Hi all,

I've searched many threads, and while I found similar symptons, nothing exactly like my issue, so I though I'd ask specifically. I have a 93 LT1 6SP with 93K miles on it.

Earlier this year after I experienced heat related issues on three occassions. I'd take the car out of storage on a warm day I'd drive 20 miles eat lunch then drive 20 miles back. On the way home the car would start to feel at first like it is running out of gas then start missing then stall. The tack would jump around like crazy, and the car would start to misfire. The more gas I gave the car, the worse it would run. I'd let the car cool down for 30 minutes or so then limp home. The next day it would start fine. The car still has 2/3rds of the tank of gas that it was stored with as well.

4 years ago I had the fuel pump replaced, and 3 years ago I had the water pump replaced. The shop I took it to (whom I trust) did a visual inspection of the opti and didn't see any water damage. I found the ICM was covered in gunk, so I removed it, cleaned it, added new heatsink grease. I let the car warm up for about 15 minutes, then after taking it around the block roughly twice same issue. Today I replaced the ICM, and same issue. I pulled codes 74 and 16 after this last time. Always heat related.

Arg! I'm open to suggestions. Thanks in advance.
-John

 

did the 2/3 of tank is fresh gas... if the car was in storage may be the gas is not the strongest and its why the car is missing...

 

Does old gas sound in line with this behavior only after warming up? Also, would it throw those codes? I've stored the car the same way for the last 8 years and I haven't encountered this issue. I appreciate the suggestion, all the same.

 

I would start with ohm-checking your fuel injectors. Check the FIC sticky at the beginning of this forum for the procedure.

If they are all over the map, I would contact Jon at Fuel Injector Connection. He has an injector specifically for the 93 LT1 engine.

SAVE the WAVE!

 

Depending on the codes, I'd consider replacing the 02 sensors, too. If they've got more than 50,000 miles on 'em they're out of their maximum service life.

 

Check the two engine temp gauges and see if they say the same thing.

 

No one mentioned the ECM. I've had 2 fail with the same symptoms.
Car gets to operating temp, rpms are erratic, cutting out, dies, runs after cool down, a lot worse during summer. I'm having both rebuilt, not solder flowing, by 2 different companies. One company (Zip) farms them out, the first time I got it back, it still had the first system problem I told them about, displays 327 oil temp when first turned on.
We'll see what the second time around produces.

Jim

 

I hade same symptoms. Ended up replacing the fuel injetors. And that is with less than 50,000 original miles.

 

I'm only showing codes 16 and 74 if that helps.

Thanks for the advice guys. I'm inclined to start with the easy solutions. So, I'll replace the gas, run injector cleaner through it, and ohm test the injectors as soon as I can.

I've got to be getting closer.

 

Not surprising to me. With so many of us not driving these cars on a daily basis, the injectors have time to clog up.

I got 106,000 miles out of mine. I drive mine daily from March to December. And in January and February, I take mine out when the roads are clear. Even in zero temperatures!

SAVE the WAVE!

 

These symptoms sure has the sound of an bad opti. It can cause these problems when hot and have seen the tack do funny things also from it.

I also think of the ICM or ECM, but that is a distant thought at this time.

 

[QUOTE=jstout30;1570930500]I'm only showing codes 16 and 74 if that helps.QUOTE]


What module are you seeing those codes?

Dave

 

I put this project down for a little bit, and decided to rule another thing out today. I drained the old gas from the tank, and replaced it with premium gas and a bottle of fuel injector cleaner. I then let it idle for about 12 minutes so it was nice and warm, then I drove it around the town for about 5 minutes. Sure enough, same thing. Started missing then losing power as I gave it gas, and by the time it was back in my garage it had died.

As the ICM and gas gave been replaced, I'm thinking my next steps in order should be:
1) to look for wiring / grounding issues. (I've not seen any arcing or sparking at night)
2) test/ replace coil, plugs, and plug wires
3) ECM
4) opti

Any help is greatly appreciated.

-John

 

I checked the codes again with the paperclip method, and I pulled:
Module 1 - 74
Module 4 - 16

While the car was still running rough, and barely running, I also looked for any signs of arcing or sparking under a dark hood, but didn't see any. I also tried turring off the ASR on a whim due to the code 74, but no difference.

 

Missing when hot and Tack jumping = replace opti. 98% of the time.

Cheers - JR

 

Before I would even think about replacing the OPTI. Follow the trouble shooting guide for your codes......then I'd test the ICM and COIL. (Simple to do, inexpensive and I've had both fail before with same symptoms 'although not on other cars not my Vette')

I have an original 157K mile opti on my impala SS...so while they fail/wear out they are not the fragile made of sugar and melt on humid days devices depicted on this website. While your OPTI may be the culpret I believe more good OPTIs were replaced in a throw parts at it aproach to troubleshooting than faulty optis.




JMHO.

Mike "never had an OPTI Failure yet"