Hello, I have a '95 305 TBI, 5-speed pickup with 120K miles and it has a problem with pinging. It will often ping at low RPM, when pulling away from a stop, or just goosing the throttle. I've even retarded the timing a bit and it still pings sometimes. It does a little better with high octane but there is still the problem, and that gas is expensive.
I have read about dribbling water into the intake, and also Seafoam, which I've done *very carefully*. When I run one of these into the throttle-body it will actually correct the problem for a few days to a week. Then it'll start pinging again.
I assume part of the problem is due to carbon deposits, because the relief from pinging the water/Seafom causes. I looked at the EGR valve and it isn't stuck and moves freely, but I don't know how to diagnos the entire EGR system.
Also, the Catalitic converter needs replacing. Its been ratling for the last 40K miles. I've read you can check the Cat conv for obstruction with a vacuum guage on the intake, which I plan on doing soon. The exaust sounds like its flowing fine, and the pinging is at low-RPM, where an obstruction might now be as big a problem, so I'm kind-of thinking the Cat isn't the cause.
Could it be caused somehow by the ignition advance curve? Is it controlled completly by the ECU or ?
I think it might all be carbon deposits because I can temporarily correct the problem by running fluid into the motor. Is there a better way to get rid of carbon, other than tearing the motor apart?
Does anyone have any other ideas on what to try?
Thanks a lot, Brian.