Some Questions

[MattWilde 10]

Hello, just have some questions i need answers to so i can hopefully solve my cars probs.

 

1. Where does the RPM dial take it's reading from? And is it an electrical or mechanical sensor? (2 for 1 with that question :wink: )

 

2. Same question as above but for the MFA reading of the engine speed.

 

3. When i went to change my knock sensor i found the blue connector of the sensor attached to the car somehow, but can't really tell how. The loom connector is free but the actual knock sensor connector is stuck, how do i remove this?

 

Thanks for any help and answers you can give in advance

[dazzyvr6 0]

dont know about corrados but the rpm usually comes from the coil,and everything is electrical apart from some early corrados which had a mechanical speedo

[dazzyvr6 0]

for some reason im thinking it could come from the alternator

[MattWilde 10]

thanks for the quick answer, my rpm dial hits the limiter at 5500rpm, but it reads lower than the mfa rpm does, and it gets worse higher up the range. i think my poor running might be from timing that has been taken from a sensor giving out incorrect readings. all very confusing and frustrating :(

[h100vw 0]

Knock sensor is held with a 13mm bolt done up to 15lbs/ft. This is CRITICAL, overtightening them makes them over sensitive.

Gavin

[24V Renshaw 0]

The rpm is sent from the ECU to the dials, it will be picked up from the pulse on the dizzy or the coil.

The speedo sender is a hall sensor on a gearded shaft which screws into the gearbox. Its the connector near the back of the gearbox with three wires going to it.

[MattWilde 10]

h100vw, that part of the removal/refitting of the knock sensor is fine, it's the blue plug at the other end that i can't get off the car. it comes out of the loom connector but is attached to the metal coolant pipe somehow but i'm not sure how.

 

G60Renshaw, so if the dizzy or coil are broken then it would send an incorrect reading to the dial there for replacing them would fix this problem? i thought the hall sensor was inside the dizzy (or so i was told) and my speedo is accurate to the roadangel gps so it's just the rpm that's incorrect which leads me to think the timing has been set wrong and thus the poor running of the car. does this seem like a valid reason?

 

sorry for the long post, but i haven't been able to use my car since i bought it due to these probs and i really want to go for a blast

thanks again

[MattWilde 10]

h100vw, that part of the removal/refitting of the knock sensor is fine, it's the blue plug at the other end that i can't get off the car. it comes out of the loom connector but is attached to the metal coolant pipe somehow but i'm not sure how.

 

G60Renshaw, so if the dizzy or coil are broken then it would send an incorrect reading to the dial there for replacing them would fix this problem? i thought the hall sensor was inside the dizzy (or so i was told) and my speedo is accurate to the roadangel gps so it's just the rpm that's incorrect which leads me to think the timing has been set wrong and thus the poor running of the car. does this seem like a valid reason?

 

sorry for the long post, but i haven't been able to use my car since i bought it due to these probs and i really want to go for a blast

thanks again

[h100vw 0]

The ECU gets a signal from the Hall sender in the dissy, which it uses to get engine speed information. The clocks could use the coil control from the ECU to get its info. I think it is more likely to be the clocks not the ECU/dissy/hall sender at fault.

The MFA is probably more accurate than the rev counter. It will be counting pulses, where the rev counter will be using the same pulses to drive it self round. If you can, I'd borrow a set of clocks to confirm which is at fault.

 

The knock sensor plug just slides into the metal bracket I think. If not then there is probably a 10mm bolt you haven't noticed holding the bracket to the pipe.

 

Make sure the knock sensor is torqued correctly, undo it and then do it up again. Use a torque wrench don't guess it.

 

Gavin

[MattWilde 10]

gavin, thanks for the explaination and i have a good torque wrench so no probs there. With regards to the rev counter problem i forgot to say that when i took it in to be looked at whilst i had an oil leak fixed, my mechanic checked the accuracy of the rev counter by attaching a rpm reader to the ht leads to read the pulses from there. this returned the same reading as the dial does on the clocks. this is what is confusing me, the mfa says one thing, the clocks and ht leads say another, so if the mfa reads the same pulses wouldn't it match? listening to the engine i 100% believe the mfa reading, not the clock reading and i'm sure it doesn't idle at 650rpm! lol.

 

really sorry for all the questions and thanks again for the help