T4 2.5 petrol drama

[Bodhi]

Hi i'm new to the forum (from the UK). Check out the Technical section our UK T4 forum, there might someone on there who has had a similar problem and maybe able to help you.

https://www.vwt4forum.co.uk

[slugger95]

t4

Cheers buddy, I will have a gander....

[Jmac]

Mate you say your mech is pulling his hair out what has he done /checked???? have you tried a substitute coil in it???????? IMO it is electrical mate. Coils are bad on these , give us a run down on what has been done /checked
Jmac

[slugger95]

2.5 drama

Geez, where do I start...

We have replaced the following:
Coil
Fuel pump
air flow sensor
air intake boot(hose)
computer(used)
fuel filter
number 30 relay
and these are the things I can remember.....I think thats about it..

Symtoms:
Slight rough idle at times hot and cold
under powered at times hot and cold, feels abit fluffy if that makes sense when on the go-pedal.
does not seem to want to rev out when under power and taking off from lights etc (periodic).
periodic non start after driving both long and short distances. Leave for 10 mins then hay presto it starts again.
periodic cut out of motor for 1 second when driving at any speed.
Finally had it stop in traffic and had to have it towed, when we got to the other end and the mechanic tried to start it fired up first thing.
On 1 ocassion and on a hot day the motor lost power and it seemed to go back to a half idle but could not move off due to lack of power and it sounded reallt strange almost light a pre ignition type of sounds, you know when it runs on after being turned off but on this occasion it was on???

That's it in a nutshell..........

The guys trying to fix it are from the Volks Shop in O'connor just off South street, really nice guys and helpful but I am feeling guilty as it is taking up so much of their time when I keep taking it back so often..

Cheers

Slugger

[gregozedobe]

A few more suggestions:

Lack of fuel (some of your symptoms remind me of a fuel vapourisation problem I had with an ancient (petrol) corolla I once had - it really disliked hot weather.

Poor earth(s).

Corrosion in connector/s (has any water gotten into somewhere it shouldn't have)

Broken wire (with the insulation surrounding it still intact).

Focus on electrical things that move with the motor (to fit in with the intermittent nature of the faults).

It is possible that you have more than 1 fault.

Carry a multi-meter with you so next time it won't start you can check for a lack of power when the fault actually exists. Even if you don't know what actually causes it this will be very valuable diagnostic info.

Take it to someone else who is good at tricky diagnostics but don't tell them what has been done ie a fresh set of eyes and minds looking at the problem, let them go back to basics.

Hope you solve it, and let us know what the problem was when you do finally fix it.

[Jmac]

Mate i think we may have missed something. That unit has a Map sensor inside the ecu. What used to happen was the vac pipe that suppies that Map sensor used to get transient oil and it used to get into the map sensor and stuff it up - symtoms poor running hot or cold and sluggishness due to MAP sensor being damaged with oil. Old fix was to try another ecu or a donor and then fit a new vac pipe, putting a couple of loops in it to make it a bit harder for the oil to track and fit a clear filter in line and that way you could also keep an eye on it.
Hope this is something elso for your cauldron ( check that vac pipe for contamination)
Jmac

[DVR68U]

try changing the complete engine loom, there might be a pulled wire in the loom or a point of hihg resistence. i had a similar problem , did lots of things and then ended up changing the loom and that fixed it. it shouldnt take long and will rule it out.
cheers brenton

[slugger95]

T4

Hi Brenton

Dont suppose you have a wiring loom left over from your wreck do you??

Cheers
Steve

[Jmac]

Have you checked that vac line???????? seen it so many times
Jmac

[DVR68U]

i gave it to matt for a swap for a 2l loom, he should still have it , but like jmac said check the vac line first
cheers brenton

[slugger95]

T4

Yep, tried the Vac line when the ECU was wapped over.... just been told today that the leads, cap etc were way dodgy as was one of the knock sensors, I pick it up today again and will see how it goes, Ill keep you posted..

Steve

[Jmac]

I tell you what else was bad on them and its a crazy one - if your coolant bottle has at all been leaking guess what is directly below it?? Dis Cap!! seen that too on them hey bloosy coolant getting into the cap. Yeah dodgy leads would cause dramas for sure
Jmac

[slugger95]

T4

This piece of S..T has done it again. Failed to start after being left over night. The night before it was going like a train after the mechanic replaced dizzy cap, all leads,and 1 of the crank angle sensors. The other crank angle sensor is on back order if needed.
When it did finally start and I took it around the block for a fang it konked out several times and did not want to kick up any revs without spluttering really badly again. Does this sound like the remaining crank angle sensor that has not been relaced yet?? I am really getting to the stage of wanting to see this van BURNT if you know what I mean............. just joking of course.

Cheers

Steve

[Silver Caravelle]

This piece of S..T has done it again. Failed to start after being left over night. The night before it was going like a train after the mechanic replaced dizzy cap, all leads,and 1 of the crank angle sensors. The other crank angle sensor is on back order if needed.
When it did finally start and I took it around the block for a fang it konked out several times and did not want to kick up any revs without spluttering really badly again. Does this sound like the remaining crank angle sensor that has not been relaced yet?? I am really getting to the stage of wanting to see this van BURNT if you know what I mean............. just joking of course.

Cheers

Steve

Hi Steve,

This is my first post to this forum, but have viewed posts for a little while now.

Having looked at the comments thus far for your issue and all the things that you have checked or replaced, I would looking very closely at the distributor itself. The hall effect sender might be stuffed internally or where the the low tensor lead plugs into the top of the distributor (where it jutts out from the side of the engine). I am also not aware of this model having crank angle sensors, as it runs via a hall effect to perform this task.

No doubt about leaking coolant dripping on to the top of the distributor will also cause such problems..... in my case when it rained I had water leaking through one of the under bonnet sound deadening fasteners on to the distributor!!

Things like dead MAF, No 30 relay and old leads whilst they will cause problems- generally shouldn't cause such extreme pooring running conditions that you are experiencing. A faulty knock sensor may. Also I assume you have checked the temperature coolant sender unit that inputs to the engine management, as this may cause very rich running. Either way very rich running will be obvious verses an electrical problem.

And it sounds like you have checked for vaccum leaks. It would have to be a fairly large vaccum leak in the intake side to cause such extreme running issues. Having said said, check very very very closely for splits in the intake hose from the air cleaner to the throttle body!!

Replacing the wiring loom seems like a very drastic step to take. The fault has gotter be some thing more fundamental than a wiring loom.

Cheers,

Scott

[Silver Caravelle]

Steve,

A few other things to check....in addition to my initial suggestions.

1. Connections to the knock sensor(s) (I think there are two on this model on front of engine block). It will not run if the plugs are disconnected or has a poor connection.
2. Blocked catalyic convertor or exhaust? Will cause poor (chocked) running.
3. It would also worth getting cylinder leak down test done to check the engine fundamentals for low compression and/or valve seat issues/burnt exhaust valves.
4 You have ruled out the coil.
5. I have seen a lot of work done looking for complicated faults. I assume the spark plugs are in good condition??
6. I don't think a faulty exhaust oxygen sensor would cause such pooring running conditions -but might be worthing checking to rule it out.

If your mechanic found a logged fault with the knock sensor(s), this would definately worth a closer look - particularly if there was no signal at all to/from the kocker sensor, or the signal is intermittant.

Regards,

Scott