[hartwellrj]

Hi all, new to this game so please have a little patience!

I obtained the T4 at the end of last year and on test driving it realised that it wasn't going to get off the lights first in most, if not all, attempts. Anyway, didn't use until early this summer when we took it away for a few days. On the first real journey I realised that I would have to get a balaclava to hide my shame and not be recognised when travelling up any reasonable hill - dragging at 30mph really was no fun and hated holding everybody up behind. So, on my return, started investigating options and possible deficiencies of the 88. First to go was the EGR valve followed by install of a s/hand 102 standard intercooler. EGR didn't really give anything but fitting the intercooler seemed to make things a little better but still 30mph up the longer hills. On returning home I did some more research and started to tinker. Took the turbo outlet pipe off, got the wife to rev it and nearly took my face off. Replaced the pressure/vacuum pipes with silicone. Checked the operation of the N75 valve which although had 36ohms across the coil didn't click when 12v applied. So swapped the N75 for the redundant N18 valve. In the meantime got hold of an OBDii reader and reloaded Torque pro onto my Android, took the beast for a run and got the highest reading of boost of 3.5psi and vac at tick over of just a couple of in Hg. Decided to have a go at shortening the wastegate actuator - took 12 flats off and took for a run, still no difference. Can find no air leaks evident anywhere and am now at my wits end thinking I'm going to have to go to the professionals for advice.

So, my question is: have I missed anything obvious before I take it in? I really love the T4 apart from the above and, of course, the arm ache from waving to all the other VW's in North Devon, couldn't believe how many there were, S Devon last week was a lot quieter!!!

Any info or advice would be very gratefully received. Many thanks for looking, Richard.

 

[thevandidit]

Try checking the maf sensor loads of info about it here.

 

[hartwellrj]

Thanks for the reply. Have a MAF/MAP sensor on order. However, on Torque Pro am getting an inlet manifold pressure with engine off of about 14.4psi (atmospheric pressure). Presumably if this reading comes from the MAF, it would suggest that it is working ok but will try new one on arrival. Cheers.

 

[welshwestie]

Are you struggling to get into turbo? When you say you are only doing 30, what gear, what rpm?

 

[thevandidit]

Thanks for the reply. Have a MAF/MAP sensor on order. However, on Torque Pro am getting an inlet manifold pressure with engine off of about 14.4psi (atmospheric pressure). Presumably if this reading comes from the MAF, it would suggest that it is working ok but will try new one on arrival. Cheers.

They are different sensors. The maf monitors air flow in, if its faulty and not reading correctly it will not allow the turbo to boost, as it doesn't think it has enough air flow. This failing doesn't normally give a fault code, you would need to look at actual vs requested reading using vcds. Sometimes unplugging and driving up the road can diagnose itT:

 

[hartwellrj]

Many thanks for the replies and suggestions. I did think the MAF/MAP were one and the same and didn't realise about the MAF on the air inlet - doh, but a newbie with diesels and until now have had others do engine work for the last 20/30 years!!! As for speed, gears and RPM 30 mph up hills with revs falling towards 2K in 3rd resulting in change down to second and revs about 3k and rising slowly but going back to 3rd reduces revs very quickly again.

Will try the MAF tomorrow and take it for a run. Cheers.

 

[MJMX3]

My 88 2.5tdi is like poo of a shovel, pulls up to over 100 mph on legal roads of course, things i done, blanked egr valve, fitted a 102bhp intercooler, opened up the air-filter air-box by removing the tube thing inside it, and yes renewed the Maf sensor which by spending a bit more money on a Bosch original and not some chinese off ebay really gave it the ummffffff, It still has its original very soon, injectors and they will be getting Rakes, plus intend to get a remap in the future.

 

[hartwellrj]

Couldn't wait till the morning so connected Torque Pro and got a variable reading through the revs and getting a reading of 28 g/s aat 2.5K RPM - seems I'm still looking for clues unless that reading is wrong!!!

 

[hartwellrj]

As for 100mph on "legal roads", I wish - get up to about 80 with slight downhill and wind behind.

 

[MJMX3]

As for 100mph on "legal roads", I wish - get up to about 80 with slight downhill and wind behind.

80 in a 2 1/2 tonne van aint bad ! just how long it takes to get to that..

 

[donecan]

Any blockages in the CAT/ exhaust? I remember as my CAT started to go the van really struggled...I'm a total novice though so I imagine there would be other telltale signs if that was the case? Bosch MAF was the one thing I swapped when I bought my van, also a 888, and it made a big difference.

 

[Dave C59]

The foam mount for the airbox can obstruct the air inlet - try removing the airbox to check - mine was down to about 20% area and had the same symptoms as you have.

 

[hartwellrj]

Once again, many thanks for spending the time to reply.

Update for today:

Following last night's suggestions did some further searching and found that the air feed pipe going into the turbo can work loose so stripped out and found the pipe was indeed really slack. Fixed back on with suggestion of previous thread by heating the pipe up and clamping, very tight now.

Took it for a run up a local hill that always ends up at 30mph and, guess what, still 30 mph. best MAF reading about 48g/s and best boost2.6psi. Both on the low side so picking up MAF & MAP sensors in the morning.

Took the air box out, no blockages there.

Reluctant to start on exhaust/cat as they were done last year.

Getting very good at stripping this lot out and putting back together but also frustrated that two weeks of tinkering is getting me absolutely nowhere. Have decided that if the new MAF/MAP sensors don't provide an improvement I will pass over to local diesel specialist.

I'll update the MAF/MAP results tomorrow. Cheers.

 

[CUMBRIA LAD]

don't think been mentioned, but have you checked fuel getting through ok?
had that prob with our 1.9td, struggled at 30 up mway hills, dangerous, was a part blocked fuel filter

 

[hartwellrj]

Will give that a check tomorrow with the MAF/MAP change. Thanks.

 

[hartwellrj]

What a great day!!! Picked up the MAF and MAP sensors, fitted this afternoon and no signal coming from either, taking back tomorrow. Checking around the engine bay and found pipe from exhaust to egr cracked and leaking bad. Tried to undo at exhaust end but nuts sized, looking for a work around before shearing the studs from the exhaust.

 

[Or_GazM]

Did you buy "genuine" sensors.....the MAF especially needs to be a Bosch part.

 

[hartwellrj]

At nearly a hundred pounds less I stupidly went for the cheaper. However, now have the Botch. Fitting tomorrow so, fingers crossed.

 

[hartwellrj]

Yes, yes, yes!!!! What a different van I have today. Fixed broken egr pipe, new MAP/MAF sensors (Bosch of course). Took it up my favourite hill at 50 in 5th effortlessly. Thank you all very much for your ideas, knowledge and time, much appreciated. Cheers, Richard.

 

[thevandidit]

Glad it's sortedT: I nearly put my van in the auctions years ago as it was so slow, then someone on here suggested unplugging the maf sensor. Trouble is the gradually get worse, so you don't alway notice it.