EM light on & low power

[ianrobbo]

Here's the story - brother-in-laws facelift 2.5V6 auto, valve spring broke, had the head off, changed it, all back together again.
When I first started the car after re-assembling it, it ran badly, just changed the leads & plugs, runs lovely now.
But, drive it down the road a bit and the engine management light comes on, and the car loses power, which I guess is limp home mode. Come back home, disconnect the battery, reconnect it again, start the car, drive off, all is well for a couple hundred yards then EM light comes on again, car loses power, etc, etc.

Being a facelift, I gather I can't do a paperclip test, is that correct?

Any suggestions for things I could check before I take it down to the robbers at the Vauxhall dealers?

[Taxi_Driver]

If its a 2.5 then yes you can.....its only the 2.2/2.6/3.2 facelifts you carnt.

So paperclip test it and post up your results  

[TheBoy]

Yes paperclip test will work on all 2.5 engines.

Wonder if it will come up with 17 - Knock Sensor 2  

[Admin]

  my thoughts exactly!

[STMO123]

You both beat me to it Exactly same symptoms as mine( knock sensor 1)

[ianrobbo]

Bang on - knock sensor 2.

Is this the RH (drivers side) one? If it is, I've already had the aux drivebelt tensioner off, wire's not trapped, no problem.

Is there anywhere else I could have trapped it, maybe the timing belt rear cover? (hope not!)

[Marks DTM Calib]

No, its the passenger side one......common for it to be trapped between the camcover and head following a re-fit.

[ianrobbo]

Didn't have the cam cover off on the passenger side, it was the other head I had off.

Looks like I need to do more investigation

[ianrobbo]

Cracked it - the passenger side knock sensor wire was crimped between the timing belt rear cover and the cooling pipe which comes from the thermostat housing.

Quite surprised really, as it hadn't snagged it that hard - I moved it out of the way without removing anything - but it was enough to short it out.

Spliced a new bit of wire in and all is well. Absolute bu**er to get to though!

[Marks DTM Calib]

Good news.......