Seems like I've been posting in here a lot lately but I have a problem I'm not sure what the symptoms point to.
'88 Cavalier Z-24, 2.8 mpi, 170K miles, has intermittent problem both with hard starting and power loss.
Sometimes I go to start it and it will fire a time or two right away but then I have to crank it another 10 seconds or better without it firing at all, but I can always coax it into starting by manipulating the throttle.
Also, when I am driving it it will lose power and surge, then come out of it, etc.
It had a starting problem about a month ago and it turned out to be a leaking injector flooding the engine, which I replaced.
Within the last 25k miles, the car has had: New ECM new MAP sensor New TPS New heads, plugs & wires New intake gasket and injector o-rings
Also, since I thought the symptoms pointed to a faulty ignition module, I replaced that, but the problem remained.
Fuel pressure is about 36 psi with engine running, althugh I did note that the pressure remains there at any throttle position, and also with the vacuum disconnected from the fuel pressure regulator. I know this indicates a faulty regulator, but I don't think that would cause the symptoms (starting, etc.) seen here. Especially since the pressure holds steady with engine shut down.
I inadvertently left the MAT sensor unplugged after changing the ign module, and hence got a check engine light alerting me to that fact. I plugged it in and light went off.
I just checked the codes and got one for MAT sensor, naturally, and also one for "lean exhaust."
This has never had an O2 sensor replaced in the 6 years I've had the car. But I wouldn't think that would come into play with cold starting when the vehicle is in open loop.
The problem seems ignition related. Could a knock sensor go bad and cause the ECM to make the ign timing go crazy?
The EGR moves freely by hand and there are no codes for it.
Just wondering if anyone has any suggestions, TIA