'88 5.7 TPI. Owned for nearly 3 months now, and have been repairing the previous owners shoddy work. Fixed multiple vacuum leaks, new cap/rotor/plugs, and have the car running much nicer.

Idle has a very slight intermittent miss, no miss is detectable off idle.

The car idles nicely at 750 RPM, unless sitting at a light idling for more than two minutes or more. Then, the idle drops suddenly to around 500 for 2-3 seconds, lights the check engine light for a code 44, O2 sensor lean, then returns to idling around 750 RPM again.

The check engine light generally goes off around 20 seconds or so after leaving the light.

I replaced the O2 sensor with the proper OEM sensor the cars came with new, but no change. IAC counts average around 26 at idle with a warm engine...so if there's any remaining vacuum leaks, I'd say they are likely very small.

Suggestions?

 

exhaust leak? malfunctioning air vavle? (O2 into headers)? Try capping off the air tubes and see if it helps.

 

Maybe some kind of evap purge attempt with no evap system present ('cept for the purge valve)?? The clue is in the time it takes after sitting at idle, when the lean code comes on...

 

code 44 is one of the hardest codes to get rid of. what did it for me was a new egr valve.