Hey... thanks all you guys who gave me feedback on the issue on the 99066
recall. The consensus is that replacing the SCFI with MFI (per the policy)
will be on my tab.
BUT... let me give you the latest. I took it in to a dealer a few days ago
have them check it out. They ended up putting it on some kind of analyzer
and found that the timing was off. The mechanic said it read 30 instead of
4. So he adjusted it. Apparently, there is also a diagnostic in some GM
system they use that told him to change settings in the ECU, which he also
followed. When I drove it home, it ran like a champ. I tried to ask the
guy what the readings meant and what was reset in the ECU (change in duty
cycle?), but he couldn't tell me. I was cautiously pleased. Not for long -
next day, I had misfires again, sometines worse than before.
The following day, something interesting happened. For starters, it took 6
or 7 seconds
of cranking before the engine fired up. It ran fine on idle. Then I left to
go to the post office (10 minutes, stop and go), coughing and sputtering all
the way. I went inside for 5 minutes to mail some stuff, came out, fired up
the truck... and it just purred. Not one hiccup all the way home. I've
encountered something like this before: that is, it runs rough (misfires)
until the engine is warm AND I turn it off for a short period (not enough
for it to cool). Could it be that a sensor is malfunctioning when cold, the
ECU takes a reading, thinks it's running rich and leans it out, causing
misfires. Then, when the hot engine is restarted - and now the sensor is
working properly - the ECU sees that all's well and keeps fuel at normal
levels? Could it be a stuck EGR valve? I've seen other posts about stuck
EGR valves on this engine, but not the same symptoms as I've been having.
I did once get a code for the EGR pintle valve (not sure if "valve" is the
right word). Not recently, though. Maybe a bad coolant sensor?
I plan to run a test each day where I start the engine and run it for 15
minutes, sitting in the driveway. Before I leave, I'll turn it off for a
few minutes, to see if it then runs smoothly as I leave for work.
Thanks for any additional thoughts or suggestions.