TD4 new problem

Hello again boys and girls, a new problem has started on my 55 plate TD4. Engine starts as normal, and reversing(slowly) off the driveway also ok, but when you go to pull away its almost as though the engine stalls and then goes and stalls again, similar the a cold petrol engine with no choke, less pressure on the go pedal and engine returns to normal. After a hundred yards all becomes ok and the engine will not misbehave any further until left for a while. I have tried leaving it ticking over for a few minutes before driving away and that seems to be normal. Just had the pump and filter changed and fault still seems to be there. Any one else had this problem.

Mine judders first thing in morning but I think it's to do with clutch as I dip it and give it more throttle it sorts it's self out.

Sounds like a throttle position sensor or accelerator speed sensor. I think the mapping includes a bit about how fast the accelerator is pushed down! Failing that, water in the fuel system or it hasn't been bled properly and has an air bubble sitting in it.

I had this issue and it was the airflow meter was faulty.

Looked at values at startup and airflow was in 60,000 somethings instead of around 500. Once running fine all day until restarted the engine.

Replaced the maf and then all good since

Worth checking the engine temperature sensor.

Further info now I have changed the pump and filter. Problem still there.
Only have the problem on the initial start each day but haven't tried if it has been left all day since initial start. Starts as per normal, first time, if you then hold the throttle at around mid position the engine hunts, revs go up and down although the peddle is not moving. If you then get to high rev, and lift foot of the problem clears and everything works ok until the next morning.

BigRog said:

Further info now I have changed the pump and filter. Problem still there.
Only have the problem on the initial start each day but haven't tried if it has been left all day since initial start. Starts as per normal, first time, if you then hold the throttle at around mid position the engine hunts, revs go up and down although the peddle is not moving. If you then get to high rev, and lift foot of the problem clears and everything works ok until the next morning.

Click to expand...

As I said, check the engine temperature sensor, even on a diesel, the mixture is enriched on a cold start, if the sensor is duff this may not happen. Diagnostics would be the way to confirm the problem.

Agree with davef2901 that the throttle position sensor may be at fault and a couple of strokes of the throttle is clearing it. Have you tried fully depressing and releasing the throttle a couple of times before you start the engine? Potentiometers can be bad for being thrown off by even the smallest amount of moisture or grease.

Cheers guys, will give these things a look or trial, I think next thing is putah time see if any codes are available.

OK more info, latched maf fault so replaced it with ebay item (cheap so not too bad if it does not fix), which it didn't. Did a 10 mile trip into town, no problem, coming back started to die and pick up around 3000 revs in any gear. Got it onto driveway and did a few tests, it still cut out and in at the same revs( as though some one switched ignition on and off), but again when you can get it revved to red line it clears the snag and it runs a dream. I went out this morning and before starting for the first time put accelerator pedal to floor and back 3 or 4 times, then started and after a minute floored it, work as advertised, switched off and went in to write this. Mrs just took it to local shop, perfect on the way there, played up on the way back.
I do not see it being temp switch as it is juddering at all temps, someone mentioned a throttle position sensor, but can only find them for petrol engines, another suggestion has been the turbo sensor/solenoid.
Any suggestions ?

have you checked the wiring to the fuel rail sensor ?

which fuel pump did you replace ?

Pressure sensor loom replaced about 18 months ago. I believe it only has one pump, near side wheel arch, high pressure. My man has it now for MoT, going to try computer connected on first start of the day and see if it gets any readings, he also suggested it may be a injector problem. I will let you know any results.

you also have a pump in the fuel tank, if you listen at switch on you can hear it wiirrring,these types of faults are very tricky to diagnose at the best of times ,even harder when not actually there to see it

I thought it was the earlier TD4 that had the in tank pump

BigRog said:

I thought it was the earlier TD4 that had the in tank pump

Click to expand...

It is.