Knock/diesling: 87 octane

HanibalTheCannibal · #1 10-08-2005, 09:36 PM

Well, I had the delaership check my truck out. There is a slight diesling/clattering when driving 35-65mph up a hill. they state it is a normal function of the timing advance system or something like that.. I recently went to 87 octane. Is this the cause? It started after going to 87. It never did it with 92 or 93 octane. I quit using it because if the price. But I am going to go back to better gas. My old ford truck does the same thing but using 89 or 93 resolves it. I thought these newer trucks had ways of dealing with low octane gas

any thoughts? SHould I go back to dealership? There are only 100 miles left on my warranty

HanibalTheCannibal · #2 10-08-2005, 10:07 PM

PS Its not the piston slap problem, it is only intermittent and is noticeable at takeoffs.

Rollingbones · #3 10-08-2005, 10:08 PM

The only thing I can think of if you have a Hypertech or Nelson tune and it's set for a higher octane, that could cause it to knock.
The only other thing I can think of you might get yourslf a new bug shield with some flames on it. That might solve the problem (sorry, I couldn't resist)

HanibalTheCannibal · #4 10-08-2005, 10:10 PM

Quote:

Originally Posted by Rollingbones

The only thing I can think of if you have a Hypertech or Nelson tune and it's set for a higher octane, that could cause it to knock.
The only other thing I can think of you might get yourslf a new bug shield with some flames on it. That might solve the problem (sorry, I couldn't resist)

LOL I have ordered a bug shield last night from ebay.
I cant get the neslon guy to reply to my emails. What is another way to get an aftermarket tune to g et better MPG, performance etc??? Is there one I can buy in a box with instructions? I saw some programmers but I imagined myself crashing the compute onboard and causing random reboots LOL

Rollingbones · #5 10-08-2005, 10:18 PM

I'm sure Mr. Nelson is the best one out there. That being said, I'm happy with my Hypertech. I just followed the instructions and it worked fine (I'm still running 87) and no crashing either. The nice part I like about the Hypertech is I can make changes on the spur of the moment (including resetting the computer to stock if needed). I've also heard that the Super Chips is supposed to work pretty good as well.
Painting you air intake wouldn't hurt either!!!

BlenderWizard · #6 10-08-2005, 10:19 PM

Allen told me that when switching to a lower octane, there is an adjustment period of a few days, and to expect some pinging then. That was after my Nelson tune, but I am sure it would apply here, too

GMMerlin · #7 10-09-2005, 06:07 AM

Quote:

Originally Posted by HanibalTheCannibal

Well, I had the delaership check my truck out. There is a slight diesling/clattering when driving 35-65mph up a hill. they state it is a normal function of the timing advance system or something like that.. I recently went to 87 octane. Is this the cause? It started after going to 87. It never did it with 92 or 93 octane. I quit using it because if the price. But I am going to go back to better gas. My old ford truck does the same thing but using 89 or 93 resolves it. I thought these newer trucks had ways of dealing with low octane gas

any thoughts? SHould I go back to dealership? There are only 100 miles left on my warranty

Higher octane fuels burn slower and will cause carbon deposits to form on valves and other combustion chamber componants if used in vehicles designed to run lower octane fuel.
The carbon deposits absorb fuel from the intake air fuel mixture and will cause the engine to run lean and is one cause of detenation.
I would have the engine intake system decarbonized and only run 87 octane fuel. (your engine is designed and calibrated for 87)
Also only use Top Tier gasoline, this is gas that is formulated to meet the standards for fuel quality set by the auto makers.
Find my thread about "truth about Gasoline" Right here

BlenderWizard · #8 10-09-2005, 08:49 AM

how do you decarbonize an engine?

GMMerlin · #9 10-09-2005, 10:26 AM

Quote:

Originally Posted by BlenderWizard

how do you decarbonize an engine?

Drive it backwards until the odometer reads 0

There is a product available from GM called Top Engine cleaner.
It has been around for over 20 years and works great in removing carbon deposits.

MT-2500 · #10 10-09-2005, 10:54 AM

One other basic idem to ckeck is for proper operation of the egr valve system. If that sucker is not working good they will ping/spark knock rattle or make all kind of noises.
MT-2500

BlenderWizard · #11 10-09-2005, 12:55 PM

Quote:

Originally Posted by GMMerlin

Drive it backwards until the odometer reads 0

There is a product available from GM called Top Engine cleaner.
It has been around for over 20 years and works great in removing carbon deposits.

Is there any place to get that other than the dealer?

GMMerlin · #12 10-09-2005, 03:09 PM

Quote:

Originally Posted by BlenderWizard

Is there any place to get that other than the dealer?

Nope

HanibalTheCannibal · #13 10-09-2005, 08:07 PM

Well, I was going to go a step up to 89 octane to just be rid of the problem. But if it will create more problems then I am back at square one. I just added some B12 because I just filled up with 87. so I am gonna have to wait this tank out. The B12 stopped the pinging, and the Mobil1 really smoothed things out too!!
I am going to ask the dealer one more time about this situation.
This decarbonizer...is it something you can just buy at the counter at GM, and do it in your driveway, or do you have to let them do it(ie special tools etc)
Thanks!!

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