Misfiring TD5 with no DTCs

Hi Everyone. I recently bought a 2003 Disco 2 TD5 and it has had a recurring intermittent misfiring / hesitation fault. So far I have: checked the wastegate (which was free) connected the wastegate actuator directly to the turbo pipe; checked the voltage on the MAF (was OK) and tried running with the MAF disconnected ( no change to the problem); Changed the injector wiring loom and used contact spray on the plug and ECU red plug (no oil evident at the red plug). In the past couple of days the misfiring has got much worse so that it goes along the road like a kangaroo!

I have bitten the bullet and purchased a Hawkeye Total which arrived today, hurray! the only DTC was "3141 Driver Demand has been faulty" so I cleared it down an went for a drive, within 100 yards the bucking started again. When I reconnected Hawkeye there was no DTC and nothing when I sat on the drive and gently accelerated in neutral even though the engine hesitated a couple of times. I unplugged Hawkeye and left it for 10 mins and now lo and behold on reconnecting it I have the 3141 DTC back!

Does this sound like I need a new accelerator pedal or could it be something else? According to Hawkeye the voltage on Driver Demand 1 is 0.83v without touching the accelerator and 3.95v fully to the floor, Driver Demad 2 is 4.22v - 1.21V and Driver Demand Sup is 0v.

Any help would be gratefully received.

Oil in the wiring loom or pedal would be my guess.

I cut back the outer flexible wiring loom cover from the injector loom plug to the point where it swan necks up to be attached to the corner of the rocker cover and there was no hint of oil, similarly where the wires exit the loom to go into the red plug it is complete free from oil.

Did I read somewhere that fuel supply problems are not detected on Hawkeye?

Hi Musher, Can you get the fuel pressure tested at the FPR. Should be 4 bar. I'm just thinking may be a fuel pump problem.
Griff

Musher3 said:

Driver Demand Sup is 0v.

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that's a problem but as long as it gives inputs as you described it's certain that there is supply in reality and as the reading is 0 then IMO the problem can be with the ECU... as about the fuel supply i confirm that it's not covered by diagnostics

Check your wastegate actuator!

FIXED IT!!!! It was the accelerator pedal, I managed to get a second hand but tested one on eBay on next day delivery. Iv'e taken it out for a couple of long runs yesterday and today and not had a single hesitation!

The voltages on Hawkeye for the old pedal all looked good but because the glitch was only occasional and for a brief moment so it was impossible to see, the only way to have seen the fault would have been with an electrical meter with a graphical output so that you could see the temporary glitches.

For anyone else trying to track down a misfire on a TD5 this problem perfectly emulated the problems with a stuck wastegate or oil in the injector loom, obviously you need to discount these two first before moving on to the accelerator pedal.

Glad you got it fixed.