LCR great missfire mystery - help needed

[jonathanp]

As some of you might know I've been having problems with missfires at high revs on my LCR.

Starts to missfire I beleive just after 4.5k up to 6k but I think I get the odd missfire at low revs as well but its more noticeable at high revs. I sometimes get the ECL flashing with a code missfre on cylinder 2 and multiple missfires detected.

Things thats have been tried so far

new coilpacks including TFSI coils
new plugs
swapped injectors for known good set
replace igntion harness/loom back to underneath the battery
new egt probe
maf has been checked
coolant temp sensor replaced
new fuel filter
new cyllinder head (old once was cracked on exhaust port)
new bosch battery 780A (old one was tired)


things I have yet to try
run some more earths (this will hopefully be done this weekend)
change crank sensor (this might have been checked by bill already)
change cam sensor
check fpr
replace ignition loom all the way back to ecu
check injection loom
replace vvt

Just wondered if anyone else would like to give some opinions on what might be causing it?

At the moment the water injection is turned off (fuse pulled), car is running off actuator only (ebc disconnected, charge pipe connected directly to actuator). I have also done an N249 bypass.

specs of car

LCR 225 (bam)
JBS 05 hybrid turbo (k04)
JBS hi-flow k04 manifold
Forge FMIC
devils own water injection
badger 5 3" tip
550cc injectors
bkr7e spark plugs

 

[Pyro]

have you tried NGK iridium plugs? pretty sure there the best plugs for these

 

[rs-tuner]

Head gasket possibly have you done a compression test?

 

[Molehill_Mike]

Find a garage with a PicoScope and software, no point in guessing and keep changing parts, waste of time/money.

 

[ibizacupra]

Head gasket possibly have you done a compression test?

compressions 200psi across the board
new now largeport head (old one was cracked on #4)
new rings
no leakdown to speak of
its had new plugs, coils, maf, injectors, crank sensor
runs a hks ebc

 

[jonathanp]

Could knock sensors do anything daft? Or could engine vibration/movement cause a problem?

I think I remember you saying something about really stiff engine mounts could cause problems?

 

[ibizacupra]

if they were lighting up high CF's yea, but they are'nt

 

[offitmassive]

compressions 200psi across the board
new now largeport head (old one was cracked on #4)
new rings
no leakdown to speak of
its had new plugs, coils, maf, injectors, crank sensor
runs a hks ebc

200PSI is a little higher than it should be. 10-13 bar are the figures it should be between (145-188psi)

 

[jonathanp]

Haven't had a chance to do the earths as yet but hopefully will this weekend.

I'm also getting hold of a complete engine loom for a reasonable price so if I find any problems with the wiring I should be able to swap parts over. Tempted to replace the whole engine loom as a temporary measure to to test but I'm thinking this could be a nightmare to do.

I've also noticed quite a lot of oil on some of the pipes under the inlet manifold. I think most of them are from the breather system. If these are sludged up is it possible they could cause issues?

 

[OVNIWCE]

You checked coil pack loom? There prone to cracking up.

 

[ibizacupra]

200PSI is a little higher than it should be. 10-13 bar are the figures it should be between (145-188psi)

maybe so, and maybe my old gauge... but its a good compression none the less

 

[ibizacupra]

You checked coil pack loom? There prone to cracking up.

replace igntion harness/loom back to underneath the battery

 

[ibizacupra]

Haven't had a chance to do the earths as yet but hopefully will this weekend.

I'm also getting hold of a complete engine loom for a reasonable price so if I find any problems with the wiring I should be able to swap parts over. Tempted to replace the whole engine loom as a temporary measure to to test but I'm thinking this could be a nightmare to do.

I've also noticed quite a lot of oil on some of the pipes under the inlet manifold. I think most of them are from the breather system. If these are sludged up is it possible they could cause issues?

your PCV pipes and suction pump gizmo...
not sure if they could cause you your misfire, but is split/leaking it would obviously throw out fueling from air leaks

 

[jonathanp]

replaced one half of the engine loom today, which includes the following wiring

coilpack harness, n249, n75, injector harness, both knock sensors, cam sensor, crank shaft sensor, throttle body, map sensor, iat sensor, vvt, single wire connector not sure what it does, sump sensor (oil level?) and a gear box sensor near the gear shift cables.

still missfiring

I've also have a rattle/tapping thats been getting worse. I can't quite pinpoint where its coming from just that its engine related, sometimes sounds like its at the bottom of the block other times it sounds like its somewhere around the rocker cover. Having the aircon on tends to bring it on (engine load/revs dependant?)

Any ideas on what else to try? Been thinking possibly swap out fuel pump relay, fpr and maybe j271 relay (believe its a relay for the coils but no idea where it is).

I'm thinking I might have to bite the bullet and replace the VVT

 

[cookieboy]

I have the same issue :-( the at is in the garage just now for new plugs coil packs maf and thermostat. Hopefully it will be ok after that. Also it's getting a compression test done an I hope the cylinders are ok.

I will let you know how I get on tomorrow night or Tuesday.

Cheers

 

[jonathanp]

That would be great, I hope you have more luck than I've had

 

[jonathanp]

Just so I can attempt to to go through this logically I'm trying to think what could possible cause a missfire no matter how remote.

My understanding is missfire could be caused by bad/no spark, fuelling issue and possibly timing?

Spark related could be the following
Ignition loom - changed
coilpacks - changed
plugs - changed
j271 (main power relay I think)
ECU

Fuelling issues
MAF - changed (could also run with MAF unplugged)
Coolant temp sensor - changed
injectors - changed
Map sensor possibly?
lambda?
EGT - changed
fuel pump
fuel relay
fpr

What could cause the coil packs to not fire at the right time?
timing
crank sensor
cam shaft sensor
knock sensors
VVT



If anyone has any thoughts on these please add.

 

[grahams81]

Do you have any idea if its missfiring over all cylinders or just one ???

Have you tried revving it to missfire and killing the engine then pulling and inspecting the plugs ?

Do you have a AFR gauge to see if it's leaning out up the rev range ?

Just for a bit of background when did the problem appear ? directly after a mod or did it get progressively worse for no apparent reason?

 

[cookieboy]

That would be great, I hope you have more luck than I've had

Went to the garage today and everything was changed and it is still not running good. Compression was 180 psi so that's good.

I will let you no when it's sorted. Cheers

 

[cookieboy]

update

I had the engine checked today out come isnt very good..

number 1 piston is covered in oil so it looks like new pistons and valves