OT: Carbon buildup in engine cylinders

HG in KC · Jan 21, 2015

Hello. I need advice from the experts on this site. Have been fighting a problem with engine ping on my car. It is a 1988 AMC Eagle with 42500 miles. I had it in the shop for a timing chain/gear replacement and they said I had a lot of carbon buildup in the cylinders. They did a compression check and they got 160-170. Spec for the engine is 120-150. The engine is a 4.2L 258cdi inline 6. My question is: anyway to get rid of the carbon buildup without an engine teardown? Would a soaking with AFT do any good?
Any help would be appreciated.

Thanks

optiman · Jan 21, 2015

Try doing a little water injection. At a fast idle apply water from a pop bottle via rubber tube into a vacuum port on intake. Old fix from old mechanics.

Den N Ms · Jan 21, 2015

HG in KC,To de carbon it get the engine up to temperature.Get a large sprat bottle and fill it with water.Remove the intake hose from the plenum.Start the engine and hold the throttle about 1/4 open and spray the whole bottle of water down the intake while keeping it running.repeated again
if needed.This will clean the pistons and valves of carbon.Don't be afraid to really put the water to it.I use a garden hose with a spray nozle to do it.

Den N Ms · Jan 21, 2015

Oh,You could use Sea Foam but water does a good job and is much cheaper.If after you do the water treatment and it still knocks check the knock sensor.

4play · Jan 21, 2015

knock sensor, that's funny stuff

gears · Jan 21, 2015

The knock sensor is tied in to the Engine Control Unit and retards the ignition when it senses knock.

+1 on the water injection - just spray away and don't let it stall (hand spray, not a garden hose).

Den N Ms · Jan 21, 2015

Gears,I should have said that I use a hose with a twist brass nozzle that really sprays a fine mist.

ASEguy · Jan 22, 2015

Agreed.

ASEguy · Jan 22, 2015

Chrysler has a product called CCC that works on small amounts of carbon build-up. With those numbers I suspect pulling the heads would be the only effective way. I would not try water in the cylinder UNLESS done by a seasoned mechanic since you can hydrolock an engine and bend rods if you give it too much. That might not be effective but may be worth a try. If you loosen carbon it can cause a noise similar to a rod knock which is why I say only let a seasoned mechanic do it.

Duner Wi · Jan 22, 2015

I have had success by metering in water via a fish tank adjustable bubbler metering valve and a clear plastic hose so I can see how much water is getting thru.
I try for 1 gallon of water in a tank of fuel.
Works best if going down the freeway or no stop and go traffic as the idle may be rough. I shut if off before end of drive to dry everything out.

HG in KC · Jan 22, 2015

As an update, this engine and computer control (ECM)was used in the Jeep line as well. Because of the slow response of the computers in that day, most every one bypassed them. In my case, the knock sensor connected to the ECM has no effect as the ECM is no longer hooked up to control the timing.

Tall T · Jan 22, 2015

I used this several years back with excellent and obvious results.

http://www.amsoil.com/shop/by-product/other-products/cleaners-and-protectants/power-foam/

OT: Carbon buildup in engine cylinders

HG in KC

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