VW T4 Forum - VW T5 Forum banner

1 - 20 of 27 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
My T4 goes very well indeed as it comes up to the 380k mile mark, but:

At 3000 rpm (in 5th) on the motorway and going up hill the power suddenly drops off and the van slows (disconcerting on overtaking).

Also, I tow a horse trailer and have done for several years, again on pulling up hill (not at 3000rpm in 5th I might say) the power suddenly drops off.

This does not happen every time when there is a high power demand.

After reading previous posts it looks like it might be the N75 valve or its associated hoses which have not been changed from new. Or the waste gate actuator.

It's not the AMF meter as I know the failures symptoms of that only too well having changed it several times (lesson - always buy a new one).

Blocking 'over boost' makes no difference.

Anyone else had this problem?

Les
 

·
Registered
Joined
·
5,259 Posts
has the nut on the acuator worked loose so its not opening / closing the waste gate properly ? i had the same thing after a turbo change, as soon as i hit 70mph the power dropped off . worth checking before you go changing things that are not needed
 

·
Premium Member
Joined
·
2,102 Posts
has the nut on the acuator worked loose so its not opening / closing the waste gate properly ? i had the same thing after a turbo change, as soon as i hit 70mph the power dropped off . worth checking before you go changing things that are not needed
Def sounds like going into limp home. Prob cos of an overboost.

Check the arm on the wastegate isn't siezed too.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #4
Over boost should take the engine into limp mode. Resetting requires the ignition to be turn off and on and this is not necessary. It just seems to recover once on the level again without such resetting.

It may, and it's only a may, recover when I release the throttle completely and then reapply the foot - it seems to pickup again.

Thanks for the input and I'll check the Waste-gate actuator settings.

Les
 

·
Registered
Joined
·
1,573 Posts
Interesting what you say about releasing and re-applying the throttle.

Next time you're out in your van on a nice A road (with no-one behind you), once you're up to speed, dab the brake pedal with your left foot whilst keeping your right foot on the accelerator.

Does this cause the same sudden power loss effect as what you've been experiencing previously?
 

·
Registered
Joined
·
130 Posts
Interesting what you say about releasing and re-applying the throttle.

Next time you're out in your van on a nice A road (with no-one behind you), once you're up to speed, dab the brake pedal with your left foot whilst keeping your right foot on the accelerator.

Does this cause the same sudden power loss effect as what you've been experiencing previously?
What would this indicate?
I have the exact same problem but ALL the time. Won't go over 85mph either!! Different investigations have been going on for 7 months. New N75, new MAF, Wastegate working OK, pipes all OK. Turbo boosting OK!
Just had new cam belt fitted - no change. Running out of patience & money!
Does anyone know of ex aa re-map going wrong? Could this be the cause?
2.5TDi ACV ex AA 1999
 

·
Registered
Joined
·
1,503 Posts
Just ha this problem , replaced n75 now fixed ,
 

·
Registered
Joined
·
1,573 Posts
What would this indicate?
I have the exact same problem but ALL the time. Won't go over 85mph either!! Different investigations have been going on for 7 months. New N75, new MAF, Wastegate working OK, pipes all OK. Turbo boosting OK!
Just had new cam belt fitted - no change. Running out of patience & money!
Does anyone know of ex aa re-map going wrong? Could this be the cause?
2.5TDi ACV ex AA 1999
There is a switch on the brake pedal that senses when you have your foot on the pedal to illuminate the brake lights.

However, it is also used by the cruise control wiring circuit to knock off the cruise control system when you brake (as otherwise when you were braking, the ECU would fight against you and try and increase engine speed to compensate).

These switches are quite troublesome, so the thought crossed my mind that if all other fault finding had been done on the engine side of things, whether or not this switch playing up might be the cause of the sudden power loss.

Just something to check really. Not saying that is definitely the cause!
 

·
Registered
Joined
·
130 Posts
OK. I am now looking for a T4/Vagcom expert - someone who knows absolutely everything there is to know about these vans & how they work! Especially fault finding!!!!

Will hopefully be taking van to Vanwest at Brean on Sunday, so someone there might be able to help a blonde damsel in distress???? :*

If not, any suggestions will be greatly received :(
 

·
Registered
Joined
·
130 Posts
Van now goes like sh*t off a stick!
When cambelt was being changed, a grey & black wire had corroded & was repaired. Now I'm assuming this was the problem. What the wire does - not a clue!
 

·
Registered
Joined
·
543 Posts
any news on what the wire was and where it is...? my ex aa is the same i reckon - not pulling as well as expected and not pulling past 70mph easily...
 

·
Registered
Joined
·
2 Posts
I am having exactly the same power loss issues with my T4 2.5 tdi.....it just feels like its stuck in limp mode. The engine used to pull all the way up to 90 now it stops at 60. Any ideas how much a Garage should charge to diagnose/Fix this problem?
 

·
Registered
Joined
·
232 Posts
i'm having the same problem,

after changing the maf, changing the map sensor, blocking of the egr valve cleaning the n75, checking the hoses, changing the brake light switches as they were coming up as a fault on the vag i am Still getting no power after 70mph.. Jesus christ does anyone know anything about these vans.. the vw mechanic now wants to change the cam belt and pump timing belt, its another 400 quid..

what in the name of bejaysus was the wire you found and where was it??

also my horn isn't working?? i've tried a new one so as to chack and it doesn't work either maybe just maybe the electrical wires are perished somewhere??

any ideas...please... sob sob
 

·
Registered
Joined
·
2 Posts
Another Ex AA owner here who seems to be spending more time under it than in it! Recently had problems with black smoke and power loss... Cleaning and then Blanking the EGR fixed the smoke, but still suffering power loss in 5th gear when trying to accelerate hard - sounds very similar to the issues raised in this thread. A few months ago the turbo was only coming in intermittently, and since my code reader couldn't access the ECU and neither could my local garage, I reluctantly took it to the main VW dealer who proceeded to rip me off in their usual manner. The bill came to £1600 and shortly afterwards the heater packed up, my horn was left disconnected and my brake light switch was broken - slightly suspicious since the guy was fiddling round with the electrics and apparently replaced 5 broken wires in the loom. Of course I didn't test everything before I drove off the forecourt and only discovered the horn when attempting to use it, and only found out about the brake lights when a mate was following me and mentioned that they weren't working. Anyway - I can feel my anger levels rising knowing that I could have replaced the entire loom for a lot less, but would still like to get the turbo running properly again. My van used to accelerate and pull surprisingly well up to 90 - but not anymore. I've not tried any of the wastegate revamps or anything yet, but the grey wire caught my attention following on from the VW dealers meddling - If anyone does have any more specific info, that would be appreciated but otherwise I will go away and tinker over the next few weeks and update on progress.
 

·
Registered
Joined
·
6 Posts
I have a 2.5L 102HP ACV 5 speed 2003 Westfalia. When I bought the van I thought it wasn't very powerful. Drove it for a year having lorries overtake me going up long hills and had to go into 3rd at times!! It drove fine, had no error codes but no power. Took it to a rolling road and found it had 52HP!! changed the MAF did nothing. Took it to a VW main dealer (JCB) to have the fuel timing checked all ok. He did find one of the bolts that holds the turbo actuator had come out. So the actuator was working but wasn't moving the turbo lever as it was just turning itself on the remaining one bolt. Put a new bolt in and now works as it should. Spoke to a another guy by chance who had the same engine and he also had the same issue so not unique.

Worth a look as costs nothing.

Before the bolt was put back in it would only do 80MPH on the flat and maybe 90 down hill. Now will sit at 90 all day long if you don't mind burning all that fuel.
 

·
Registered
Joined
·
37 Posts
First post here, but I bet you can guess why?

I have read so many posts on this problem that my eyes are going funny, I have the same problem...I think.

The van pulls well and will red line no problem in 1st to 4th. When I stick it in 5th it loses all torque. It is ok off motorways, but hills and motorway driving means that it maxes out at 75-80mph. Changing down does no good as in 4th it would never do more than 65-70mph even red lining it (and I don't really want to drive around on the red line :* )

Motorways mean that safe overtaking is a bit risky. I am no speed freak, but to overtake someone doing 65mph safely, I need to be able to accelerate to about 80mph quite quickly, and that is where the fun starts, it hits 75mph, and all torque just vanishes. If I am on a hill it simply slows down in 5th.

Are there any pics anywhere of where these various bolts, screws and wires are, as they would be a huge help for someone like me.

Cheers

Rob G
 

·
Registered
Joined
·
37 Posts
If it helps...I have a conical air filter, and it was looking sorry for itself, so took it off and sprayed two cans of degreaser through it. I can now hear the turbo whistle right through the revs, and it hit 90mph today without too much trouble. I have no idea what the performance should be for an 88, which is what I think I have, but it definately pulls better than it did. I am guessing that the turbo was cutting out in 5th due to a lack of air, and the ECU was shutting it down. I may be talking complete and utter (insert your own word here), but it was a step in the right direction.
 

·
Registered
Joined
·
439 Posts
If it helps...I have a conical air filter, and it was looking sorry for itself, so took it off and sprayed two cans of degreaser through it. I can now hear the turbo whistle right through the revs, and it hit 90mph today without too much trouble. I have no idea what the performance should be for an 88, which is what I think I have, but it definately pulls better than it did. I am guessing that the turbo was cutting out in 5th due to a lack of air, and the ECU was shutting it down. I may be talking complete and utter (insert your own word here), but it was a step in the right direction.
Possible MAF? Best to get it on VCDS and log what the MAF is doing. The other quick way is to take the connector off of the MAF and go for a spin, if it runs better then the MAF needs replacing.
 
1 - 20 of 27 Posts
Top