Truck is pinging pretty bad.

[waynetd]

Here is another problem with my 98 ext-cab Z71. Truck has 77,400 miles on it. Lately the truck has been pinging pretty bad while accelerating on a straight stretch and going up hills. Coil, cap & rotor have about 36,200 miles them. Coil module has about 33,700 miles on it. Wires have about 31,900 miles on it and plugs have about 21,600 miles on them All replacement parts are AC-Delco. O2 sensors are original.

 

At around 24,000 miles when the dealer replaced the intake manifold gaskets, they forgot to tighten down the ground wire that bolts down to the thermostat housing. I didn't catch it until about 41,000 miles. Ever since then, I seem to have pinging problems. Any relationship or just coincidence? What else should I look at that might be causing the pinging? Thanks for any info.

 

Wayne

[Stocklook]

Have you been getting your gas from the same place, Bad Octane levels could be the problem IMO

[desrtrat]

try some upper engin cleaner. with that many miles, you may have a carbon bield up

in your cylinders. gm sells it and i think also there is a product called sea foam

 

good luck

 

[Yankee7985]

I use one can of Seafoam about every 10,000 miles. I use the brake booster vacuum line to get it into the engine. When the engine starts bogging down, I shut the engine off and let it sit for about 15 minutes. When you start it, increase the RPM's to about 3000, and you will get a smoke show.

[99Silver6.0]

I second the SeaFoam. I usually run 2 cans through mine before an oil change via the booster line. Stuff works wonders.

[GM Maniac]

If it happened after the dealer did your Intake manifold gasket, take it back and have them check the cam retard. The oe specs should be -2 - +2 degrees above 1000 rpm at operating temp. I found my intake gasket leaking, changed it and set my cam retard to +3 - +4 degrees at 1500 rpm. No more pinging My power output has increased, gas mileage improved, and most importantly no check engine light. By the way I have a '99 Suburban obs w/ 122,000 miles.

[miket]

Reading your post it sounds as though the pinging started after you tightened down the ground bolt. If your pinging started right after the dealer replaced the intake manifold, I would be looking at a leaking intake manifold...then my guess would be either a vac leak or coolant. But since it didn't do it after visiting the dealer, and only after tightening the bolt...hmmm....thats odd.

 

I am not familiar with where that bolt actually is on your motor....did it effect the intake manifold at all? When you tightened it, did you move or accidentally disconnect anything? Are you loosing coolant but not seeing it on the ground?

[waynetd]

My pinging problems have come and gone since 36,000 miles. The point I was trying to make was that I think something in my electrical system in regards to me ignition system was permanently messed up when the ground wire was left loose for such a long time. Right now, the pinging is the worst it has ever been. Yesterday I put new plugs, wires, coil, cap & rotor on the truck and it didn't make any difference. The truck is still pinging pretty bad and feels very sluggish.

 

The ground wire that was left loose was one that is bolted down on top of one of the bolts holding down the thermostat housing. Its one of the major ground wires for the truck.

 

My neighbor seems to think its the gas around here because his truck is pinging also. I guess I'm just going to have to live with it for now. Thanks for all of the input.

 

Wayne

[miket]

Knock sensor?

 

I went through this with my Dad's 90 Suburban. We checked everything. Finally it ended up being a leaking intake manifold. Unfortunately the shop that changed it, didn't change the oil, coolant got into the oil, spun a rod bearing and thus, he has a new engine.

 

In trying to diagnose the pinging, we changed the timing, changed the plugs (actually went to non-plat tipped which made a difference), thermostat change, wires-coil, and we checked the 02 and the knock sensor.

 

Hope you find it.

[firestorm91tt]

Pinging/knocking can come from serveral places.

 

What level octane are you running and are you getting gas at the same place?

When was the last time you changed your fuel filter?

How do your motor mounts look?

What condition is your knock sensor in?

 

I would persoanlly run some seafoam through her and see if that helps. I have 2 3/S that are twin turbo charged and knock always plays a part while tuning. At times when I would turn up the boost (even though not directly related to this post) I would get crazy knock counts on my datalogger. It took me 4 months to finally chase down the problem. Turned out to be a faulty wire connection at the ecu.

 

During that time, I changed the following on my car: upgraded fuel pump, fpr, hot wire kit, o2 sensors, knock sensor, upgraded fuel loop, plugs, wires and the list goes on and on.

 

Im not to sure if just having a loose ground wire would cause this problem, but I'm sure it didnt help you any. I have heard that you should run 4 seperate grounds from the battery itself using a marine terminal to the following locations: body, engine, transmission and frame.

[waynetd]

The Knock sensor is the original one. I would think that the SES light would come on if the knock sensor was out. As far as gas, I'm still using the recommended 87 octane and have been getting it at different stations. I may have to move up in octane. I still need to try the Seafoam.

 

My fuel filter was changed a few months ago and has less than 10,000 miles on it so I don't think its that but you never know. I change my fuel filter every 15,000 miles. I have noticed recently that my fuel pump sounds a little louder than it used to. This fuel pump has about 40,000 miles on it. I changed the original one out because it got very loud and I figured it was going to go out and I wanted to fix it before I got stranded. Thanks for the input and ideas.

 

Wayne