Prob with my '96 VR6 - please help!

[gman]

Hi everyone - I'm new to the forum!

I've got a '96 Golf VR6 (manual) which I bought in January.

Its a great little car, aside from a nagging problem I was wondering you might be able to offer some advice about.. The problem relates to the drivetrain (I think). Its a difficult problem to describe - I'll do my best..

The car makes a jolting 'thud' when the car goes from coasting (in gear and moving but without the accelerator pressed) to power.

When the car is under acceleration, there is no problem.

However when I go from coasting (no accelerator applied) to applying the accelerator, there is that jolting thud as the engine takes up the momentum.

So for example, if I'm cruising at 80km/h and go down a gentle hill, I lift the accelerator (so I'm not going too fast) and the car JOLTS as the momentum goes from the engine pulling the car to it coasting along under its own momentum. Then when the speed decreases and I want to re-apply power, the car JOLTS again as the engine takes up the power.

Also, when the aircon is on, if the compressor kicks in and takes some of the power from the engine, there is the same thud as the momentum of the car shifts from the engine pulling the car to the car coasting along.

Of course it thuds again when the accelerator is pressed to compensate and the engine starts pulling the car again.

I've had a friend who has more mechanical understanding that I have a drive and it puzzled him - this problem occurs in all gears, leading him to think it is a problem with the gearbox main drive gear.

Its a wierd problem especially because its a manual car!

VW V!illage thought it was an engine mount problem and replaced the rear engine mount. But this made no difference.

Any ideas what this might be???

I'm located in Sydney's east and I'm having a tough time finding a mechanic with some good knowledge who won't charge me a bucket just to look at it and try diagnose the problem.. Any suggestions where to take it? Barl0world VW seemed too expensive to me.

Any advice you could offer would be muchly appreciated!

Attached is pic of the lovely (aside from this problem) beast.

Thanks!
G-man

[william]

your looking at an engine mount problem quite common mine has the same problem which iam currently fixing because they are fluid filled they crack and the fluid leaks out look for a leaking mount can be spotted in the engine bay

[gman]

Thanks for your response William.

I don't think its an engine mount problem as the only engine mount that was worn (the rear one) was replaced and this did not solve the problem.

I just went and had a look at all the engine mounts and they all seem to be intact.

Any other ideas?

[DubSteve]

Gday mate and welcome to the forum. I would also said engine mounts because I had the same problem as well.

The only other thing that I could think of is possibly think of is a loose bolt or something. Maybe a flat spot somewhere in the transmission I'm not sure.

You could try Wolfsburg motors which is in Alexandria, they are not to bad and are priced OK.

[WABIT]

drive shafts? anyone think so?

wabit

[DubSteve]

drive shafts? anyone think so?

wabit

You would have to have a look at it wouldn't you.

[gman]

I just spoke to Shurek (i think that's his name) at Wolfsburg Motors - he thinks it sounds like a problem with the diff.

He said that the diff rivets sometimes come loose, but it could be a pretty costly exercise if the diff is buggered.

He's going to have a look at it on Tuesday for me. I'll let you know what he says!

[DubSteve]

I just spoke to Shurek (i think that's his name) at Wolfsburg Motors - he thinks it sounds like a problem with the diff.

He said that the diff rivets sometimes come loose, but it could be a pretty costly exercise if the diff is buggered.

He's going to have a look at it on Tuesday for me. I'll let you know what he says!

Yeha hes not to bad. his names Shirik there brothers that own that place. Inside they have a photo with a Combi at the Salt planes in America and its got a big Supercharger on it MASSIVE LOL.j:

[gman]

Hey all,

I took the VR6 to Shirik at Wolfsburg Motors today.

His brother thinks the problem with the car isn't the engine mounts, gearbox or diff. Thinks it is an engine control problem.

Booked it in for next thursday to be properly checked...

Whilst I'm writing - does anyone know where I can get the little black end-caps for the sideskirts? (the ones beneath the doors) I think other MK3 Golfs aside from the VR6 have these skirts?

I'm missing the rear driver's and front passengers caps.

Cheers all!
Gman

[DubSteve]

What are they can show us what they are?

[gman]

Gday all

Just got the VR6 back from Wolfsburg Motors - good guys!

The problem was with the Throttle and not mechanical - phew..

Loving the car now.

Gman

[wakdog]

hey do you reckon i could get some more info on exactly what was wrong with it??? Mine has had the same problem and i have replaced all the engine mounts with VF Engineering mounts and it still does it, so i think i may have the same problem as you had

[DubSteve]

Awesome good to see that they do a good job. Hows the cars responce now? Heaps better?

[gman]

mmn steve the car's response is similar to how it performed before, just without the crazy jerkiness between coasting and onto the power.

there is still a rattle from the engine mounts though.

wakdog - what is the deal with those engine mounts you describe? are they better than the original ones (which by all accounts seem to be way too soft)? are they expensive?

to go into more detail about the problem, as wolfsburg guys described it, there was a carbon build up in the throttle body. though the units are meant to be sealed, they managed to disassemble it and clean it, which fixed the problem!

and its a biatch of a problem if that's what is happening to your car wakdog :(, i too had had an engine mount replaced in order to try to fix this problem to no success.. maybe you could have your car's throttle inspected?

apparently the injectors in my car need a proper service to improve performance.. anyone know how much such an operation costs or if there is some cheap alternative? can this be done by an enthusiastic amateur? anyone know how to do this?

cheers all!
gman

[wakdog]

VF Engineering engine mounts are available from ECStuning.com for $410USD for all three (front, rear and transmission mounts) but i would recommend only getting the front mount for $159USD as if you get all three you will get alot of vibration from the engine.

I am looking at getting my injectors cleaned at the moment too and i have been quoted $140 for mine to be done, but this is at trade price.

[Draco]

gman It's great to hear that you got your problem fixed.. Mine has the same problem only intermittently and only on accelerating from coasting (Or changing gears). I'll have to look into this as well.. I too had the mounts, drivetrain, etc cgecked... How much did the repair set you back?

I always thought that it was a sensor or something as one day it's purrfect and the next, it's like I've just started to drive manual.. It's embarasing at times when i have a passenger... And of course the scanner tool didn't show anything up :(

As for cleaning the injectors, you could always try a bottle of Nulon Total Fuel System Cleaner (TFSC)..

[gman]

gday draco and everyone else,

just got back from the snowy mountains - driving the vr6 through the mt kosciuszko national park's quiet, banked, winding roads was just brilliant - gave me a chance to enjoy the car far more than the usual city traffic grind allows. the little car has such great grip and power!

i think the bill for the throttle cleaning came to $160, i thought this was quite reasonably priced, given that they had to spend time to troubleshoot the problem to determine what it was..

its amazing - no one was able to diagnose the problem - i thought i was up for thousands of dollars of gearbox or drivetrain repairs..

it made a big, big improvement to the driving experience in the car so was well worth the effort.

the guys at wolfsburg told me that the throttle body is actually not meant to be opened and cleaned - they said it is meant to be a 'sealed system', but they managed to open it and clean it anyway..

since having the problem fixed i bought a throttle body from golf loon (just in case the problem re-appears). having received the throttle body i don't really understand how it is a 'sealed system' as the wolfsburg guys said..

hang on i'll attach a pic of the throttle body i bought from golf loon - anyone know why i was told its a sealed system?

gman.

[deemoE36]

i had similar problem, happened when engine is down low in rpm and i try to accelerate
checked spark plugs and they were in there since the car was built, bought new ones and that was the end of that...i would recommend checking them before taking it to the mechanic, cus they can take ur money while only replacing the plugs and telling you that it was something huge

[gman]

hey deemo that's good advice, thanks for that. i am fairly confident that these guys are genuine though, the car has had a good service history with the plugs replaced just a year ago.

any ideas about the throttle body being sealed though??

[Draco]

Great to hear that you had a great time with your VR6, I'm still amazed at the torque this puts out and I've had it for 3.5 years now..

The only think I can see that could be sealed is the Throttlebody Position Sensor.

Thanks for the pix...

[Golf Loon]

I think they say they are sealed cos a layman can bugger up the settings easily.

[h100vw]

The only sealed bit is the position sensor. They would normally be sealed to stop the **** getting in causing failures.

There would normally be a throttle closed and wide open resistance to allow the ECU to know when to idle and when you are after full steam. The resistance in between giving the load to the ECU.

What often happens is that after years of driving round at the posted speed limits, the tracks in the TPS getting dirty at certain places which correspond to the throttle required to maintain particular road speeds.

When you open or close the throttle past this position the ECU would get an inaccurate signal, maybe one which tells it to cut the fuel as it should be at tickover, this would also kill the timng too. Big loss of power would happen until you get back to a place where the signal is again valid. I see this quite often at work on various aircraft instruments and sensors. In the workshop we can strip and clean the offending parts before testing and certifying them. We usually clean them up with brasso and a squirt of contact oil for lubrication and to stop oxidation.

The way to check it would be to find the varying resistance on probably 2 pins of the TPS and monitor this resistance with a meter while opening the Throttle very, very slowly looking for sudden jumps in resistance or open circuits. I would expect the TPS to run from close to zero to maybe 2-300 OHMS over the full range of movement.

If you get problems again it may be a case of repalcing the TPS with the one from the spare TB. You still need to set the TPS correctly so the ECU knows where it's at.

In more modern Dubs this would be a TB adaptation.

Gavin