erratic idling

Old 01-04-2005, 11:24 AM
1st Gear
Thread Starter
Join Date: Jul 2004
Posts: 6
Default erratic idling

Hello all.

My car is giving me some problems, so I hope someone will be able to offer some help or advice. Thanks in advance, and here's the lowdown:

I drive a 1994 80 2.0E 8v. When I let the car idle (e.g. at lights, in traffic) the revs drop to approx 800rpm, as I believe they should.

However, whilst idling the revs periodically dip to approx 500rpm, usually before picking-up again with revs peaking at approx 1200rpm before returning to approx 800rpm. The complete idle-dip-pickup-idle cycle only takes a few seconds and will happen several times a minute but with no real regularity. Generally, this is more of an annoyance than a problem, but sometimes the engine will stall completely during the idle-dip-pickup-idlecycle.

The car has had it's plugs, oil, and air/oil filters routinely changed recently. This doesn't appear to have had any effect (good or bad) on the problem. Aside from this idling issue, the car drives well and with it's usual good fuel economy.

Old 01-04-2005, 05:56 PM
2nd Gear
Join Date: Mar 2004
Location: Swamplands of NJ
Posts: 761
Default RE: erratic idling

It sounds almost as if the engine is "hunting" indicating improper air/fuel mixture but 300 rpm difference might be something else. Does you car have an AIC, automatic idle control, valve if so clean it as this might be the cause. Hook up a vacuum gauge, you should get between 17 and 21 inHg. A bad or a sticking valve could also give you similar problem.
Old 01-05-2005, 08:20 PM
Join Date: Jan 2005
Posts: 3
Default RE: erratic idling

it is a good idea to check the ISV (Idle Stabilizer Valve), which is the silver canister that is attached to the intake boot by the airbox, sometimes it gets a carbon buildup, and if you soak it in carb cleaner it should eliminate your wandering idle.
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