Need some help . I have an 88 IROC convertable with an LB9 engine and 700R4 transmission. Engine starts fine and will idle all day at 750 rpm. As soon as i put it in drive, the rpm drops and the car stalls. It will restart right away, but wont idle in gear. Any help with this problem would be greatly appreciated.

Rob C

 

Check and clean the idle control valve, adjust the minimum idle air and TPS voltage.

GD

 

Thanks GD, i'll check these units and revert back when i know more. Offshore now won't be home for a while.

 

Always start here.
Do you have a data logger of some sort? Can you see the IAC counts when it stalls?

 

I would definitely check the TPS and fuel pressure as well if you haven't yet. Car been sitting at all or have any other known problems?

 

Also, check the P/N input to the ECM. It uses it to help prevent stalling and idle speed. Easiest is to use a scan tool. But a DVM can also be used. This switch is on the shifter assembly.

RBob.