sleeping_forest

Hey HTers... I did a search on engine pinging already and read through most of the applicable threads, but I didn't find any concrete advice that's been of help so far.

Here's the situation:
Car - 1992 Civic Si (D16Z6), 220000 kms; no engine mods.
Prob - Engine pinging (metallic rattling noise) under acceleration at low (sub-3000) rpms. I'm assuming it's pinging due to pre-ignition (a friend also came to the same conclusion while sitting in the car), and my mechanic has told me that it's likely due to high cylinder head temperatures.

My distributor died last summer (bearing was shot) so I put in a rebuilt one and the car ran fine, but it was pinging. I don't have a timing light (it's on the to-buy list lol), so I retarded ignition timing until it stopped pinging and then took it to my local mechanic a while later to get it timed precisely.

About 3 weeks ago, the engine started pinging again so I tried retarding the ignition timing by rotating the distributor, but that wasn't sufficient to eliminate the noise even after rotating the distributor as far as possible.

I moved to a colder heat range spark plug (NGK ZFR5 to a ZFR6, which is the only other spark plug listed for the D16Z6 from NGK that I could find), but that didn't solve the problem either, although the noise seems to have been reduced somewhat (not sure if this is true or if the spark plugs are just a placebo lol).

My mechanic also suggested that there may either be something wrong with the engine cooling system (although my thermostat seems to be operating fine, the engine warms up normally and the radiator and hoses aren't visibly damaged), or that there is excessive carbon build-up in the cylinders that needs to be removed (using a motor-vaccum to clean out the head, which I have no experience with, and which he told me is a service that costs about 200 CN).

With regards to gas, I usually use 89 octane (Chevron), but I put in about half a tank of 91 octane after retarding the ignition timing failed to solve the problem. The higher octane gas didn't seem to affect the pinging that much either, though.

So, just wondering if anybody has any other (cheaper) solutions that I can try before letting the mechanics take a crack at it. Thanks for any advice! Please let me know if there is any additional information that could be of help!

_Cyclone_

It sounds like you've tried almost everything that I would try so far, almost. Before taking it in for service and paying lots of $$$, buy a can of Seafoam to clean excess carbon out of the combustion chamber. You can get it at Partsource or Canadian Tire. This might help the problem. Good luck bro

00Red_SiR

Yep, your problem isn't to do with cooling , it's carbon build up in the combustion chambers that causes the pinging because it effectively raises the compression ratio by physically reducing the size of the combustion chamber. I would use seafoam on the motor and that should fix it. If running high octane gas and retarding the ignition all the way back didn't stop the pinging I would check to make sure you don't have any loose heat shields or anything rattling around the exhaust. Normally those 2 things combined would certainly stop the pinging from carbon buildup, so you wanna make sure that you're not mistaking a rattle for pinging.

PS- tell that mechanic to go back to school and relearn the basics..

sleeping_forest

Hey guys (fellow Canadians ^.^), thanks for the advice so far! I'll definitely go to CT and look for SeaFoam ASAP.

Btw, my mechanic is actually quite competent, he's ran his own garage for at least 20 years, passed down from his dad. The advice he gave me was in response to me asking what to do if the engine pings (he never test drove the car or anything)... plus he never charges me for tips or small stuff hehe so dun get the wrong idea, he's a pretty cool guy.

Anyways, thanks again for the advice!

00Red_SiR

The main reason I made the comment about the mechanic is because it's basic mechanical knowledge to suspect carbon buildup in a high mileage engine, to cause pinging. He suggested high cylinder head temperatures??? which is very very unlikely.

JDM_Ej

well... if the compression is raised, it would increase the temp in the cylinder head. In theory.

00Red_SiR

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDM_Ej &raquo;</TD></TR><TR><TD CLASS="quote">well... if the compression is raised, it would increase the temp in the cylinder head. In theory. </TD></TR></TABLE>

That's not what the mechanic was getting at though, he was suggesting it had to do with the cooling system which is way off.