The new life of the formula fastback

[Fierofool]

I have an 85 and 87 ECM I can loan you to verify your diagnostics.  I can get it to you today if you want. 

[NoMad]

Both for 2.8 manual?

[Fierofool]

Yes.  both manual GT.  Air and Cruise.

[TopNotch]

There's a box of ECM's in the parts barn.

[GTRS Fiero]

Note that the '85 ECM seems to be different from the other years.

[Fierofool]

The one I loaned him may have the shift light activated.  85 V6 ECM's had a knock sensor program in them but it was disabled.  If the shift light is active, it will only indicate through 3rd gear as opposed to the 87 which if activated will indicate through 4th gear. 

[NoMad]

So a quick 100 miles seems to indicate that the ECU chamge has almost completely cured the issue. It acted up twice in very minor ways but nothing like it was. I also did this test with the center console off. I added a heat reflector to try and act like the console does for the last 30 or so miles. Still worked well enough. Will have to get a similar ECU from the barn so I can return Charlie's to him.

[Raydar]

Good show!
For what it's worth, I had a chip that would quit working when the ECM got really hot. (I got a code "51" or something like that. "Missing PROM".)
The ECM reverted to "limp mode". I had reduced power and very rich operation (the "rich" might have been due to the big injectors I was running) and the A/C compressor was locked out. It also would pop and crackle on decel. The Check Engine light would flash very rapidly, like a strobe.
When things cooled off, everything returned to normal. (I had removed my firewall insulation. The ECM got HOT when I was stuck in traffic.)
If you see those symptoms, it's a pretty good bet...

[GTRS Fiero]

Interesting.  I do wonder if the ECU is overheating.  Is the shield on the firewall adequate?

[Fierofool]

On my first 85, after the transmission was replaced with a 5-speed, I noticed that the console armrest would get very hot.  For some reason, I had the console out one day and also the ECM and found that the garage hadn't replaced the shift cable rubber grommets back into the firewall.  Lots of heat was coming in there.  It's a wonder it hadn't fried the ECM.  I know you've had the ECM out and probably would have noticed if the grommets were out of place. 

[NoMad]

So driving around with the console off for testing I had the borrowed ECU start acting up today. I also went ahead and did some heat testing. So the firewall area was slightly warm, but the ECU was really warm. The heat was coming from the ecm itself.

I got into the ECU from the fastback tonight and found that there was an off the shelf EPROM performance chip from one of the big wonderchip shops. That led me down a rabbit hole that turned out to support my seems to be rich till it is hot then lean and stumbling like there is no fuel.... So if you EGR delete without a custom chip to remove the EGR function the car goes super lean. With the "wonder chip" it was likely getting hot much faster and thus causing the EGR to want to function and the motor to go lean and have the issues I have been dealing with. Looks like a custom chip might be the answer to this whole long thing. Ugh! Going to try to find a local tuner to burn one for me tomorrow a d if not I will find a fiero related retailer who will burn me one asap.

Ugh. Just Ugh. Even more reason to go MS3x when I swap the LQ1 in. No matter the motor I can just make thw changes myself!

[GTRS Fiero]

Hmmm.  But the car ran fine for several months since you had it!

It would be interesting to know how that chip is programmed.

The EGR should only work during cruise--not idle or WOT.  Basically, the EGR works when you let off the throttle after accelerating.

Did you use the chip in the loaner ECU to test?

[NoMad]

No, ran the eprom that was in the loaner ECU.

Ya, worry is it is part of the problem and thus as each bit went bad it all had to be redone.

I know the wonder chip doesn't have the egr deleted from the program cause it still throws the EGR code.

How much more will there be to sorting this all out?

[GTRS Fiero]

Well, it is very educational, reading through this, so thanks for that.

I did post that this was an "in-progress" thread.  Hang in there.  I think I have you beat for Fieeo troubles.

[mweldon]

No, ran the eprom that was in the loaner ECU.

Ya, worry is it is part of the problem and thus as each bit went bad it all had to be redone.

I know the wonder chip doesn't have the egr deleted from the program cause it still throws the EGR code.

How much more will there be to sorting this all out?

Not sure how interested you are since you'll be doing the LQ1 soon but since I'm bypassing converting my car to a getrag manual first before the LF3/LF4 - F40 swap I just remembered I have a manual EGR deleted programmed EPROM I purchased from a vendor on fiero.nl.  MIght have a couple more coded tidbits in it..can't remember off top of my head and will have to look up my PMs with the vendor.