Gray exhaust residue
Thread Starter
Intermediate
Joined: Jul 2002
Posts: 48
Likes: 0
From: Camarillo CA
Gray exhaust residue -- please help
Recently the color of the residue inside my tailpipes has turned from black carbon to a whitish-gray color, almost like ash. This started with the left exhaust pipe and to a lesser extent has progressed over to the right. The car seems to be running a little ‘different’, with a mild miss and slight power reduction. However, I notice a totally different ‘tone’ to the sound of the exhaust (almost more ‘hollow’ for lack of a better term). Anyone seen this before or have any ideas?
Thanx.
[Modified by jrz01, 5:35 AM 5/4/2004]
[Modified by jrz01, 5:36 AM 5/4/2004]
Thanx.
[Modified by jrz01, 5:35 AM 5/4/2004]
[Modified by jrz01, 5:36 AM 5/4/2004]
Pro
Joined: Sep 2003
Posts: 731
Likes: 0
From: Calgary Alberta
Re: Gray exhaust residue -- please help (jrz01)
I don't really know. Usually grey is a sign of burning antifreeze, and brown is a sign of running lean, however this is not an exact science. Have you thrown any codes?
Did you recently do a decarb procedure? the decarb tends to turn things greyish for a while after it is done.
Some high octane mixtures also leave a bit of a grey residue, depending upon what additives are placed in the fuel (e.g. Toluene, xylene, etc.)
Did you change your fuel supplier?
Maybe someone who has experienced a similer situation could chime in.
I wouldn't be too concerned if you haven't thrown a code.
Did you recently do a decarb procedure? the decarb tends to turn things greyish for a while after it is done.
Some high octane mixtures also leave a bit of a grey residue, depending upon what additives are placed in the fuel (e.g. Toluene, xylene, etc.)
Did you change your fuel supplier?
Maybe someone who has experienced a similer situation could chime in.
I wouldn't be too concerned if you haven't thrown a code.
Team Owner
Joined: Mar 2001
Posts: 21,325
Likes: 3,841
From: small town in S.E Pa. PA
St. Jude Donor '03-'04
Re: Gray exhaust residue -- please help (jrz01)
Colors can vary slightly, but black usually means a rich condition... common with C5.. the lighter color usually means a leaner mixture... too much air... etc. I would check the plugs first... without LS1 edit or a scan tool it is difficult to see what is going on... worst case scenario . a really lean motor could burn a valve, checking the plugs for melt down would be something easy to check... pitting or melted ceramic insulator around the center electrode...
Dont panic... if the car seems to be running ok.. your not having a melt down.. but something has changed in the air /fuel ratio...
[Modified by Evil-Twin, 9:02 PM 5/4/2004]
Dont panic... if the car seems to be running ok.. your not having a melt down.. but something has changed in the air /fuel ratio...
[Modified by Evil-Twin, 9:02 PM 5/4/2004]
Racer
Joined: Jul 2003
Posts: 460
Likes: 18
From: Conroe, TX
Re: Gray exhaust residue -- please help (jrz01)
Could be your catalytic converters are failing. The internal ceramic struture starts to break down and produces a light gray colored dust. This could also explain the change in exhaust tone.
You might want to tap your converters with a rubber mallet. If you hear anything loose moving around, you'll know its time for some Random Tech hi-flows! :jester
You might want to tap your converters with a rubber mallet. If you hear anything loose moving around, you'll know its time for some Random Tech hi-flows! :jester
Le Mans Master
Joined: Oct 2000
Posts: 6,507
Likes: 722
From: Sausalito CA
Re: Gray exhaust residue -- please help (jrz01)
Good advise...check your cats and pull the plugs.
Might also check the whole system for a leak.
Brown is good/ black is rich. Grey...we'll see
Might also check the whole system for a leak.
Brown is good/ black is rich. Grey...we'll see
Thread Starter
Intermediate
Joined: Jul 2002
Posts: 48
Likes: 0
From: Camarillo CA
Re: Gray exhaust residue -- please help (Kenny94945)
First off, thanx much for the comments and suggestions.
I haven't changed fuel suppliers or had any recent work done. No apparent water in the oil, the coolent level seems to be holding strong, and I don't detect any steam or color to the exhaust. I was thinking (or hoping) a clogged injector was most likely. The car has 40K miles, and the injectors haven't been cleaned, aside from the occasional bottle of Techron additive. I've run a tank of treated fuel over the last week, and this seems to be smoothing out the miss and returning the sound, but I'm not sure that isn't just wishfull thinking. Any thoughts on the injector idea (ie. is clogging common?) and if the Techron additive really works to correct a clog?
One other thought: about 10K miles ago, installed a '02 Z06 cam, 918 springs, hardened push rods, with light porting on the stock C5 heads. Anything that would likely burn a valve?
I haven't changed fuel suppliers or had any recent work done. No apparent water in the oil, the coolent level seems to be holding strong, and I don't detect any steam or color to the exhaust. I was thinking (or hoping) a clogged injector was most likely. The car has 40K miles, and the injectors haven't been cleaned, aside from the occasional bottle of Techron additive. I've run a tank of treated fuel over the last week, and this seems to be smoothing out the miss and returning the sound, but I'm not sure that isn't just wishfull thinking. Any thoughts on the injector idea (ie. is clogging common?) and if the Techron additive really works to correct a clog?
One other thought: about 10K miles ago, installed a '02 Z06 cam, 918 springs, hardened push rods, with light porting on the stock C5 heads. Anything that would likely burn a valve?
