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.

[rayf3262]

Originally Posted by pablo0874

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.

You pretty much have it summed up, so it's either down to test & check or substitution.
The CKP looks like it could well be the root cause, but until you have either checked the signal from it or swapped it out..................?

Anyhow, stuff the price of two liters of fuel in the membership box, it will make sense.
Cheers

[pablo0874]

Originally Posted by rayf3262

You pretty much have it summed up, so it's either down to test & check or substitution.
The CKP looks like it could well be the root cause, but until you have either checked the signal from it or swapped it out..................?

Anyhow, stuff the price of two liters of fuel in the membership box, it will make sense.
Cheers

am i right in thinking if i remember its the last two pins on the plug that you join together to get the codes??

[pablo0874]

Originally Posted by makeitfit

It could be the ecu
Codes will help though. Have you done them with a reader or the safety pin method? If you have the code number, we can translate

hello again pulled the codes from the plug today on the flashing mil light,
it gave ne 47 and 11 ,so i then cleared the codes using the methiod in the download , and it displayed 55 no codes ,
ran it for a bit and then checked codes again and only giving me 11 now but i think thats because i ran it stationary and did not drive it but 47 on the chart is pointing at ckp sensor and 11 is injection sensor ithink., do you think the best way forweard would be to reolace the ckp sensor???then see what goes

[pablo0874]

where is the ckpm nsensor as the motor factors said it dont exist on my car , i know where the cam sensor is at the top behind the belts but whers the ckp