engine pinging + "Smoke" out tail pipre @ high RPM

Taaaaaaahoe? · December 19, 2003

I have an 01 tahoe bout 75k miles 5.3L

Noticed under full throttle or so I ge this sound from the engine like broken glass in a bag being shook...bes way to explain it. Im runnign mid grade fuel as it is! How can I make this go away.

Also, i notice...mostly at night lets say im on the expressway, and I step on it to the point where it downshifts. I notice in my rearview mirror a Smoke between me and the car behind me.

i dont notice it int he day, only reason I see it is b/c of the headlights between myself and the other car. Any idea what it is.... Its not burning oil or anything. Maybe carbon? Do I just need to get on it more? is it related to the pinging?

ANy info would be great!!

Thanks!

Mike

Shaners · December 19, 2003

It probably wouldn't be a bad idea to "cuff" on it a little more... All engines will load up a little if they are lugged alot.

Be careful though with the pinging that you aren't too hard on it. It sounds like the timing is advanced a little too far. This could be caused by a faulty sensor somewhere.

Disconnect the battery for about 15 minutes to reset the computer, and see if the pinging goes away. Of course if you have a sensor that is going bad, or is dirty, it will eventually start to ping again.

The only other thing could be the fuel that you are running. Try a different brand and see if it helps.

Markeaux · December 19, 2003

That smoke is probably carbon being knocked out of the combustion chamber. Supposedly carbon that is built up on the chamber can glow red hot and cause preignition especially under load/acceleration. Higher octane gas can usually help prevent the pinging, but the carbon probably needs to be removed, too.

Taaaaaaahoe? · December 20, 2003

I have had the batt discoed for that time before with no change. What sensor could be bad?

I ran some combustion chamber cleaner in in a few Kmiles ago, but didnt notice much crap (smoke) come out the tail pipe in that process...maybe it needs it again. but the pinging is a deal, I can hear it at high rpms, so I dont like getting it up there to clean it out

MIke

CapnDean · December 20, 2003

Causes of Ping. AKA Valve rattle, preignition, valve clatter, crushed glass in bag.

#1 Cheap Gas

#2 Improper timing (too much advance)

#3 Carbon Buildup

#4 Hot spots in combustion chamber*

#5 Anything that artificially increases compression (see #3).

Nutshell: In a gas engine the spark plug is supposed to be the only thing that lights off the explosion in the combustion chamber. If the timing is too far ahead...the spark gets there before the piston is all the way to where it needs to be in the compression stroke.

Carbon buildup - - Decreases the amount of space between the top of the piston and the top of the combustion chamber (the cylinder head). This raises the compression on that cylinder and causes pre-ignition via the same process a diesel engine uses...compresses the crap out of the mixture til it blows. In a detroit 671...that's a good thing... in a GM 5.3 gas motor...NOT a good thing.

Hot spots - - Okay a little bitty piece of aluminum slag... say a nicked piston or something....that lil sliver can get cherry hot....and it can light off the mix on ya.

Artificially increased compression - - -Well old Boudreax planed the head before he sold ya that truck, or stuffed the wrong pistons in there...or you got some pistons that were out of tolerance from autozone.....you get the deal...it happens.

Cheap gas: Never really understood it but better gas is LESS likely to blow under compression than the cheap stuff. Conventional wisdom would tell ya that better gas would probably be MORE volatile (like nitro glycerin there Wyle E. Coyote) but that's not the case...the higher the grade the more it can tolerate high compression before it blows.....

Oh yeah...KNOCK Sensors....all they really do is retard the timing when they detect knock.... In your factory truck..they are good things...in your 1/8 mile dragster they are performance killers... Why? Well optimum performance occurs on the bitter edge of knock. Just as optimum efficiency in a gaslone motor is at 211 degrees a gnats butt away from overheating is peak efficiency.

Hope this helps in the Philosophy dept!

CapnDean

Taaaaaaahoe? · December 20, 2003

Thanks! Thats a lot of good info!

I usually try and stay away from the cheepo gas....

I did run a combustion chamber cleaner in it...but maybe needs more, what do you all suggest?

How would I fix #2? Have computer reflashed? anytting I can do?

And do the knock sensors go bad? However it sounds like the knock sensor would jusy "mask" my problem..

Thanks for great info!

mike

Shaners · December 20, 2003

The knock sensor will retard the timing when predetination is detected.

Awhile back, there was alot of talk about "SeaFoam" top engine cleaner. I have never used it, but I understand it is very similar to the stuff that GM uses...

CapnDean · December 20, 2003

Seafoam and combustion chamber cleaners:

How do ya know? The Capn is a skeptic. I suppose that the only way to know for sure is to pull the head and look. Of course if you have pulled the head to look, why not clean it out then with tools rather than snake oil?

Don't wanna pull the head> Squirt some of that crap down in there and SEE what it does....I would be more afraid of gumming up an o2 sensor on the way out. Probably a dozen things that you could screw up in the process of seafoaming your motor. I seriously doubt that the product can really have a major impact.

To me it's like a touchless car wash...how ya gonna get the dirt off if you don't wipe it off? If you get enought water pressure to really shine your truck...it'll probably take the paint off too

Oh yeah...while I am being the skeptic.....anybody ever get an extra 20K miles out of a motor because they used Richard Petty's favorite STP earl treatment? Oh yeah...how could you tell anyway? Who really knows when that motor is gonna go?

Try this one on your State Farm agent after your charming wife wraps your Sierra around a tree and totals it:

" Hey there Mr. Adjuster....you say that my truck is toatalled and you're gonna give me $7200 on it....Well sir I'll have you know....I used STP oil treatment in it at every 3000 mile oil change....So...that engine HAS to be worth another $800! pay up buddy!"

HA

Merry Christmas yall!