Misfire - items changed but still not cured

[ronnie1]

Right I posted a tread the other week about a misfire that developed on my car whilst on cadwell park.

Between 5k and 6k revs it seems to misfire and also the shift light flashes (not sure if thats important or normal for a misfire)

Anyhow ive since changed the coilpack, leads and plugs. The leads were split and the plugs had seen better days so happy to change them. Ive tried the test with the injectors (removing one at a time and each one made the car tick over awful) and all seem to be fine.

So im at a bit of a loss, ive had it on a diagnostic and theres no faults recorded.

So any help will be much appreciated -

 

[LowLife.]

Try a compression test?

 

[ronnie1]

That sounds pricey if it isnt a favourable result

 

[Bassplayer]

First off, it isn't a shift light. It is to indicate over revving, you have long passed max power when it lights up. Anyway, if it is flickering I would reckon a bad connection or broken wire somewhere. First up, check the battery terminals (remove them and clean/grease). Check the earth connectors from the battery to body and from body to engine. Check the wires to the coil pack too. Check all the other connectors to the throttle body etc - but these are less likely.
When you have this sort of problem, it is usually the vibration of the engine that will cause it. when it reaches a certain frequency / revs that will cause the poor connection /break etc to break up or spark and cause a misfire. Good luck! Let us know how you get on.

 

[ronnie1]

Cheers bassplayer!!! Top info. Will get them all checked.

 

[Laine_16v]

I would be swapping out the crank sensor. THe shift light will be controlled by the ECU, which will be controlled by engine speed read by the crank sensor. If you are getting a missfire at a cerain at certain revs and the light is triggering at this point too, then there lies your problem IMO

 

[scotty2hotty81]

lambda sensor maybe? swop them front to back there the same.

 

[ronnie1]

Right its currently in a garage being diagnosed after it wouldnt start, it was turning over but not catching

They tried a new crank sensor but that didnt help. They have said that they have had an oscilloscope (?) on it and it seems no information is going from the ecu or back to the ecu from the crank sensor. Any idea what this could mean? I kinda wanna understand so im not ripped off. He also asked if it had been chipped, i explained it had an rstuner map on before i bought it. Said he has a megane in and the ecu from that is sending the signal to the crank sensor...my ecu f**ked?

Oh, the car does bump start and run, but the issue at 5.5k is there

Sorry for long post and thanks for any help

 

[Bassplayer]

Still say bad connection. If it bump starts the jolt is causing the connection to happen. If they aren't seeing a signal at the crank sensor with a 'scope, next thing is to check for 5volts at the sensor. Let me explain. The ecu supplies 5v to the sensor. The passing of teeth on the flywheel etc will cause a pulse back up to the ecu to tell it that the engine is turning.
Soooo, check for 5v to the sensor and a wave form coming out. Chipping etc won't normally affect it. Keep us posted.