RPM Limited

[speedracer23]

This may fall under the FI section. Mods - please move if this is the case.

1991 MT CTSC - comptech supercharge (race car)

Under racing over a period the car will decide to go into limp mode. Requiring a power down (ignition off and then on). The problem I am seeing is there is a 6000 rpm limit cut.

No CEL comes on. VTEC engages and then the rpm limit cuts in right away.

Any suggestions as to what to trace for?

**
Reading on the forum seems like there is discussions with possible bad coils or a possible bad VTEC solenoid

 

[Briank]

I would check for a code even though you are not getting a light. RPM limit will kick in if the engine temp is to low or to high. Check connections to or replace the engine temp sensor for the ECU.

 

[Larry Bastanza]

Also check your coolant level. I had a car recently doing this same thing. The coolant was low, and the coolant temp sensor was loosing contact with the coolant, giving false readings, and this led to very strange RPM behavior like you desribe.

Unfortunately this came down to needing head gaskets.

Regards,
LarryB

 

[speedracer23]

No codes but I will check into the engine temp sensor.

Thanks for the suggestion - Still a noob at this engine.

Also check your coolant level. I had a car recently doing this same thing. The coolant was low, and the coolant temp sensor was loosing contact with the coolant, giving false readings, and this led to very strange RPM behavior like you desribe.

Hmm didn't know there was a sensor.

 

[Briank]

Hmm didn't know there was a sensor.

FYI, There are 3 temp sensors, one for the fan control one for the ECU and one for the gauge.

Having a service manual is always a good idea.

 

[Larry Bastanza]

Having a service manual is always a good idea.

Sage advise

LarryB