Haven't been on here in a while chaps, busy life and all that lol. So I have bought myself a nice little mk4 golf gt tdi 115 ajm, very tidy. It has a running issue I can solve, with no codes. When pulling away, accelerating in the lower rpms, and to some extent even in the upper rpms, the car seems to lack a power one moment, stuggling to accelerate up a hill, then after a few seconds the power kicks in and it accelerates like you would expect, then it will go flat again. All the time it is doing this its still pulling through the gears, just like its a non turbo one min, and a tdi the next. There are no codes, no boost leaks. Maf is clean and I believe is working ok all though im not sure what value should be seen at idle and wot etc (my reader reads in ib/s) with 0.02 ib/s at idle. has anyone got any ideas? I am leaning towards sticking turbo veins but i am not sure.
115 doesn't have veins Sounds like a maf ..these don't always show up on vag com What would I check ..Vacuum pipes to and from boost control valves and turbo ..them all
Funny mine has a vnt turbo with vanes The 115 ajm is a pd Eddie your thinking of the 110 non pd My guess would be the maf When the vanes stick it go's into limp mode that if you put your foot down nothing happens Stop the engine and restart and it clears
Yip it dose Vac pipes tend the chaf through at the clips that hold them on The one nearest the turbo is a favourite
HA, was going to say, last time I checked the pd's had vnt's, not that wet behind the ears when it comes to derv lol. I have checked all that, every visual check I can think of, I am not sure about the maf. Does anyone know what healthy readings should be?
Not off the top of my head no But when my maf went it started like this I took it the a friend of a friends garage He didn't even look at said aye it's the maf I cleaned it and it was a bit better for about a week then it failed altogether The light on the dash only when it failed You could try unplugging the maf if it runs better it's that Mines run the same ever way till it failed though
I had a similar sounding problem on my 2003 VW Sharan that had the same PD engine and I struggled to diagnose for 2 years. Eventually cured it by replacing the pedal mechanism as it was fly by wire rather than mechanical throttle linkage and wasn't sending a clear message to the ECU. Not sure if this is any help as I've never had a Mk4 golf
That is exactly what my gut is telling me rooster because that is what it feels like. I will check the tp readings tommorow and check for fluctations. Im still hoping its the turbo. After missfueling last night and breaking down, i now have a starting issue which feels like diesel draining back to the tank when left off for a few mins. Got a feeling thats the tandem pump fried lol.
Best of luck. If it's any consolation I was ready to get shot of the car before replacing the pedAl 89 later it was like new so well worth it
Ok, so I have checked TP readings and they are normal, MAF sensor is fine, turbo actuator seems to move freely, all vac lines are either new or ok, new coolant temp sensor and thermostat (needed anyway) and full service. Still having this surging issue, most noticable pulling away in 1st when it gets to 1200rpm and surges like its suddenly found more power. MPG is great, averaging 53mpg tank to tank i did missfuel it with a full tank of petrol at the weekend, drained it all out and flushed with diesel, since this it seems to suffer with fuel draining back to the tank if left a while as it winds over a bit before it starts, even when hot. So im of the opinion that the either that tandem pump is letting air in due to a failed seal, or something else like the in tank pump maybe having a one way valve that has failed??? This issue only presents its self when parked facing up a hill or after being sat a while. Important to point out that the above happened AFTER the surging issue, so they are not linked. I am at a loss as to what to do, the MAP sensor shows a steady gain in psi to a spike of 35psi (above atmospheric so 14psi at idle) and settles to 29psi. It really feels like fuel issue, it kicks quiet hard at 1200rpm in first gear, almost like a break caliper is on then suddenly releasing! (its not) Could it be a failing tandem pump anyway? I believe they are supposed to supply 100psi to the head in order to force the fuel into the injector bodies and ramp up the pressue. Still no codes and no limp mode.
Ok so I have found info that says the correct figures for a healthy tandem pump are 3.5bar at idle and 7.5bar at 4000rpm. If this figure is not reached, to test at 4000rpm, use a hose clamp to clamp off the return line out of the tandem pump. If 7.5 bar is now seen, there is pressure loss at the injectors, if pressure target is not seen then the tandem pump is faulty. I have also just discovered I am getting engine oil into the diesel (black fuel, black fuel filter). All starting to point towards the tandem pump! Its not leaking outwards which is unusual.
Sounds like guessing ...could be injector seals. Changed these in the past due to poor starting running problems/oil diesel mixing.
Worth a look, I may change them anyway as its done 140k. If not that then is the tandem pump no doubt. Injector seals will show up in the return flow test.
Update: Confirmed as the tandem pump not supplying anywhere near the pressure required. And also feeding a small amount of engine oil into the fuel return. New tandem pump has improved MPG by 10 extra average mpg's, regained low end pickup off idle and removed the 2-3k flat spot.
