Engine Performance problem
1999 Chevy Astro 6 cyl Two Wheel Drive Automatic 96000 miles
My Astro is running rough, with an intermittant stumble off idle. If it sits for a few days, it is VERY hard to start, especially if it is wet and rainy out. I am also getting a engine check light, and code P0300, which I understand means " multiple misfires on varioius cylinders. In other words, the engine is running crappy. If I clean the fuel injectors with a pressure cannister ( runs off the air compressor ) it fixes it right up and the car runs smooth for a few days. This has been going on for about two years,
and now I have to fix it ASAP because otherwise it won't pass smog.
This is what I have done so far:
* Replaced sparkplugs, wires, distributor cap, rotor.
. After this, I discovered that the problem was fuel-related, even though my oscilloscope showed variations in spark voltage - seems a lean mixture takes more voltage for the plugs to fire.
* Cleaned the fuel injectors with cleaner in the tank. No difference.
* Cleaned the fuel injectors with a compressor-operated cannister cleaner. This got the car running great for maybe a week.
* Replaced the (SCPI ) injectors with the complete MFI upgrade kit from GM. Also replaced the spider bracket and upper intake manifold gaskets. Referred to GM Special Policy Bulletin 99066G, service bulletin 00-06-04-003B,
and the 1999 M/L factory service manual.
( I really expected this to fix it. Was VERY disappointed when it did not. It still starts hard ( 2 or 3 minutes of cranking ) after sitting a few days. And it runs rough. The second start of the day is
always easy. )
* Replaced the fuel filter.
Put a fuel pressure gauge on the schrader test port. It reads 61PSI with the ignition key on but not running or cranking. It goes down to 52 PSI at idle, and when you stomp on it, it goes up to 58
Now I'm pretty much at my wits end with this thing. I did see some mention of replacing the gas tank fill pipe - apparently California gas eats it - and have ordered a new one. But I have little faith in that.
Is there anything common that I'm just overlooking?
Monday, March 2nd, 2009 AT 4:57 PM