Been dealing with this issue for years on my 94 GT

For years I have had the following issues with my 94 5.0...

The vehicle is an automatic, when I shift say from park or neutral, to drive or reverse, the car will try to stall..

When the car is warmed up it will sometimes, well now almost all the time, the car will start and immediately stall out and I have to wait for the car to cool off some before she will properly operate again.

The only codes I get are 311 and 314 running, and 553 when the car is off, all Thermactor codes.

I have thrown so many parts at this old car, which I do not regret since she is a 30 year old car and gets more alive with every new part. But I am very unfamiliar with these Thermactor codes, and I am not even sure if it is causing my problems. Any help is greatly appreciated.

AeroCoupe said:

How many miles and be specific as to what parts you have changed. Has the transmission ever been rebuilt? Have you serviced the transmission I.e. and filter and fluid change? The guys need as much detail as you can provide to even have a shot at helping.

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To be honest, really didn't think it was the transmission, seems more like an idle, air issue. Transmission has been serviced recently, car has about 250k miles. Replaced MAF, IAT, PCV, IAC, TPS, ignition module, distributor, coil. A while back it I did the smog pump, pvc.. I know there are some other parts as well, I just really can't remember.. I went crazy with parts since almost everything was original, and she never, never would give me a code until now. Not that I regret it, the old car really needed some of those parts anyway.

The problem started when I would shift from neutral or park, to reverse or drive. The car would rev down, get worse and worse until she started cutting off at times. She would only do this warmed up, never cold. Now she has gotten to the point she will not start when warmed up, will crank up for a second and cut off. I am really good with newer mustangs and classics, but this era is odd to me. All these vacuum lines and hoses.....

Update.. I found two issues, that for now have resolved the issue of the car stalling and not wanting to start when warmed up. The pipe connecting my EGR valve to the exhaust was cracked open, who knows how bad that was affecting the EGR system. I also found that while my PVC valve was good and installed properly and was connected to the side of the upper intake. It was not connected underneath to the upper intake, where it splits off. That hose had shrunk with age and no longer was long enough to make the proper connection. The car still likes to rev down some when shifting into gear, but I went ahead and changed out the transmission filter again. But didn't make much of a difference, car still shifts like butter when driving normal and on time when really getting on it.

Does anyone know what code 6 means on an OBDI scan? Yes, just 6, single digit. I get that code every time I run a scan, not much information out there on a single digit code. I even resorted to asking AI and it suggested it was a TPS (throttle position sensor) code. I did hook a voltmeter to ground and signal on the TPS. Car idles at .9 volts and around 4.7 volts with throttle fully open. I have been having issues for years with the car sometimes jerking and trying to stall when going from park/neutral to reverse/drive. Today it was just completely cutting off when going into gear and even for the first time starting to idle rough for example, sitting a light and trying to stall. I have tested and replaced every vacuum line in the car, my PVC hoses were rotted out in some places and my exhaust connection to my EGR was broken. I did have an issue where the car would not run after it was warmed up. I had fixed all of that and was just left with the one issue of the car idling down to around 400 to 500 RPMs when going from park/neutral to reverse/drive. Which is an issue I have had with that car for almost 15 years!! I am at my wits end and about to sell this 94 and put the money towards my 66. Just it is my first mustang I have owned for decades now. Another think I have noticed, is the voltmeter in the instrument cluster will jerk down randomly at times??

The car is a 94, 302v8 with an automatic transmission. The car is all original and bone stock mechanically. The car does have around 230 to 250k miles, which I am guessing since the odometer broken a decade ago. The motor still has strong compression. The transmission still shifts firm and on time when getting on it and smoothly when driving normal. I did think the torque converter was acting up, I did change the filter and fluid a few weeks ago. Everything was clean and the fluid was still red. I have replaced so much, all controls and sensors to the EGR, replaced the TPS, IAC, compete PVC system, ECT, MAF and the other sensor right next to it. Cleaned and tested Throttle body replaced the Distributer, Ignition Coil and Ignition Module. Rebuilt the Alternator which now charging at 14.5 volts. I even replaced the power steering pump since it was starting to whine at me, which it did need to be replaced. I have replaced almost every sensor or control that talks to the computer at this point. This car has me very tired, I am good working on the purely mechanical classic stangs or the newer purely mechanical and electronic OBD2 stangs.. But this OBD1, with vacuum lines and sometimes a bolt being metric or standard...... This car has me very tired.

Any suggestions at this point are welcome.

Noobz347 said:

Combined this with your other thread.

It's not good practice to spread diagnostic info about the same car across multiple threads. Stick in all in one place so folks can refer.


By the way: All OBD 1 codes are 2 digit.

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I really needed this to be a new thread, since it's a new problem.. And yes, I would normally agree all codes for a mustang with an OBDI system, starts with 11.. But I assure you, I am getting 6.

AeroCoupe said:

Can you walk us through how you are pulling the codes and at what point you get a code 6?

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I hook my OBDI (81-95 Ford specific) scanner up to the harness under the hood near the passenger firewall, start the car up, turn on the scanner and hit "test". The scanner will cycle and test all systems while the car is running. The first code I get is 6, followed by the code that tells me my overdrive is on and my parking brake is set. So, I know the tool is working properly, plus I get code 6 with another, cheaper code scanner.. The computer keeps kicking a code 6..

66gt94gt05gt said:

I hook my OBDI (81-95 Ford specific) scanner up to the harness under the hood near the passenger firewall, start the car up, turn on the scanner and hit "test". The scanner will cycle and test all systems while the car is running. The first code I get is 6, followed by the code that tells me my overdrive is on and my parking brake is set. So, I know the tool is working properly, plus I get code 6 with another, cheaper code scanner.. The computer keeps kicking a code 6..

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Just in case anyone doesn't believe me. I also read the manual that comes with this scanner front and back to make sure it doesn't display any single digits at any time during use to maybe communicate anything else besides OBDI codes. Also, the manual itself doesn't list any single digit codes, it only starts at 10 or 11, forgot which one.

66gt94gt05gt said:

I hook my OBDI (81-95 Ford specific) scanner up to the harness under the hood near the passenger firewall, start the car up, turn on the scanner and hit "test". The scanner will cycle and test all systems while the car is running. The first code I get is 6, followed by the code that tells me my overdrive is on and my parking brake is set. So, I know the tool is working properly, plus I get code 6 with another, cheaper code scanner.. The computer keeps kicking a code 6..

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So, after some more digging and being able to actually read the icon on the scanner above the "6" with the enlarged picture.. Guess my eyes are getting old.... This scanner displays the number of cylinders when starting a scan. Which is very confusing to me, since the car is a V8 302...

AeroCoupe said:

So you are doing KOER (key on engine running). Is the motor up to temperature? What about KOEO (key on engine off)? See Post #3 in the following with regards to 6 cylinders:

Engine - 93 Mustang GT, Code 41/91, KOER Cylinder ID shows 6 and not 8

Hello everyone, I have been jumping around multiple forums for the past 2-3 weeks now trying to gather as much information as possible and could not find some answers to a few questions. I have a 93 Mustang GT, 5 speed, with CAI, BBK Shortys, E-303, 70MM T/B and spacer, 70MM Mass air with...

stangnet.com

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Thank you, I did see others on F 150 forums with the same issue of a scanner showing 6 cylinder when it should of been 8..

I ran a scan several times yesterday, cold and warmed up, car running and just key in start position.. Here is what I got.

With car running:
- 314 Thermactor inoperative left side, When car is cold or warmed up.
-311 Thermactor inoperative right side, when car is cold or warmed up.
-116 ECT out of self test range, only when car is warmed up.

With car not running, key in start position:
-553 Air management 2 circuit failure, when car is cold or warmed up.
-10 I hate this one, Cylinder #1 failed balance test, when car is cold or warmed up
-118 ECT circuit failed above max volts, only when car is warmed up.

I have replaced and tested my ECT several times. Also, I can't find anything wrong in my secondary air injection system. I even deleted the whole system at one time, did nothing to get rid of the 311 and 314 codes. I really hate that code 10, the car runs so strong!

Any suggestions would be appreciated, Thank you

AeroCoupe said:

ECT is probably wiring or ten pin connectors.

ECT wiring ?

I've been having some issues with my 89 vert...so I pulled the codes. I came up ECT low voltage and BPS low. So I got a new ECT form Motorcraft and it has been updated. New sensor is different and comes with a pig tail plug. The problem is...the pig tail has 2 white wires ...and the instruction...

stangnet.com

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I had the same, new pigtail with the new ECT.. Maybe double checking my wiring is in order.

AeroCoupe said:

ECT is probably wiring or ten pin connectors.

ECT wiring ?

I've been having some issues with my 89 vert...so I pulled the codes. I came up ECT low voltage and BPS low. So I got a new ECT form Motorcraft and it has been updated. New sensor is different and comes with a pig tail plug. The problem is...the pig tail has 2 white wires ...and the instruction...

stangnet.com

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So, After referring to a wiring diagram, I may of had reference and ground mixed up.... Not that it matters, the ohms on the ECT is not right when cold or warmed up, so I ordered yet another ECT. My biggest fear, I should be having 5v coming from the computer, I only have 4.6v..... I will check wiring from the computer to the ECT and if there are any fuses.

AeroCoupe said:

ECT is probably wiring or ten pin connectors.

ECT wiring ?

I've been having some issues with my 89 vert...so I pulled the codes. I came up ECT low voltage and BPS low. So I got a new ECT form Motorcraft and it has been updated. New sensor is different and comes with a pig tail plug. The problem is...the pig tail has 2 white wires ...and the instruction...

stangnet.com

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And forgive my ignorance, what do you mean by ten pin connectors?