Too much valve noise when accelerating..

I have a '91 S-10, 2.8 L. with 148 k miles. I've had it about 3 yrs now
and the pinging while accelerating has grown and grown. It's pretty bad
now and I'm thinking it might need a valve job. The enging runs really
good besides, no other problems. Since I've owned it I've replaced the
plugs, wires, and cap. I've taken it to 2 different garages for the problem
in the past. One place did some kind of super fuel system cleaning, that
did not help. The other place (cleaned) my oxygen sensor, he also said
he thought it was running lean, but that didn't help too much either. One
other thing, on the highway if I have it up to 75 or so it will pretty much
do it nonstop. Have I given enough info? Any suggestions?

I have a '91 S-10, 2.8 L. with 148 k miles. I've had it about 3 yrs now
and the pinging while accelerating has grown and grown. It's pretty bad
now and I'm thinking it might need a valve job. The enging runs really
good besides, no other problems. Since I've owned it I've replaced the
plugs, wires, and cap. I've taken it to 2 different garages for the problem
in the past. One place did some kind of super fuel system cleaning, that
did not help. The other place (cleaned) my oxygen sensor, he also said
he thought it was running lean, but that didn't help too much either. One
other thing, on the highway if I have it up to 75 or so it will pretty much
do it nonstop. Have I given enough info? Any suggestions?

since it has progressed over time, i'd say you have carbon buildup in the combustion chambers. this would raise the compression ratio, and thus cause the the air/fuel charge to ignite from the heat of combustion.

secondly, and im not totally sure on this, if your engine has a knock sensor, it could be faulty, and not telling the ECM to adjust the timing. maybe someone can shed more light on that possibility.

what octane gas are you using? the next time you fill up, you could try the highest octane you can get and add a bottle of octane booster.

Thanks for the reply, gas didn't do it though, I tried that a long time ago.
If anyone has any more info on the (knock sensor) I'd like to know, (as well as where it's located).

My truck is pretty much top shape again for now! I took it to a mechanic
I never tried before in town but heard good things about. I developed
a few new problems in the last week. For 1 my heater core went out
and I did the bitch myself just to save a couple hundred. That's a light
enough job for me to handle, just a pain in the ass though. Also I then
noticed I had developed a huge oil stain underneath and it was dripping
badly around the back of the tranny. So I took it down and told the
mechanic about the pinging and the oil leak. He thought the pinging was
going to be a clogged egr valve, but that he'd check the timing too. For
the oil leak it turned out to be a bad o-ring on the distributor. The egr
valve was ok but he noticed also that the cap and rotor looked bad. I
had replaced these with aftermarket parts when I got the vehicle but
he said sometimes aftermarket caps and rotors can cause a spark to jump anyway (hmm), but in any case they looked bad now. So
he replaced the o-ring, cap and rotor and re-set the timing, also tightened my valve covers a tad (they were seeping), in addition my
cat con heat shield had a slight rattle so he bent it away so it wouldn't
make contact anymore. Now there's virtually no ping, or oil leaks, I'm
set for the winter. He charged me about $225, I'm happy..

It's the knock sensor :smile:

Those older S10s are jewels, nothing real fancy but just keep doing the job.