Last week I changed my upper and lower engine mounts on my 2008 TD4.

The test drive afterwards ran perfectly, but the next day while reaching about 80kph / 50mph I got some violent lurching and jerking and the engine sounded like it was going to die. I released the throttle and it recovered, but occurred a few more times before getting home. The engine never cut out and recovered each time.

Diagnostics shows error code P0336 Crankshaft Position Sensor, so I got a genuine replacement sensor and put it in.

The vehicle is still doing the same thing - it starts and runs perfectly at lower speeds, but as soon as I reach higher speeds it misfires and hesitates, then recovers, with the same P0336 error code coming up.

I'm certain that while replacing the engine mounts I didn't go anywhere near the CPS and it's wiring was not pinched or caught anywhere, so I'm thinking it's just a coincidence that this started the day after I changed the mounts.

What could be causing this, specifically only at higher speeds? Could it be that the wiring from the ECM to the CPS is going dodgy and the connection between the two is intermittently failing, as I have read on other posts in this forum?

How likely is it that it's the trigger wheel on the crankshaft that's failing, has anyone experienced this? or any other ideas?

Thanks in advance!

Why did you replace the mounts?

It's been found that some wiring on the crank position sensor can fail. Maybe your failing mounts allowed faulty wiring to stay in contact, but now the engine has moved slightly, the wiring is now failing? Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Can you get hold of a known good sensor to try on the car.

It's known that even new sensors can fail, happened to me. I thought I would replace the existing sensor with a new one as part of a service around the time I replaced the belts.

Ended up having to put the old one back in

Nodge68 wrote:

Why did you replace the mounts?

It's been found that some wiring on the crank position sensor can fail. Maybe your failing mounts allowed faulty wiring to stay in contact, but now the engine has moved slightly, the wiring is now failing?

I Like Chips wrote:

Can you get hold of a known good sensor to try on the car.

It's known that even new sensors can fail, happened to me. I thought I would replace the existing sensor with a new one as part of a service around the time I replaced the belts.

Ended up having to put the old one back in

Just an update on this - took the vehicle in to an auto electrician, it was indeed dodgy wiring in both the crankshaft sensor plug and further up the wiring from the sensor where it joins the harness to the turbo solonoid. All repaired and running again!

This is a pic the auto elec sent me. He said he un-taped the wires and just gave them gentle pull and this is what happened, so it was holding on by just a few copper strands

Nice easy fix