magician

Has anyone here heard of a process that actually works to clean the combustion chamber, pistons and such thats done without an engine teardown? I have searched this site and read the posts on Seafoam and others and I've tried several products to stop the pinging and knocking the engine does, with no lasting results. My Tahoe had 120k miles on it when I bought it and now has 155K. I have run out of ideas and possible fixes for this problem.
List of attempts,
Numerous Seafoam applications in the tank.
BG Products 44K severak times in the tank.
New O2 sensors.
New injector coil packs.
New plugs.
New MAF Sensor.

Im considering doing the water injection cleaning or having the dealer or someone lese do the combustion cleaning since I suspect my motor has pretty extensive carbon build up?

Any help I can get would be much appreciated.

MDTAHOE

The likelihood of that being your actual problem is not very high. Unfortunately to find out for sure someone who is qualified needs to do some specific testing. You can try to have a BG fuel injection service done.

justimagination

GM @ one time made a TOP ENGINE CLEANER, which was used on a lot of the BIG BLOCK era. This stuff really works, follow directions. When carbeurators were prominent, you removed the air cleaner and ran the engine at around 2500 RPM's while pouring the can contents into the carbeurator actually stalling the engine. Turn OFF the ignition and let it SET while the carbon is dissolved.
JMHO, I've used it in the past and know from experience..........not hear say, Good luck,
david

in2pro

I would speculate that the fuel additives are going to be the least invasive of the options for cleaning then up but you will need to get to the root cause of why you are getting heavy deposits to begin with...

Is it a high mileage vehicle? is it regularly tuned and kept up?

magician

MDTAHOE - Could you be a little more specific about the tests you suggested? The problem I'm having I believe, is caused by excessive carbon build up in several or all of the combustion chambers and I believe this was caused by the previous owner not doing the recommended oil changes and more than anything else, the way the DOD works and the PCV system employed by this vehicle. I believe it is these factors combined that are causing the pinging/knocking that I cant seem to get rid of. This is just my opinion based on what I've read and heard and seen in the last year and half I've had the Tahoe. Make no mistake, I'm not downing the Tahoe in fact, I love the truck and want to be buried in it when its my time. Any suggestions you could give especially since your tag says your a GM Mech, would be much appreciated.
In2Pro - It is currently very well maintained but I've only had it for last 38K miles. I bought it @ 122K and it now has 155K. I dont know how well it was taken care of prior.

shamrock246

what year is it?TBI or MPI?

magician

07 and TBI?

Its an 07 Tahoe LT 4x2, Silver Mist w/20" Factory Rims, 2nd Row Buckets and Tow Pkg. It currently has 155K miles on it and I have changed all the fluids on it, most with Synthetics. All the belts, the 02 sensors, the MAF Sensor, removed the PCV Orifice tbe and replaced it with a catch can set up.

MDTAHOE

It could be the cause all though in the 15 years of working on cars I have never seen carbon build up excessive enough to cause any problems. I have heard rumors of it in the olden days though. I work in a very equipped shop that owns all the best test equipment. I do all of the performance and electrical work. We work on every make and model. Since the owner has a radio talk show, a TV show and is on Motor Week we get all kinds of strange problems. Usually I get them after they have been to several shops and have half the parts store on them. The tail pipe emissions need to be checked to seen if it running lean. The data for the computer controlled ignition timing need to be looked at to see if the timing is being commanded correctly (knock sensors working correctly). What kind of plugs are in it? Is top tier fuel being used? The list could go on and on. Did you try to take it to a shop to be checked? When does it ping? full throttle? partial throttle?

magician

Plugs are standard NJK's and its never been on an Emissions stand since we dont have that as a requirement in SC. Fuel is whatever is cheapest locally and is usually of the 89 octane variety.
I have done some data logging on the tahoe using an after market tuning program(HP Tuners), I've even changed the spark tables(pulled timing) a few times to try and decrease the pinging. I did a compression test on all the cylinders. All of this has not changed anything for any significant length of time? It has made it ping less at times but not significantly. It does the most pinging @ part throttle, usually between the 2 -3 shift as the engine is settling and, after the torque converter locks up. It will do the same in Tow Mode also. It also pngs going into and coming out of DOD?
I would like to borescope the cylinders to verify the carbon build up and may get to that this weekend. Knock sensors are something I havent tried though? I will have to do some research and locate them and see exactly what I can do myself as far as checking them out, if nothing I will take it in to a service shop as I'm kind of at my wits end here. Maybe I'm expecting too much from this truck and should just accept that it has and always will run like this??

shamrock246

I'm with MDTAHOE on the carbon build up these newer engines run extremely clean,i would look into your knock sensor,i think they had a problem with water building up in the knock sensor area and causing problems with the sensor on the GEN 3's,you should be able to run on 87 with no problems