I was at Hockenheim last week and was testing my new racing suspension settings at HockenHeim racetrack..I ran real well that night, blew by a Porsche GT3 and passed a Porsche 959 in Sachs Curve....more of that to be posted in the kill section. Anyways, the next day, I ran it out some and I get some hesitation at partial acceleration around 3000RPM or so, I run it WOT to see WTFO and it blows a lot of rich exhaust out the back, runs a little smoother, but some misifre as well, as I decelerate the car shakes and shudders due to the misfires. I pulled out my Predator scan tool and check the computer to see what I have...I have P300 (Random Misfires)and 2 oxygen sensors not working correctly,, something about low circuit.

I made a run to the dealer to see what they can find out and they verified with TECH II that I have a misfire in almost every cylinder! I don't understand why? I have headers and Kool Sox coverings on the plug wires, The dealer changed the wires and it is still doing it. The dealer says that it is the heat from the headers. I checked all of the plugs to see if they were fouled and none of them appeared so, I check the gap and verified a .040 on each plug. I called the dealer again to see if we can change the injectors and coil packs. I am clueless as to what may have caused it to do that. I have a major race next weekend at Hockenheim against some Vipers and Corvettes http://www.scci.ch and I will not be able to race with this problem I plan on getting some temp plugs form some other C5 here to test my plugs and see if they went bad on me somehow. Help, this race is this Saturday. This happened before I put my cam in also, so I am not sure. Is it a lean condition. Will LS1 edit help me fix it?

Thanks,

Nick
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Breathless longtube headers / LAPD carbon Fiber power duct / VaraRam Intake / Movit Big Brake Kit Front and Rear 345MM Rotors (PORSCHE GT2) GM "HotCam"/ C5R timing chain /RD Motorpsorts 5 point Harness Bar and Camera Mount / Ecklers Partition / Loyds Z06 Floor Mats/ Grannateli MAF/ Predator Diablo Power Tuner / Hurst Shifter / T1 Sway Bars and Metal end links/ 04 Sachs Shocks

 

I noticed you said that the scanner told you 2 O2 sensors were not working correctly, yet you never said anything about having those checked/replaced.... that sounds like the first place *I* would check.

Mike

 

If both O2 sensors aren't happy it could be a blown fuse (check the simple stuff first) or it could be the rich condition caused by the misfires (most likely).

It is likely ignition, not fuel, and not something LS1Edit will fix. For sure not the fuel injectors.

So if the fuse is good, check the electrical connections and connectors to things that are common to all cylinders in the ignition system.

Good luck, and this is just my .02, other opinions will vary.

Les

 

Do you still get the O2 codes?

With misfires in every cylinder you are dealing with a common cause versus one bad coil pack/injector. Check the components common to all.

Have you cleared all the codes?

Check your wiring harnesses carefully - good luck..

 

Computer controlling ignition or coil packs?


[Modified by 3window, 5:11 AM 7/6/2004]

 

Did you ever find out what caused the problem?

 

I know this is an old thread, but I currently have the same issue.

My 'Vette ran fine at a Dec 04 Road Atlanta track day weekend and remains so as a daily driver, but I'm unsure as to what's causing my P0300, P0140 and P0160 codes.

Installer says the P0300 code was an "idiot code" due to my aftermarket cam and should have been erased in the computer tuning he had done.

I've yet to get the 'Vette down to him for a total look-see. (It does seem to run a little rich.) So, the 140 & 160 codes are still a mystery.

Thanks in advance for the feedback.

 

I would give the 02 sensors a strong look. If they're not up to speed your gonna have problems. Just my thoughts. Good luck.