Acroyer

'86 Trans AM, 305 carb'd. Under 30K miles.

I'm still working on replacing stuff that dried out, failed, and whatnot while previous owner had it stored.

Recently, I had the cat converter replaced. About a week after that, the Check Engine light came on. I was thinking that maybe it was the O2 sensor, since the cat was so clogged. But, just to make sure, I used the ole paperclip trick to check the codes. I get no flashes, just a constant light. The car starts up just fine, and initially drives just the way it should, other than the cruise no longer working. After it warms up, the rpms drop to around 500-600 rpms in drive at a stop, and 1400-1500 in park. It diesels like crazy if I turn it off in park. I'm thinking timing issue, but am not sure if it is an ECM problem or a distributor problem. No flashes makes me think ECM, but it runs fun till it hits operating temp. Is there something in the vacuum system that changes when it warms up? Maybe I have a leak somewhere. I disconnected the battery overnight, on the outside chance that the computer needed a reset, with no change. I'd rather not just throw parts at it.

Any ideas?
Thanks,
Tony

Bishopts

Pull the plugs and look at them. Are they clean? Sooty? Oily? Reak of liquid fuel?
check intake vacuum at idle.
If you have a timing light look and see if it's advanced or retarded.
Start with the plugs tho. Plugs don't lie

Acroyer

Sometimes it's the simplest things. I finally got some time to give everything a good looking over, and it turns out that the brake booster line going to the carb was loose. Really loose! I snugged that up, and made sure everything else was tight and went for a 20 minute drive.

Drive-ability is fixed! I still have the engine light on, and no cruise, but at least I can drive it around.

Thanks.

Acroyer

Well, that wasn't it after all.
I did notice that when I drive around and the car's temp gets to that first mark on the gauge, everything is fine. Stop and go traffic seems to be the issue. When the temp gauge gets to just under the 220 degree mark, that's when the problem arises. I tested the theory a couple of times just a few minutes ago, and that's how it seems to go.

So, I'm thinking something is happening, besides the electric fans kicking on, which is causing the issue, I just have very little idea what..

Good times!

Bishopts

mine starts running hot if I let it sit and idle with the ac on for too long. The fan design sucks because it doesn't have a real shroud but I think the weak link is the radiator. It's too thin. I have a friend at work with the same engine and fans but he has a 4 core radiator and he can let his car sit and idle all day long in 100 degree texas heat and it won't go past 180.

crazymex83

Hang on, you have an 86 Trans Am with a carburetor? Wasn't this car originally built with EFI, either TPI or TBI? If you have a carb then it sounds like the ecm isn't doing much, if anything. Maybe controlling the cooling fans but they won't turn on until 230deg F, or some where close to this.
I assume you didn't get any codes because it's not connected to anything, hence the constant light.
Please correct me where I'm wrong.

Bishopts

my brother has an 86 Camaro with a carb from the factory. Its a 305 car with no ground effects and the small slits in the nose cone. I would assume the pontiac counterparts would have the same engine options.

RBob

iTrader: (1)

'82 - '84 V8 f-body cars could be had with either TBI (x-fire) or a carb. The '85 - '87 cars could be had with TPI or a carb.

In '88 the carb was no longer available, and the 2-bbl TBI setup became available. So for '88 - '92 the V8 cars were either TBI or TPI.

I guess that MAF versus SD years should be the next to discuss

RBob.

Acroyer

Well, I went out to check everything over again, and decided to crown myself "King of Assuming the Worst."

I had a blown ECM fuse. Replaced it, and now it runs great again.

And yep, it has the carb! That let's it start and run with no computer signal at all. It just doesn't run well.