idabomb00

UPDATE:
I replaced the coil and 36 went away. I still get these codes:

42 - EST Grounded
71 - A/C Evaporator Temperature Sensor Circuit

I'm not worried about the A/C problem, but I am about the EST. It still misses when it runs after 5 minutes.

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Sorry if this is posted in the wrong section but I do know that my Formula is basically a Camaro. I am new to ls1tech.com.

I have a 1994 Pontiac Firebird Formula. It has a 5.7L engine, 6-speed manual transmission. It has 119K original miles. When I first start it it runs fine until it starts getting warm it starts missing and gets worse as it gets hotter.

Let's assume that the heads are fine.

I've already replaced the spark plugs and plug wires (I feel like a real mechanic now), they are in tight, the wires are on the plugs and opti good and tight and I did NOT cross wires. I used a OBD1 reader on it and got 3 codes:

42 - EST Grounded
36 - High Resolution Pulse Failure
71 - A/C Evaporator Temperature Sensor Circuit

I've checked the voltage to the coil and got battery voltage as indicated by my Hanes repair manual.

When I bought the car it wasn't running, so far I have replace the fuel pump assembly, spark plugs and plug wires, and the map sensor. They guy I bought it from said he was tired of dumping money into it and told me he put a new ECM and Optispark in it so those are not likely, he is family and considering he sold me the car for $400 (which he could've junked it for that), he was telling the truth. I'd greatly appreciate if someone could point me in the right direction or show me a trouble shooting guide. Pictures would also be nice. Thanks in advance.

TransamGCS

iTrader: (2)

you might get a better response if you post your question in the lt1-lt4 modifications section since you have a lt1 and not a ls1. good luck

idabomb00

Sorry, I must've overlooked it. I guess a moderator moved if for me.

LT1FirebirdSLP

iTrader: (2)

36 is the Optispark. It could be a loose ground. It could be a gremlin in your electrical system. It could be an ICM. It could be a 1000 things. However, from experience, everytime I have seen 36, it was the Optispark. Save yourself from having to do it again. Put in a new waterpump and gaskets, additionally, use only ACDelco for the Optispark. It is a good time to learn how to get upclose and personal with the LT1.

Good luck.

idabomb00

Thanks for your help, hope I'm not asking too much out of you but do you know how/where I can find a good trouble shooting procedure for this?

rich5368

iTrader: (2)

I'm going through the same thing on my 94 formula right now. Runs like a raped ape until it gets good and warm and then boom missfire. I've troubleshot mine down to the ICM and the opti. I honestly think on mine it's the ICM getting hot as hell and causing the problem. Try taking it off cleaning it and reapply thermal paste and do the ICM cooling mod on shbox.com. For me that mod just lengthened the time until it got hot and started missing. I'm looking into modifying mine and moving it off the head to see if that fixes my problem.

idabomb00

Okay, let me know how that goes for you.

BlackBird87

iTrader: (6)

haha same car and i had the same problem with the same codes. i ruled out the icm and opti harness. i changed the opti and that solved the problem