Chevy & GMC Vans

Been having a lot of problems with knocking under anything but idle. Checked the timing, was at zero*. Even using mid-grade gas. Already changed out the knock sensor. And recently put in new cap; rotor; plugs; Summit Hi-output coil and 8.5mm wires.

Changed the timing to 2*-3* after zero. Much better but I can still hear the knocking sometimes. Not nearly as bad as before. I'm afraid to go back to reg-gas. My wallet sure could use the break. I fill up 2-3 times a week.

I kinda thought that the timing chain was getting loose and causing spark scatter. Well, the timing mark is rock solid steady.

Any thoughts out there ? ? ?

Hi WaterBoy
Hmmm, pinging,knocking. Plugged PCV Valve, Worn Timing chain, Bad Gas (regardless of octane), To much carbon build up in the motor (piston, valves). A cheap way to figure this out is run 92+ for a while in it, at least 2 tank fulls and see what happens after that. Just a thought.

M~

A) I checked the PVC. OK.
B) If the timing chain was worn, I would be getting spark scatter with the timing light. But I'm not.
C) Don't think it is the gas. Many tank fulls from various stations.
D) Carbon. Possible.
E) Could give it a try on the 92+ hi-test.

did you check the EGR valve , if it's stuck or clogged it will cause pinging . go ahead ask me how i know !!!

A carbon deposit that is glowing red will ignite the fuel out of sequence. A carbon deposit that is large enough to make contact with a piston will also make a knocking noise. A cure that I've used is to dribble some water into the intake manifold while the engine is running. The combustion temperatures will turn the water into super heated steam and it will clean out the deposites.

A carbon deposit that is glowing red will ignite the fuel out of sequence. A carbon deposit that is large enough to make contact with a piston will also make a knocking noise. A cure that I've used is to dribble some water into the intake manifold while the engine is running. The combustion temperatures will turn the water into super heated steam and it will clean out the deposits.

skippy wrote:did you check the EGR valve , if it's stuck or clogged it will cause pinging . go ahead ask me how i know !!!

I'm askin'....

How the 2 worst plugs looked.

Hi Water Boy
Are those the correct plugs for that motor? They look abit cold.
Yes they are in bad shape. Have you considered Platinum plugs? Also might I suggest testing your plug wires for resistance and Spark from the coil. if you have a weak coil it won't light the plugs properly either. Hopefully your van is running better now.

M~
Those I pulled when I recently did a tune up. At that time I also installed a new cap and rotor. As well as new Hi-output coil and 8.5mm wires. Those are the correct AcDelco plugs as per the book.

Have not looked at the plugs since the tuneup.

As to running now?
Still getting some knock but not nearly as bad before it changed the timing.

Smiliesafari wrote:A carbon deposit that is glowing red will ignite the fuel out of sequence. A cure that I've used is to dribble some water into the intake manifold while the engine is running. The combustion temperatures will turn the water into super heated steam and it will clean out the deposites.

Ahh you're talking to "Waterboy", think he can get his hand on good water? Sorry I had to chuckle.. then smile almost laughed. Ironic but he if it works I'll roll over laughing.

But back to the suggestion. How would you get the water into the intake past all the intake air management? Different in the downdraft carb engines of old. Some kind of carb out like lucas fuel treatment may work.

Sorry my face is cracking (waterboy) cheers. Ha ha