Car is cutting out- Help!
08-24-2005, 01:39 AM
#31
Rennlist Member
Thread Starter
The misfire is gone but the problem is not fixed!
A bit of background. The car is a 951 track car that I run in SCCA ITE class. Prior to the Watkins Glen race in July the car developed a bad misfire. At about 4,200 RPM and at full boost the engine would cut off with lots of backfire. As soon as I backed off the throttle, it ran fine. I decided not to race and instead I dropped the car at a “highly respected” and as it turned out, very busy independent P-shop.
The car was in that shop for exactly four weeks. While there, I had it street-registered to make it easier to duplicate the problem under load. In between of mostly sitting idle, every possible related component was allegedly tested, including static and under load DME/KLR, primary electrical, wastegate, TPS, fuel pressure and volume. Then all of a sudden the misfire was gone!
The car is running fine again but the problem was not actually diagnosed. So I’m not comfortable towing 5+ hours to the next race only for the problem to come back. The owner and chief P-tech seemed to be honest. He followed the factory testing regiment but I’m not sure whether this is good or not. Actually the only parts replaced were the cycling valve and the temperature censor, which made no difference.
I’m pretty frustrated with the car being in the shop for four weeks, in the middle of the racing season. If I had to take the car back to this shop I wouldn’t want to deal with this again. As I said, the owner seemed honest but he tends to over commit and perhaps under deliver in my opinion. When everything was said and done I was $925 poorer.
I thank everyone for their input. I hope that this is the end of this chapter but I somehow have the feeling that there is more to come.
A bit of background. The car is a 951 track car that I run in SCCA ITE class. Prior to the Watkins Glen race in July the car developed a bad misfire. At about 4,200 RPM and at full boost the engine would cut off with lots of backfire. As soon as I backed off the throttle, it ran fine. I decided not to race and instead I dropped the car at a “highly respected” and as it turned out, very busy independent P-shop.
The car was in that shop for exactly four weeks. While there, I had it street-registered to make it easier to duplicate the problem under load. In between of mostly sitting idle, every possible related component was allegedly tested, including static and under load DME/KLR, primary electrical, wastegate, TPS, fuel pressure and volume. Then all of a sudden the misfire was gone!
The car is running fine again but the problem was not actually diagnosed. So I’m not comfortable towing 5+ hours to the next race only for the problem to come back. The owner and chief P-tech seemed to be honest. He followed the factory testing regiment but I’m not sure whether this is good or not. Actually the only parts replaced were the cycling valve and the temperature censor, which made no difference.
I’m pretty frustrated with the car being in the shop for four weeks, in the middle of the racing season. If I had to take the car back to this shop I wouldn’t want to deal with this again. As I said, the owner seemed honest but he tends to over commit and perhaps under deliver in my opinion. When everything was said and done I was $925 poorer.
I thank everyone for their input. I hope that this is the end of this chapter but I somehow have the feeling that there is more to come.
08-24-2005, 02:14 AM
#32
Rennlist Member
Sounds like a harness or electrical connector issue. If so, unfortunately, it may resurface. I fought a glitch for a long time until I finally found a cracked reference sensor connector.
08-29-2005, 10:33 PM
#34
Rennlist Member
Thread Starter
BigTurboFan,
My problem was never fully diagnosed but the car runs fine now. The last thing that tech who worked on did was to adjust the TPS from rich to lean and back a few times. I'm not sure if that had any effect or it it was a coincidence.
Even thought your engine might seem to be running rich, these engines can usually handle it. Any black smoke coming from the exhaust? I read your thread and it sounds to me like an electrical problem. Make sure that the basics are OK such as coil and plugs. If these are Ok my next guess will be the TPS.
Good luck. Let us know what you find out.
My problem was never fully diagnosed but the car runs fine now. The last thing that tech who worked on did was to adjust the TPS from rich to lean and back a few times. I'm not sure if that had any effect or it it was a coincidence.
Even thought your engine might seem to be running rich, these engines can usually handle it. Any black smoke coming from the exhaust? I read your thread and it sounds to me like an electrical problem. Make sure that the basics are OK such as coil and plugs. If these are Ok my next guess will be the TPS.
Good luck. Let us know what you find out.
09-26-2005, 03:23 PM
#35
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there are many similar posts. check this one;
https://rennlist.com/forums/showthre...cle+valve+test
have you actually tried replacing the entire KLR unit? or just the chips? the unit itself could be fried.
https://rennlist.com/forums/showthre...cle+valve+test
have you actually tried replacing the entire KLR unit? or just the chips? the unit itself could be fried.
