Slow going uphill in my 2002 T4 2.5 TDI

[Fossil]

I have recently purchased a 2002 2.5 TDI T4 Transporter and Pete from Newcastle VW Center diagnosed the MAF sensor as faulty using his diagnostic laptop. it seems to drive beautifully on an open flat road but lacks power when going uphill with barely a load in it. It just seems like the turbo isn't kicking in and I presume this is from the maf fault as I'm yet to test the wiring. I've tried another MAF sensor but the error remained. I've attached an image I took today and does this seem about right regarding the revs to speed ratio. Any help is appreciated? As you could probable tell I am very new to veedub.

[Seano]

That's exactly the revs it should be doing for that speed.

[Rebuild]

Not sure on T4's, but weren't there a few different TDI engines.Maybe yours is a lower powered type?

Were there any other engine codes at the time?Turbo related codes?
So, you have a new MAF in there now?

You can try disconnecting the MAF and run it.If there is no change(reduction) in engine performance, the MAF is faulty(providing there are no other faults).

[jets]

Were there any other engine codes at the time?Turbo related codes?

Only overseas. If his is Aust. delivered it will be an ACV, 75Kw/102hp.
When I bought my first T4, I drove it back from Sydney with a dud MAF & while I could cruise at the speed limit on the level, as soon as I crossed the river & started to climb, the traffic behind me would build up. My wife was driving our GTI behind me & in the end passed me.
I think she was embarrassed for me. As soon as I fitted a new MAF, the van would spin the wheels on our steep drive.
I agree with unplugging the MAF to see if performance is restored.

[Vwnumpty]

Hi - I had the same issue with a 2001 Caravelle 2.5 tdi and it transpired it was a split hose on the turbo (I think). On the flat the hose would 'reseal' and voila power restored. Took a few trips to the mechanic though to discover this


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[Sunny43.5]

Hi - I had the same issue with a 2001 Caravelle 2.5 tdi and it transpired it was a split hose on the turbo (I think). On the flat the hose would 'reseal' and voila power restored. Took a few trips to the mechanic though to discover this


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I would agree with Vwnumpty we had the Turbo changed on our older T5 and it still ran like crap afterwards , the useless mechanics did the job but did not bother checking how it drove afterwards . I only got a few kilometres from them and realised there was still a problem , when I got home I found a small split in one hose for the vacumm line . It was not visible but I could hear a tiny sucking sort of sound and found the split on the underside of the hose . Cut away the split and she was chirping the front wheels again !

[Ronka1]

Not sure about the 2.5 TDI but have a 2L TDI Passat and if the hose that feeds waste gate actuator under vacum is leaking it will leave the waste gate in open position thus reducing boost, its home position with out vacuum is waste gate open, so may be worth a check as on the Passat 08 model there are 2 metal 3 mm pipes roughly that run near the waste gate actuator vacuum hose and if there is one sitn under vacuum hose to waste gate hose they wear through, i replaced mine with heavier gauge vacuum tube problem solved, Actuator is metal can bout half size of cup exhaust side of engine with one electrical connector and one vacuum hose. hope this helps cheers Ron, ur speed to tacho revs is set and not really good indicator unless u had a slipping clutch then revs may show higher than normal road speed, indication of power loss is how much time it takes to get to 100kmh all things being equal, as example u take car to section road for test flat steep doesn't matter,so u take off from startn point and see how much time to get to say 100kmh, now if u did same again with turbo actuator hose of waste gate on turbo open less boost it will take u longer to get to the 100kmh.

[Fossil]

Pete checked all wires from the MAF and there okay. I put in another maf and made no difference. I even disconnected the MAF and drove and it clearly shows the maf is okay as it ran crook with it disconnected. Pete from Newcastle VW Center suggested to get the ecu checked but a bloke I spoke to reckons there is a blockage in the turbo somewhere and that's why the vagcomm shows up MAF sensor error. I don't even know where to begin to check any hoses or anything in regards to the turbo. I have noticed a strange ticking sound in the motor as well. Its just like a diesel with no turbo as it runs fine otherwise. No smoke or anything and fuel consumption is around the 1,000 kilometres to a tank. I will be scooting along at 100 k's and come to a hill and it'll drop right back to say 60 k's trying to get up it. Very frustrating. No other errors show on the vagcomm except the MAF?

[Sunny43.5]

There are lots of small rubber hoses feeding vacumm into various parts of the engine , Iwould suggest to check each one carefully for a hole or split as I explained I could hear when ours was leaking , there are quite afew on the T5 and I would imagine about the same for the T4 . Like disconnecting the MAF try and disconnect the vacumm lines to ensure good suction , most times they will split right where they join some part of the engine systems related to Turbo .

[Seano]

Next step to my mind is the intercooler connections. The connection either side is plastic and a poor seal can develop. Your revs and engine speed are fine if the image in your OP was taken when climbing but if your boost is affected then compressed air is potentially getting away... perhaps that is what the maf is sensing?

[ericcs]

Can you somehow hook up a boost gauge, that will at least tell you there is a problem to start with?

[aprr32]

With no maf signal(open or short to ground) there will be no boost as a protection feature. I have line tested the harness from the maf to the ecu and it was all good. I starting to think there is a fault in the ecu and that is easy to check by sending it to someone like Injetronics who can test the input/output.