Huge over boost problem.

[Joss 9]

Well I'm going to go through all the options with you guys and see if I can eliminate the components. A while back I mentiond that the JTD used to overboost occasionally while on track. This would put it into safe mode and I'd have to turn it off and on again to sort it. I could only ever replicate the problem on track and so I never got round to seeing if the problem had been fixed. It used to boost to about 1.8 bar when it did this error. Now the mrs has been driving it for a few weeks as she is too lazy to sort out her own car (thats another story which I will probably rant about at some point) and she said that it went into safe mode the other day. It did it once with me the other week too but as I wasn't expecting it I wasn't looking at the boost gauge. Well today I took the JTD to work and it would seem the problem has got massively worse. Got onto the dual carriageway and on it came as I accelerated up to 70. Pulled over in a layby and switched it off. Pulled out and accelerated and it did it again. So pulled over again to pay attention to the gauge. It's a defi electronic gauge which are known for there accuracy and it measures boost pressure at the beginning of the plenum so I'm confident these figues ar correct. Under hard acceleration it goes off the end of the gauge at 2 bar Then you get the light after a second or too. Trying various things I can't use full throttle for more than a second or it spikes the boost and it seems to be running about 1 bar in 6th at 70mph or partial throttle when it used to be running aroun 0.5-0.7 bar so there is definitely a boost issue at all parts of the rev range. If you drive it at high revs (3.5K+) it overboosts even on partial throttle. Also when trying not to get it to spike the boost which used to bleed at 1.6 bar and stay static ish at 1.6 bar is now all over the place between 1.4 and 1.8 bar. It's like it can't bleed it off in a controlled fashion.

 

So things I have done in the past.

Changed the VNT hoses

Cleaned the MAP sensor which was clogged.

 

Possible things I think it could be

Need to clean MAP sensor again

MAP sensor is bust

VNT solenoid ( one on the back of the rad) is not functioning properly

Turbo issues with the vains getting stuck.

 

The car is remapped, has full turbo back exhaust with no cat and one silencer, egr delete, and high flow filter.

 

Any suggestions would be appreciated

[Smaky 73]

I strongly suspect that this is all down to the remap and please don't say it was done by Autodelta. But I would think all of this has started since you got rid of the cat? The filter is a BNC? I also take it that this is the 1.9 JTDm.

 

The thoery for the orries...

 

Lack of Cat on the exhaust is not creating the back pressure required to hold down the acceleration of the turbo spindle, this is then overspeeding causing the overboost which the MAP sensor is correctly picking up and throwing the ECU into limp mode, an ECU reset would resolve it but only for 50 or so miles, the problem I'm affraid is the remap and exhaust, I'm also not a fan of high flow filters on these as there is no point to them as the stock filter already allows 250% more air through than can pass through the throttle body so what's the point?

[Joss 9]

Yes the map was done by autodelta. However these mods have been done for several years now. The last thing I did was egr delete probably about a year ago and not had problems before except for on track but even then it was very occasionally. This boost issue has only popped up in the last week or so. I spoke to Adie at AHM at the time when I had the original track fault who told me to clean the MAP sensor and change the VNT pipes, change solenoid. Never got round to checking the solenoid as it never happened again but I never put it on track again although he said if I got past this point then it was more likely to be a turbo issue. The car is very high mileage (164,000 on the original turbo) so would it not make sense to be a failing component as the I hear lots of stories where the turbos give issues and solenoids too at higher mileage.

 

and no it's a 1.9 JTD 16v M-jet (140bhp originally)not a later jtdm oh and filter is a k&n in orignal airbox. Car has FMIC too. decat was done separately to exhaust too. Comes from JS tuning. lots of guys were using them with no issues

[Smaky 73]

The car is very high mileage (164,000 on the original turbo) so would it not make sense to be a failing component as the I hear lots of stories where the turbos give issues and solenoids too at higher mileage.

 

 

A faulty turbo doesn't tend to overboost, normally if thevanes get damaged they start to jam up and this causes the bearing to go, but I don't think it's the turbo itself, it doesn't sound right, without the car it's hard to check things, really it needs the live diags on it as it's playing up to see which figures are wrong.

[Joss 9]

I can do that on FiatECUScan can't I or am I getting confused somehere? Could go for a drive and log it. I presume I'd want to look at boost pressure but what other perameters?

[Smaky 73]

Throttle %

Boost pressure

RPM

Load %

Air flow

Manifold pressure

[Joss 9]

ok I'll go try it out and come back with the log

[Joss 9]

Well I never got round to doing the log. On friday I went to see a mate who happened to have the solenoid that sits just behind the rad on the 156 spare. Think it was a Saab one he had stuffed in the bottom of his roll cab. Thought we'd chuck it on just to rule it out............and what do ya know. Boost issues gone We both took out the JTD and thrashed the (ahem) out of it up the bypass. Could not get it to error where as before even a wiff of full power would have put it in safe mode. At least I know my turbo is still healthy. Stayed at 1.6/7 bar before trailing back to about 1.4/5 towards top of the rev range.

[ChrisO 2]

Is that the VNT solenoid ?

 

I have read (at the other place) a number of threads regarding these and the vacumn pipe failing, and am begining to wonder if this is the signs of a issue with all JTDs

[Joss 9]

Yes it is the VNT solenoid I'm taking about . Yes the vac pipes become britle and split causing boost issues. Easy to change them all on the 156. Think its a little bit more tricky on the 147 as it is loacated on the side of the airbox I think.

[Smaky 73]

Well I never got round to doing the log. On friday I went to see a mate who happened to have the solenoid that sits just behind the rad on the 156 spare. Think it was a Saab one he had stuffed in the bottom of his roll cab. Thought we'd chuck it on just to rule it out............and what do ya know. Boost issues gone We both took out the JTD and thrashed the (ahem) out of it up the bypass. Could not get it to error where as before even a wiff of full power would have put it in safe mode. At least I know my turbo is still healthy. Stayed at 1.6/7 bar before trailing back to about 1.4/5 towards top of the rev range.

 

 

There you go Joss, I was convinced it wasn't the turbo and on another forum there is somehow exactly the same problem as yours and on there they are convinced it's turbo and a dutch apprentice is trying to convince him to remove the turbo and send it to his friend for repair... who just so happens to be asking about the same issue on the dutch forums...

 

The readings I'd asked you to monitor would have picked that up so you've just bypassed a diagnostic stage and changed what I'd probably have suggested, nice one

[Joss 9]

give yourself a pat on the back . We were just about to go out with the texa diagnostic too but as it wasn't needed. Perhaps you can pass on this thread to the europeans!

[Smaky 73]

Don't think I'll bother passing this on, they are turning out to be arrogant asses, the guy with the problem is in the UK but is just being blinded by their fancy workshop, just a shame that every post they write seems to contradict the last.

[Joss 9]

Wonder if it the same guy I had dealings with on AO a while back. He was an idiot

[Smaky 73]

I think it is.

[Joss 9]

Oh dear.