loss of power

[chiefmechanic]

Hi, My rs4 has 146634 miles on it and does not as quick as it used to be. I have had it over 2 years now. Between 1000 and 2500 revs it is very sluggish but after that it appears to boost ok. No faults on vagcom. I did have a boost hose leak but i changed that hose. The temperature gauge rarely goes above 75 although on vagcom it will read 81. Any ideas.

[neckarsulm]

81 is still a bit low for coolant temp if that's the most you ever see.
The relationship between what the sensor reads and what the gauge shows isn't always equal as the gauge is mapped to show 90 degrees from around 80-100 degrees to stop it moving around naturally while you drive so you know that when it does move you really do have a problem.
Thermostats are a big problem and should be done at each belt change but rarely are, you may find the gauge and sensor readings get lower as the ambient temps reduce as we get toward winter, if so it's def thermostat.
As for power loss, unlikely to be related unless it's been reading low for a long time and the car has been driven hard with effectively a cold engine.
Have you tried a MAF?
Log the g/s reading in VAG COM with measuring blocks, do a 4000-6500 rpm run in 3rd gear and this figure should peak at approx 4/5 of your bhp figure, so a stock car should be just over 300 g/s

[chiefmechanic]

Thanks for the reply.
What do you mean g/s.
When i log the blocks what number of block do i log as the four blocks in the window measure different sensors depending on which one i pick.
I am beginning to suspect that a previous owner has had the thermostat taken out or that it has failed in the open position.
Brian

[neckarsulm]

Thermostats stick open frequently so very common
With regards to logging try measuring block 003 and look at field 3
You can see the data you need here which is a log from my car

g/s means "grams per stroke", it's how air mass is measured


http://www.volkswizard.co.uk/images/car ... NSEP10.xls

[rickoshea]

I would say the thermostat is more likely to have failed than to have been removed, as it's a cam belt off job to get to the thermostat. Thermostats on RS4's are notoriously unreliable anyway