1.8T Sport - How can you test the turbo?

[A4Chris]

I've had my 1997 T Sport for about 6 weeks now and have been enjoying driving it. However, the more I drive it the more convinced I become that the turbo is not working and I am effectively driving a normally aspirated 1.8.

There is bugger all low down urge and to get any decent power for overtaking etc... you have to thrash the engine up past 5000rpm. As soemone with a lot of mechanical sympathy, I hate doing this !

There is no obvious point when the turbo kicks in (although this may be normal??) and there is no sound whatsoever from the turbo (even with my head under the bonnet).

Is there a way for the home mechanic to test if the turbo is generating any boost and what are the areas to check are functioning correctly?

There was a post under the VW Golf section about lubricating the wastegate linkage - how do you do this? Also, I hear the standard plastic Bosch Dump Valves are prone to failing?

Any thoughts would be appreciated.

Thanks

[norchip.co.uk]

Plumb in a boost gauge or get someone with VAG-COM to see what boost you are running.

For the boost gauge if it is only a temp thing find a small pipe on your plenum chamber that has suction on it when at idle and "T" into it. Off the top of my head I cant think of a pipe, try and find the fuel pressure regulator and T into it. Not the best place but will do for testing. Go for a quick spin and see if you are getting boost.

[PBC97]

Hi A4 Chris,
I also have a 97 A4 Turbo with exactly the same problem you mentioned. Did you get anywhere sorting yours out? As much as I hate to I am planning on going to an Audi dealer to get a diagnostics check but wondered if you had cured your problem? Thanks

[Paul A4 1.8t]

hi all
Just got mine back from garage after feeling as if the car had little power. Had the MAF changed and also the wastegate (N75) regulator changed. Also had the mechanic check my turbo to make sure it was working. There are no faults now on the diagnostic machine and yes performance has improved.... but only slightly. My A4 has very little mileage and the engine is in good order, i think these engines arent suppose to be that powerful!!
My next move now is to have it chipped and probably to upgrade the turbo, wastegate and all hoses replaced, then hopefully i will be happy with her!!
If anyone finds any cure that the diagnostic machine cant find (or any tips) that would be great!

[A4Chris]

Hi A4 Chris,
I also have a 97 A4 Turbo with exactly the same problem you mentioned. Did you get anywhere sorting yours out? As much as I hate to I am planning on going to an Audi dealer to get a diagnostics check but wondered if you had cured your problem? Thanks

Yes, got mine sorted and now runs as I always knew if should. Problems where as follows (greatest performance increase first).

1) Wastegate actuator to wastgate control rod snapped - fixed by fitting a replacement Forge Wastegate Actuator - massive increase in performance as wastegate now functioning properly and therefore turbo spinning up properly (note this will not show on a diagnostics as is a 'mechanical' fault rather than an 'ECU' fault)

2) N75 boost control solenoid valve replaced (with 'J' version). Turbo boost felt lower down rev range (from 2500rpm) and very strong above 4000rpm (car now an excellent A and B road overtaking machine!!)


3) Forge recirculating boost diverter valve (i.e. non-atmospheric dump valve) fitted. Slightly notable increase in performance between gear changes noted as turbo no longer 'stalling' between gear shifts (likely the original Bosch plastic valve had failed)

4) New coolant temperature sensor fitted as routine maintenance when replacing coolant - surprised to find a slight performance increase after replacement

5) New MAF fitted - only a slight performance increase but notably smoother running throughout the rev range and improved MPG!!


That's the lot and as a result I'm probably around £700 lighter! (all work done myself)

Finally, note that in standard tune (150bhp) and weighing in at 1300Kg, these cars are never going to feel violently quick like an Impreza Turbo or Volvo T5. However, they are certainly no slouch. The power delivery is fairly progressive and the engine doesn't really pull strong until the momentum and revs have built up. However, by 4000rpm in 3rd ger you should be feeling a definite 'push into the seat' and speed should be piling on quickly (hence why they are superb for overtaking).

My advice is to wait until your engine is cold and then feel in behind the turbo beneath the exhaust manifold. You should feel the wastegate actuator at the front end of the turbo with a rod running backwards to conect to the turbo wastegate. Check that the rod is intact and has a little play (i.e. not jammed solid). Like I say, the rod on mine was broken and fixing this definitely provided the greatest performance increase!

Good luck!

[Paul A4 1.8t]

Hi Chris
You say you replaced the N75 (wastegate regulator) and also the wastegate actuator?? I didnt realise there were 2 items related to the wastegate. I take it you have to be under the car to check the actuator?? Will try your advise as need to get my car running quicker!!

[jkay2008]

Hi Chris
You say you replaced the N75 (wastegate regulator) and also the wastegate actuator?? I didnt realise there were 2 items related to the wastegate. I take it you have to be under the car to check the actuator?? Will try your advise as need to get my car running quicker!!

The wastegate is vacuum operated, this vacuum is controlled/fed by the valve.

[A4Chris]

Essentially the N75 solenoid controls the vacum applied to the wastegate actuator based on ECU signals. If the actuator to wastegate linkage is broken then the actuator can't physically open and close the wastgate and hence the wastegate will flap open as soon as any exhaust gas pressure rises. Very hard to physically see the actuator to wastegate linkage without removing exhaust manifold (which isn't that hard) but first call is to feel in below the exhaust manifold (with a cold engine!) and see if you can feel the rod and check it is intact.

See link below

https://www.vwaudiforum.co.uk/forum/s...ad.php?t=14326