lrbodnar

Since ive had my 94, 6sp for the past month, its been running rough. Some what of a lumpy idle, and running very rough at around 1000 rpms. On the road though, It seems to run quite fine.

Ive posted a video on youtube somewhat showing what Ive been running into. It doesnt show how it runs rough at 1000 rpms very well, but both times I get down next to the exhaust pipes, you can hear how it misfires abit.... I think... or is this just how lt1 engines run?

As a back ground, ive replaced plugs and wires, cleaned egr, replaced coolant temp sensor, cleaned IAC, replaced ignition coil, checked for vacuum leaks, tested injectors. Everythings coming up good.

I will say though, I left the car over night with the battery unhooked, because I was unplugging sensors trying to find a problem. In the mouring before starting I installed the new coil. After starting it for the first time.... it ran GREAT!!... for about 5 minutes . Then it went back to the way it has been. Ive tried to duplicate this by getting it running in a closed loop again, with a cleared computer... but still seems to run rough.

Ill also note that, after driving the car, and getting it hot, and up to operating temperature... then parking it... then restarting it in like 20 minutes or so, It will run extremely rough for about a minute, then smooth out alittle.

Im lost, and need help, or suggestions.

https://www.youtube.com/watch?v=ufKa...ature=youtu.be

I hope I posted this video the right way, and also sorry for being sideways!!

DanielRicany

Hard to hear on my phone but it sounds like you're having small backfires out the exhaust. Things that can cause this is running rich, vacuum leaks, valves not sealing properly, misfires, crossed wires, and retarded timing.

Have you confirmed that there are no misfires by performing a power balance test?

Also, sometimes you can have a slight misfire such as weak voltage or low compression.

The first thing I would check is to see if it has enough timing advance. I don't think the LT1s have anyway of measuring timing so you'd have to create your own pointer and balancer mark.

I'd go over anything that can make a car misfire. Spark, fuel, timing, compression, AFR.

lrbodnar

I know for a fact wires arent crossed, and there shouldn't be any vacuum leaks..... as far as the rest, I dont know, This is starting to get above my head, and tools.

cudamax

Thats a bad video. Real trippy. Nothing but wind sounds and whistles and gurgling sounds.
Hard to tell anything from that video
https://www.corvetteforum.com/forums...questions.html

lrbodnar

haha, right on, maybe I should try this in the garage..... give me a hour or so and ill have a better one

BucfanTitan

I had a problem with my 95 that in R or D it ran very ruff. Put the car in P or N everything was fine. After searching for a long time I found the issue. On the passenger side under the removable covers the vacuum lines were destroyed. A little critter made a nest and ate the wires. fixed the leak and all is better.

lrbodnar

Thanks for the tip, ive been through all the vacuum lines on the car front to back, Im quite sure its not a vacuum leak..... I think.

I tried recording a second video in the garage, and it came out worst than the first, guess my phone cant pick it up well.

I will say though, that today is the best its been running since ive had it. After I installed the ignition coil.... leading me to believe this is ignition related.

DanielRicany

I was confident that I found all the vacuum leaks too. Until I did a smoke test. Found 5 more leaks in places I never would have thought of.

lrbodnar

Never thought to do a smoke test like that.... going to have to try this, this weekend. Can something similar be done to find "hairline" exhaust leaks? I can hear one kinda of, but cant seem to see it.

BucfanTitan

any updates?

VikingTrad3r

i dont smoke but im looking forward to tryin scotty kilmers cigar test to find my vac leaks. my car runs pretty good but guaranteed i have vac leaks after 27 years! id wager so does yours.

Hey, happy halloween all!! had the first above freezing halloween in my memory and scared quite a fee kids!!

lrbodnar

Since ive had the car, its ran rough, and not smooth. Well about a week ago I did the cigar smoke test, and came up good, but ended up changing a large amount of the rubber vacuum hoses, since they were looking rough.

Couple days went by, still running like crap, park the car for the day, and drove my other car to work. I came back home, and started working on the corvette again, but when I started it to move it to my work area, it ran PERFECT!!!! Smooth at idle, all the way through the revs, perfect!!!

So I took it out for a couple of hours just to finally enjoy the car. Stopped a few places, restarting it along the way, still running great. Had it sat over night, and started right up in the mourning perfect like the day before. Im thinking "great it fixed its self"...... Was I wrong.

The wife wanted to get burritos, so we took the car, parked it, came back from eating, started the car, and it would barely run!!! Wouldnt idle, couldnt give it gas, stalled a few times...

Now since that day, for the past few days, its been back to running like it always has, rough.

So, im out of ideas, but have a very good feeling that this problem is ignition related, so I just ordered a new opti spark, water pump, etc.... hopefully this is the end, and I can start enjoying this car.