Stalls seem completely random and have been getting worse over the last few months. Usually the stall will occur at highway speed but has occurred in park while idling or at any speed. Often the stall immediately clears with no action, and is of very short duration (so short that the only way you may notice it is cruise control disconnect). There seems to be nothing to correlate - tank level, terrain, acceleration, temperature, or time running. Engine codes are rarely seen, but when they do appear it's P0171. If the engine code is set before the stall, it normally clears as a result of the stall.
Fuel pressure when running normally is about 40lbs, 47lbs before starting with ignition switch ON
Vacuum is 19in idle, 21in at 200 RPM
Fuel filter is about 3 years old.
Recently replaced:
Water Pump (due to leakage)
Plugs and Plug wires
MAF sensor
TPS sensor
Crankshaft Position Sensor
pre-cat O2 sensor
PCM (rebuilt, reprogrammed at GM dealership)
ICM and all coil packs
Air filter
The EGR valve was cleaned and it did not look excessively dirty or otherwise damaged.
For several years I have operated with regular grade unleaded, but over the last month or so I have been using only the recommended premium octane.
When revving engine in park, I noticed a pulsing at 4000RPM and RPM is limited there (torque converter possibly?).
Exhaust is new, but only AFTER the cat converter.
I have some limited data collected with a Davis Driveright Carchip E/X.
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Saturday, July 10th, 2010 AT 12:55 PM
