MK5 Golf GTI

All Things Mk5 => Mk5 General Area => Topic started by: DomBacon on June 18, 2015, 06:53:37 pm

Title: misfire and running too lean!
Post by: DomBacon on June 18, 2015, 06:53:37 pm
Car doesn't seem to be running quite right lately so plugged in vcds to have a look
No fault codes

But on logging i have misfire on cylinder 3 and 4
Replaced coil packs, plugs and done a compression test and all held about 160psi!

Then when I was looking at other bits i found out its running too lean

(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fface_ulser%2FMobile_Uploads%2Fimage_8.jpg&hash=932a5ecc8bccddc1d6e59e532b27d52843d0b379)

I replaced the cam follower and its still the same.
Heard that vacuum leaks can cause it to run lean so replaced my forge dv for the better oem one and my pcv blank to the oem pcv. Car still runs crap!
Rail pressure is fine as well.

What else could it be?
Anyway i can check injectors using vcds?

Any help would be much appreciated  :happy2:
Cheers Dom.
Title: Re: misfire and running too lean!
Post by: jhook661 on June 18, 2015, 07:24:32 pm
If you've got a miss fire on both cylinders and you've changed all above ^^ it's most likely to be injectors
Title: Re: misfire and running too lean!
Post by: DomBacon on June 18, 2015, 07:38:02 pm
Just don't want to spend the money on injectors and it's not the problem as they cost quite a lot!
Title: Re: misfire and running too lean!
Post by: jhook661 on June 18, 2015, 07:55:41 pm
It's running lean and misfiring in two cylinders it's looking that way to be honest
Title: Re: misfire and running too lean!
Post by: DomBacon on June 18, 2015, 10:34:54 pm
Could be the carbon build up on the valves
Title: Re: misfire and running too lean!
Post by: jhook661 on June 19, 2015, 06:19:16 am
Yes it could be that too I completely forgot about they get chocked up badly well remembered  :happy2:
Title: Re: misfire and running too lean!
Post by: Dan_FR on June 19, 2015, 06:31:48 am
What intake are you running? What were your LTFT's before you had this issue?  How many misfires are we talking about and are they all the time including at idle, or just when driving/under load? Are you K03 or K04? You mention you replaced coil packs, but what about the plugs? If not, change them. Did you examine the plugs colour/condition? if so then details or pictures would be good

Lots more info needed, but the short answer is no you can not check them with VCDS. You can sometimes hear them after you have had the car running by removing a spark plug and listening in to the affected cylinder for a slight hiss
Title: Re: misfire and running too lean!
Post by: DomBacon on June 19, 2015, 10:46:53 am
Forge twin take the moment but changing to a different one when I get a chance to change them over
Edition 30 so ko4
I said I replaced the spark plugs as well
Not sure on LTFTs
About 7-10 every minute I'd say and only at idle
Title: Re: misfire and running too lean!
Post by: Dan_FR on June 19, 2015, 12:38:56 pm
Missed the mention of plugs. Does sound very much like the injectors, getting to be common with K04 cars as they are getting older.

Did you check the condition of the plugs when you changed them? Were the 2 wet / soaked in fuel? Removing the plug and listening for a faint hiss from inside the cylinder shortly after switching the engine off would be next
Title: Re: misfire and running too lean!
Post by: DomBacon on June 19, 2015, 02:09:28 pm
The plugs were quite burnt but don't remember them being wet or anything
Someone told me that all cars misfire on idle and 7-10 misfires a minute or 2 isn't anything to worry about!
He said the reason the car is running lean is because of the Revo map, his seen it happen before apparently.
Title: Re: misfire and running too lean!
Post by: DomBacon on June 20, 2015, 06:30:31 pm
Are the S3 injectors the same as the standard ones in ed30?
Ive seen places say they flow 13% better
or
RS4 injectors? going to go stage2+ once this problem is sorted and then bigger turbo
The rs4 injectors are about £120 cheaper than the s3 ones
Title: Re: misfire and running too lean!
Post by: bacillus on June 20, 2015, 07:53:44 pm
Are the S3 injectors the same as the standard ones in ed30?
Yes

Ive seen places say they flow 13% better
That's compared with the k03 injectors.

Imo stick with the standard k04 injectors as their spray pattern is better suited to the gti engine.
Title: Re: misfire and running too lean!
Post by: DomBacon on June 21, 2015, 01:25:24 pm
Was only going to replace them for rs4 ones as there much cheaper, I can send mine off to get tested and cleaned but that takes 5 days