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Old 05-11-2007, 08:50 PM
Greely Greely is offline
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Join Date: Jan 2007
Posts: 6
Check Engine Light Fixed...I think

Check engine light came on occasionally. Finally fixed...I think.

This is my saga

new distributor cap, wires, rotor, plugs...light still came on, they were due anyway.
error code indicated o2 sensor.
New 02 sensor...light still came on
New EGR Valve...this was needed the old one was bad.
Swapped out 02 sensor with another known good one...light still came on.
checked 02 sensor voltage per a post in this forum...light still came on
checked all the vacuum lines (almost)...light still came on.
checked the OVP...ok
swapped out the MAS with a known good one...light still came on.
checked EHA and POT...no obvious problems there.
checked the cold start valve...acceptable, no leaks.
checked the duty cycle...high and low rpms...close to 50%...fine.

I decided to live with it for a while.

About a month (3000+ miles) ago, I was changing my oil and air filter. While removing the air cleaner, I bumped the vacuum check valve in the brake booster vacuum line. It broke. The bottom of the valve was badly deteriorated, but the top looked fine. Looks like it may have been cracked (and leaking?) on the bottom side. I really don't know if I sprayed that valve when I was checking for leaks. It sits right on top and is too obvious.

Additionally, when I changed the air filter, I noticed that the rubber gasket on the bottom of the air cleaner had folded in on itself. I have no idea how long its been like that. I've had the air cleaner on and off so often that it could have been a month or a year. But there was obviously not a good seal there.

I fixed the air cleaner gasket and replaced the vacuum line with the check valve about a month ago. As has become my habit, I reset the CEL before I closed the hood. That was a month ago and to this day, not a glimmer out of the CEL.

I don't know if it was a cracked check valve or a bad air cleaner gasket which was causing the light to come on, or whether it was a combination of the two, but the light appears to be fixed. Now maybe I'll buy that new electric antenna which died several months back.

I learned for the umpteenth time to stick to the basics, hopefully my journey through CEL HEL helps somebody else.
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