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SuperDave Auto
SuperDave Auto, ASE Certified Technician
Category: Chevy
Satisfied Customers: 329
Experience:  ASE Master Auto and Truck Technician, 24+ years shop owner
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Chevy Cavalier Z24: It idles high when stopped, 1500-2000..RPM.

Customer Question

I have a Chevy Cavalier Z24, 3.1 EFI. It idles high when stopped, 1500-2000 RPM. Can someone tell me what is causing this. I''ve already replaced the IAC, TPS & Oxygen sensor. Also when you push the clutch in it idles at 2000 RPM until you come to a COMPLETE stop, then goes down, momentarily, then continues to climb again.
Submitted: 9 years ago.
Category: Chevy
Expert:  SuperDave Auto replied 9 years ago.


Do you have a check engine light on???

Customer: replied 9 years ago.
The check engine light usually only comes on when I am stopped for awhile ( like @ a long light ), and the idle reaches 2000 RPM
Expert:  SuperDave Auto replied 9 years ago.
Do you have the capability to read the codes or have the codes read for you??
Customer: replied 9 years ago.
I've had Auto Zone read them for me, they said it was the IAC & Oxygen Sensor. Apparently it wasn't. That's when I decided to go ahead and replace the TPS too.
Expert:  SuperDave Auto replied 9 years ago.
What I need you to do is remove your negative battery cable for 5 minutes, then replace it and tighten. Drive it until the light comes back on. Have them recheck the codes. Get the code #'s and get back to me. Most of the time there are more to the codes than just reading what the little machine tells you. Dave.
Customer: replied 9 years ago.
Thanks Dave. I'll try to do that tommorow and get back to you!!
Expert:  SuperDave Auto replied 9 years ago.
Will be waiting on you !!!!
Customer: replied 9 years ago.
Hi Dave. Unfortunately I won't be able to get to Auto Zone today. I have to leave work early to get my kids from school. I will try to do it tonight or tommorow morning. Question though. You don't mean literally drive it until the check engine light comes right after disconnecting the battery? In other words, can I disconnect the battery go home and wait till the next day to drive any long distance ( sometimes it takes a while for light to start coming on again ). Also I have a key to read the codes. If you could explain it I could do it myself. What do you think??
Expert:  SuperDave Auto replied 9 years ago.
Disconnecting the battery on your car resets and clears your computer. I want you to do that. Then drive your car long enought for the check engine light to come on. After the light comes on, then I want you to have the codes read and get back to me. I believe you can get purchase an inexpensive simple code reader at Auto ZOne if you would like to have one of your own. Make sure it is for your car .... pre 1995 GM Dave
Customer: replied 9 years ago.
OK. I'll get back to you as soon as I can. Thanks
Expert:  SuperDave Auto replied 9 years ago.
I'll be here !!! Good Luck.
Customer: replied 9 years ago.
Hey Dave, did what you said to do, the code was 34 & 35, the MAP Sensor & Computer. It's not the computer I know because it's already been replaced. I went ahead and bought MAP sensor and installed it. It didn't work. So what do you think???
Expert:  SuperDave Auto replied 9 years ago.


First off, stop buying parts and throwing them on. You are wasting a lot of money. And, just because you've replaced the ECM doesn't mean it is not bad. With that said.... code 34 is MAP sensor voltage low - you need to jumper the 5 volt reference wire at the map sensor to a known good 5 volt signal. If it shows better then you have a wiring issue. If not, you have a faulty map sensor. Your old one may not be bad. AND yes, you can have a bad new one out of the box. Happened to me many, many times. Code 35 is IAC idle speed error. I suspect that you have not correctly calibrated your IAC when you intalled it. Unfortunately, you will need to access the driver within the computer system with a good scan tool. You may also have a vacuum leak. Do you hear any hissing sounds with the engine running?? Look for vacuum leaks and repair as necessary. If you do not find any, and if you do not have a good scan tool, I would recommend taking to a shop to get a good proper diagnostic test. Stop spending money on parts that you don't need. Stop listening to the "technicians" at Autozone. Sorry. Dave

Customer: replied 9 years ago.
Dave, don't mean to be rude, but what would you have said if I had just told what the code was?? You would have probably told me to try replacing the MAP sensor since thats what code was for. The only reason I went ahead got the part was because the guy told me if it didn't work, then I could return as long as I didn't install it by bolting it onto the car itself. If it wasn't for that I would'nt have went ahead and tried it. Sorry if I've wasted your time, but if I could aford to have a real tech. look at my car and fix it I would'nt have tried this web site. Thanks for the advice.
Customer: replied 9 years ago.
I'm currently putting my mission to find out what is wrong with my car on hold for now till I have more time to really get into the solution.