Necron

iTrader: (1)

Issue just started yesterday and it's been running great since I owned.
-1991 Z28 350 L98 w/Auto
-Car is Stock with 89k miles
-Fuel Pressure is low 40s after prime and holds strong
-Was running around 38 at idle
-The SES light isn't on when running but I put a OBD1 scanner on it and it showed code 41.

Drove it to work and picked up some hardware came back out (still warm) and it started a few times but just immediately died and turned back off. It did have some cranking time between these starts though as a note. I let it sit for about 20 mins and it did the same thing but I got it started one more time and reved the engine for 10 seconds and the car idled fine. I was able to get it home without a hiccup but as soon as I got it in the garage I turned it off and restarted and it was doing the same thing.

I started the car tonight (cold) and it ran great. I turned it off again within a min and once again it started fine but once it warmed up closer to operational temp it was back not starting just like yesterday. As I type this I'm letting it cool down to do one more cooler start in a bit here.

My current theory is it's the ICM since it seems to not start when warm but I think it's weird it's not cutting out once warm/still running. The issue only pops up currently when the car is restarted warm.

I may go unplug the IAC to see if that could be culprit.

Any other thoughts/ideas?

Tuned Performance

iTrader: (92)

Code 41 is for cylinder select error. I doubt the memcal has failed. The ecm might be faulty.
here is a 90-92 tpi ecm for a good price.
https://www.thirdgen.org/forums/engi...92-sd-tpi.html

Necron

iTrader: (1)

Last night I tried to start it again with the engine at 120 and it died 3 times.

This morning I went out and started it real quick and once again it started fine since it was cold.

I unplugged the negative battery cable to just verify the code. The scanner I have is older but still seems to work great so I'm just making sure.

Tuned, all I need to do is buy the ECM and plug my computer chip into that unit correct? Doesn't matter if it's a V6 etc?


Funny story out of this is the car started doing this the day after I test drove a 2019 1SS 1LE and brought it home for a bit. My lady thinks I made the 91 jealous lol

Tuned Performance

iTrader: (92)

You are correct just swap over your memcal chip. Your chip is for a v8 and will be labeled anjf of aujp. The 1227730 ecm was used on v6 and v8 only difference is the memcal.
I think your wife’s onto something with the car jealousy lol

Necron

iTrader: (1)

So I realized I'm a bit silly.

The scanner I was using you need to redo the config manual to get it to scan so I was seeing a old code from another car. My SES hasn't been on when running so it makes more sense now. The car isn't throwing any codes at this time. I'm just so use to newer cars and OBD2 type of stuff.

Something is degrading with heat. The fuel pressure isn't dropping at all so I'm back thinking it might be the ICM going out. This car doesn't have the original crap fuel injectors but I suppose I can't rule those out either so I'm going to test the ohms tomorrow when hot.

The big thing is if you get it started when hot and then immediately rev the engine it will stay running. Just letting it come back down to idle is more then likely will die which is also why i was also thinking IAC but it's fine when cold though?

Tuned Performance

iTrader: (92)

It doesnt hurt to clean and reset the iac but I think it’s a wise choice to ohm the injectors and maybe replace the icm.

Necron

iTrader: (1)

I've got tune parts/icm on the way. Figured I should just do the cap/rotor etc.while I'm there.

I did OHM the injectors tonight while hot they are all within 10% and above the range I've read should be good.
14.6, 14.7, 14.8, 14.7 15.0, 14.9, 14.6 14.8

I definitely think is odd. The car starts when cold and runs perfect even when it get's hot. Just when you turn it off good-luck getting it restarted.

Necron

iTrader: (1)

I wanted to finalize this thread with my final update.

The ICM was the culprit here. I replaced the cap/rotor/ICM and the car is running great again.