Slight problem with 84 Olds 3.8 mixture control - Third Generation F-Body Message Boards

99Hawk120 · 09-09-2002, 10:52 AM

I recently swapped my 2bbl intake for a 4bbl intake, and in the process changing from the original dualjet to an E4ME Qjet.

The motor doesn't really want to idle down, I'm sure I have a vacuum leak, but other than that it runs good at part and full throttle.

While watching the scanner, however, I noticed the the MC solenoid duty cycle is doing some WACKY stuff.

It'll sit at 5% at idle (probably cuase of the vac leak) for a little while, then it will suddenly jump up to 54% and sit there for a few seconds, and then jump right back down to 5%. You can hear the motor change idle speed and sound when it does this, so I have to think that it really is happening. The motor also wants to stall when it's at 54%.

Why the HELL is it doing this? the O2 sensor is still reading somewhat lean when it's sitting at 5%, so there should be no reason in the world why it should suddenly decide to pull fuel. When my Camaro was in a similar situation, it sat at 5% and eventually tossed a lean exhaust code, exactly how it should behave.

Also, the ECM does not throw a code when I disconnect the MC solenoid connector

. It will throw one for EGR malfunction though

.

I'm leaning towards it being something wrong with the ECM. I've never seen one of these cars randomly change the MC dwell like that without falling out of closed loop.