The following has happened twice to me on the same sweeping left hand highway entrance when I accelerate up the ramp....The tack jumps up 2000 rpm over what it should read and stays about 2000 high until I restart the car and then everything is normal again. I would just swap the instrument cluster but I had this one programmed to the correct mileage of my car and also had the face plates all converted to yellow so I don really want to replace it long term. Another problem is I am about ship the car to Laguna seca for a bucket list track event in november with some other firends. I don't want the tach giving me the wrong readings....Any suggestions on what the issue may be and is it even fixable.

 

The Crankshaft Position Sensor (CPS) is what reads your engine RPM and sends data to the Tachometer. Curious it would not throw a code as I know the CPS is famous for creating issues for owners when they fail. They are pretty cheap and you should be able to get a new one before your track day. I hate recommending throwing parts at a problem without a diagnosis first but it would be a cheap thing to check with your fingers crossed..

 

I concur on the CPS. If it were me I would buy a new one and install. Good place to start.

 

Try checking the RPMs against an OBD-II dongle and phone app. That would tell you if it's in the cluster or a deeper problem.

 

Great suggestion guys...I will get with my mechanic and discuss

 

Ordered a CPS and we will put it in this weekend...hope that fixes it.

 

I don't think it's the TPS. That sensor either works or it doesn't when it doesn't the engine shuts off. But if it is old, it is worth replacing. If you do, cut the wire open and peel back the outside insulation that covers all the wires and then, check out the insulation on the individual wires. Mine were cracked beyond belief.

 

Wyovino's suggestion is really excellent because I just remembered you have your Dundon Frankenporsche which likely needed some trickery to get the stock instruments to talk to the M97. There could be something funky going on with that communication. I'm glad you got the CPS as a safety since it's cheap and returnable, but see if your mechanic can take a look at communications between the instrument cluster and the car. I'm wondering if your sweeping left causes some wires to come into contact due to inertia that causes some funkyness (technical term.)

 

So here is the update....probably the cps magnets picked up some metal shavings from the rebuild or being open for several months...looks like these particles could change magnetic readings....so i think your suggestions were a good place to start...will see if it happens again.

Thanks again for your helps....i will report back if anything changes

 

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Something is shedding metal in the clutch area. Is the started properly engaging?

 

Starter seems fine....my guess is that since the car was completely disassembled for 9 months and the engine and transmission were procured used separately that it was likely some debris that was already there. Will keep an eye on it though.