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Rpm Stuck On Tacho

shotter

By shotter,
in Engines & Forced Induction

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shotter Rising Star

shotter

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As usuall i get a problem that is sometimes there and sometimes not.

Sometimes the rpm will rise and fall as normal.

Other times when you turn the key to on (with the engine off) the rpm will jump to 500rmp and stay there. Then when you start the car it will just sit around 3000 or 4000rpm and not move, Even at idle. Then it may very slowly move between 4000 and 3000rpm, then even down to 2000rpm. And then it may just start working as normal.....

Now i have connected my laptop to the ecu while the problem is happening and the rpm is perfectly fine.

HELP PLEASE

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260tech Proficient

260tech

Posted
Posted
As usuall i get a problem that is sometimes there and sometimes not.

Sometimes the rpm will rise and fall as normal.

Other times when you turn the key to on (with the engine off) the rpm will jump to 500rmp and stay there. Then when you start the car it will just sit around 3000 or 4000rpm and not move, Even at idle. Then it may very slowly move between 4000 and 3000rpm, then even down to 2000rpm. And then it may just start working as normal.....

Now i have connected my laptop to the ecu while the problem is happening and the rpm is perfectly fine.

HELP PLEASE

Hi there, if the rpm signal is clean from the source or somewhere downstream of the source as displayed on your laptop then perhaps the next area to check is wiring loom after that.

No doubt you have checked all connections, made sure they are clean (as in not corroded). Weird intermittent faults can be due to corrupted primary signal/power/earth paths for the circuit, whatever the item or system is, particularly if it has evolved rather than "happened" after some other work has been carried out. Next thing to check (if it was me) would be for dry joints on combination meter circuit board.

My 2c

Good hunting, GW

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shotter Rising Star

shotter

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The only things that happened before this started was i got the car tuned and the CAS was swapped with another one to try and trouble shoot a problem we were having, Swapping the CAS didn't fix the problem we were having but the other one was left on the car. A few days later i started noticing this problem

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260tech Proficient

260tech

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Swap a dash cluster with someone, see if it's the problem.

You said;

"Swapping the CAS didn't fix the problem we were having but the other one was left on the car. A few days later i started noticing this problem"

Still got original CAS? Worth a shot I reckon although I have no idea were the source tacho signal comes from, never had to dig it up............yet.

Cheers GW

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