Help please - Misfire holding revs - Video inside - Track day in 7 days

[GrahamS]

Evening chaps - Post on behalf of @Martin.
Next weekend we're meant to be going to Bedford so are desperately trying to sort this.
On Thursday just gone Mart failed the noise test at Brands due to this misfire but eventually got through. http://www.cliosport.net/threads/martins-track-clio-182-project-thread.767120/page-13#post-11187818

Symptoms
When building up the revs the car starts to misfire around 4k which then of course makes it burble and fail the noise test. There is some hesitation around this rev range when on part throttle driving.
When flat out there doesn't appear to be the issue and when building up the revs quicker it doesn't do this.
All the plugs are black like it's running rich.

What we've tried
Different and known good coilpack and leads
Clean the plugs
Looking at diagnostics - there really are only limited meaningful codes we can pull from the car. From a basic look at the OMEX and CLIP we can't spot anything although the OMEX software isn't a forte of mine.

Spec
Car has an OMEX with bodies

Thanks in advance for you help and ideas everyone

 

[bloke]

looked at live data? will it rev past that ok?

 

[GrahamS]

looked at live data? will it rev past that ok?

Yeah we have, not 100% what to look for really though.

Revs past there no problem, we just noticed it kicked in there particularly badly and it's what caused the noise test fail.

 

[bloke]

had cranks sensors causing a hard misfire/cut but not like yours. would say look at what the lambda is doing, had a run over the last three or four weeks of iffy sensors either not bringing up a fault code or bringing random ones up. had some head scratching for sure!!

 

[GrahamS]

@bloke yeah, we thought sensors but it seems to only have an air temp sensor on the intake. The omex has its own crank sensors as its acting as a piggy back but the lambda sensor isn't used at all within the map. Coolant and air temp appear to be reading correctly.

 

[bloke]

lambda definitely isn't used?

 

[Martin.]

Thanks for starting the post G man.

@bloke nope, it doesn't use Lambda at all..

 

[bloke]

don't suppose you can scope the crank sensor and see what it's like at 4,000? or chuck another one on if you've got a spare?

the times i've had them play up they've given more of a hard cut rev limiter issue though.

 

[GrahamS]

Just to update it's a spark/fueling issue. @AlexW came down this morning and plugged in his AFR gauge. On idle it's reading correct then as the revs build it become very rich down to 10 and at times 9. When flat out it's fine. Spark from the coil appears to be quite weak.

 

[bloke]

that's why i was thinking lambda but if you ain't running one and fueling is solely down to the map then that's next to look at?

iat and cts both ok?

 

[GrahamS]

Yeah IAT and CTS both reading correctly. It doesn't appear to be a sensor issue and the map can't change with the OMEX, the sensors can only change where in the map the fueling is.
From our test it's spark related and the lack of strong spark is causing incomplete combustion. This though we can't explain, it's fine when we've swapped the plugs for new ones but it soots up and comes back quickly.

 

[bloke]

got to be worth trying a crank sensor then, you never know.

 

[GrahamS]

got to be worth trying a crank sensor then, you never know.

Timing signals on OMEX is spot on so its very unlikely and there's no timing error.

Last night we checked the spark again with a better earth and it's strong. Compression test came back good. Even swapped the dephaser solenoid just incase.

 

[bloke]

Take it you looked at the signal at the rev range when it's running rough?

This is going to turn out to be one of those daft things that's causing it and you'll probably kick yourself when you find it!!!!!

 

[GrahamS]

Yeah we did, no problems with it at all.

It sure is, we're honestly totally out of ideas now and are down to wiggling wires.

 

[bloke]

What ate fuel trims doing when it runs rough?

Can you get it on an emissions tester and see what it's doing as well? That might give you a bit of a clue.

Is it running ecu as stand alone or piggy backed?

 

[Martin.]

Piggy back ECU. Still has the standard ECU running the clocks, central locking etc.

We even removed the shift lift wiring away from the coil wiring just in case there was any interference.

Not sure what fuel trims are @bloke?

Going to phone OMEX back in a min and see if they have any ideas or suggestions.

 

[bloke]

Ignore me about fuel trims, forgot you weren't running a lambda.

 

[Martin.]

Just to update this.

Engine Dynamics fixed the issue.

I'm not sure on the specifics, but a load of wires were left looped behind the standard ECU when the OMEX was installed by the previous specialist. ED trimmed back these unused wires and tidied it all up with electrical tape. They also reloaded the map file on the OMEX.

It's been running sweet since and they've not been able to replicate any cornering issues or misfires.