1993 Chevy Beretta Rough idling

HARLEY17701

MEMBER
1993 CHEVROLET BERETTA
6 CYL
FWD
AUTOMATIC
194,000 MILES

I have a 93 beretta with the 3.1 V6 just bought it. It has a rough idle when braking for a stop light and while in gear sounds like maybe its missing a little bit. Also I just have replaced the MAP sensor with very little difference in it. IF any at all. And the tester codes come back to the MAP sensor. Even though I just replaced it. Also another question. The Air cleaner sensor. I think thats what its called. It plugs into the air filter box to read back air flow I would imagine. Now this seems to be plugged in but doesnt seem to make a difference. And also wondering if its supposed to have power going to that plug at all times? Or is it an intermittent type plug that only applies power during like accel. Or climbing hills?. Would I be able to use a light tester to make find out if it was getting power? And if so. What would be reason if it wasnt getting any power?

Monday, January 26th, 2009 AT 3:03 PM

3 Replies

ZACKMAN

MECHANIC
4,202 POSTS

[quote]and the tester codes come back to the MAP sensor. Even though I just replaced it. [Quote]

It is quite possible that the problem lies in the wiring. You may want to check your wires to the MAP sensor. You may have loose, frayed, broken, or disconnected wire along the way from the sensor to the ECM.

[quote]. It plugs into the air filter box to read back air flow I would imagine. [Quote]

That is your Intake Air Temperature (IAT) Sensor. You should have continuous approx. 5 volts to the sensor at all times. At cold temperatures, you should high resistance across the two terminals (70 degrees F = 3400 ohms) and higher ambient temperature will have lower resistance (212 degree F = 185 ohms)

[quote]would I be able to use a light tester to make find out if it was getting power? And if so. What would be reason if it wasnt getting any power?[Quote]

You can't use test light. You have to use DVOM - digital voltage/ohm meter. First check the voltage on the harness to the sensor, and check the resistance across the terminals. If there is no power to the harness, then you need to check for broken, frayed, etc wires, just like your MAP sensor.

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Wednesday, January 28th, 2009 AT 11:14 PM

HARLEY17701

MEMBER
2 POSTS

Alright. I can check over wires but the check engine light isn't on. Indicating that its not working matter of fact it is working but. What I plug into the computer I am getting code 33. Which is an indication that the signal voltage is to high?. I am pretty sure thats it and as for the air filter plug I will have to check that out. Also with code 33. Notes also say it can be reading 33 because of another problem. Which also I think rough idling like missing at idle when in drive with the brake on?. I just bought into this thing so far I have done quite a bit of work. Just trying to come up with some sort of reasoning for the rough idle. It rough idles when it warms up but while cold it isnt no where near so bad.

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Friday, January 30th, 2009 AT 1:56 AM

ZACKMAN