1985 rough idle oscilating
Thread Starter
Instructor
Joined: Nov 2006
Posts: 166
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From: Madison WI
1985 rough idle oscilating
My 1985 started oscillates sometimes at stop signs causing it to want to jump ahead. I replaced the tps and set it correctly. Is there someother sensor that could be causing this? Thanks
Instructor
Joined: Mar 2006
Posts: 111
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From: San Antonio Texas
85-auto Every since I bought my car I had never had it running right until today. I started off replacing the injectors, cleaning the tb, setting the idle and IAC and complete tune up. Results were better but overall, same hesitation and poor idling. It was when I had replaced the rear intake vacuum lines that it made considerable improvement. I figured it was an old car and it wouldn't be perfect. Only today did I realize the front vacuum intake hose (larger diameter) above the iac was split. I replaced it and now it runs better than ever. Now there is no hesitation or surging and it idles fine. I would start with the easy stuff first. Vacuum hoses are cheap.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
idle
take a pair of pliers, wrap the jaws with masking tape, open the hood, start the car, leave in park, take the pliers, and squeeze the hose that goes to the brake booster. if any change at all, your booster is leaking
Thread Starter
Instructor
Joined: Nov 2006
Posts: 166
Likes: 0
From: Madison WI
I replaced the hose on the vacuum line above the IAC and tightened the ends down with hose clamps to makes sure there was no leaks. I unplugged the IAC and the car revved to 2000 rpm and didnt move so i think that shows that the IAC is working correctly. Also I unplugged the MAF and it didnt fix the oscillating problem. Although usually on start up my car revs to 2000 rpm and then slowly within like 10-15 secs works its way back down to 800 rpm. But when i unplugged the MAF and started it up it went to 1200 rpm then immediatly dropped to 800. Does this mean my MAF is bad or are they suppose to rev sort of high at start up and then work there way down. Thanks
Thread Starter
Instructor
Joined: Nov 2006
Posts: 166
Likes: 0
From: Madison WI
It also will pop the gauge fuse in stop and go driving. When i replace that fuse it use to run good again. Is there some ground connected to that fuse or something that would point to a problem in my car. thanks
