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92 K2500 350/TBI badly pinging when warmed up

Tiny
OFACE
  • MEMBER
  • 2012 CHEVROLET TRUCK
Alright, well here we go.

The truck starts right up, whether it's cold OR hot. When the truck gets up to operating temperature, it will ping terribly - (THE WORST PINGING I'VE EVER HEARD) mostly at part throttle. It seems not to ping so much under WOT, but it bogs and smokes big time.
(None of this behavoir happens when the truck is cold)

After getting the infamous code 32, I replaced the EGR valve and EGR module. It didn't fix anything - the EGR port was blocked with carbon. Next I removed the intake and cleaned the sludge (lots of sludge from the previous owner) from the top end and had the intake soaked in an acid hot-tank for a weekend. The truck STILL pings very badly once it gets warm (when it's cold, it runs fine) and it's smoking quite a bit too.

It has a new O2 sensor and a fresh set of plugs. New MAP sensor, and the EGR vacuum lines are clear. The timing is set to 0, as it's supposed to be. Stock exhaust, stock thermostat, stock everything.

I'm stumped. Any ideas?
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Saturday, November 10th, 2007 AT 5:25 PM

16 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Yes warm the engine to when it pings, then retard the timing off 0, the factory figure of 0 degrees is arrived at by using the average of 100 or so engines and were they run best, there are always exceptions to the rule, your must be one of em! Try 10BTDC
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Saturday, November 10th, 2007 AT 5:33 PM
Tiny
OFACE
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I've tried that too. This is a fairly new problem - and with horrible timing, it'll be snowing in just a few months - I HAVE TO get to the bottom of this.

My next step is a fuel filter. I will probably check Fuel PSI then too.

Is it possible the ECM isn't firing the EGR module correctly?
I thought maybe the timing chain has too much slack, but like I said, it's a new problam, and it's fine when it's cold.
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Saturday, November 10th, 2007 AT 5:43 PM
Tiny
MERLIN2021
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Years ago when carbs were the norm there were products we could buy to break up carbon in the combustion chamber, see if you can find one. If the intake had a lot of sludge the cylinders have carbon! If you can't find it, GM makes one, make a trip to the dealer parts counter.
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Saturday, November 10th, 2007 AT 6:50 PM
Tiny
OFACE
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  • 9 POSTS
I've heard Sea-Foam is the product of choice here.
I will def. Look into it.

Thanks for your thoughts on the topic. I'll let you know how I make out.
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Saturday, November 10th, 2007 AT 6:57 PM
Tiny
MERLIN2021
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OK.
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Sunday, November 11th, 2007 AT 7:57 AM
Tiny
OFACE
  • MEMBER
  • 9 POSTS
I have to admit, I was a skeptic.

. But I used a can of that SeaFoam. It's like a miracle drug or something. An entire can through a vacuum line and 1/2 of the pinging is gone. I plan on using another can in a day or so. A fresh fuel filter and a half tank of Super shouldn't hurt either.

Just to put it out there - when I removed the intake to check for sludge (at the beginning of this project) I found a lot. I filled a Home Depot Homer bucket 1/2 way up with sludge from the valve covers and below the manifold.
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Thursday, November 15th, 2007 AT 8:36 AM
Tiny
MERLIN2021
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Thats good, it's a good idea to stay clear of the 87 octane stuff. TROUBLEMAKER.89 at least!
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Thursday, November 15th, 2007 AT 1:14 PM
Tiny
OFACE
  • MEMBER
  • 9 POSTS
I hear that! 93 only - for my other car (blown mustang).

Have you had much experience with the Top End cleaners (ie: SeaFoam, GM cleaner, etc)? Any idea if it's bad to use a lot of it? It seams to work wonders on my truck - but the fix doesnt last. Seams to only NOT ping for about 20 miles or so, then the ping comes back. There must be LOTS of carbon comming loose in there.
Any thoughts?
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Thursday, November 15th, 2007 AT 2:25 PM
Tiny
JASON R
  • MEMBER
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If you had enough time and experince and tools id take it apart and clean everything.
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Thursday, November 15th, 2007 AT 3:10 PM
Tiny
MERLIN2021
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The other problem may be quality of gas you use? 87 is crap, move to 89 at least. Drive with a few tank fulls.
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Thursday, November 15th, 2007 AT 3:56 PM
Tiny
MERLIN2021
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The other thing to check is the EGR for any problems, excessive carbon or sticking valve, what color is the smoke?
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Thursday, November 15th, 2007 AT 4:16 PM
Tiny
OFACE
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I have checked the EGR, and it's ok. New EGR valve, new EGR control module, checked all of the EGR lines (all clear - no obstructions).

The only thing stopping me from pulling the heads and honing the cylinders, is time. The weather is getting worse and worse, and the shop's already full of unfinished projects. I think I might just leave it in the hands of SeaFoam. I guess I'll try my luck with that.

So far, after 1 can of SeaFoam, the smoking (mostly black, with a hint of blue) has almost stopped, but. The pinging has come back a bit. It's less than it once was, and I think I'm moving in the right direction.
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Thursday, November 15th, 2007 AT 6:31 PM
Tiny
MERLIN2021
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You might want to try a can of risolone ring restore as a temp fix. Can stop oil burning issue. It's in a red and yellow plastic bottle, 8 cly treatment goes about 10.00!
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Friday, November 16th, 2007 AT 2:07 PM
Tiny
OFACE
  • MEMBER
  • 9 POSTS
I ohmed out the knock sensor - totally dead, no resistance. I finally replaced the sensor, and I RE-adjusted the timing (again).

Still smoking a bit, but most of the pinging is gone. With winter (and snow) around the corner, I think I'm gonna' have to run it AS IS. With 170k on the clock, it may be time to go big block after the winter.
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Saturday, November 17th, 2007 AT 2:52 PM
Tiny
MERLIN2021
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You are one of the lucky ones, most bad knock sensors cause way more trouble. Good work!
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Saturday, November 17th, 2007 AT 3:12 PM
Tiny
OFACE
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Thanks for the help.
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Sunday, November 18th, 2007 AT 10:59 AM

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