Vr gearbox ratio's/diff issues?!

[Son_of_Thor 0]

Recently bought a VR and there seems to be something strange with the gearing:

 

30MPH in 5th is 1800RPM, 70MPH in 5th is 4400RPM - As you can imagine, the car is going through a fair amount of fuel! I adore the car, but I need to sort the fuel economy ASAP if it's gonna stay!

 

I've established that the rev. counter is from a valver and so the readings aren't 100% accurate, although they don't seem too far out. Fuel economy suggests that the car is revving higher than it should in a given gear at a given speed

 

Can anyone help? It's been mentioned that the final drive may have been altered or the diff. changed and that might be why the car revs so high?

 

Cheers

 

Si

[Son_of_Thor 0]

Anyone??? Filled the car up last night and it's averaging 12MPG!!!

[dr_mat 0]

Plug in VAG-COM. It'll tell you what the ECU thinks the engine revs are. I think you have two problems:

 

1) valver dash meaning you *think* it's revving too high when it isn't

2) some other failure causing high fuel consumption. probably the lambda probe.

 

VAG-COM will diagnose both.

 

Over-revving by 20-30% won't cause 12mpg.

[Son_of_Thor 0]

Thanks for the help - I have VAG-COM and an OBD2 cable, just waiting for the OBD1 adaptor to arrive...

 

Si

[Son_of_Thor 0]

Right, had VAG-COM on the car and the rev reading from the ECU suggest that the engine revs are normal and it's the rev counter clock that's wrong as predicted....

 

Revving the engine on the drive when warm gives a LAMBDA reading of between 1.000 and 1.203 - Is this a normal reading and what else should I be looking at?! I've already replaced the yellow temp. sender and drained/replaced the coolant....

[dr_mat 0]

Right, had VAG-COM on the car and the rev reading from the ECU suggest that the engine revs are normal and it's the rev counter clock that's wrong as predicted....

 

I win! ;)

 

Revving the engine on the drive when warm gives a LAMBDA reading of between 1.000 and 1.203 - Is this a normal reading and what else should I be looking at?! I've already replaced the yellow temp. sender and drained/replaced the coolant....

 

Sounds a little high, it should fluctuate only from 0.95-1.05 ish...

 

Time to try a replacement lambda methinks.

[Son_of_Thor 0]

Yep, u defo win!!

 

Where's the best place to get a new Lambda - I've heard GSF ones can be a bit iffy? And how much should I expect to pay for one?

 

Also gonna replace the blue temp sender as well - Seems to be reading about 15 degrees lower than the new yellow sender at warm idle....

[steve @ 0]

Yep, u defo win!!

 

Where's the best place to get a new Lambda - I've heard GSF ones can be a bit iffy? And how much should I expect to pay for one?

 

Also gonna replace the blue temp sender as well - Seems to be reading about 15 degrees lower than the new yellow sender at warm idle....

 

If the lambda from gsf is a bosch unit you should be fine. Yeah change the blue temp sensor, half the price of the yellow and will/should improve your mpg.