Hi guys, got a problem with my magna, TJ 2002 exec 3.5, 5 speed manual. ralliart cams, rpw intake.

the problem is i have piston pinging that comes in around 3500rpm at 3/4 to full throttle running 91ron, if i run 98ron there is no piston pinging, ive owned the car for 2 years, only last year when the problem started ive had to start runing 98ron, prior to this ive only needed to run 91ron. i also have around 30% loss of power, and lastly, i have very low idle, sits around 400rpm. fuel economy appears ok, sits around 7.5l/100k highway. had a full timing kit put in last year by a mechanic, 1 month after ive had all these problems with my car.

now things ive done.
Changed the fuel pump and that little filter
Changed the fuel filter
Had the tank cleaned
Injectors cleaned
Checked/replaced all vacuum lines.
cleaned and re-kitted the throttle body
compression test 218-220psi/pot

one thing i have noticed is the timing belt first thing in the morning before i start the car is nothing but slop, i can almost lift the timing belt off the cams, but the second the motor turns over it tightens up. i shall be pulling the timing covers off today and seeing if the belt has skipped a tooth. to me it sounds like all my problems are timing related (too far advanced) but any other thoughts would be great guys.
thanks for listening to my story, and im looking forward to hearing about any other suggestions guys, this is driving me nuts.

It's normal for the cam belt to appear loose with the engine off.
If it jumps a tooth, that cam will be retarded, not advanced.
Checked the ISC?
Try the E10 fuel, 95 octane IIRC.

Was the timing kit put in at the same time as the cams?

sorry for the late reply guys, just checked the timing marks and all is good, belt was actually tight before i started the car this morning. checked the ignition timing and its registering between 8-10deg before top dead center, so thats in spec. jimbo the cams were put in 2 years before the new timing kit. madmax using higher octane fuel is fine, it actually stops the piston pinging, but i never had to for a year, and it still didnt solve my power lose. so, im back to square 1 now. lose of power, piston pinging, and low idle, isc is fine btw. i just keep coming up against brick walls on this. And yes, the car went to a mechanic, spent $300 to be told "We dont know". thanks for the replies guys

Check your spark plugs. Compare all 6 and if there is a difference, there is your problem cylinder. You can then check compression pressures, spark plug leads and the plug itself. That may foind the cause of loss of power and pinging.

Check your spark plugs. Compare all 6 and if there is a difference, there is your problem cylinder. You can then check compression pressures, spark plug leads and the plug itself. That may foind the cause of loss of power and pinging.

all spark plugs are exact same colour, and not running lean? compression tests were done a couple of months back 218-220psi/pot. leads are 12 months old, all 6 spark plugs 6 months old. i have some surging?? in low revs, could be misfiring???. would an ignition coil be responsible?

Scan for error codes.

Scan for error codes.

Yeah that's happening on Monday

well scanned for errors and nothing showed up, but even the mechanic this time believed me after he took it for a drive he heard the piston pinging, and the obvious low idle. he then went straight to the o2 sensor and did a test on it and he said it was not functioning properly and it would more then likely be causing all my problems. he did say the car is running lean as well, just higher octane fuel was masking the problem. i didnt suspect the o2 sensor before because it was new, rockauto new, but still new (12months). i still dont trust a lot of mechanics here in Mackay. could this really be my issue, a funny o2?

As I understand it, when narrowband oxygen sensors die they normally signal a lean mixture so that the ECU richens the mixture in response (hence poor fuel economy etc). That said, there is the possibility that it might read rich causing the ECU to lean the mixture.

To check whether the sensor is causing the problem, disconnect it and reset the ECU (disconnect & reconnect the battery, very important as it clears the fuel trims). Then drive the car to see whether it behaves differently. If it runs better with the oxygen sensor disconnected than with the sensor connected, the sensor is more than likely to be bad.

Other than that, you'd need to look at anything which might be choking the fuel supply or allowing additional air into the intake after the MAF - though I see you've already tried a lot of things in this area. Pinging might also be due to a weak or inconsistent spark too; it can also be a result of too much ignition advance but with a stock ECU and correct timing belt fitment I can't see how that could happen.

Just to bring this thread back up and call it 3/4 solved, i bit the bullet and bought a genuine O2 sensor and fitted it the other day, reset the computer and all, and the car is almost back to normal, no piston pinging, massive amount of power back, idle is all good, just a little intermittent surge??? down low rpm. Waiting on a new coil to arrive and i suspect that should make an improvement.

I would like to thank you guys for all the help

Glad to hear that you're most of the way there...