I have run into a problem today where my car goes rich to lean even when I am just sitting in the driveway at idle. It swings from 11 to 15 and the car stumbles. It actually stalled twice on the way home today from being too rich on one of the swings. This happens at idle and part throttle, the AFR meter swings wildly and the car stumbles.

I am thinking some kind of electical/loose wire somewhere... maybe the GM map sensor. I have not investigated yet but thought I would see if anyone else ran into something like this.

 

check all the basic sensors first then report back

 

When you have a misfire, the fuel and oxygen isn't burned. A rich misfire looks like a lean condition, since the o2 sensor only reads one obvious molecule - but not fuel. If its getting very rich, <10:1, chances are you too rich to jump the spark plugs' gaps. Having cold plugs would make the problem worse, since the extra fuel is sucking lots of heat from the cylinder. Cold motors don't like to idle, so its turning into a domino effect.

 

1. Resolve your MILs if you have any (malfunction indication lights)
2. Get with your tuner & have him datalog the issue to try and figure out that is causing it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LST2 &raquo;</TD></TR><TR><TD CLASS="quote">I am thinking some kind of electical/loose wire somewhere... maybe the GM map sensor. I have not investigated yet but thought I would see if anyone else ran into something like this.</TD></TR></TABLE>

Usually when you have map sensor issues, you'll be dumping fuel like no tomorrow.