Hoping for some help finding pinging on my 94 Z with A4 and 3.23's with 109k on it. It rattles pretty bad as you lean into it. It runs ok at light throttle. I did an Opti, plugs, wires, tb water bypass, and filters last year and it came to life to the tune of 13.70's all stock. It's my wifes car so it didnt get beat too much. The cars been at my buddys shop for months and he cant find anything obvious, no codes, he says knock sensor is ok. He even replaced the opti again with a GM because we doubted the quality of the rebuilt we used. Any ideas, I couldnt find anything with a search. Is this an unusual problem? Thanks in advance, springs coming....someday here in NY.

 

What octane gas are you using? They will ping a bit on low octane. Try some octane booster from your local auto parts store. I would try the basics since you have already done most of the normal maint.

 

Fuel is OK. Thought I saw someone say that a clogged or bad fuel filter could cause a lean condition and result in a knock condition, any thoughts? The car is unuseable until I can figure this out. Thanks in advance.


Jack

 

"It rattles pretty bad as you lean into it. It runs ok at light throttle."


I own a 94Z as well. What rattles pretty bad? Engine, whole car, what area is the noice coming from? Is light throttle say just normal driving around, no punching on the gas, no quick and sudden turns or movements? Just trying to find out more about the noise because there are specific conditions that relate to opti failure/ing. Ok

-Mike

 

If you are sure the knock sensor is good, the signal does indeed get to the PCM and the PCM is good. (there is a lot that can go wrong here such as wires & connectors) Than it's worth 10 bucks to run 2 cans of Seafoam through the intake. Put one in the tank and have your injectors cleaned.

High amounts of carbon build up can cause detonation. $10.00 is cheap investigation money. Takes 5 minutes to do.

Incidently, has the problem just showed up? Was any recent work done? Did you own the car since it was new? If not, is possible the previous owner wasn't real good at changing the air filter? This causes a rich condition and carbon build up. Has your fuel filter been changed regularly? Lean condition can cause detonation very easily. Again an easy item to change.

I know it must be a hassle with 2 drivers and one of the cars down. Good luck to you.

 

No, the problem just popped up out of nowhere. It used to run really great. It doesnt miss, it just pings really bad as you lean on the gas, not hammering it. My buddy has a sneaky suspicion its a connector or wire somewhere too. That should be a pain in the ****. I think I need a '70 LT-1.....with points.

Jack

 

You might want to put a scanner on it, and check for knock retard. If you think about it, a correctly functioning knock sensor/PCM will pull out up to 15 degrees of timing in response to knock, rendering it virtually inaudible for the brief instant it takes the KS to pick it up. If you can hear it rattling pretty bad, either there is a huge amount of knock, beyond what the PCM can control with timing retard, or the PCM isn't pulling the timing.

A scan would show you what's happening, and perhaps help you prevent damage to your engine.