Does anyone have any idea what would cause the engine to not run over 3000 rpm? It seems like it is hitting the rev limiter.

Thanks, Mike

 

Wonky MAF putting you into limp mode? Are you throwing any codes?

 

It's Jim Child's car and started this in the 4th lap of the race today at Putnam Park. No check engine light but I dpn't think they checked for codes. It is very consistent at not running past 3-3200 like it is is hitting a rev limiter. No problem driving around the paddock or onto the trailer but nothing past 3k.

 

I had a car years ago that did kind of what you describe. It turned out that the spark plugs were all caked up with crap to the point it almost quit running. Probably not what you got going on there, but thought I'd throw that out just in case.

 

Racing usually keeps the plugs pretty clean as there isn't much low speed running! I'm sure he will check them.

 

MAF passed visual inspection and plugs are clean. We still need to check for codes. The car was running great, posting pole position and fastest race lap before deciding it didn't want to run past 3K.

 

Sure sounds like "limp home" has been activated. IIRC, a number of things can invoke it (knock sensor, lacking MAF signal, etc.). Any chance someone has a Bosch Hammer at the track? Else, start unplugging and reconnecting the sensors you suspect and can find. Could be nothing more than wear in 20-year-old wiring harness.

Likely, it's a "soft" code, so once the issue is found and corrected, it should reset or clear via ignition off / on cycle.

Good luck!


Dave in Chicago
'92 968 Midnight Blue, E-Stock #662

 

Knock sensors usually retard the timing by 6 degrees, IIRC. Limp mode is when the MAF is wonky and the DME runs only two injector pulse widths. Again IIRC, one test is to unplug the MAF and see if the engine improves.

 

I had a sorta similar symptom when my throttle position sensor died on a 924s. I couldn't get the revs past about 3k but it was definitely related to throttle position.
Jon

 

I had that on my 911, it was just the MAF.

Let us know what it ends up being too please and good luck.

 

I have a spare, fresh MAF if it's needed.

 

Did you find the gremlin ?

 

Yes, Jim was having a great weekend, a couple of seconds faster than I could do, was wondering what happened during the race. PiM Jim on the side to find out what happen.
Please let us know the out come.
I think I'm slowly building a whole other car in spare parts that I keep putting in the trailer :-)