Stumbling idle when cold...1500 rpm idle when warm
01-30-2003, 01:17 PM
#1
Racer
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Stumbling idle when cold...1500 rpm idle when warm
Recently the car has started to stumble after starting it when it's cold out...in fact leaving the office yesterday I actually had to give it gas to keep it running. It hesitates quite a bit for the first 5 minutes of driving...the power kind of pulsates. My POS a/f ratio gauge shows roughly stoichiometric, but I don't put any faith in it. Once the car is warm it idles smoothly at around 1400-1500. For what it's worth I set the idle at around 1050 over the summer.
What could this be? O2 sensor? ISV? The Europroducts Chips providing a less than ideal mixture? Anything else? What's the best way to check the 02 sensor? TIA
What could this be? O2 sensor? ISV? The Europroducts Chips providing a less than ideal mixture? Anything else? What's the best way to check the 02 sensor? TIA
01-30-2003, 02:15 PM
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Burning Brakes
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poss. idle stabilizer, try tapping on the valve while the car is running, sometimes this will cause it to start working again. If it does then replace the valve. Check your throttle switch, does it click at idle? Is your idle air screw still there? I have seen them blow out. If you suspect O2 sensor problems, disconnect it and see what happens. You can check sensor output with a voltmeter, voltage should fluctuate between 0 and 1 volt. It is unlikely that your prob. is the O2 sensor however as it does not work untill it reaches approx 600 degrees. Good luck Mark T.
01-30-2003, 02:41 PM
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Racer
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Thanks for the advice. I checked the TPS about a month ago and all was well. I'll check again. I would think the O2 sensor is working as my a/f ratio gauge swings between full lean and the rich side of stoichiometric. It's really just a voltmeter with an LED display, so the output must be in the correct range. It's on the lean side though. Is it possible for the O2 sensor to malfunction yet give the described output? Is the reported lean condition a sign of the faulty O2 output? I don't think so as the DME should correct. I recently replaced and adjusted the idle air screw. My bet is on the ISV. I'll mess with it and see what I come up with.
01-30-2003, 03:04 PM
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That was the signs of my fuel pump going out. I had the same problem when I bought mine, I just though that was normal. When I started it in the morning, it ran rough until it warmed up, almost like my carbureted 69 AMX with no choke.
Problem turned out to be the fuel pump. About three weeks after purchasing the car, it just quit. Since I replaced it though, I no longer have any trouble - car runs smooth as soon as I turn over the key.
Problem turned out to be the fuel pump. About three weeks after purchasing the car, it just quit. Since I replaced it though, I no longer have any trouble - car runs smooth as soon as I turn over the key.
01-30-2003, 05:35 PM
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Drifting
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Also sounds like what my S2 was doing when I had a screwed up vacuum line. Not quite as high as a 1500 rpm idle but it was a good 12-1300 or so. Stumbling idle as well, sometimes it would just die. Might wanna check for cracks or splits in your hoses.
01-30-2003, 06:24 PM
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I'll check for vacuum leaks (did so and had none over the summer, but I one could have developed) and keep my fingers crossed that fuel pump keeps pumping. Any idea why the car runs wierd under partial throttle when cold (the surging)?
01-30-2003, 07:45 PM
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I was chasing that vacuum leak pretty much ever since we got the car 2 years ago..it started out mild and got progressively worse.
It ended up being the vacuum hose right under the intake manifold that goes under the fuel rail (the one impossible to see and impossible to get to, basically)..I'm not sure if there is one there on the turbo or not since mine is an S2.
Won't hurt to check them anyway..it makes sense that it happens more when its hot because the heat makes the hoses more flexible and such. If it's cold it would be hard and just be stuck open or something hence the idle problem. When it heats up it may flex and change the symptoms like the high idle etc. That was my problem anyway it may be something completely different for you.
It ended up being the vacuum hose right under the intake manifold that goes under the fuel rail (the one impossible to see and impossible to get to, basically)..I'm not sure if there is one there on the turbo or not since mine is an S2.
Won't hurt to check them anyway..it makes sense that it happens more when its hot because the heat makes the hoses more flexible and such. If it's cold it would be hard and just be stuck open or something hence the idle problem. When it heats up it may flex and change the symptoms like the high idle etc. That was my problem anyway it may be something completely different for you.
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01-30-2003, 08:33 PM
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I had a problem very similar to yours a while back, where the car would warm-up very roughly, and having to hold the throttle a bit so it wouldn't stall. After about 5 minutes or so, it would be okay. If I were to wait until it fully warmed up, you could hear it all of a sudden switch from misfiring to smooth running. I changed my oxygen sensor and the problem never returned -- don't ask me why, it just did...
