Engine Light keeps coming on Cavalier 1.8 8V

A friend of mine has a problem that has me stumped any help would be
appreciated

1.8 8v Cavalier with single point injection.

Engine light comes on at regular intervals any thing from 30-80 MPH in any
gear. The only codes registered are for a weak mixture.

I have blanked off the vacumm powered EGR valve as it was leaking, run
injector cleaner through the system (From looking into the throttle body
spray pattern looks ok). Changed MAP sesor and looked over engine looking
for loose/damaged hoses etc. Checked plugs/leads etc cannot find any reason
for the mixture to keep going lean/weak. Any one had this problem or have
any other ideas

 

How many crosscounts are there on the oxygen sensor?

 

Only going on blink codes no access to Tech 1 or 2 to check O2 sensor. No
surging on light throttle etc or codes to show duff sensor.

 

You can measure the crosscounts with a standard dvom.
login as a guest at the following site for instructions:
http://forums.delphiforums.com/cartune/messages?msg=38.1

Exactly what fault code are you getting?

 

Error code 44 (lambda sensor too weak)

I will test o2 sensor as per link. I have a Fluke Scope meter which I can
hook up

Steve

 

The fluke meter is more than adequate. Code 44 has three possibilties. O2
sensor / wiring / ECM.
If the sensor passes the crosscount test, measure the signal at the ECM. If
the signal is present, suspect the worst.
If it is the ECM, you should be able to get a secondhand one without too
much trouble.