v6 tdi quattro throttle surge / issue

pilla

Old ones are the best ones
Hi guys, back in an old quattro for the winter, very pleased to be back, forgot how much i missed quattro drivetrain after running some rwd and fwd vehicles, I have purchased an old v6 tdi its done over 200k but still going strong, now i have an issue.

At full throttle at the pedal, it seems sluggish and whistles/hisses like it has an intercooler leak or a split hose, I havent been under it yet but i will do, then when you release the pedal, it has a surge of power during the release, so i quickly realised it was performing better at half throttle, so i have been gently letting off the throttle under acceleration to find the sweet spot, its around halfway. Doesnt hiss and pulls harder.

Im thinking its maybe boost/fuel mixturte related possibly or a faulty TPS, but they dont have a throttle do they? Ive only been used to 2.7t lumps in previous B5 S4's so the v6 tdi is a new beast for me. My viscous fan is stuck on so it sounds like a train.

Can anybody tell me why it seems to be pulling harder at half throttle and not good at all at full throttle and what i can check?

Many thanks folks.
 

amiram

A6 C5 Allroad 2.5L TDI Tip Still on air :)
Can you pull a fault codes ?
 

pilla

Old ones are the best ones
Hi, did a vagcom scan today, no codes, there is a small weep at on the left bank middle cylibder injector line at the pump but i cant see that causing my problem. I pressure washed the engine so i could see it!, everything else seems fine. Thanks.
 

amiram

A6 C5 Allroad 2.5L TDI Tip Still on air :)
Let's make some guesses. Check the electrical contacts of the MAF sensor and the MAP sensor. Check that the turbo rotates freely, look for pressure leakage from the Intake system

























מתבצע ניסיון חוזר...
Check that the turbo rotates freely, look for pressure leakage from the suction system
 

pilla

Old ones are the best ones
ive been running it as it wasd for a few weeks but the other day my siezed viscous fan exploded during a 2nd gear pull and took my radiator out too, i have removed the fan assembly completely now and fitted a new rad, i also cleaned and tightened the intercooler, throttle body and inlet pipes, the vehicle seems to pull a lot better now, i think it was down to maybe a slight boost leak and the viscous fan sapping a lot of power as it was always on and in the end went bang, a very loud bang in moving traffic!



DRJgF1D

3TFCQDc
 

amiram

A6 C5 Allroad 2.5L TDI Tip Still on air :)
The viscous fan exploded when the viscous fan clutch is stuck. Replace both
 
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