Peixinho

So i am interested in sending my pcm in to get tuned but I wanted to explain my personal situation before I send it in.

1998 Black Vert mn6 8x,000 miles, does not burn oil, does not leak oil. Passes emission, runs great (minus pinging problem). I have not been able to find out a lot of history on the car

I bought the corvette a year ago and I have been battling a problem ever since... I have a pinging problem. I have tried everything from higher octane gas, octane booster, new knock sensors, new knock sensors again, new knock sensor harness, new wires all the way back to the pcm, I tried decarbonizing the motor with many different products, cleaned MAF, cleaned IAT, new spark plugs, checked for vacuum leaks ...

you get the picture... Oh and I currently dont have any check engine lights... and other than the pinging problem the car runs great and gets great gas mileage

The only mod is a double cone K&N air intake (which might be causing the car to run lean)

I get slight pinging every time i press the gas pedal for just a split second and then it goes away. I also get pinging at WOT... especially near the end of the rpm band. I am convinced that the car is running lean and everything I have read points to needing a good tune.


Anybody have any other good ideas?
Do you guys think a tune will help?

lucky131969

First of all, knock sensors "sense" knock, they don't cause knocking/pinging.....

What do you know of the car's history?

Peixinho

I figured if they were sensing knock that they would retard the timing to make it go away or at least throw a code... everyone I have talked to said to start with making sure I don't have a problem with the knock sensors

I do not know a lot of history but I forgot to post all of the information on it...

1998 Black Vert mn6 8x,000 miles, does not burn oil, does not leak oil. Passes emission, runs great (minus pinging problem). I have not been able to find out a lot of history on the car

Bill Curlee

Have someone with EFI Live, HP Tuners data log the PCM. If you TRULY have KR,,,,,,,,,,,,,,,,,,,,,, it will show up and the reason its happening will/should be apparent!!!

Stop second guessing your self and have the PCM data logged. ANYONE with HP Tuners or EFI Live can do this and its FREE....

Theres a "REASON" for your issues,, NO Corvette will or have Pre-ignition (KNOCK) without a specific reason!! ARE YOU SURE,, its KR??

Ive run 87 Octane in my 02 Z without issue (I did NOT try to maximize power with that fuel) when I was empty and there was NO premium or MID Premium available at that station.

Yes, a good TUNER can Tailor your tune to eliminate issues like your experiencing IF,,,,,,,,,,,,,,,,,,,,,,,, theres NOT issues with the vehicle!

lucky131969

Reason I asked, is if you know (or could tell) if the car was previously modified, and demodded for sale. If so, you could have any tune, that is not just right for stock.

Peixinho

This is one of the reasons why I am so confused (and ripping my hair out at the same time!!!)

I do know what pinging sounds like and I can tell you that when it his 117 degrees here in az and the car was running a little warm that the pinging got much worse. Sounds like junk rattling around in a tin can, only when the car is under load...

As far as I understand it... if you run 87 octane the car will use the lower octane table and detune the car slightly so that it will not ping... I have not tried runnin 87 octane because I only use 91 chevron with techron I guess I could try that and see what happens.

Peixinho

That is a very good point... I have been thinking about that a lot lately but I have not been able to find any history on the car. The only signs of any mods would be the the double cone K&N intake... other than that everything that I can see is stock... not sure what signs to look for to find out if it has been modded

Peixinho

I have taken it to a couple of normal mechanics and they are stumped... they are unsure of what more I could do...

I guess I need to start making more friends with vette and tuner people here locally so I can get some help...


Anybody live here in the phoenix/mesa area that would like to try and help me out with my problem???

Evil-Twin

You can tell alot about the combustion chamber temperature by the plugs. Each plug tells a story about that individual cylinder. Color and condition of the electrode, and insulator are things to check. If you know what to look for. Black and gritty is rich,, white insulator is lean, detonation is revealed by pitting of the insulator, etc. All the plugs should look the same, if one plug is dramatically different, it points to a specific cylinder
Good Luck
Bill aka ET

SoDiezl350

Edmund's long term Z06 had an ongoing pinging problem which turned out to be due to a bad MAF. You have a KN intake, which when cleaned improperly are known to throw off MAF sensors. It's actually quite common. The oil in the filter can burn into the MAF and is difficult if not impossible to clean off. When the MAF element begins to fail, it will typically cause low readings resulting in a lean condition(pinging).

What others have said here is very good advice and I would like to add that in addition to EFILive or HPTuner, it's possible to log Air Fuel Ratio with a Predator handheld tuner as well.

One way to narrow it down to the MAF(although not 100% accurate) is to unplug the MAF and see if the car is still experiencing the same problem. This will throw a CEL but it will force the car into open loop mode under which it runs under a much more conservative(rich) tune.

Check out the Edmunds blog to see if this sounds familiar:
http://blogs.insideline.com/roadtest...-progress.html

http://blogs.insideline.com/roadtest...in-action.html

Bill Curlee

I did not want you to run low octane fuel but was using it as an example that the car will run on it (yes it most likely went to the low octane timing table)

I have to agree with LUCKY as you may have a previously tuned PCM with the removed MODS.

EFI LIVE or HP Tuners can tell you if there are changes in a tune by comparing a STOCK TUNE to what you have now. It’s worth checking out.

Yes a malfunctioning MAF can and will cause issues like this.. Using the data log, you can see what the MAF frequency is doing and if it properly responding to load.

4SFED Z

Im thinking your K&N filter was oiled way to much, damaging the MAF. Thats just my opinion.

RTE61

I had the same issues that i tried everything to fix with no avail.. went back to maf for recleaning and sprayed a whole can of cleaner on it just to eliminate it from the options of it being dirty. to my surprise no more ping at wot. i also was using k&n filter previously. good luck. its worth a try.

Peixinho

I have thought that maybe it was the MAF sensor so I cleaned it... maybe it is time to replace it... I am going to try unplugging it and see what happens

I am just afraid I am gonig to be throwing parts at it instead of finding out what is wrong...

I need to take all of your advice and get it data logged to try and figure out what is wrong...

I should have paid better attention to the spark plugs when I pulled them out. I think I might have saved them so I am gonna check but from what I remember they were just slightly white, dont remember any pitting.



On a side note I hope you all dont think I am romping the heck out of such a wonderful car while it is not running right. Its my wifes car and I don't think she gets it above 2500 rpm and she does not drive very far.

Thanks for all the help

4SFED Z

Borrow a MAF....

David426

I had this problem when my car was tuned.. Last winter when it was cold.. Ran great in cold weather.. As the summer neared I noticed pinging, the hotter the temp the worse it got.. Turned out the tuner had advanced the timing a bit too much.. He pulled out a few degrees of timing and things are fine

mnpoika

Especially your last comment about how the car is driven reminds me of my own situation. My 2004 6-speed roadster has pinged a few times. I concluded it was driver error - I should have been in a lower gear at the time. These cars are geared so tall for fuel economy that I believe it's easy to cause an engine overload, resulting in the pinging, while trying to accelerate without downshifting into the appropriate lower gear.

Peixinho

anybody live in az and wanna let me borrow a MAF???

Peixinho

Well i don't get to drive the car very often but i definitely drive more aggressive than she does... but i hate driving the car right now because i am worried about long term affects.

It doesnt ping so much when lugging the motor... Mostly during high rpm and WOT

dankhts

\HMMMMMMMMMMMMMMM...... are you sure it's pinging or is it your cats rattling??