rboorgu

I am actually in the process of doing a major tune up including plugs, wires, caps, rotors, timing belt etc. I am sure this will help the running of the car.

What I am describing though is the slightest evidence of pinging at high load from 3-5 k rpm. This usually lasts just a fraction of the second and I can tell the motor is retarding timing. I was under the impression that the ecu is supposed to do this to maximize efficiency. Maybe HKG Harrier can comment. BTW, my car was making close to 200rwhp by g-tech. I'll see what she'll do after the tune up.

Also unfortunately, I know about those apex seals first hand on my old 88 TII.

Raj

SCV8

Sounds normal,like you've just described anyways.
I was going to do a motor-vac on my car here soon,it's a neat system that cleans out the carbon and stuff left in the combustion chamber,which can also cause pinging as well.After my old plugs and wires were tossed for some new parts,I've been wondering what was left behind from before the tune up.

Lex Luthor

007, the computer will not store a code if the knock sensor retards the timing, as this can happen frequently, scanning the ALDL connector will likely not help you, unless you've stored codes from a related problem. Raj, the knock sensor's function is not really for optimization, it's more of a fail-safe. If the engine and sensors are functioning properly, and the fuel is the recommended octane, then the ECM will allow the full 'mechanical' initial timing as well as advance, without any retarding. It is only when something does not fall within spec ( a load of bad gas or inferior octane, excessive carbon buildup in the combustion chamber, advanced timing, etc, etc ) that the ECM is forced to take precautions by retarding the timing. Oh, and those Turbo II's were a great bang for the buck.

bolts_cj77

I have noticed in the past that when I have used Regular Unleaded then I get pinging at WOT. This disappears when I fill it with premium.

In Aus, I am 90% sure that regular unleaded is 91 RON, premium is 96 RON and Optimax/Synergy 8000 is 98 RON.

I generally only use Optimax/Synergy 8000. Get a lot better fuel economy too.

Bean

iTrader: (1)

Hey if you want to waste your money on a dyno just to attempt to find pinging; then be my guest. There's easier and much cheaper ways to diagnose what is wrong without spending $50-$75/hr.

But mark my words, you weren't seeing pinging itself; you were seeing the horsepower loss from the reciprocating mass being forced in another direction. Which does no good because you already KNOW its pinging; it does NOTHING to tell you what's causing it; and thats my point here; its a waste of money.

Lex Luthor

Thank you, Bean. Well said, you know your sh#t.

SSmith

iTrader: (7)

I get to put my 2 cents in!! I'm thinking BAD GAS. Could be a timing problem, but my understanding on our cars the timing is totally manipulated by the ECU. If you haven't been having pinging probs before, you probably got some bad gas. Throw a can of octane boost in an see if that makes a difference.

S

Purplexed

Greetings,
IMHO, I would go with the most obvious and simple to address first , then get more complicated.
One cause of predetonation is carbon build. For a few bucks I would buy two bottles of Techron CONCENTRATE, not the weak stuff, or Redline S-1 cleane4(if you can find it), follow directions.
I know of several Mercedes guys with higher mileage engines that had the same pinging problems. This cured the problem.
Go here first , then follow the troubleshooting path toward addressing all that can affect the pinging.

machinegt

can someone help to describe how loud the pinging sound usually is? i just wanted to know if it was like really obvious, or maybe sometimes very hard to detect because of how quiet our engines are.

SupraCoup3

If you read earlier in the post, they described it as marbles in a tin can, and I'm sure you can pick it up because It'll sound different than normal -- That kinda stuff usally jumps out and grabs you (well maybe not GRABS you but you know what I mean)... but I may be wrong, it's been know to happen from time to all the time

errr I mean time to time



PS You may be confusing it w/ the pinging of the heat sheild which has been addressed B4, correct?

007lexus

hey lex and/or keith,

Got my car checked this weekend for the pinging noise. My mechanic and lexus mechanic told me that the timing on my sc400 is not adjustable cuz its computer adjusted. I asked to have my timing checked but was told this. Not sure what else their is to be done.

thanks,