Engine Performance problem
1997 Chevy Astro 6 cyl Two Wheel Drive Automatic 200000 miles
the car was needing a tune up so we got wires and plugs, fuel filter, and it had an engine code which said to replace one o2 sensor
after this the car wouldnt start, so it sat for a few months. About a month ago I was reading that someone else had a no start problem and put on a cap and rotor, I cleaned them first and it fired off so I replaced both
now it surges at idle, replaced the throttle position and checked for vac leaks, and cleaned egr
vac gauge reads around 16-18 and holds somewhat steady. Fuel pressure stays around 60. The only thing that seems to make the idle smooth out is when I disconnect the maf sensor. Of course the computer doesnt know what to think so I guess it sets a default. But it idles then, when I reconnect and reset the code it starts to stumble again.I got a used one that is suppose to be good and it didnt help.I want to make sure that is the problem before spending alot of money.I have an idle air control valve arriving today because the old one was making noise. The old iac valve seemed to work though
Ok if you pull the vacuum line off the map and it runs better then that would tell me that is running lean to begin with. So I would first clean the mass air flow unit with mass air flow cleaner nothing else. Now if that is fine then we need to have an actual fuel pressure reading. It needs to be between 60-66 psi not less. If it is less then the upper plenum need to be removed to see if the fuel lines into the main injector body are cracked. This is common and most parts stores can get or carry the repair kit for it. Let me know what you find.