My "Service Engine Soon" light comes on. It happens if I am traveling over 20 MPH and only if I take my foot off the gas. For example if I am on the highway and take my foot off the gas the light comes on, then goes off when I give the car gas. I assume a sensor is going out and will cost loads of $$$ to replace.

This is on a 1990 Cutlass Ciera with a V6.

Ideas?

 

Does this happen when you first start up in the morning or after you get up and running? Have you got FI or carburetor?

 

After I am up and running. FI.

 

EGR valve sticking can cause these intermittent lights, some cars reset themselves and some must be turned off by computer/scanner/whatever.

 

I'll check it. May not be a bad idea to replace it anyhow. Who do I see about resetting the light?

 

Too many things can trip the check engine light , try to get a code and post what it is . This will give a better idea what circuit is causing your light to come on

 

And where do I get a code from?

 

Nedd to locate the diagnostic connector under the driveside of the dash it is a retangle that is black' should be near the front edge There will be 2 rows on it jump the 2 female terminals in the top right corner, this is the row closest to where the screws go thru to hold it to the dash, when the key is turned to thr run position the service engine light will flash the trouble code do not start the car during this.It will flash code twelve 3 times which is a long flash followed by two short ones ,this same pattern will be repeated for the other codes stored. Code 12 means the car is not running once the other codes stored are flashed it will loop around to code 12. The computer is reset by disconnecting the battery for several minutes or by taking the power off the computer, disconnecting the battery is easier. Post the codes and we will see what they mean.

 

My little box has screws on both sides. Sounds complicated. can't i just have a mechanic tell me the code? Would any auto parts store have a computer that plugs in that I could borrow?

 

Most places like AutoZone will have a scanner and be able to pull the codes for you. After you know what's causing the light to come on, then you have a better direction to go in.

One thing I will mention. Generally speaking, I have seen a LOT of O2 sensor codes thrown, and then someone automatically assumes it's a failed sensor. That's rarely the case. Usually it's something else in the fuel delivery/engine management system causing a rich/lean condition, and then it throws the code. Just a little tip as it's possibly the most common thing that will throw out a check engine light for any vehicle.

You'll end up having the salesman at the parts store trying to sell you a new sensor, you get that installed, and it works fine for a little while, and you think problem solved. Then over a bit of time, it starts tossing a code again. Back to square one and you're out the money for the sensor and still hunting for the problem.

Not to say the sensor was aged and may need replaced anyway, but it's not going to solve the underlying issue.

-Jeff