civic vx - occasional pinging, looking for cause

[dlb]

my wife's VX has been running great for several months since i finished doing the input shaft bearing, clutch, brakes, etc, but the other day it was pretty hot out (30* C, or 90* F for you yanks) and i noticed a bit of pinging when my dear wife would lug the engine. it was minor but i noticed it, and i know my wife well enough that she is not likely to change her driving habits, so i'd like to prevent any ping if possible. don't suggest ditching the wife, she's pretty good besides her driving style, haha.

i went through my list of ping suspects and everything checks out so far. ignition timing is correct, proper heat range of spark plugs, no vacuum leaks, the temp is rock steady at a bit under halfway on the gauge, and oil and coolant are full with no noticeable consumption. i have never had the head off to inspect the combustion chamber but i guess carbon buildup could be a possibility. i did a compression test a few months ago and the #s were

1 - 200 psi
2 - 205 psi
3 - 200 psi
4 - 200 psi

those seem a little high and also suggest carbon buildup so i'm considering pulling the plugs, filling the chambers with seafoam, and letting it sit for a few days before driving it again. does anyone have any suggestions on other routes for easy combustion chamber cleaning, or anything else i might want to investigate as a possible cause of ping?

thanks in advance.

[Ecky]

I'd try pulling the ignition timing 1-2° and see if it helps before putting Seafoam in. You'll still be within factory specs.

[user removed]

Did you clean the EGR passageways in the intake manifold.

I would try some BG44K for combustion chamber cleaning (pour it in the tank).

How about one lousy tank of gas?

I'm not too keen on pouring seafoam into the combustion chambers. If I knew that was the problem, take a paint gun and fill it with water. Feed the highly atomized water into the intake to steam clean the carbon deposits.

regards
Mech

[dlb]

where are the EGR passageways in the intake manifold?

never heard of BG44K but i will look into it.

i've had good results with seafoam, both by adding it to the oil to clean the oil scraper rings and letting it sit in the combustion chamber to clean the chamber out. why are you hesitant about it? i'm not being critical of you, i am legit curious and wonder if there's something i should be aware of.

i have heard of steam cleaning the combustion chamber with water but have been warned that it can go badly if one is not careful. i'm not sure how or why it could go badly but that's what i was told. i don't have a paint gun, is there another way to do it? what about a small spray bottle? would the water droplets still be too large?

i will probably wait to see if the problem persists on future hot days. if it does i will try retarding the timing slightly, and if that doesn't work i'll contemplate the above approaches some more.

thanks!

[user removed]

BG44K is (or was) the only additive apporved by Mercedes Benz when I worked for them a long time ago. I used it in my ranger as well as seafoam to get rid of light load pinging.

I'm not a great fan of pouring stuff into combustion chambers, unless you use extreme caution to preveny a liquid lock.

The VX egr passageways are under therunners in the intake manifold, there are several plugs that you would need to pull out and then tap them and put threaded plugs in to cover the holes. Blocked EGR passageways are a principle cause of pinging since you are not getting the proper amount of EGR in the combustion chambers which reduces peak combustion chamber temperatures, reduces NOX emissions, and allows more adbvanced timing without pinging.

We used the spray gun-water treatment on Nissan 280ZXs, the last versions made had flat top pistons and part of the cylinder head combsution chamber was also flat. There was 1 MM of clearance between the piston and head over about 30% of the piston surface. I would pull the air cleaner off, clamp the throttle to hold it at 2k RPM. Clamp the trigger on the spray gun and adjust the spray pattern and volume. Then I just let it run until it had consumed a quart of water, rinse and repeat. Looking into the plug hole you could see how clean it got the top of the piston and the heavy carbon knock went away.

I once towed a car 180 miles to put an engine in it (other shops diagnosis), ued the spray gun technique and it was good for another decade. The owner always came to my shop after that, since he was already one engine ahead of the competition.

regards
Mech

[dlb]

great info. thanks, mech. i have more questions for you now, though.

i just had to read up on liquid lock, aka hydrolock, and realized i have heard of it before. i don't think i would encounter it with the way i have seafoamed CC's before. when i have done it, i unplugged the dizzy (to prevent sparking), pulled the plugs, poured seafoam in until it reached the spark plug holes, loosely put the spark plugs back in just to cover the holes, closed the hood, let it sit for 1-2 days, opened the hood, pulled the plugs, and cranked the engine a couple times. this shot the dirty seafoam out (in hindsight, i would have a friend hold a rag over the spark plug holes to catch the stuff). then i plugged the dizzy back in, put the spark plugs back in, and drove the hell out of the thing for 5 minutes, blowing black and grey and white smoke all over the place. i think i did it on two separate vehicles with no problems. i assumed that cranking the engine with the plugs removed would be sufficient to prevent hydrolock, no?

would a plugged EGR not throw a CEL? i don't know if there's a sensor that measures resistance in that system or not. the car throws no CELs but i agree that any 20-yr old car with unknown engine history should probably have the EGR thoroughly cleaned out.

regarding the steam cleaning, what do you mean by "Then I just let it run until it had consumed a quart of water, rinse and repeat"? what are you rinsing, and with what? it sounds like i could accomplish a home version of this with a simple spray bottle so i might try that.

thanks again.