I've had the P0235 error pop up a few time recently so I've replaced the MAP sensor, Boost Valve and the small boost valve pipes in an effort to pin point my problem.

So positive and negative pressure pipes relating to the turbo have been checked and suspect parts replaced but still when the car hasn't been used for a while I get the same error(P0235).

If I drive the car for 10 - 15 minutes then clear the error no matter what I do I cannot reproduce the error. However, if I wait a few hours, jump in the car drive to a local dual carriageway and floor it, up pops the P0235 error. The car drives great, no noticable loss of power apart from when the error pops up, she pulls like a tank even with the error displayed???

Attached is 3 graphs.

The vertical line on the top one is second gear.

The vertical line on the middle one is third gear.

The vertical line on the bottom one is fourth gear.

Can anyone see a problem or suggest other parametersI should test?

It seems to me, that VNT blading do not move properly when turbocharger/engine is cold... but I'm not sure...

hanzs said:

It seems to me, that VNT blading do not move properly when turbocharger/engine is cold... but I'm not sure...

Click to expand...

Hello hanz.

If thats true and the blades are not moving as they should when cold, what could cause it?

Edit.
Its just been suggested to me that it may be a build up of soot causing the blades to stick while cold and making the engine management light to come on. This can be solved by puting the engine under a heavy load at around 3500rpm, example, accelerating hard up an onramp to the motorway. This burns off the soot deposits allowing the blades to move freely again?

Sounds feasible to me as the car rarely gets a good run. We do lots of short journeys.

Just been out to pick up my grandson's, no P0235 error ...

Stu,
Mine has been doing this too.
Like you i have changed everything boost valve ,pipes, maf ,map etc etc.
It still pops up and infact today has been going mental.
I,m at a loss to offer any advice but if you find the problem let me know !!

Cheers for now

Hello Kev.

I think Hanz is correct, the vanes in the turbo may be sticking due to a build up of soot from lots of short low speed journey's. What makes things worse for me is the boost valve pipes on mine had holes in so the actuator wasn't traveling its full amount. Now I've repaired the pipes the vanes are getting stuck on the build up of soot that has accumulated while the vanes/turbo wasn't working properly.

I think a blast along the M54 during the early hours of tomorrow morning may cure my problem by burning of the accumulated soot.

If that fails I think I'll give this a try.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=350470008499

Edit.
Innotec PDF attached to this post

Stu,

Cheers for this.
I do like the sound of a midnight blast i must say!!
I think i may make an ivestment in the turbo cleaner at the end of the month, and give it a go .
Going to be an expensive month again as i need 2 new tyres on the front, already sorted them pair of kumho's at 68 each side fitted.

Cheers and thanks for posting that link

Kev, take a look a this:
http://www.technologie-entwicklung.de/Gasturbines/VNT15-Turbo/vnt15-turbo.html

has photo's of what I think is causing my(possibley yours) P0235 error. SOOT ..

Thanks Hanz, I suspect you have solved another problem for me.

A common problem for those that "Drive Like Miss Daisy" according to R-Tech anyway.
http://www.r-techpower.co.uk

Let's hope, that you are right!

I've just brought the Innotec Turbo Cleaning Kit, might just give it a clean anyway.

I've attached the Instructions(PDF) to this post.

So, here's the data I just collected on a local dual carriageway. I've included desired boost and actual boost plus desired fuel presure and actual fuel presure. Desired fuel presure and actual fuel presure drop seriously before desired boost and actual boost do. Is this a fuel presure problem thats causing the ECU to dump boost?


Edit.
Just had a text message from a friend telling me to check the cold start sensor.

Does the JTD have such a thing?

If so, where is it and how do I check its working?

So here's the data from that long straight private road my uncle owns.

Car has 105,000 miles her and is completely standard apart from runing on Bio-Diesel.

Rolling start, according to the speedo about 75mph, changed from 4th into 5th and floored it, held her at 120mph for a while.

Lets hope that burnt off any soot, lets see if I still get the P0235 error in the morning.

Have you tried the actuator test on fes.I think it's engine off but needs a bit of vac in system,if your quick(or have a long lead) you can see the actuator pulling in about 10mm .you only get a go or 2 till run out of vac.if your going to inotec it ,I would stick to manually moving the lever whilst soaking.I've just stripped a spare turbo(scrappy) and the vnt blades were stuck to the housing,with a lot of soot in back the vnt ring.

I've done 2 school runs and 2 quick prints up a local dual carriageway this morning and no P0235 error.

Fingers crossed thats cured it.

Did as sussexa suggested and activated the boost valve using FES, here's the result. Still seems a little "jerky" to me?

[ame="http://s296.photobucket.com/albums/mm189/Shadeyman67/?action=view&current=15062011071.mp4"]15062011071.mp4 video by Shadeyman67 - Photobucket@@AMEPARAM@@http://vid296.photobucket.com/player.swf?file=http://vid296.photobucket.com/albums/mm189/Shadeyman67/15062011071.mp4@@AMEPARAM@@vid296@@AMEPARAM@@296@@AMEPARAM@@mm189/Shadeyman67/15062011071@@AMEPARAM@@mp4[/ame]

Hi all,
Well my car is now driving me insane.
Everytime P0235 is stored. I have cleaned the map sensor, looked and checked all the other suspect things. I have run FES and one thing i have noticed is the desired boost pressure is higher than the actual pressure, could this mean something. Any help/ideas gratefullyt received !!

Cheers for now

Kev,

My car is runing great now(still going to clean the turbo though) and my actual boost is always higher than desired boost so I guess thats the way its should be.

Got fed up of guessing what my problems where so brought a new MAP sensor, new boost valve and new boost valve pipes gave my car a new lease of life.