G60 misfire under load

[P3rks 11]

After having a nightmare with my new G60 and after replacing the headgasket/head I'm now getting a misfire under load. Whether it's related or not I don't know.

 

The car drove fine for about 200 miles. Then suddenly started misfiring under load.

 

The car will drive perfect on part throttle. I can get up to about 8psi of boost (according to my boost gauge which will show 10psi of boost on WOT). The car will rev all the way through the rev range (on part throttle). The car idles fine. I actually drove 100 miles with this issue, on part throttle so I can confirm it only does it on WOT.

 

As soon as I give it WOT at any revs the car bogs down/hesitates and misfires; in a high gear and low revs on WOT it still misfires. Being low RPM it doesn't get up to boost but still misses, which shows it's not boost related.

 

I've not tried WOT from cold, only from warm. 80+ degrees and I don't want to give it beans from cold. The car drives fine on part throttle from cold.

 

The timing is spot on, the ignition timing is spot on (6 degrees BTDC). Both idle and WOT switches are 'clicked' by the throttle cable. The ECU hose is a brand new VAG hose, 1m. It's had a new fuel filter. It's had a new throttle body to coil housing earth strap, the earth from the battery to body/gearbox look to be in good condition.

 

I have some new Golf Gti 8v HT leads I can try, I'm picking up a new dizzy cap and rotor arm on the way home from work tonight. It has the W6DP0 plugs; the age and condition of these are negligible. The coil looks to be in a fairly new condition - on that note which way should the black and green wire be fastened to the coil? I.e. Which is positive and which is negative?

 

How can I check the idle and WOT switches are working correctly?

 

How can I check the hall sender?

 

What other checks should I be doing?

 

Any help or advice would be greatly appreciated. :luvlove:

 

---------- Post added at 10:27 AM ---------- Previous post was at 09:57 AM ----------

 

Just ordered a beru dizzy cap and rotor arm which I'll try tonight.

 

Also, ordered some W5DP0 plugs which come tomorrow. (Car is tuned, 68mm pulley, stage 5 charger, exhaust, P&P head etc). or should I go for W6DP0?

[Sideways Steve 10]

Having owned many "boosted" cars I can safely say it sounds like you are suffering from ignition breakdown going by what you have described.

 

What this effectively means is that that your spark is being "blown out" This is usually down to the spark being too weak which in turn is usually due to either duff plugs or your HT leads tracking. It can also be due to badly gapped plugs or worn dizzy arm/cap.

 

If you have spare leads swap those first and see how you get on as about 90% of the time I have had this issue has been through HT leads failing or coilpacks deteriorating.

[P3rks 11]

This is exactly what I though.

 

Well, The new HT's (well, 1 week of use from my old PB engine) will go on tonight. Same with the dizzy cap and rotor arm. See if that fixes it..

 

Also, regarding the spark plug gap, I've read it should be .24 or 0.6mm.. I'm confused? I've never set a gap before can anyone explain the basics?

[domwells27 0]

Plug gap would be 0,6mm or 0.024"

[P3rks 11]

Plug gap would be 0,6mm or 0.024"

 

Right..

 

So literally a 0.6mm feeler gauge under the spark plug and bend the electrode to suit?

Edited August 1, 2011 by P3rks

[Sideways Steve 10]

Exactly mate, however take care as you are not able to re-gap some plugs ( or at least your not really meant to )

 

Which plugs are you running on it ?

[P3rks 11]

Currently running on W6DP0's.. But like I say they look pretty tired.

 

I have some W5DP0's ordered which come tomorrow. The car's running about 200bhp so they should be a little better.

[Sideways Steve 10]

Ah ok yes, as I thought those are not "traditional" plugs and are similar to the likes of the Iridium NGK ones I used to use on all my boosted cars. As such you should not really re-gap them as they come pre gapped from the factory and there quite delicate.

 

The other issue with that type of plug is that they are really crap if they get fouled and it can pretty much destroy them so if your exisitng ones are manky then that may well be causing your misfire.

 

---------- Post added at 01:56 PM ---------- Previous post was at 01:42 PM ----------

 

 

See new reply below

Edited August 1, 2011 by Sideways Steve
To prevent confusion - Incorrect info !

[P3rks 11]

Are you sure?

 

I was under the impression that the lower the number in Bosch terms the colder it is? The W5DP0 is the plugs the G40 uses and is colder.. Aimed at G60's with 190bhp+

 

NGK is the other way around. So The higher the number the colder it is..

Edited August 1, 2011 by P3rks

[Sideways Steve 10]

Are you sure?

 

I was under the impression that the lower the number in Bosch terms the colder it is? The W5DP0 is the plugs the G40 uses and is colder.. Aimed at G60's with 190bhp+

 

NGK is the other way around. So The higher the number the colder it is..

 

Forgive me, your completely right im getting them mixed up again ! I always get them the wrong way round when chopping and changing LOL

 

NGK = Higher Number for Cooler Plug

Bosch = Lower Number for Cooler Plug

 

You would be looking at a BP7EVX or BP8EVX in NGK terms. the BP7EVX is equivelant to your Bosch W5DP0

 

Sorry for the confusion !

[P3rks 11]

Forgive me, your completely right im getting them mixed up again ! I always get them the wrong way round when chopping and changing LOL

 

NGK = Higher Number for Cooler Plug

Bosch = Lower Number for Cooler Plug

 

You would be looking at a BP7EVX or BP8EVX in NGK terms. the BP7EVX is equivelant to your Bosch W5DP0

 

Sorry for the confusion !

 

Phew...Glad thats sorted!

 

But I've fixed it.. Changed the HT's, Dizzy cap and rotor arm... Turns out the dizzy cap was cracked where the king lead fastens so it was arcing..

 

Yay!