P38A DSE won't rev

Downunder11 · May 27, 2019

My 2.5 DSE 1996 will start okay and idle OK. It will rev until redline when stationary. As soon as it goes into drive it won't rev past 1,000rpm 90% of the time. Occasionally it will drive normally, but not often. Specialist says no fault codes are coming up on Nanocom however is suggesting either faulty potentiometer or Map sensor. Does anyone have any ideas??

gold rover · May 27, 2019

Have you tried different diagnostics and the following handy book

Addit: @Saint.V8 , @Grrrrrr , @Henry_b and the other P38 owners, is the potentiometer the same as the TPS*? Or is the idle control thingy?

*Nooooo, not tyre pressure sensor

Grrrrrr · May 27, 2019

Think they mean the throttle position sensor but if that was shot then I don't think it would rev at all.

MAP is worth checking. The pipe runs from fuel filter to under the inlet manifold. Need to make sure the inlet manifold end is clear and pipe is good. Diagnostics should show change in pressure as turbo spools up.

Datatek · May 27, 2019

Downunder11 said:
My 2.5 DSE 1996 will start okay and idle OK. It will rev until redline when stationary. As soon as it goes into drive it won't rev past 1,000rpm 90% of the time. Occasionally it will drive normally, but not often. Specialist says no fault codes are coming up on Nanocom however is suggesting either faulty potentiometer or Map sensor. Does anyone have any ideas??

Faulty potentiometer? More details needed, do you mean the fuel quantity servo potentiometer?

Grrrrrr · May 27, 2019

Any smoke out the back when revving? Easy to check the lift pump is working properly so I'd be tempted to rule that out. There's a how to by @wammers in the Technical Section.

Grrrrrr · May 27, 2019

Datatek said:
Faulty potentiometer? More details needed, do you mean the fuel quantity servo potentiometer?

On reflection they must be. TPS wouldn't rev in neutral.

Downunder11 · May 27, 2019

Grrrrrr said:
Any smoke out the back when revving? Easy to check the lift pump is working properly so I'd be tempted to rule that out. There's a how to by @wammers in the Technical Section.

No smoke really, revs fine in park too.

Downunder11 · May 27, 2019

Datatek said:
Faulty potentiometer? More details needed, do you mean the fuel quantity servo potentiometer?

Think he was talking about accelerator pedal potentiometer but will check.

Datatek · May 27, 2019

Downunder11 said:
No smoke really, revs fine in park too.

It's pre EGR so I'd look at the MAP sensor on live data for starters, a duff sensor will put it into limp mode. If the guy has a Nanocom looking at live data from the CPS, needle lift sensor, modulation etc should give some clue as to what is happening.

Datatek · May 27, 2019

Downunder11 said:
Think he was talking about accelerator pedal potentiometer but will check.

If it revs in neutral it's unlikely to be that.

Grrrrrr · May 27, 2019

Nanocom can record a trace of what is going on. Then you can zip the CSV file and upload it here. One of the gurus might spot something. Think there are 2 or maybe 3 sections in the EDC module.

Downunder11 · May 27, 2019

Datatek said:
If it revs in neutral it's unlikely to be that.

OK Thanks

Downunder11 · May 27, 2019

Grrrrrr said:
Nanocom can record a trace of what is going on. Then you can zip the CSV file and upload it here. One of the gurus might spot something. Think there are 2 or maybe 3 sections in the EDC module.

OK will check tomorrow and update you, thank you.

Grrrrrr · May 27, 2019

Downunder11 said:
OK will check tomorrow and update you, thank you.

It'll need an SD card. Take yours and he can drop the files straight onto it for you.

P38A DSE won't rev

Downunder11

New Member

gold rover

Well-Known Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

Datatek

Well-Known Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

Grrrrrr

Technician, Bodgit & Scarper Ltd

Downunder11

New Member

Downunder11

New Member

Datatek

Well-Known Member

Datatek

Well-Known Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

Downunder11

New Member

Downunder11

New Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

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