VVT and timming

[andyg]

Hi guys,

for the past year or so I have been trying to fix a problem with my GTi, its 25bhp low on power.

After lots of money being poured into it the garage has found the problem:
the VVT isn't functioning. The garage has been able to overide the VVT actuator solenoid and force it to switch on and they say it does work, but the ECU wont switch it on and off.

Has anyone had any dealings with this kind of problem? The garage says the car is putting out a fault code which says the crankshaft sensor and the camshaft sensor are giving conflicting readings. The timming is spot on aparantly.

If anyone is breaking a GTi let me know because I want the top end.

cheers

andy

[Dangerous Dave]

It might be worth replacing both the crankshaft and camshaft sensor if this hasn't already not been done. I would assume the ECU is chosing not to activate the VVT due to these conflicting readings from the sensors,if the senors are not at fault the next port of call would be the wiring back to the ECU especailly checking for bad earths. If this turns out OK I would attempt to swap the ecu with a known working one, easy enough to do to rule it out.

If all that still returns the same results the only other thing could be what ever the sensors take there reading off could be damaged. i.e mark on belt/pulley or a cog if its ran off one etc.

Hope this helps.


(if the sensors have been changed I would still attempt to at least swap it with a known working one as its not unknown for a new sensor to be supplied faulty)

[andyg]

Thanks for the response dave,

The crankshaft and camshaft position sensors have been replaced. The car was hooked up to VAG COM and apparently the sensors are outputting values over the manufactuers tollerance.

According to BOSCH, the timming values for the crankshaft should be between 76 - 90 and for the camshaft to be between 27 - 31, the readout the car was giving were 92 and 33 respectivly. So the garage thinks that is why the ECU isn't triggering the VVT. BUT they don't know why the sensors are outputting higher values, perhaps broken VVT mechanism?

According to the garage, replacing the ECU is a pretty expensive job.

[Dangerous Dave]

What you want is some nice person near by with a Polo GTI, that you can swap the parts over etc and take readings from there sensors to compare. I doubt its the VVT mechanism if the garage are able to get it working by manually activating it.

Does seem strange problem. If anyone with vagcom and a GTI is on here it may be worth them taking readings from the senors to see what they are getting.

[andyg]

agreed!

The garage suggested that perhaps there is somthing worn within the sprocket that turns the camshaft. causing it to be out by a couple of teeth.

If anyone on here is willing to meet up with me and compare readings from VAG COM or if anyone can take their own timming readings I will pay you.

If somone finds a solution to my problem there is money in it for you.

thanks

andy

[Si_GTi]

Andy, I potentially have got the same or a similar problem with my car. Will collect some readings from VAG COM and let you know the results