Back in may i had an issue with the crank sensor. The engine would idle fine, but wouldnt rev at all, you could coax it upto 1500rpm, and any more it would start popping and farting. Got a new crank sensor, fitted it, problem solved.

The old thread is here:
https://rangerovers.pub/topic/930-strange-missfire-undrivable-when-warm-hot

Fast forward 6 months, its just done the same thing. Pulled onto the local dual carriageway, gave it full beans upto 70mph, and when i lifted and settled to a cruise it started bucking and the RPM needle dropped to 0. It flicked back up to normal RPM a few times and power returned, then dropped out again etc. Managed to pull off the road and stopped in a layby. As before, it idled perfectly. This time any throttle input at all would cause it to start spluttering popping and belching smoke. Just like last time, but at a lower RPM.

I managed to drive it home at 5mph by just letting it idle along on the torque converter.

So my first thaught was simply "these aftermarket sensors are fkn shit, i should just go buy a genuine landrover one..."

However when digging that old thread out i realised something. Both this time and the previous time, the thing has failed immediately after a full throttle high RPM blast up the same duallie. The previous time it died a bit further down the road right enough, after i'd turned off the duallie and was back on the local road. Which got me thinking, could high RPM's somehow be related? I mean clearly its not the first time in 6 months its been at max RPM, it gets full beans a reasonable amount, but it certainly got me wondering!

Thoughts?

Is it the crank sensor or could it be the throttle position sensor? That will cause a lack of revs as the throttle butterfly is open allowing lots of air in but the throttle position sensor is telling the ECU that the throttle is closed. Giving it a good welly may just shift some muck off the end of the track.

Given the fact the tacho signal dropped out, and then was flickering all over the shop with the throttle shut and just coasting along at 60mph leads me to point the finger at the crank sensor just like last time.

The last time it also did the characteristic running perfect when cold and going pete tong when warm, that crank sensors often exhibit. I'll need to fire it up later when its completely cooled down and see if it also repeats that symptom.

Could a cracked flex plate damage the crank sensor? I know these can suffer from the flex plate cracking...

I've ordered a new old stock LDV crank sensor from ebay which will hopefully work with the V8 spacer fitted. Half the price of a genuine landrover one, but hopefully actually genuine rather than the tat thats being sold as OEM...

This is the third or fourth crank sensor this car will have had. The previous owner fitted one, which was doing the characteristic "dying after 10minutes" thing when i bought the car. I fitted a "Lucas" one from ebay, which looked exactly the same as the cheapo one the previous guy had fitted. That one lasted a year, before it broke again in May this year. I fitted a "Bearmach OEM" one in May and thats now failed again. They're all the same cheap shit though, so fingers crossed its simply just cheap garbage failing, rather than something else.

Ok some further reading and i think it cant be the flex plate thats causing it. The reluctor for the CPS is fitted to the back of a flywheel which has the starter ring gear. The flex plate is a seperate piece that bolts onto the other side of the flywheel.

So hopefully a nice genuine sensor will sort it.

When I rebuilt my engine about 80k ago, I replaced the crank sensor with an intermotor one. There wasn't anything wrong with the one that was in there and I've kept it in the boot as a spare but I've had no problems with either.

Whilst the flex plate can't cause issues with the crank sensor - the reluctor ring teeth on the flywheel can. On a GEMS it has welded teeth on the ring, which can get bent and either a) cause a bad reading on the sensor or b) clobber the end of the crank sensor an bend it. It's possible one of the teeth has even just been rubbing up against the sensor and as it wears it gets to the point where the signal is affected.

The later Thor versions had a revised flywheel/reluctor ring setup, and this doesn't happen - but I have seen people with GEMS vehicles have many a bent sensor tip - or even if one of the teeth comes off the reluctor ring, then you end up with 2 empty spaces (there should only be one) and this can cause issues with timing/firing aswell as the ECU is getting bad data.

If this is it's 4th sensor the vehicle has had, and most of them in a fairly short period of time, then I think the reluctor ring is worth checking.

yeh, there was no obvious signs of contact on the tip the last time, but i'll certainly check it closely this time around.

I guess if i just creep the engine round with a bar while inspecting in thru the hole i should be able to see any oddness?

Thinking back carefully, the first sensor i fitted when i took ownership didnt actually fix the issue it was having back then. Things were a little less clear.

The previous owner had issues with it cutting out after 10minutes or so, once the engine warmed up. The story i got was a garage had installed a new crank sensor, that that fixed it, but it had broken again some period of time later. The guy had taken it back to the garage, and the garage had said that the new crank sensor had failed due to the oil leaking from a leaky rear crank seal, and that fixing it would require the engine to come out, and the seals replacing. Thus he parked it for a few years then sold it cheap.

So the first thing i did was simply install a new sensor. I figured that the oil story was probably bullshit, and even if not, a new sensor would at least get it working as a proof of concept and get it thru an MOT. When i pulled out the old sensor, it had next to no oil on it at all. But since i was in there i installed the new one anyway, it was a Lucas boxed one, from ebay, but i realise now Lucas doesnt exist and its clearly just a sticker on some junk.

However that infact didnt cure the issue, and when it got warm it still died on its arse. It also wouldnt run at all once it got hot, rather than the RPM related issue i get now. I eventually traced the fault to the MAF replaced that with a good used one, and issue solved. I then did a year and a half on that Lucas sensor with no issues, until its MOT this year in March. It failed its MOT on some balljoints and another bad MAF causing crazy CO readings.

Got all the balljoints sorted out and stuck another MAF on it, and it passed the MOT, then on its maiden voyage with a fresh ticket it died just like it did this time around.

Eventually traced it to the crank sensor back then and bought a bearmach one which claimed to be OEM, which sorted it. That one now appears to have failed after about 6 months.

So i guess the reluctor deserves some inspection, i just dont know how much can be seen without removing the flywheel?

You should be able to see a bent tag easily enough just by turning it over slowly. It'll be the one that isn't in line with all the others and will have a shiny mark on it where it has been touching the sensor.

Fired it up this morning and sure enough, runs perfectly when cold. Just need to wait on the new sensor now!

Hi Aragorn
Just a guess. Have You checked Your fuel pump?
Had comparable issues with two p38, which were related to fuel pump after some time running.
Maybe worth a try?
best regards
KCR

Thanks for the idea, but when it did this it was running on LPG and switching between LPG and petrol made no difference.
Everything points to a loss of crank signal. I just need to try and ascertain if it was just a poor quality sensor, or if something has damaged it.

Just to report back, new crank sensor in and its fixed. Hopefully the genuine rover (LDV) one actually lasts this time!

I did turn the engine over by hand and inspect the teeth on the reluctor, nothing bent or out of place.