Rough Idle

[1988SS]

I hadn't started the car in around a month. As I was cranking it felt/sounded like it backfired through the carb. It started right after that but it now idles a bit rough.....runs okay but almost acts like a vacuum leak at idle. Should I just try and chase a vacuum leak or do I now have a potential carb issue?

1988 Monte Carlo SS - stock set-up with CCC in place.

 

[69hurstolds]

Hard to say. I wouldn't necessarily go chasing a vacuum leak full bore, but you could check carb mounting bolt tightness just for fun. Cursory check any vacuum lines for breaks/cracks on a quick visual.

The question is why did it backfire, if that's what it was? It may be ignition related. Those Montes have some weird ignition setups from what I'm used to. Problem with backfires is they can cause vacuum leaks where none used to exist as well as a potential for blowing out A.I.R. check valves. Unless you've blown a gasket in the carb, I doubt you damaged anything carb-wise.

There's just not much to go on here. Sorry couldn't be more help.

 

[79 USA 1]

I had a similar issue with my 88 SS, Check for a vacuum leak especially the hard nylon hoses which break from heat. GM loved to use these lines on these cars. I ended up replacing most of mine with rubber hose. I also replaced the emissions canister purge valve which did seem to take care of the rough running issue in my car.

 

[1988SS]

I found it....a plug had come loose and had a big vacuum leak. I'm not sure if it was a backfire or a hiccup or whatever but it may have knocked the cap loose. Car is running very nice now.

Thanks for everyone's replies and support here. I panicked when it happened since I seemed to remember back in the day that if you were running the holley doublepumpers that if it backfired thru the carb then the power valve was shot....so I over reacted thinking a potential carb problem. Hopefully no other issues.

Thanks again for the quick responses and words of encouragement!!! Have a good weekend !