97 S-10 Clatters Like A Diesel

neonhomer · October 21, 2008

I think this is a common problem with these motors. My S-10 has the 2.2L 4cyl, and it has about 130k on it. The thing sounds like a diesel. You hear it mostly from the top end of the motor, under the valvecover. So... short of a top end rebuild, what can be done?

I am running 10w-40 in it, and just recently started running Mobil 1 in it.

2000DV4.8 · October 21, 2008

You sure it isn't an exhaust leak? Leaky manifolds can sound like a knock.

pm26 · October 21, 2008

Are you sure the engine is not pinging (=preignition)? This could be caused by considerable carbon buildup on top of the pistons, which will raise the compression in the cylinders. Do a compression test and see what you get. Carbon like this can be successfully removed with GM top engine cleaner sold by GM dealers.

Noisy valvetrain can also be the source of the mentioned noise.

Base ignition timing, if advnaced too far, can also cause pinging. Check that and make sure it is within spec.

Also, how is the EGR valve? If it does not work (=failed closed), you may get pinging with regular gas. You need to go to higher octane fuel, or replace the EGR valve.

Leaky exhaust manifold gaskets usually cause clatter type noise under acceleration.

neonhomer · October 22, 2008

Not sure on the EGR valve. I will check this this weekend and see what I find. Would a bad EGR valve also cause the tendacy to hesitate upon take off?

Timing is controlled by the PCM, and this motor doesn't have a distributor, so if the timing is off, either the PCM is hosed, or the crank and/or cam sensor is bad. I am not getting any CEL or codes.

As for the carbon buildup, I am not sure. The truck has about 130k on it, has mostly seen regular unleaded gas. Hardly ever gets premium. Is that GM stuff similar to Seafoam?

Draenor · October 22, 2008

Did the noise start before or after you put in Mobile1?

..Yes, seafoam is the same as the GM Cleaner.

merlin5577 · October 22, 2008

Pull the spark plugs. If the gap is wrong or they are covered with carbon it could cause pinging.

pm26 · October 23, 2008

Would a bad EGR valve also cause the tendacy to hesitate upon take off?

Only if it was stuck open due to excessive carbon build up on the stem of the valve. The spring would not be strong enough to close it. In this case yes, you would have excessive exhaust drawn into the intake and it would cause very sluggish performance and bad fuel economy. I had this happen to an '83 Pontiac Boneville.

If the valve is stuck closed (as in a failed diaphragm), there is no performance penalty, except for engine pinging with regular gas.

neonhomer · October 25, 2008

I don't think it is really pinging... this motor has sounded like this for the past year or so. We just recently switched to Mobil 1 (within the past few weeks).

Going to pick up a can of Seafoam and run it through. As for the EGR valve, I am going to have to find it and take a look. Any ideas on where the EGR is on a 2.2L truck motor?