CDTI struggles over 2000 RPM

Geoff130 · 23rd March 2020, 14:12

My CDTI has been running fine since changing the fuel pump relay (Intermittent starting) and unplugging the MAF sensor (wouldn't rev over 3000 RPM) Recently it's learned a new trick, somewhere around 2000 to 3000 RPM it feels like it's misfiring and won't rev any more. It's not always at the same point and sometimes it's not evident until really pushed. TOAF says the LP pressure is a little over 3 bar at idle and drops to 3 when revved, no ECU faults. Any ideas where to start looking. It may be a coincidence but this started after I topped up the tank with about 10 litres of fuel. I did check the receipt and it was definitely diesel.

Geoff130 · 25th March 2020, 17:34

Today just to be sure I checked the plenum was dry and it is, tried with and without the MAF but no difference and also disconnected and blanked off the control pipe to the EGR still the same.

COLVERT · 26th March 2020, 18:16

A failing crank sensor has been known to cause a misfire at higher revs.--

willster · 26th March 2020, 19:15

I had virtually exactly those symptoms. For me it was one of the wires going to the injectors, get some one to hold it at set revs and have a good wiggle on all those wires going into the injectors. It was a break as the wire entered the plastic connector. I got a full new harness from a scrapper and that sorted it.

Geoff130 · 28th March 2020, 14:31

Thanks, as I've got a bit more time on my hands than usual i'll take the loom off from the ECU and check it all end to end.

Geoff130 · 25th April 2020, 12:04

I have now tried wiggling the injector harness as suggested with no effect but I did find the ECU end of the harness came off quite easily so re-seated it but still the same. I've also tried a new filter but no change. I've just checked the fuel flow and it's around 1.5 litres/min at the inlet to the filter. When driving it won't respond to the throttle over 2000 RPM then suddenly will shoot off at full power then die again. I have noticed with the ignition on but engine not started the under bonnet pump is running continuously, is that correct?

23rd March 2020, 14:12	#1
Geoff130 Loves to post MG ZT 190, Rover 75 CDTi, Honda VFR 750, Honda CB550F Join Date: Aug 2010 Location: Derby Posts: 393 Thanks: 75 Thanked 36 Times in 28 Posts	CDTI struggles over 2000 RPM My CDTI has been running fine since changing the fuel pump relay (Intermittent starting) and unplugging the MAF sensor (wouldn't rev over 3000 RPM) Recently it's learned a new trick, somewhere around 2000 to 3000 RPM it feels like it's misfiring and won't rev any more. It's not always at the same point and sometimes it's not evident until really pushed. TOAF says the LP pressure is a little over 3 bar at idle and drops to 3 when revved, no ECU faults. Any ideas where to start looking. It may be a coincidence but this started after I topped up the tank with about 10 litres of fuel. I did check the receipt and it was definitely diesel.

26th March 2020, 19:15	#4
willster Loves to post Rover 75 Tourer Auto CDT Join Date: May 2009 Location: Rochdale Posts: 319 Thanks: 8 Thanked 20 Times in 18 Posts	I had virtually exactly those symptoms. For me it was one of the wires going to the injectors, get some one to hold it at set revs and have a good wiggle on all those wires going into the injectors. It was a break as the wire entered the plastic connector. I got a full new harness from a scrapper and that sorted it. __________________ Our greatest hopes and our worst fears are seldom recognized

25th March 2020, 17:34	#2
Geoff130 Loves to post MG ZT 190, Rover 75 CDTi, Honda VFR 750, Honda CB550F Join Date: Aug 2010 Location: Derby Posts: 393 Thanks: 75 Thanked 36 Times in 28 Posts	Today just to be sure I checked the plenum was dry and it is, tried with and without the MAF but no difference and also disconnected and blanked off the control pipe to the EGR still the same.

26th March 2020, 18:16	#3
COLVERT This is my second home R75 Saloon. Join Date: Feb 2009 Location: France/or Devon. Posts: 14,003 Thanks: 3,851 Thanked 2,167 Times in 1,816 Posts	A failing crank sensor has been known to cause a misfire at higher revs.--

28th March 2020, 14:31	#5
Geoff130 Loves to post MG ZT 190, Rover 75 CDTi, Honda VFR 750, Honda CB550F Join Date: Aug 2010 Location: Derby Posts: 393 Thanks: 75 Thanked 36 Times in 28 Posts	Thanks, as I've got a bit more time on my hands than usual i'll take the loom off from the ECU and check it all end to end.

25th April 2020, 12:04	#6
Geoff130 Loves to post MG ZT 190, Rover 75 CDTi, Honda VFR 750, Honda CB550F Join Date: Aug 2010 Location: Derby Posts: 393 Thanks: 75 Thanked 36 Times in 28 Posts	I have now tried wiggling the injector harness as suggested with no effect but I did find the ECU end of the harness came off quite easily so re-seated it but still the same. I've also tried a new filter but no change. I've just checked the fuel flow and it's around 1.5 litres/min at the inlet to the filter. When driving it won't respond to the throttle over 2000 RPM then suddenly will shoot off at full power then die again. I have noticed with the ignition on but engine not started the under bonnet pump is running continuously, is that correct?