Audi A4 power loss

[mikbish]

Can anyone help before a costly unnecessary visit to the local Audi dealer ! I've an A4, 51 plate, 1.9tdi

twice recently , and both times after heavy overnight rain ?, the car started fine but on accelerating there seemed to be a loss of ' power '..it just gradually increased in speed , but after several seconds it seems to kick in .. It occurs in any gear , but just when you 'put your foot down ' !
for instance approach a roundabout , drop a gear then when accelerating out of it there is no power ..until 5 - 10 secs when it kicks in ?

This could last for sometime , but after 30 - 60 mins of driving it seems ok again ! Is as if something is getting wet and drying out ??

have looked under bonnet ans all seems dry under there ??

any ideas , thanks in anticipation

 

[^neo^]

Really need to get any fault codes that may be stored in the ecu read so you know where to start.

I'd guess if it happens mainly in heavy rain you've got damp in one of the thousands of multi-pin plugs under the bonnet.

 

[mikbish]

how do I get these codes ,do I need to visit Audi at a cost ????

and what will these codes do - can they pinpoint the fault ?

 

[^neo^]

Basically the ECU (computer in the car) will detect any faults with any of the sensors in the engine. When a fault happens, the ECU will log the problem in it's memory so it can be read by the mechanic to basically tell them whats wrong with the car (or give them an idea of where to start looking!).

You can buy fault code readers from halfrauds, or ebay but if you're friendly with a backstreet mechanic somewhere they will probably plug it in and read the codes for a drink.

Make sure you write down any codes that are registered, then ask the garae to clear the codes.

Ideally, you want to drive for 20 miles or so after having the codes read and cleared, then go back and get them checked again to see if they come back.

When you got some codes, come back and i'll give you some sort of idea of where to start!

 

[mikbish]

I'll try and find somwhere to do it on the cheap , but so far so good with the fault as not occured recenly even after a downpour yesterday ...Like I said , it only seems to occur after a heavy downpour whilst left standing and then clears when warm / dryed out ??

I will monitor and get back ...cheers

 

[mikbish]

another downpour last night and aslo had used pressure washer ...

looks like prob occurs only below 2000rpm

As once revs exceed this that when it 'kicks in ' ok , and also if by drooping down a gear this then gives greater revs and power is ok !

Does this help anyone in posting a suggestion as to a fix

 

[^neo^]

Could well just be a wet coil (or coilpack.......... dunno what the newer audis use), plug leads, or plugs

 

[mikbish]

Plugs ?? Plug leads ???

its a diesel !!!

 

[^neo^]

Teach me to skim read!!!!!!

 

[glyn999]

Sounds like the airflow meter on its way out, you can pick them up new on auction sites for around £50. Has the air filter been replaced recently? There are plenty of good garages out there who are Audi freindly who could plug it in for the fault codes, with out charging Audi rates.
Good luck

 

[kev25v6]

another downpour last night and aslo had used pressure washer ...

looks like prob occurs only below 2000rpm

As once revs exceed this that when it 'kicks in ' ok , and also if by drooping down a gear this then gives greater revs and power is ok !

Does this help anyone in posting a suggestion as to a fix

This just sounds like your turbo kicking in, it will be low on power and acceleration below 1900 rpm as the turbo is not spinning up like it does on boost. The MAF sensor is a big problem on golfs. Try uplugging the maf and driving the car, if it runs better you have a faulty maf, if not just plug it back in. VW were doing a free replacement on maf sensors on certain age cars, yours might just be in the time limit. A faulty maf does not always show up a fault code.

 

[mikbish]

cheers ...will try that on next downpour

 

[mikbish]

no real downpour..but done it again !! weather just damp/grey

disconnected the MAF as suggested ...this didn't cure the fault as such but car just accelerated as a normal car without turbo would ie. it appeared as if the 'turbo boost' was not present !!

reconnected the MAF and fault still present but only below about 2000rpm

looks like a costly visit to VAG ??

Unless any other suggestions ?

 

[long jon]

as gyn said, suspect airflow meter (in the inlet pipe after the air box). Try unplugging this when fault occurs as will revert to a substitute value.

 

[mikbish]

long jon : is this the same as what others are talking about when they mention MAF ??
when you say unplug , do you mean leave it unplugged as I drive or unplug and then refit before driving off ??