Please help strange boost problem THINK I'VE SOLVED IT

[dpbayly]

Hi all
Right i recently became an owner of a Y 2001 blue 1.4tdi arosa i saved it from the scrap heap it came into our garage with water loss and signs of head gasket anyway the owner decided to call it a day and asked us if we knew a company that could scrap it, i felt it was far to good condition to scrap (mint) and asked if i could take off there hands, i went on to have the head removed tested skimed andi rebuilt it, problem solved but i have noticed a strange boost problem, it drives great but from cold if i drive it normally i lose the boost so i have to turn the ignition off and on to restore it anyway if instead of driving normally i keep the rev's up not pushing hard but just letting the rev's get up to 3500 before changing basically keeping the overall rpm above 2500 i dont lose the boost i only have to drive like that to the next village just under 1 mile then i can drive nicely again ive removed and cleaned the N75 the MAP sensor and MAF sensor but the problems still there i've pluged it in and there was an error code i cant remember exactly what it was but it was to do with the boost control valve but it works as when the engine is very slightly warmer it runs well and it ticks away like it should so im at a loss im hoping someone has come across this problem and spare me from going insane i have to have my cars running perfect, its driving me nuts

 

[Boo]

Have you checked that the fuel pump isnt blocked. Could be the EGR valve or even a dodgy glowplug ?

 

[dpbayly]

i fitted new glowplugs when fitted new headgasket, ive been thinking of blocking off the EGR valve but was'nt sure if it would throw up the management light do you know anyone who has blocked it off and has it increased the performance?

 

[Boo]

If it was the EGR valve though I wouldve thought you would have an engine management warning light come up on the dash ? So Im inclined to think its something wrong fuel wise if its fine when it warms up. My car is a 1.4 petrol automatic and when its extremely cold it really takes some effort to start up and judders a wee bit. I cleaned the throttle body out (which is a common problem) and it seems to be fine now. Dirty throttle bodies are a common contributor to engine stalling issues though.

 

[dpbayly]

i too am thinking it could be a fueling problem i have seen in another thread on the TDI forum about the diesel fuel gelling in cold weather where the fuel i guess thicken sligthtly and the fuel pump struggles, in the thread i was reading a good quality fuel cleaner cured the fault so im thinking of trying that as i have nothing to lose they say the pump gums up and loses performance and so when its cold and the fuel is thicker it struggles which makes sense and sound like whats happening to me as when the engine warms up just a tiny bit (fuel thins) problem disapears.

 

[Boo]

Worth a try as you said, you have nothing to lose. Let us know how you get on

 

[dpbayly]

i put the fuel system cleaner through and there was no change but i did notice a strong smell of diesel so i popped the top plastic cover off the engine but could see no leaks but i could really smell it i looked under the car and saw some drips so took it into work and put it up on the ramp, removed the bottom cover and there was diesel all over the place weird thing was it seemed to be coming from where the dip stick tube enters the sump, i checked the level and it was really high so i dropped out the oil and to my shock i drained out 7.5ltrs (it only holds 4.2) and it was really watery so i had to figuer out how i was getting so much diesel into the oil system, it could only be entering from 3 places being a PD engine the injectors are internal with the fuel rail being part of the head so it could be the tandum fuel pump seal, injector seals or disasterously a craked fuel rail anyway i knew the fuel pump was ok as i fitted new seals when i fitted the head and the injectors where refitted by the place that skimmed and presure tested the head so decided to check them as i could not be sure it had the seals replaced and hey presto fuel leak sorted and now the loss of boost when cold is sorted too i guess it lost boost when cold due to when it's cold the engine feeds more fuel to the injectors and with the leak and loss of pressure it could not supply enough so it would put it into limp mode, I guess thats what was happening anyway im chuffed to have sorted it.

 

[Boo]

Crumbs - a small mission then ! Glad you got it fixed and thanks for letting us know.