rev counter???? what goes???

[pablo0874]

Originally Posted by rayf3262

The tachometer is driven by an engine speed output from the ecu.

The engine speed output from the ecu is PRIMARILY derived from the crank position sensor (CKP).

If this fails the ecu/engine will continue to work, after a fashion based on the timing info from the No1 injector, but, the engine speed info will no longer be valid, hence,.. tacho indeterminacy.

As per Clive's suggestions, the symptoms you describe are consistent with a failing CKP sensor. This could be due to the sensor itself failing or bad connections/faulty connections in this area.

If it's been operating for a good while, the most likely synopsis is that the CKP sensor is operating on marginal levels,..

You could do what the dealers do, and just substitute the part to prove the problem or measure what is actually happening, which is not always easy.

The earlier comments on the effects of temperature on the CKP sensor should be given considered thought, they do (when aged) suffer more when heated.

thats what i was thinking surely the throttles sensor could not tell the tacho what speed the engine is doing i thought ,please do correct me if i am wrong because im not a know it all thats why im asking ,i was thinking the ckp sensor tells the ecu what speed the engine is turning is that right so if this was failing it would not convey the signal therefore no signal at the other end tacho.