Car running horrible and cutting out

[REDSLED]

Took the race car out to the local SCCA regional race and at about 3 laps into the first practice session the car starts jerking, hesitating and the RPM's are fluctating violently. Once the car hits 3000 RPMS the car literaly wants to shut down. Any thoughts? The car had plenty of fuel. Once in the pits I did notice that one of the wires to the MAP sensor was broken and was just hanging there, but we soldered it back together and replaced the MAP sensor just in case. I also installed a spare ECU and unplugged the battery to reset everyhing. Still no luck. The car will fire right up, but the idle will fluctuate more than usual and as I drive the car up to 3000 RPMS it will drive rough, but once it hits 3000 RPMS it almost dies. Is the car running in safe mode? Also noticed thatthe car is running very rich as my exhaust pipes are very black (more than usual) Any ideas would be appreciated.
Thanks

 

[dansauto]

non working 02 sensor may cause a rich condition in closed loop (after the car is warmed up) Is the check engine lite on? You really need to get a dia tool on this in order to tell what the problem is.

 

[Qualitywires.com]

May want to check the crank & cam sensor. If the car runs fine under 3k RPM and when you hit a certain rpm each time it could be one of those sensors. Cheap and easy fix.

 

[REDSLED]

Thanks for the ideas Dan, Adam.

 

[grcforce327]

Just a wild stab............Take a data scanner w/movie mode with you to the track!Should eliminate tons of guesswork!

 

[dansauto]

the last time I had a cam or crank sensor issue the car wouldnt even run. I am betting its TPS, MAP, or 02's, break out the scan tool and look at the values after the car is warmed up (in closed loop)

 

[REDSLED]

Problem solved. It was a MAP sensor issue, but not the MAP sensor itself. I'm not too up to date on the technical jargon for what we did, but I wil ltry my best to explain. Got the scan tool and the MAP sensor reading was way off. There was a wire inside the connector that was broken, but since it was being covered by the waterproof piece of rubber that goes inside the connector it appeared to not have any issues. After checking vacuum pressures off the manifold, and connectivity of the wires leading to the MAP sensor we took the connector apart, down to the naked wires and that is where we noticed the break in the wire. The MAP sensor was working properly, but the ECU was not getting the signal from the MAP sensor so it was putting the car in limp mode. We soldered the lines back together rechecked oall the connections and everything appears to be back to normal. The car is idling normal again and it is not cutting out at 3000 RPMS. Thanks for the suggestions. Amazing how such a small issue, such as a wire connection, can ruin your whole weekend. I'm buying a scan tool to keep in the trailer! Any suggestions on a scan tool? Thanks for all the ideas.

 

[dave6666]

Yeah... It seems the scan tool topic comes up every now and then and would be a handy item to have.