After going through a lot of different options and tests, I finally
found the cold-start (rough running) problem on the truck.
I know a few others have had this same problem and it could also be a
fix for you...but you'll need to check first.
Problem:
On initial (early AM startup), the engine runs rather rough (like it's
got some sort of huge cam in it) and back-fires through the intake.
Went through TPS, MAP, O2, IAT, and a few other options as well
(including fuel sync and distributor alignment). Everything checked out
fine and well within spec.
Solution:
Coolant Temp Sensor was off by 4K ohm (lower than normal) causing a
leanout condition. Remember, the CTS also works like the old chokes on
carbureted engines (engine warm-up). Early AM CTS resistance should be
about 9.4-9.8K ohm for my area (74-78 degrees F). Sensor was at 5.7K
ohm...this equates to 104 degrees at cold-start (not good). PCM thought
engine was warmer than actual temp and was leaning out the fuel a little
early.
No more backfire or lean-out condition.
- Bernd
This archive was generated by hypermail 2b29 : Fri Feb 06 2004 - 11:46:21 EST