severe misfire at idle

4.2 V8 40v biturbo - 450 bhp
4.2 V8 40v biturbo - 480 bhp (plus)
bam_bam
Cruising
Posts: 14440
Joined: Mon Jan 18, 2010 9:08 pm
Location: London

Re: severe misfire at idle

Post by bam_bam » Thu Jul 05, 2012 7:55 pm

Shoppinit wrote:I accept all contributions of alcoholic persuasion... :drink: :thumbs:
If you did accept those contributions, you'd drink day and night without an end in sight.
We all owe you a trankerload of p1ss.
No matter where you go, there you are.

stealthyspeeder
1st Gear
Posts: 82
Joined: Tue Jun 21, 2011 9:38 pm

Re: severe misfire at idle

Post by stealthyspeeder » Thu Jul 05, 2012 9:02 pm

lol very true! If your ever in Dublin drop me a PM and I'll make sure you see the only the best bars (and strip joints!)

User avatar
Shoppinit
Cruising
Posts: 20308
Joined: Wed Dec 31, 2008 6:24 pm

Re: severe misfire at idle

Post by Shoppinit » Thu Jul 05, 2012 9:07 pm

I might just take you up on that. :)
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

stealthyspeeder
1st Gear
Posts: 82
Joined: Tue Jun 21, 2011 9:38 pm

Re: severe misfire at idle

Post by stealthyspeeder » Fri Jul 06, 2012 9:06 am

Oh dear.....

Went down this morning and put the car in D.

Same thing happened immediately, idle back to rough as fcuk. I can only assume the fuse has blown again (I had too much inner fury to check this morning!)

So what would cause the fuse to keep blowing? any ideas?

Ryan_Pestell
3rd Gear
Posts: 455
Joined: Mon Oct 24, 2011 7:44 am

Re: severe misfire at idle

Post by Ryan_Pestell » Fri Jul 06, 2012 9:27 am

if its a slow blow, it will be a gradual current over load.

if its an instant fuse blow its probably a short to ground somewhere, i.e a pinched or knicked wire
Daytona RS6+ Sold :(
Now Building a 500HP Lotus Exige

stealthyspeeder
1st Gear
Posts: 82
Joined: Tue Jun 21, 2011 9:38 pm

Re: severe misfire at idle

Post by stealthyspeeder » Fri Jul 06, 2012 9:32 am

Cheers Ryan, do you know how would I find out if the 20 amp fuse at number 32 in the fusebox is instant or slow blow?

Ryan_Pestell
3rd Gear
Posts: 455
Joined: Mon Oct 24, 2011 7:44 am

Re: severe misfire at idle

Post by Ryan_Pestell » Fri Jul 06, 2012 9:39 am

change the fuse, run the car, if the fuse blows instantly you run the car thats a short.

if it takes a while, i.e a second or two thats a slow blow
Daytona RS6+ Sold :(
Now Building a 500HP Lotus Exige

stealthyspeeder
1st Gear
Posts: 82
Joined: Tue Jun 21, 2011 9:38 pm

Re: severe misfire at idle

Post by stealthyspeeder » Fri Jul 06, 2012 9:44 am

so if it runs fine when in neutral, 30 seconds easily, then blows instantly when shifted to drive, what would that be?

number 32 is the fuse for the engine control unit.

Ryan_Pestell
3rd Gear
Posts: 455
Joined: Mon Oct 24, 2011 7:44 am

Re: severe misfire at idle

Post by Ryan_Pestell » Fri Jul 06, 2012 9:47 am

does it rev freely in in neutral?
Daytona RS6+ Sold :(
Now Building a 500HP Lotus Exige

stealthyspeeder
1st Gear
Posts: 82
Joined: Tue Jun 21, 2011 9:38 pm

Re: severe misfire at idle

Post by stealthyspeeder » Fri Jul 06, 2012 9:53 am

I didnt put it past 3 thousand as it hadnt warmed up, but yea it seemed to rev freely in neutral yesterday.

User avatar
Shoppinit
Cruising
Posts: 20308
Joined: Wed Dec 31, 2008 6:24 pm

Re: severe misfire at idle

Post by Shoppinit » Fri Jul 06, 2012 6:45 pm

Looking on the bright side, there are a very limited number of places the fault can be.

My money is on a faulty coil pack causing the fuse to blow.

How long does it take to blow the fuse? I would be tempted to buy 8 fuses and unplug the coil packs one at a time to see which one *doesn't* blow the fuse. Don't run forget to unplug the corresponding injector, too, so as not to send unburnt fuel to the cats.

That or change all the coil packs.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

stealthyspeeder
1st Gear
Posts: 82
Joined: Tue Jun 21, 2011 9:38 pm

Re: severe misfire at idle

Post by stealthyspeeder » Fri Jul 06, 2012 7:20 pm

Ok, so seems I may have jumped the gun yesterday with my analysis of what caused and fixed the problem.

Yesterday I was sitting depressed in the driver seat after cheecking the wire to the coilpacks for the umteenth time, while rereading this thread on my phone. I reread Shots post and realised I hadnt checked the fuse. Excited, I whipped of the cover, found the fuse and pulled it it out (as it came out, it dropped and I cant find it) so I put a new one in and immediately fired up the car. The idle was normal, I was exstatic! In the next 5 mins of delerious excitement, I put the Airbox back on, reconnected the MAFS and induction pipes (I think something in my mind twigged that that was a bit wierd but I was too happy to notice). Then turned the car on again and the idle was normal. That was when I posted up yesterday with my good news.

So then this morning, turned the car on, grand, put into D and then problem instantly occured again. I throw a rager and storm off to busw*nk my way to work (assuming the fuse which I thought had blown had reblown).

So went down this evening and checked the fuse. It was grand! Im now guessing that the 1st one I took and lost before inspecting was grand too! So that means it wasnt the fuse that made the car run grand, it was something else. What? The air box off and MAF's disconnected!

Right enough, I took off the box and disconnected the MAF's - perfect idle!

Any ideas what to do next? relpace MAF's?

User avatar
Shoppinit
Cruising
Posts: 20308
Joined: Wed Dec 31, 2008 6:24 pm

Re: severe misfire at idle

Post by Shoppinit » Fri Jul 06, 2012 7:40 pm

Back to square one then.

If the car runs OK with the MAFs unplugged then it's safe to assume it's not the coil packs.

If you clear the DTCs, what comes back?
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

stealthyspeeder
1st Gear
Posts: 82
Joined: Tue Jun 21, 2011 9:38 pm

Re: severe misfire at idle

Post by stealthyspeeder » Fri Jul 06, 2012 7:51 pm

Cheers!

just to check, airbox is currently off, I should keep it off, plug VCDS in and see if it brings up any fault codes? not putting the airbox back on during this check yea? Its safe to rev ok without the MAF's plugged in?

User avatar
Shoppinit
Cruising
Posts: 20308
Joined: Wed Dec 31, 2008 6:24 pm

Re: severe misfire at idle

Post by Shoppinit » Fri Jul 06, 2012 7:57 pm

I'm not sure that we will get meaningful codes with MAFs disconnected. Still, if the airbox is already off, then you could do both. Don't forget to clear the DTCs to see what is fresh.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

Post Reply

Return to “RS6 / RS6 plus (C5 Typ 4B) 2002-2004”

Who is online

Users browsing this forum: steve2003rs6 and 69 guests