Firm

I've got a bone stock 85 Trans Am with the LG4. Low mileage car. I've owned it for a few months now and it's been running pretty good. Always starts easy, strong acceleration and cruises very smooth. The only issue I've been having recently is a rough idle when warm which will occasionally stall out.

Basically, I'll start the car and the choke will keep the idle high until it warms up - no issues there. Once it is warm it runs perfectly until i get to a stop light, with the car in gear (automatic) and my foot on the brake it idles right around 500rpm, but it's often pretty rough. Typically it doesn't stall, but yesterday it did stall twice in about 2-hours worth of driving.

Today I poked around looking for vacuum leaks but I didn't find anything obvious, I didn't have any carb cleaner to spray, so that'll be one of the next things I try. Are there "common" places to find vacuum leaks on these cars?

The carb itself looks like it's been replaced in the not so distant past, but maybe it needs to be cleaned? How would i know?

Anything else I should be checking with these symptoms?

Ozz1967

iTrader: (4)

Replace all the vacuum lines anyway. The idle in drive should be around 600.

Also, check your timing and do a tune up. Plugs, plug-wires, cap, rotor.

The last time mine started stumbling a while back and it was a a plug wire shorting to my manifolds.

The time before that I didn't get a a plug wire seated properly and my number 6 cylinder wasn't firing. The car would run fine under throttle but would stutter, have a really low idle and want to die when stopped and in gear.

So, start with the tune up and see if that helps any. Once we know all the parts are good, we can check other things.

MSgt Luttrell

If a simple tune up doesn't fix it, I'd inspect the EGR system, the valve could be stuck open causing a lean condition after the engine is warmed up.

Firm

Good suggestions. I've ordered everything for a tune up, so I'll start there - it can't hurt anyway. I am also going to keep looking for vacuum leaks, this time using some carb cleaner. Hopefully I'll be able to get to it this weekend and I'll report back.

gearhead141

Did you ever find a solution for your low idle problem. My 1985 Trans Am LG4 just started doing the same thing. I'll be looking at the PCV hose and valve, as well as the fuel filter. Would be great to find out what yours turned out to be.