

 

[96blak54]

Does unplugging the mass air flow sensor improve running quality....or is it the same or worst?

Try unplugging the maf sensor before taking it around the block just to note its response. If the situation improves, point your finger at the maf

 

[mic_lx]

Does unplugging the mass air flow sensor improve running quality....or is it the same or worst?

Try unplugging the maf sensor before taking it around the block just to note its response. If the situation improves, point your finger at the maf

Never tried that before as it runs normal unless you dont leave idling for some time
I will sure try that! Basically if I unplug the MAF, it should run worse, otherwise if I dont notice any change at all, MAF should be cleaned and/or replaced, right?

 

[96blak54]

Under normal operation, unplugging the maf sends the ecu into a safe mode making the air/fuel ratio rich.

If the maf is not efficient, causing the ecu to think differently like in you scenario, unplugging the maf will improve air fuel ratio in turn run better.

 

[mic_lx]

Under normal operation, unplugging the maf sends the ecu into a safe mode making the air/fuel ratio rich.

If the maf is not efficient, causing the ecu to think differently like in you scenario, unplugging the maf will improve air fuel ratio in turn run better.

Ok, I'll try that! I've never messed with the MAF in the thinking that it was working fine since no codes for the MAF have ever shown, but hopefully that will do. Thanks a lot

So, the EGR delete should not make the car run that rich? This before I start messing again with trying to make it work

 

[lutter94]

I'd replace that MSD coil. They can't build a coil to save their life. Throw a parts store one on there, try that too. Poor spark makes it look rich out the tailpipe I assume. And even if it isn't the coil today, it will try to leave you stranded one day in the future. Ask me how I know........

 

[evilcw311]

Ford motorcraft coil first. Then clean maf and test as blak mentioned. Then get ready to replace the dizzy.


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[mic_lx]

I'd replace that MSD coil. They can't build a coil to save their life. Throw a parts store one on there, try that too. Poor spark makes it look rich out the tailpipe I assume. And even if it isn't the coil today, it will try to leave you stranded one day in the future. Ask me how I know........

at one time I did replaced the coil with a "Standard" brand one because I was checking something (had a misfire at that time), and while I had that other coil, the issue still happened.

Now that I remember, I also replaced at that time (when it had the misfire) the DIS and the stator (hall effect sensor) and while the misfire was caused by the stator, the running rich condition continued.

It would seem that when the AC is turned on, more gas is "dumped" into the engine and will cause it to stumble and die quicker than when the AC is not on. If you are just driving normally, it will never do it.

 

[mic_lx]

Under normal operation, unplugging the maf sends the ecu into a safe mode making the air/fuel ratio rich.

If the maf is not efficient, causing the ecu to think differently like in you scenario, unplugging the maf will improve air fuel ratio in turn run better.

well this weekend I drove the car.
I started the car and went to unplug the MAF while running. Immediately after unplugging the MAF the car started running poorly and almost wanted to stall.
I couldn't drive the car without the MAF plugged in since it wanted to die on me, but as soon as I plugged the MAF again, the idle smoothed out and ran OK. Although whenever I reached a place (using AC), turned off the car for around 10mins and turned it on again, it would throw out black somke and I had to give it gas until everything cleared out and then the car would run fine and I could tun on the AC again.

So I guess my next step is still to clean the MAF and see if anything improves.

 

[07GtS197]

Have you checked fuel pressure? Could be an injector stuck or something for all we know. Also do you have the fox intake and egr/spacer you can throw on to test?


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[mic_lx]

Have you checked fuel pressure? Could be an injector stuck or something for all we know. Also do you have the fox intake and egr/spacer you can throw on to test?


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I've never actually checked the fuel pressure since it's using an OEM regulator and still stock injectors, but also not tested the injectors to see if one or some might be suck open.

No EGR or Fox intake spacer. The intake that I'm running with is an original 94-95 5.0 Cobra one (curved elbow, not the 90* one).
The previous owner just welded shut the EGR pipe that comes from the header, but the EGR is still in place, connected to its sensor and vaccum. I've never messed on removing the EGR to try to block it in any other way.

 

[07GtS197]

Those headers must be from an sn95 then because fox headers dont need that provision for the egr because the egr passes through the intake straight into the egr valve. So the egr valve on it right now is just open to atmosphere?

Might as well check fuel pressure while youre at it. See if it drops quickly after the ignition is shut off.


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[mic_lx]

Those headers must be from an sn95 then because fox headers dont need that provision for the egr because the egr passes through the intake straight into the egr valve. So the egr valve on it right now is just open to atmosphere?

Right, SN95 headers (actually only passenger side) have a tube that connects to the EGR valve directly. What the previous owner did was, cut the tube, welded both ends of the remaining tube, one on the header and the other on the EGR, and leave everything else still plugged in (EGR, sensor, vacuum line, etc).
Not sure if by doing that the EGR might still be sucking air from outside.

Might as well check fuel pressure while youre at it. See if it drops quickly after the ignition is shut off.

Never thought of that, good idea.... but even with the engine off, injectors could still be dripping fuel into the cylinders?

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[07GtS197]

Right, SN95 headers (actually only passenger side) have a tube that connects to the EGR valve directly. What the previous owner did was, cut the tube, welded both ends of the remaining tube, one on the header and the other on the EGR, and leave everything else still plugged in (EGR, sensor, vacuum line, etc).
Not sure if by doing that the EGR might still be sucking air from outside.



Never thought of that, good idea.... but even with the engine off, injectors could still be dripping fuel into the cylinders?

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[/QUOTE]

Its possible it could still be getting air somewhere. Sometimes with an egr delete you can run lean at cruising speed, not really your problem so I wouldnt look closely at the egr yet but wanted to throw that out there.

As long as the injectors are good they shouldnt be letting any fuel get into the cylinders. Theyre just a solenoid that opens and closes. Not much wrong can come of them other than stuck open or closed. Both can be easily identified.


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[TT94SVT]

Pull your spark plugs and post pictures. You can tell if the ecu has been tuned if the tape is removed. Check the resistance of your all of grounds. The EEC is VERYYYY sensitive to grounds and that is how it fires your injectors and signals the ignition module as well

 

[dcm0123]

Had problems in the past with connectors- the ignition control module and the engine coolant temperature sensor. At one time you could buy both from Ford and splice into your harness. RockAuto has the ignition module connector.

The engine coolant temperature sensor (MOTORCRAFT DY1145) monitors the temperature for the computer to set the fuel ratio. I believe there is another temperature sensor which controls the idiot light or gauge. Do not think the ignition control module could cause this.

I would look for possible problems with connectors, possible shorts in the harness where the connectors terminate including the cable junction to the O2 sensors. The radical change you are experiencing sounds like it could be an intermittent electrical problem which causes the fuel ratio to go off.

Pull the vacuum line of the fuel pressure regulator. If there is signs of gas in the hose or the hose smells like gas, replace the regulator.

Look at the ground connections which are part of the engine control system. Make sure they are good. Keep the spark plug wires away from your engine control wires.

Run the engine on self test program. One part of his test checks the engine cylinder balance which may indicate a bad fuel injector.

Turning the AC on should increase the idle speed. It should not alter the fuel mixture.

I do not see the MAP sensor, MAF sensor or engine coolant temperature sensor on your list of replaced parts. If would replace them as well since they controls fuel ratio. Not sure if your engine will have a MAP sensor. Make sure you do not have vacuum leaks which could cause bad readings.

Spray WD40 at suspected areas and see if the engine speed increases which indicates a leak. I would spray at the gaskets on the intake manifold as well as around the fuel injector o-rings. Install a vacuum test gauge to verify the vacuum is proper. Low vacuum may indicate a leak.

 

[mic_lx]

Guys, thanks for all your replies and help. I haven't forgotten about this, but my Explorer decided to develop a transmission leak and also run rich so I had to address those issues first since it's my daily driver.

Still, I was able to clean the MAF sensor and MAF harness connectors. Aside of that, I was able to do an Idle reset and was able to set idle speed to around 900rpms instead of 1,200 that I had done previously.

I went out for a drive, didn't have much time, but I could feel the car more responsive and idling smoother after the MAF cleanup, though I wasn't able to try to recreate the issue of shutting the car down and restart it after a few mins to see if it's still running rich.

Hopefully I'll have some time during this weekend or take the risk to drive the car to work and see how it drives.

 

[mic_lx]

Had problems in the past with connectors- the ignition control module and the engine coolant temperature sensor. At one time you could buy both from Ford and splice into your harness. RockAuto has the ignition module connector.

The engine coolant temperature sensor (MOTORCRAFT DY1145) monitors the temperature for the computer to set the fuel ratio. I believe there is another temperature sensor which controls the idiot light or gauge. Do not think the ignition control module could cause this.

I would look for possible problems with connectors, possible shorts in the harness where the connectors terminate including the cable junction to the O2 sensors. The radical change you are experiencing sounds like it could be an intermittent electrical problem which causes the fuel ratio to go off.

Pull the vacuum line of the fuel pressure regulator. If there is signs of gas in the hose or the hose smells like gas, replace the regulator.

Look at the ground connections which are part of the engine control system. Make sure they are good. Keep the spark plug wires away from your engine control wires.

Run the engine on self test program. One part of his test checks the engine cylinder balance which may indicate a bad fuel injector.

Turning the AC on should increase the idle speed. It should not alter the fuel mixture.

I do not see the MAP sensor, MAF sensor or engine coolant temperature sensor on your list of replaced parts. If would replace them as well since they controls fuel ratio. Not sure if your engine will have a MAP sensor. Make sure you do not have vacuum leaks which could cause bad readings.

Spray WD40 at suspected areas and see if the engine speed increases which indicates a leak. I would spray at the gaskets on the intake manifold as well as around the fuel injector o-rings. Install a vacuum test gauge to verify the vacuum is proper. Low vacuum may indicate a leak.

I haven't check any grounds nor check for vacuum leaks... having fixed my Explorer which the issue was some O2 sensor wires shorting between them (insulation cracked and fell) this might also be the case for the Mustang.