Rough idle at start-up

[99hdtop]

Another question for the forum P car gurus. My '85 Coupe idles rough for ten seconds when engine is cold. Idle rises to about 1200rpm for a second or so then it clears right up. Why is that? Thanks.

[thumbdoctor]

Do you see any smoke out of the tail pipe on cold start up ?

[99hdtop]

Sometimes, but not always. The brake booster was replaced , it was causing a vacuum leak. A previous owner had re set the Motronic to accomadate the leak. My mechanic told me that they went somewhere they shouldn't have. He replaced the booster and reset the module. Car runs great after the initial cold start.

[Hunt3R]

There is no module to "reset" on the 3.2 motronic. Perhaps your mechanic was referring to the fuel quality switch? Sometimes people (incorrectly) adjust that to increase fuel and compensate for air leaks. But it's just a switch that you turn with a screwdriver on the back of the DME.

And there's many possibilities causing your rough idle, if you want to find it yourself you're just going to have to start checking things like searching for more air leaks and checking your fuel pressure, ignition, plugs, wires, base idle setting, base A/F ratio, injectors, etc...

[99hdtop]

Thank You for the clarification on this little issue. I will look at that all of the possible causes. Wife and I went for a great drive today from Tulsa, OK to Siloam Springs, AR. We took Scenic SH 412 East, nice curves some are posted 30mph. Then the missus says 'What's that smell?' Says it reminds her of sourkrout, then she said it smelled hot. Oil temp and pressure were fine, sniffed around fuse box, nothing there. No leaks anywhere, then the smell disappeared. Car ran flawlessly. Thanks again!