95 GT PCM issue?

[RatFink]

I’ll start by apologizing for the lengthy post. I’m new to this site, and this is my first post.



I have a 95 GT convertible, auto, with minor mods – Trick Flow heads, Trick Flow upper & lower intakes, BBK 75MM throttle body, E303 cam (no cam card, but has a similar “bump” to cars I’ve owned with verified cam), smog and O2 delete. Mods were in place when I bought the car and am unsure of what other things may have been done to it. The work appears very neat and clean, and the car also only has 65k original miles. I mention this to potentially rule out shotty work, etc. I've daily-driven the car for around a year and it has performed flawlessly until this point.

My reason for the post is because last week while driving, the engine died and would not start again. I found there was no spark to the plugs, so I replaced the coil and ICM using parts I had around the shop. The distributor was finally replaced, which got the car running again. It had MSD and was replaced with stock. I thought it was fixed, but taking it down the road it began to pop loudly from the exhaust, shift erratically, and the throttle would almost “hang open” (it would run around 35MPH without touching the pedal). The CEL also began to periodically aluminate very faintly. Timing has been set and rechecked a dozen times. I’m being told the PCM could now be the culprit. Is there a chance when the MSD failed, it sent back-voltage that altered the PCM? I’m at a loss and would appreciate any guidance you all have to offer.

 

[RossA81]

Any idea how it's tuned? I had one in the past that I tuned with a Moates "quarterhorse" and every so often it would just drop the tune and I would have to reload it.

It is also possible your new distributor is already bad. It would be the "pickup" inside the fails, and you also need to rule out the "TFI"

Ross

 

[duh09]

I'm sure you did, but just to make sure, when setting the intial timing, were you pulling the spout?

You can pull the PCM out and open the case and do a little searching on the board itself to see if you spot any damage. Popped caps or overheat damage from an over voltage should be noticeable if you look closely. I've never heard of a failed dizzy roasting one but I'm not an expert in anything.

The car likely has been tuned if it was running well beforehand, especially if it's running with no O2 sensors. Ross brings up a good point of the Moates. Pulling the PCM would also answer the question pretty quickly on if it's running a Moates or not to at least start to narrow down options.

I'm all on board to swap these cars to a more modern standalone. I've slapped a Microsquirt in mine, I know there's a handful of guys in here running Holley setups... tuning gets a lot easier with modern ECUs and the computing power of anything semi-modern is way over what a EEC-IV system can do. But regardless, I'd pull the kickpanel off and pull the ECU out and just give it a once over for good measure.

 

[RAU03MACH]

if it has the TFI in it check it first

 

[RatFink]

Any idea how it's tuned? I had one in the past that I tuned with a Moates "quarterhorse" and every so often it would just drop the tune and I would have to reload it.

It is also possible your new distributor is already bad. It would be the "pickup" inside the fails, and you also need to rule out the "TFI"

Ross

What I called the ICM is actually the TFI. Error on my part. As for the tune, I have no idea at all. There's a lead that runs into the glove box with a rotatable switch attached. I've never messed with it. I'll attach a Pic I snapped of the PCM. I'm pretty sure the handwriting on it is just the part #. I haven't removed it or tried opening it.

I have another new distributor on the way, but with the holiday it's delayed getting here.

 

[RatFink]

I'm sure you did, but just to make sure, when setting the intial timing, were you pulling the spout?

You can pull the PCM out and open the case and do a little searching on the board itself to see if you spot any damage. Popped caps or overheat damage from an over voltage should be noticeable if you look closely. I've never heard of a failed dizzy roasting one but I'm not an expert in anything.

The car likely has been tuned if it was running well beforehand, especially if it's running with no O2 sensors. Ross brings up a good point of the Moates. Pulling the PCM would also answer the question pretty quickly on if it's running a Moates or not to at least start to narrow down options.

I'm all on board to swap these cars to a more modern standalone. I've slapped a Microsquirt in mine, I know there's a handful of guys in here running Holley setups... tuning gets a lot easier with modern ECUs and the computing power of anything semi-modern is way over what a EEC-IV system can do. But regardless, I'd pull the kickpanel off and pull the ECU out and just give it a once over for good measure.

Spout was unplugged when timing, but I appreciate you double-checking me. I agree with you on it being tuned. The CEL is in working order and only illuminates prior to starting (normally). I've looked into a more modern alternative but was hoping to fix it in a cheaper way. Ultimately, I'll do whatever necessary with the electronics. I'm away from the car for a few days, but I'll dive into checking the PCM when I return.

 

[RatFink]

if it has the TFI in it check it first

I've always called the TFI the ignition control module. Uneducated on my part. I replaced the TFI prior to the distributor and had no change.

 

[RAU03MACH]

Then I would check the pick up in the distributor
And the pick ups on the distributor shaft
Broken or worn down bent

 

[RatFink]

Then I would check the pick up in the distributor
And the pick ups on the distributor shaft
Broken or worn down bent

Thanks. I have another new one on the way. Hoping the first new one was faulty out of the box. Like I said earlier, it didn't run at all until I swapped the MSD out for a factory.

 

[duh09]

What I called the ICM is actually the TFI. Error on my part. As for the tune, I have no idea at all. There's a lead that runs into the glove box with a rotatable switch attached. I've never messed with it. I'll attach a Pic I snapped of the PCM. I'm pretty sure the handwriting on it is just the part #. I haven't removed it or tried opening it.

I have another new distributor on the way, but with the holiday it's delayed getting here. View attachment 39999

A rotary switch is different but a pretty good hint. I vaguely remember something with a switch back in the day but boy I can’t think of it right now. I’d be interested to see what you find when you pull it out.

I’ve been pretty happy with my Microsquirt. The PnP version is like $550. You’d need to purchase a wideband to go with it as well, so another $150 and an afternoon of tinkering and a little bit of tune work. It was about the most economical option I could come up with for my car.

 

[shovel]

O2 delete

On a EFI car, eh?

 

[RatFink]

A rotary switch is different but a pretty good hint. I vaguely remember something with a switch back in the day but boy I can’t think of it right now. I’d be interested to see what you find when you pull it out.

I’ve been pretty happy with my Microsquirt. The PnP version is like $550. You’d need to purchase a wideband to go with it as well, so another $150 and an afternoon of tinkering and a little bit of tune work. It was about the most economical option I could come up with for my car.

If this other distributor doesn't fix it, I'll definitely be reaching out to make sure I order the correct system. To my knowledge there's not much else it can be at this point.

 

[RatFink]

On a EFI car, eh?

Previous owner went with long tube's and no cats. I really don't know much about the car, other than it's been really reliable for the last year.

 

[RossA81]

Computer has definitely been out!

Ross

 

[weendoggy]

If the "rotary switch" in the glove box has 4 settings, it sounds like a TwEECer-RT, which allowed you to have 4 preset tunes (that you made) and were able to change "on the fly". I know, I had one. The PCM/ECU had/has a chip attached (inside the PCM) and leads coming off going to the switch. The only way you're able to "tune" the engine is via software, i.e. Excel, and, you better know what you're doing or you can create a mess. I know one of the settings was stock. I had several tunes in mine (on a F5 Cobra) when I was still using the Ford ECU, and even had one tune for valet, just in case. I made it run like crap!

I thought I junked all the files from my PC, but, I did look on my backups and still have all the data and information re: the program, including the "How to Use" in Word and a pdf file of instructions. Again, I'm not saying that's what you have, but maybe. The program is so archaic by todays standard and you'd be better off going with a Microsquirt or something better and easier to tune. Reading through all this old stuff makes my head hurt.

 

[RatFink]

Good to know. I appreciate the info. I'll be back tomorrow and hope to come up with some answers.

 

[ttocs]

my bama chip had the little selector to pick different tunes. None of them were worth a crap.

 

[Wmac]

^ Have the same sct chip from Bama for w4h0 ecu.

 

[weendoggy]

^ Have the same sct chip from Bama for w4h0 ecu.

That looks just like the early TwEECer-RT that I had. I scrapped all that crap 20yrs ago. However, at the time, not bad.

 

[95opal]

I’ll start by apologizing for the lengthy post. I’m new to this site, and this is my first post.



I have a 95 GT convertible, auto, with minor mods – Trick Flow heads, Trick Flow upper & lower intakes, BBK 75MM throttle body, E303 cam (no cam card, but has a similar “bump” to cars I’ve owned with verified cam), smog and O2 delete. Mods were in place when I bought the car and am unsure of what other things may have been done to it. The work appears very neat and clean, and the car also only has 65k original miles. I mention this to potentially rule out shotty work, etc. I've daily-driven the car for around a year and it has performed flawlessly until this point.

My reason for the post is because last week while driving, the engine died and would not start again. I found there was no spark to the plugs, so I replaced the coil and ICM using parts I had around the shop. The distributor was finally replaced, which got the car running again. It had MSD and was replaced with stock. I thought it was fixed, but taking it down the road it began to pop loudly from the exhaust, shift erratically, and the throttle would almost “hang open” (it would run around 35MPH without touching the pedal). The CEL also began to periodically aluminate very faintly. Timing has been set and rechecked a dozen times. I’m being told the PCM could now be the culprit. Is there a chance when the MSD failed, it sent back-voltage that altered the PCM? I’m at a loss and would appreciate any guidance you all have to offer.

Before you go hog wild on a PCM issue. Did you pull the codes? What you describe sounds like a vac leak or possible TPS issue.