S2 ABY Jerking/Juddering under hard acceleration

[haaran]

I need some help to solve the first of the major niggles with my car. Apologies if this has already been addressed before but I'm struggling to find a definitive answer.

The car seems to drive fine first thing when cold (although I don't drive it hard until it has warmed up), but once it has warmed up and I try and floor it, it starts to judder. Under gentle acceleration though, it will quite happily rev through the full range. When cold, the boost is apparent, but when warm it's much less so if not non-existent. What could be the cause of this? Would a diagnostic give me an answer?

My 'research' tells me it may be the coilpack, plugs, wastegate (valve, diaphragm, loose pipe), boost leak or MAF. In which order and how should I check these?

The water temperature varies between just below 90 (when driving) to just over 90 (when standstill) but the fan doesn't kick in until it's a couple of notches above 90 - is that okay? There seems to be an awful lot of heat coming from the engine bay when stood next to it.

Finally, can anyone recommend an S2 expert in the West Yorkshire region who I could trust to work on my car.

Cheers

[Knight Rider S4]

First bet would be POS unit

Happy reading

http://www.sjmautotechnik.com/trouble_shooting/S4_Ignition.htm

[Fat Audi 80]

Your temperatures sound fine. The car does indeed kick out a lot of heat before the fan kicks in, especially if you are standing by the drivers front wing where the excess heat from the turbo escapes.

May I also suggest you check for "fault codes" if you have or can find the facilities. It is possible a sensor is playing up and limiting boost when the car is warm.

A boost leak would likely manefest itself by feeling like you are driving into a brick wall (safetly boost cut) as umetered air allowed into the intake circuit.

The ignition problems (coilpacks or POS's) would feel like it was running on 4 or less cylinders and should be quite obvious what is happening.

I would recommend the fault codes are read as a starting point, otherwise you are chasing your tail to begin with...

HTH

Cheers,

Steve.

[AndyP]

Finally, can anyone recommend an S2 expert in the West Yorkshire region who I could trust to work on my car.

Cheers

Contact member GT500 ( Rob ) on here, he will sort it out for you.

http://www.s2forum.com/forum/member.php?u=3192

[haaran]

The engine doesn't seem to be misfiring but it does feel more like what Steve described as 'driving into a brick wall'. The jerking is quite violent practically bringing the car to a standstill unless I ease off the accelerator and then GENTLY resume acceleration.

I guess first thing is getting the fault codes looked at.

Cheers

[BRY]

Search for "overboost protection"

[haaran]

I went to see my friendly local diagnostic man who has the VAG-COM software but didn't know where to connect his machine.

Can you help? We couldn't find the connector plug that are on newer cars.

[Fat Audi 80]

Under the bonnet at the back of the fuse box (this is just under the windscreen)

Have a look at www.S2central.net for lots of information.

cheers,

Steve.

[BRY]

It hasn't got the standard plug - you need to have the 2x2 connector.

[S2central.net]

Sounds like classic air leak to me and overboost protection mode - a la 'brick wall' description when fuel supply is cut off.

[Key Walshe]

Just recently had a boost leak myself, after an initial check of the pipes with no apparant holes we started to check all the other possibilities. Unplugged the MAF and that seemed to restore some power, but it wasn't that as a new RS2 MAF proved once fitted. The car would refuse to rev past 3k rpm and would jerk violently around those revs in all but 1st gear, though you could slowly accelerate through it.

Check all the pipe work, leave the engine running and keep it rev'ing high to get the boost up, starting at the airbox, follow it down to the turbo. Check for holes and squeeze them, they should be firm unless they have a leak. The one to the turbo from the airbox has 3 small off pipes so check they haven't split too. Then there's the one going into the engine just behind the aux. radiator which comes from the inter-cooler. Also, from there (this was one mine which had gone, and hard to spot too due the fixings above it!) check the small rubber section going into the throttle body, mine had split where the clip goes round it.

There's also one under the car going from the lower part of the inter-cooler into the turbo. This had also gone on mine, you'll want to get the car on a ramp or a jack. This pipe has a smaller one coming off it going back into the one from the airbox-turbo. Where it joined if must be a weak spot after time as there was a small hole starting. A quick sealing job with glue, puncture repair kit and tape cured the leak enough to get the car boosting again, that part soon to be on order from Roose Motorsports!

Have a good feel as boost leaks do seem very common place at the moment given the age and milage of most of the S2's. Plus they're an easy fix and don't always cost an arm and a leg to sort.

If that proves unsuccessful and you want to try a working MAF then I have a spare one now if you don't mind travelling over the Pennines to Wigan!