The car has done this since I bought it a few months ago. I scanned it a while ago and got a TPS code (voltage too low). I checked the voltage of the TPS a few days ago and tried to adjust it but it wouldnt go anywhere near where it should so I replaced it and set the new one and its right where it should be.

The past few days the CEL flashes on and off while driving. Its on for a quick second and then gone. I had a guy scan it last night with a professional type scanner and he did the KOEO and KOER tests and couldnt pull any codes from the car. After that the light still comes on and goes off.

Other problems Im having is a drop in RPM's when coming to a stop (goes down to 500 and comes back up when Im fully stopped) and the idle is a bit rough and surges at times.

I already replaced the TPS and cleaned the IAC and the throttle body (neither were carboned up) and put Seafoam in the vacuum line to the brake booster to clean the motor out.

I unplugged the IAC last night and the idle didnt change. However the guy with the scanner was able to manipulate the IAC with the scanner.

Off idle the car runs fine. It doesnt lose power or stumble.

 

o2 sensors will do the flash of the light when they momentarily go out of voltage range. also sometimes they won't leave a code. its a good idea to place o2's every 60k anyway, for max performance.

 

Id hate to spend 80 bucks and have that not be the problem though. Is there a way to test them? Im not sure if the previous owner replaced them or not when he changed the H pipe with a stock replacement (still has cats). If he did change them they definately dont have 60k on them.

 

what exactly was this 'professional' type scanner. if it was a snapop scanner, you should be able to watch the voltages as its running. also you can go into a section of the software(i forget the name atm) and see the data log of what every sensors value was at the time of the fault. along with mph.

 

What he said is actually correct... and totally true. A failing o2 sensor will cause the light to come on, but if its only a once in a while thing, the ecu will get proper readings off the o2 sensors, and the code will be cleared from memory. I would change them anyway.... but thats just me!

 

I dont remember the brand but it wasnt a Snap On. He didnt check sensor voltages because he was just trying to retrieve codes. It was capable of doing that though.
This was just in a parking lot where we hang out with our cars so he just did a quick check with it.
Ill have to replace the sensors when I get a chance then.

 

Most pro scanners should be able to record. I know my Snap On can. If you can get the car to flash the light when you have the scanner connected and record it then you can play it back and maybe see what is glitching.

 

It usually just comes on while driving, not idle though. Due to the location of the plugs its hard to drive with a scanner connected.

 

How many 02 sensors are on a car two or four?Somebody told me four I thought there was only two.Anyway I have the same type of problem it dosen't seem to affect performance but I want to get them changed the car has 97,000 miles on it..........

 

there are 4 sensors, the front 2 are for air/fuel ratio, and the rear 2 monitor catalyst efficiency. thats why o/r h-pipes cause check engine lights. no cats = 0% efficiency.