issues with 1.9 tdi 110

[v0id]

hey guys,

ive had the car nearly a month now and ive been getting really bad MPG no matter how I drive, around 350 miles to a full tank (50 quid) at most, which is like 30 mpg.

a couple of weeks ago I noticed a turbo overboost problem. got diagnostics on it and fault was:
17965 - Charge Pressure Control: Positive Deviation
P1557 - 35-10 - - - Intermittent

anyway, I basically:
- replaced N75 valve
- replaced valve that goes underneath EGR (not N19)
- fitted new timing belt (as it was squealing).
- timing was off, car took ages to start. sorted now.
- replaced waterpump
- got car fully serviced (air/fuel/oil filters + oil change + glow plugs)
- checked MAF by unplugging it, car ran much worse so I assume MAF is ok
- replaced engine temp sensor (G2?)
- replaced vacuum hoses
all using genuine oem parts

after all that, the car kept going into limp mode but not as often. I put in some forte diesel treatment and all of a sudden the limp mode is gone. i confirmed this by going uphill at high load which ALWAYS put it into limp mode but this time it was fine.

anyway, Im still getting really bad mpg (30mpg) even when I drive nice and easy. It also takes a while to start the car in the morning. any common reasons why?

any help is appreciated.
thanks

update: when my mechanic did the timing belt change, he said there was a lot of carbon buildup. he recommended I clean the intake manifold/egr valve. would this contribute to the problem?

 

[MrBen2k7]

Yeh, you got a definate problem there mate... I get 450-520 miles a tank... on my 110 SE...

If you have had a full service, check they did a fuel filter change.

 

[v0id]

yeah I was there during the service. they replaced fuel filter and changed oil as well.

 

[seantdi]

try replacing the glow plugs.

 

[v0id]

hi mate,

glow plugs changed at service as well. I've pretty much done everything I could think of and it hasnt improved the mpg by even a little a bit

ill update the first post.

 

[seantdi]

did you try clean out the erg valve and inlet manifold

 

[v0id]

not yet, could that be the cause of getting 20 mpg less? the car has done 124000 miles and I doubt the previous owner ever cleaned it out.

would you say I would be able to do this on my own? ive got basic mechanical skills but am afraid of breaking stuff!

thanks for the replies.

 

[rallynut]

bit of a fiddly job but easy enough and you will be shocked to the amount of crap in there if its done 124000 and never been cleaned,have a search in the tdi section theres a guide in there somewhere may be worth plugging the vacum line after to keep it all clean.,you may/may not get a engine light come on.

 

[tolly_tdi]

try this also...

Sorry to hear you're having the dreaded TDI limp mode problem.

I have the same engine so if you haven't cleaned out the EGR/intake system I would try out disconnecting the N18 valve that is located on the bulkhead next to the N75 this will disable the EGR and indicate how the car would run without it (its not a necessary function it just exists to lower exhaust gas temperatures and emissions early TDIs didn't have them)

This thread will give some good advice- good luck!

http://www.seatcupra.net/forums/showthread.php?p=2371808&posted=1#post2371808

 

[Muttley]

I'll second the suggestion to remove the inlet manifold and clean it out. At your mileage the manifold could well be seriously choked up, restricting the airflow into the engine, which hurts a diesel all over the rev range. Do you notice if it smokes a lot?

There is a guide on the tdiclub site - it is on a VW Jetta in the States, but the engine is the same. Look towards the bottom of the page to see the amount of debris that was removed from the manifold.

As for the EGR I have disconnected mine to prevent this build-up and would recommend the process to others. EGR reduces NOx but increases soot emission, and combined with the gradual worsening of performance, my estimate is that over the life of the engine, EGR is detrimental to the ecology. US regulations mean that car manufacturers have to do something to reduce NOx, though. It isn't tested at MOT.

 

[tolly_tdi]

I also got the intake cleaning DVD which is really good worked out about £15 when I got it. The guide is good but I was too lazy to go through it (rather have someone just show me hence the DVD!)

 

[v0id]

thanks for the replies everyone. some more points to note:

- turbo kicks in at 2000 rpm (i thought it was supposed to be 1500?). still whistles alright.
- i havent really noticed any smoke but there is a bit when I put my foot down (whitish smoke)

btw guys, I understand this would cause the limp mode issue. but would this also reduce my MPG? I dread that after I clean out the intake manifold my MPG stays the same .

 

[tolly_tdi]

tbh the mpg should improve as there will be better combustion ratios of air:fuel as to some extent it has been limited by the clogging reducing the intakes internal diameter.

The fact that it is not pulling until later in the rev range could mean your MAF needs changing as you previously mentioned that you checked it was working but did not say when it was changed. I had the same problem recently changed the MAF and the pull was so much more immediate. After you have tried disconnecting the EGR valve you can test the MAFs responsiveness by changing at a higher RPM that usual 3/4k.

Limp mode sounds worst than it is and is just a fail safe the ECU initiates to prevent overboosts etc from reocurring and distrubutes a default level of fuel it therefore does not damage the engine in any way.

 

[rallynut]

whitish smoke indicates water burning(steam)is the car overheating at all?you shouldnt be seeing white smoke is that when its warm or just first thing in the morning

 

[Muttley]

Best way to find out what colour the smoke is is to have someone follow you. Unless you're putting out clouds, you only get a distant view in the mirror. Black or greyish smoke indicates fuelling issues, and it's the carbon in that smoke that clogs up the VNT vanes in the turbo.

I think your inlet manifold is choked up enough to seriously affect your mpg. The engine isn't breathing properly, you aren't getting enough air into the cylinders so the effective compression ratio is dropping (even after turbocharging). You're demanding power, and the only thing the ecu can do is inject more fuel up to the smoke limit, leading to poor economy and excessive smoke production.

This thread on the tdiclub forums has the pictures I was looking for earlier. Man had 160K on his passat, never cleaned out, found inlet manifold heavily choked up. Cleaning produced increased performance and improved mpg.

 

[v0id]

I used to see a LOT of white/grey smoke first thing in the morning, but after timing belt change thats gone. smoke smelt like unburnt diesel.
I only get it when I put my foot down now when engine is warm (I never see black smoke).

car never overheats. stays at 90C at all times.

edit: thanks for the reply Muttley. ill have a look at that thread.

 

[brightsideteeem]

any joy?

 

[v0id]

i havent cleaned the intake manifold out yet, waiting for a sunny/clear day... hopefully tomorrow.
I've tried unplugging the EGR/N18 valve and Ive noticed better throttle response but not much improvement.

i will update this thread soon to keep you guys posted.

 

[v0id]

hi there guys, sorry for the late update.
i finally got around to cleaning the egr+intake manifold. egr was full of gunk but the intake manifold only had a 1-2mm film so it wasnt as bad as I was expecting. I even checked the actuator arm on the turbo and it was perfect.

took it for a spin afterwards and still the same issues. feels like its lacking power in higher revs and MPG is really really bad. also, turbo kicks in at 2000+ rpm. is that right? or is it meant to be 1500.

anything else that could be causing my problem? Ive pretty much approached every angle.

 

[brightsideteeem]

sounds like something to do with the fuel pump then to me.