RPMs jumping up and down
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From: Aspen, CO
RPMs jumping up and down
Hello!
I have a 1989 Audi 90. There is something weird going on with the RPMs. They jump up and down...seemingly only from 1000-1200. But the car is new to me so maybe I just haven't seen it do it other places. Whenever the car is around 1000 it'll do this. Foot on the gas or not...doesn't matter. Also doesn't matter if I am in drive going down the road or idleing in park/neutral.
Additionally, this morning it was pretty cold. Started the car, which takes a little foot on gas, and it was idling very low for about 30 secs and then killed. Is it ok to give it some gas when starting the car? I don't rev is over 2000. Car is in park, not neutral usually because my driveway is on a angle.
I have a 1989 Audi 90. There is something weird going on with the RPMs. They jump up and down...seemingly only from 1000-1200. But the car is new to me so maybe I just haven't seen it do it other places. Whenever the car is around 1000 it'll do this. Foot on the gas or not...doesn't matter. Also doesn't matter if I am in drive going down the road or idleing in park/neutral.
Additionally, this morning it was pretty cold. Started the car, which takes a little foot on gas, and it was idling very low for about 30 secs and then killed. Is it ok to give it some gas when starting the car? I don't rev is over 2000. Car is in park, not neutral usually because my driveway is on a angle.
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From: Aspen, CO
I've done a little research and it seems like it could be the throttle position sensor, idle control valve, or 02 sensor? Does that seem right? If so, are these parts easy to replace? Where do I find what kind of TPS or IAC valve to buy?
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could also be the Mass Airflow sensor. You could try getting some cleaner and spraying it out. I had a problem with my rpms and it ended up being the combo of a dirty MAF and a junk air filter. Rpms can also die out with a bad vehicle speed sensor. Are you getting any check engine codes?
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He won't have a MAF sensor since his is CIS-E injection. First is Vacuum leaks, I had a Coolant semp sensor gone bad on my early Audi that cause rich running and RPMs can act up. If no vacuum leaks then check and clean the Idle valve, then check the O2 sensor. I wouldn't just replace parts as that adds up and its a simple system on your 89' 90. Duane, MI. Feel free to PM
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From: Aspen, CO
How would I know if it's a vaccuum leak? I'm not getting any error messages, so that's probably good. A vaccuum leak sounds expensive.
It seems that if I clean these things up, that may help. Is there a good online video/how to to show me where these things are in the engine and how to clean them? The friend I bought the car from would easily help me with this, but he had to leave town for a bit for a family emergency. I could probably find some other guy friends, but I'd rather try it myself first.
Thanks for the input thus far!!!
It seems that if I clean these things up, that may help. Is there a good online video/how to to show me where these things are in the engine and how to clean them? The friend I bought the car from would easily help me with this, but he had to leave town for a bit for a family emergency. I could probably find some other guy friends, but I'd rather try it myself first.
Thanks for the input thus far!!!
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Joined: Apr 2007
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From: Canada
Here is a CIS-E trouble-shooting checklist from Hugh Powell's excellent site...
that you may not have seen.
http://www.humanspeakers.com/audi/tuning-cise.htm
I agree with Duane in that you may have a simple air leak or sticky idle stabilizer. Air leak hunting and stabilizer cleaning is not expensive, nor difficult. This is why you should look at these first. This list should help get you started thinking about trying to do some maintenance and diagnosis before replacing parts perhaps unnecessarily. Please report back what you find.
http://www.humanspeakers.com/audi/tuning-cise.htm
I agree with Duane in that you may have a simple air leak or sticky idle stabilizer. Air leak hunting and stabilizer cleaning is not expensive, nor difficult. This is why you should look at these first. This list should help get you started thinking about trying to do some maintenance and diagnosis before replacing parts perhaps unnecessarily. Please report back what you find.
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From: Aspen, CO
Originally Posted by Lago Blue;24223243 [url
http://www.humanspeakers.com/audi/tuning-cise.htm[/url]
I've noticed something else is the past two days. I've driven it to do some errands/go to work. When I arrive at my destination and turn the car off, I hear a buzzing noise. It seems to be coming from the right rear of the car.
This is where the fuel tank is located which makes me concerned that it's the fuel pump and/or filter....???? Is that something to think about? Could it affect my RPM's? I've noticed that it's been idleing very low and I have to rev it when I first start the car or it will kill.
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From: Charlotte, NC
This may sound off the wall, but she is in Aspen, elevation 7890 feet. Back in the day (1978) when I was driving my corvette through Eisenhower Pass, (high elevation) the car ran rough and RPM was unstable. I opened the hood and in the twilight, I could see the spark jumping off the ignition wires and grounding out on the block. The higher elevation led to lower resistance in the plug wire insulation. I got shocked when I moved them, too! Operated normally at lower altitude. Those wires were only 2 years old and original carbon type. Of course, Audi being smarter than GM, this should not to be a problem, but opening the hood at night will answer that.
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From: Canada
Re: "I've noticed something else ..."
The vacuum pump for the door-locking system perhaps? Probably not related to your idle issue.
Depressing the throttle should not help during starting, it may not hurt anything, but it may not be useful.
I agree with Duane and as Hubturn says, looking for stray spark leakage at night is a simple check anyone can do to eliminate a possible cause.
These cars are prone to suffer from <i>unmetered</i> (not measured by the air meter, no matter what type) leaks of air <i>into</i> the intake tract anywhere between the air-meter and the intake valve. Not all these leaks are engine vacuum. The injection system can only compensate for very small imperceptible leakage.
I have seen an oily/dirty CIS air-meter plate and housing which was sticky hurting idle performance and QPower is correct to suggest checking the air filter and do a code pull.
Also, has your idle-stabilizer ever been properly cleaned internally? It may be otherwise still serviceable yet not able to regulate (respond) quickly enough to "hold" idle speed steady, causing you to have to intervene and keep the engine speed above idle, to allow the engine to remain running or running without hunting back and forth between almost dieing and too fast.
Depressing the throttle should not help during starting, it may not hurt anything, but it may not be useful.
I agree with Duane and as Hubturn says, looking for stray spark leakage at night is a simple check anyone can do to eliminate a possible cause.
These cars are prone to suffer from <i>unmetered</i> (not measured by the air meter, no matter what type) leaks of air <i>into</i> the intake tract anywhere between the air-meter and the intake valve. Not all these leaks are engine vacuum. The injection system can only compensate for very small imperceptible leakage.
I have seen an oily/dirty CIS air-meter plate and housing which was sticky hurting idle performance and QPower is correct to suggest checking the air filter and do a code pull.
Also, has your idle-stabilizer ever been properly cleaned internally? It may be otherwise still serviceable yet not able to regulate (respond) quickly enough to "hold" idle speed steady, causing you to have to intervene and keep the engine speed above idle, to allow the engine to remain running or running without hunting back and forth between almost dieing and too fast.
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