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Discussion Starter · #1 ·
What could cause a sometimes fluctuating idle....as in a "hunting" idle on a PL 16v motor in my '88 Rocco? Sometimes when I stab the clutch in to come to a stop the revs will drop suddenly and then hang up for a little around like 1500 revs and the drop back down to idle and proceed to hunt up and down a few hundred revs, like really really low to the point of literally stalling sometimes and then back up to about 1300-1400 revs and then back down, etc. Eventually it will clear up. I mean, really, I sometimes get a very erratic idle situation....it will idle higher like 1200 or so and then when I tap the gas just a bit the revs will usually drop back down to factory spec (about 920-950 ish revs). HELP...this little driveability issue has turned into an obsession to resolve as it is really starting to bug the shart out of me. The idle stabilizer valve seems to vibrate and "hum" but I haven't actually pulled my lazy ass outside with a multimeter yet to check it out.
I was told that generally when these go bad, the car will idle at like 1500 revs or so rather consistently. Sorry for the length but I try to explain my issues in detail....could it also be a idle return switch issue or general setup issue???
 

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Re: Random idle issue question (Mk1Power)

Sounds like an O2 sensor. When I got my 16v rocco, my car did the same thing, drove me nutz. I cleaned the idle stabilizer with carb cleaner, replaced the plugs, wired, cap, rotor all kinds of normal tune up stuff.
Eventually thought maybe the fuel/air mix was off, read about how to set it and when I hooked the voltmeter up, I found a bad setting which lead to a bad O2 sensor. I replaced the sensor and some ground wires and the problem went away. Untill I cracked the downpipe due to bad motor mounts and now the O2 doesn't get enough exhaust gases to make it work right and I have light hunting at first start.
If you haven't replaced the O2 sensor, then chances are it's original and way past it's end of life. They arn't cheap, but you can get one at http://www.oxygensensors.com for a bit less price. Don't fool with the generic ones that don't come with the full pigtail/plug. Those are cheap, but you will have to solder the proper connection on. If you're real good at that, then go for it. If you can't solder, then pay the extra and get the full sensor and plug.
Just incase you don't know, the O2 sensor is under the car, and screws into the catalitic converter. It's a pain to get at, but can be done. The wiring goes up and behind the intake manafold. There are 2 seperate connections (electrical) to the sensor.
 

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Re: Random idle issue question (Calimus)

Umm, you know, do the idle thingy and the satabilizier valve with the screw, and then glue it int, and your like all good to go man, my ca r never had that problem but you know, hawtever, i hear paoeple talking bout it and they say these things soy aknow...do it......NOW....
 

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Discussion Starter · #5 ·
Re: Random idle issue question (Calimus)

Actaully, I have a Techtonics 16v street header and when I installed it I deciced to go with a mustang 3 wire o2 sensor as it is the same but alot cheaper and went with the soldering in idea, however I did not do the soldering job....could be an issue. Hmmm what do you guys think
 
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