Seafoam is in my tank right now, it works..
L98 Rough Idle
Melting Slicks
Joined: May 2002
Posts: 3,161
Likes: 8
From: Beverly Hills Florida
CI 7-8 Veteran
.........My shop tuned my car Friday, it would idle bad dumping fuel, so it needed an ECM, and the old one had a hypertech chip, which was making the old computer inject too much gas I think, also I needed new plugs, and I.A.C. motor...now it runs fine...but the ECm was definitely bad, and a reman one is cheap, actually
Drifting
Joined: Mar 2004
Posts: 1,504
Likes: 0
From: Byron Center MI
Here are my thoughts. You have old gas and the car has been sitting for quite awhile. I would put a full can of Seafoam in the tank and top the tank off with fresh gas. Drive it as much as you can. This will only cost you $8 for the Seafoam and what the gas will cost you.
It seem the more you drive it the better it gets. This is what makes me think it is gummed up injectors and old gas.
Also you asked what it would help putting Seafoam in the booster. What people are trying to say is remove the vacuum line from the booster and slowly pour the Seafoam in the vacuum line.
Hope this helps. Tim
It seem the more you drive it the better it gets. This is what makes me think it is gummed up injectors and old gas.
Also you asked what it would help putting Seafoam in the booster. What people are trying to say is remove the vacuum line from the booster and slowly pour the Seafoam in the vacuum line.
Hope this helps. Tim
Thread Starter
Instructor
Joined: Nov 2007
Posts: 108
Likes: 0
From: Waukesha WI
So how would that help pouring into the vaccuum system? I understand that it'll smoke like hell and probably help me in locating a vaccuum leak if i have one, but what else does that do? I don't understand how a carbon cleaner or what not would do anything to the vaccuum system which should only have air in it, how does it get gummed up?
Drifting
Joined: Mar 2004
Posts: 1,504
Likes: 0
From: Byron Center MI
So how would that help pouring into the vaccuum system? I understand that it'll smoke like hell and probably help me in locating a vaccuum leak if i have one, but what else does that do? I don't understand how a carbon cleaner or what not would do anything to the vaccuum system which should only have air in it, how does it get gummed up?
By pouring it in the Booster vacuum line the engine will suck the cleaner in the plenum and run it through your engine and burn it.
Doing this will not help you find a vacuum leak. The only way to find a vacuum leak is to spray something at the areas that could be leaking while the engine is running. While the engine is running and you are spraying something and the engine RPM increases or the idle becomes smoother you have found your vacuum leak.
When I said your injectors are gummed up is when fuel is left setting it will varnish and become sticky. This will somewhat clog your injectors causing a poor spray pattern. If this has happen the fuel will not atomize well and the engine will run poorly at idle. As your RPMs increase the additional air flow will help atomize the fuel. This is why I think you have a rough idle and it runs better at higher RPMs.
I could be totally wrong but if I am it will cost you very little compared to some of the other suggestions.
In my opinion when trying to figure something out keep it simple and don't think the worst.
Thread Starter
Instructor
Joined: Nov 2007
Posts: 108
Likes: 0
From: Waukesha WI
I do have quite a bit of knowledge about cars and know what happens when gas sits 
Unfortunately, i'll probably have to bring this problem back to life in the spring as i drove the car last saturday for the last time until the spring. Thanks for all the help though. First thing i'll do when i pull it out of storage is try the seafoam thing.
Unfortunately, i'll probably have to bring this problem back to life in the spring as i drove the car last saturday for the last time until the spring. Thanks for all the help though. First thing i'll do when i pull it out of storage is try the seafoam thing.
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Drifting
Joined: Mar 2004
Posts: 1,504
Likes: 0
From: Byron Center MI
I do have quite a bit of knowledge about cars and know what happens when gas sits
Unfortunately, i'll probably have to bring this problem back to life in the spring as i drove the car last saturday for the last time until the spring. Thanks for all the help though. First thing i'll do when i pull it out of storage is try the seafoam thing.
Unfortunately, i'll probably have to bring this problem back to life in the spring as i drove the car last saturday for the last time until the spring. Thanks for all the help though. First thing i'll do when i pull it out of storage is try the seafoam thing.
Thread Starter
Instructor
Joined: Nov 2007
Posts: 108
Likes: 0
From: Waukesha WI
Pulled the car out today to take it into for emmissions and i am happy to say that it passed. Hopefully, this means my injectors should be ok because if they were bad i'm not so sure that it would have passed. What do you guys think?
Thread Starter
Instructor
Joined: Nov 2007
Posts: 108
Likes: 0
From: Waukesha WI
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Very simple, you simply unplug the injector connectors, two wires go into each connector. DON'T worry about what they're supposed to read, although my FSM for an 87 says above 10 ohms, mine read around 16. What you're really looking for is consistency, they should all read within +/- .5 ohms. You should read them both hot and cold. Doing this will give you a read on the injector coil health, next follow it up with a fuel pressure test.
Melting Slicks
Joined: Nov 2013
Posts: 2,264
Likes: 3
From: Orchard Park NY
Hey guys, just picked up an 85 last night. Driving it home, i made some observations (Got it for 2500 from the fiance's dad).
First, what would cause a rough idle on a FI engine when the plugs and wires are all new? Throttle pisition sensor? isn't there some kind of idle sensor as well? Or should i start by replacing the distributor? It's going to get new wires next spring btw (i think he just put the regular stockers on there but i'll get something a little more HP)
Second, rattle trap. Is that normal for a vette with 73k on it? Seems that the top and the dash rattle the most. I tried to tighten down the bolts that hold the top on, but the tool that the car came with is basically a ratchet with a torx on it and the ratchet was broken. What size torx is that? I can't seem to get the torx tool off of the ratchet.
Third, not sure if this is a problem or just a trait of the steering. Car seemed to be all over the road. When i turn the steering wheel from left to right real fast, it doesn't feel like anything is loose. Steering is very tight and VERY responsive. I can turn the wheel like 1 degree and the car wants to turn, unlike any other cars i've driven. Any input would be great, plus anything else i need to look for as well.
Thanks,
Mike
First, what would cause a rough idle on a FI engine when the plugs and wires are all new? Throttle pisition sensor? isn't there some kind of idle sensor as well? Or should i start by replacing the distributor? It's going to get new wires next spring btw (i think he just put the regular stockers on there but i'll get something a little more HP)
Second, rattle trap. Is that normal for a vette with 73k on it? Seems that the top and the dash rattle the most. I tried to tighten down the bolts that hold the top on, but the tool that the car came with is basically a ratchet with a torx on it and the ratchet was broken. What size torx is that? I can't seem to get the torx tool off of the ratchet.
Third, not sure if this is a problem or just a trait of the steering. Car seemed to be all over the road. When i turn the steering wheel from left to right real fast, it doesn't feel like anything is loose. Steering is very tight and VERY responsive. I can turn the wheel like 1 degree and the car wants to turn, unlike any other cars i've driven. Any input would be great, plus anything else i need to look for as well.
Thanks,
Mike
Also, my 140k mile corvette has NO rattles/creaks etc in it.
Burning Brakes
Joined: May 2001
Posts: 1,223
Likes: 6
From: Highlands Ranch Colorado
Third, not sure if this is a problem or just a trait of the steering. Car seemed to be all over the road.
How old are the tires? Just got my 85 a few months back. It was all over the road, I looked and the tires and they were 12 years old. Put new ones on, it made a world of difference, like driving a completely different car.
How old are the tires? Just got my 85 a few months back. It was all over the road, I looked and the tires and they were 12 years old. Put new ones on, it made a world of difference, like driving a completely different car.
Burning Brakes
Joined: Dec 2014
Posts: 1,038
Likes: 44
From: Pensacola Florida
+1 on checking the injectors, that was the problem with my 89's rough idle. They threw no codes either, it was bad coils in several so no amount of sea foam helped. DO NOT replace with 21lb Accels, you will lose considerable power.
Rick
Rick
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
Why even check them? They are old and not ethanol resistance. I'd just toss them for new rebuilt ones.
