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Car Forum / Chevrolet / Chevrolet Trucks / October 2004'95 305 pinging problem
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. Hello Brian: I have had similar problems in the past with different auto. What I have usually found is that the car is running too hot. Check to be sure that the coolant temperature sensor is actually showing the correct temperature. Check to see that the fan clutch speeds up when you speed up the engine, if not, it needs replacing. If the truck has very many miles on it, its probably the radiator causing the problem. I agree with you about the CAT, it needs replacing because it is broken, but I dont believe its causing the pinging problem. Another sure way to test for restriction is to put an rpm meter on engine, run engine for five minutes or so at moderate rate, enough to heat up CAT then speed up the engine around 3500 rpms and release the accelerator quickly, the rpms should drop off quickly, if not you have major restriction in exhaust system. I have just went through the same thing on my chevy truck. Ive seen it on lots of others as well. I would start with verifying that the cooling system is in fact cool enough. Hope this helps somewhat Best regards, Robie > Hello Brian: I have had similar problems in the past with different auto. > What I have usually found is that the car is running too hot. Check to be [quoted text clipped - 11 lines] > others as well. I would start with verifying that the cooling system is in > fact cool enough. Hope this helps somewhat Best regards, Robie Hey Robie, Thanks very much for the ideas. I hadn't thought about a temperature problem. I'll check it out. Thanks, Brian. Hey Brian: When you get this problem solved, do a post and let us know what the problem was and how you fixed it..ok.. Thanks Robie > Hey Brian: When you get this problem solved, do a post and let us know > what > the problem was and how you fixed it..ok.. > Thanks Robie Well.... I'm not sure if I found the cause or not, but the problem is better. To get an idea of whether or not the problem was heat related I went ahead and swapped the 195 deg thermostat for a 180. Maybe a kind of bandaid approach, but I was curious if it would make a difference. So, it seems to have fixed the problem. I don't know if running the motor cooler is correcting a carbon deposit, or some other type of problem. Or, possibly the other 195 therostat was out of calibration, and making the motor run hotter than it should have. The dash guage now reads about 160 degrees, so I'm sort of leaning toward both the old thermostat and the temp guage being out-of-wack, as you suggested. What I should do is throw the 195 into a pot and boil it, to see when it opens, but I don't have a thermometer convenient. I'll probably get around to the sometime, and find out if that was the only problem with my motor. I think running a slightly cooler thermostat is good for performance too, no? Cooler motor, slightly richer mixture, a little more timing advance = peppier motor? As long as it doesn't kick it out of closed-loop, but I haven't got a check engine light yet. So, thats where I stand. Not sure if I fixed the problem, or just band-aid'd it, but I pretty happy that its running really well. This problem has been bugging me for a while. Thanks for your help, Brian. |
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