Hi guys, having problem with No 4 cylinder. I found last week a knackered injector on no 4, replaced all working fine took for a spin after getting home switched off thinking all was ok. But when i came to start the car again found cylinder no4 down again. Since then Ive:-

 

Changed the spark plugs.

New coil pack fitted.

Cylinders 2 & 4 coil packs checked against each other on top of the plenum both sparks the same.

Checked injector again hear a clicking sound. injector working.

Changed coil packs over from 4 to 1.

Checked ECU Signal to injector.

Changed ECU.

 

Just taken all 6 spark plugs out of the engine and all of the spark plugs apart from No 4 are darkish, No4 like new.

 

Any Help what to check for?

Have you checked the resistance on the new injector you've fitted, in case that ones gone bad?

Yes mate its 12 ohms, i have tried everything i can think of. I'm running out of ideas. Open to any suggestions, thanks Baz.

Dare I say.... Compression test?

Yep i did not want to say it myself but...... going to get one this weekend mate.

I'm not sure if your symptoms point towards that Paul, but at least it will be something you can rule out if they are all ok :)

I thought that but always wondering if cylinders ok or not so ill get it out of the way mate. i think halfords sell them.

Halfords do them yeah you need the one with a long hose to reach the plug. Theres only 3 things required spark, fuel and compression, after that its all down to timing. a process of elimination really. I would wonder if this is a classic issue with the loom, broken or damaged cabling. The injector is good, plugs good coil packs good if compression is good, and all the others are firing correctly its unlikely timing to me that says the signal to the inj es ctor or coil ids duff.

Thanks mate for info im buying one today will carry out compression test, going to bring home a megger from work, disconnect all devices in the loom and megger to earth.

Could the ptu be at fault?

Didn't notice you hadn't tried changing the ptu! Could be that, or a poor connection to it so clean up the terminals on the ptu and check for green ness on the wiring connector

Cheers baz will check after

Really if you've got to the point of isolating the issue to the looms, spark or fuel cabling, you've got to make your way back and do continuity tests on the wires, test the PTU etc etc. if it was the CAS at fault or that side id expect to have more than one miss, I'm not 100% how it works but I'm fairly sure the CAS side is 4 connections then the PTU divides it into 6 connections. So logically the issue if its spark cabling related its PTU and forward to the cylinders. If you've got the budjet and the original EFI harness then it would probably be sensible to change it regardless, they get jiggered under that bonnet.

Cheers mate for info how much r u looking at for new harness?

new harness or good second hand one ?

Any mate.

difficult this one spend £250 on new ones and it does not fix it or put second hand ones in that maybe crxx

yeah new ones a few hundred quid from the states...that's why I say if you've got the budget, its most likely jiggered anyways. However you would need to be sure its loom related before you go splashing that cash, often replacing the pig tails is good enough to limp it on. Mines crap, but it does work, I know its coming one day.

Thanks pal for info will be meggering tomorrow hopefuly will find something. Cheers Paul

you booked into japfest again this year?

Yes mate but staying at frome near Bath from Fri to Sunday my oldest lad is at uni there so making a weekend of it. Both of my lads r going this year, r u there this year? Im hope i get this sorted before then.

How about JAE :rockon:

Oh right that makes life easier. Yeah I'll be rolling up pretty early :) reducing that damn queuing time.

Ho yes my footballing mate, how about u Baz. Football again this year? Will sort it out nearer the time.

Yes my mate was on the RX8 stand he was telling me he arrived at 8 but did not get in till 10.30!

Ho yes my footballing mate, how about u Baz. Football again this year? Will sort it out nearer the time.

 

Oh yes can't wait! Will come prepared this time... lol :)

R u going to Japfest Baz?

Im not getting to Japfest till 8.30ish. it will be nice to see everone again!