Rs2 not running smooth, Misfires when boost

[quattrojan]

Hi again folks.

I thought i had a blown MAF yesterday so after S2Central asured me that i could use an AAN maf i tested it today, but still the car is running like crap.

It started out a few weeks ago, sometimes when starting in 1.gear the car hesitated for a second or 2 before it came like a rocket, then the same did happened a few times in 2.gear, otherwise running strong and great.

The other day it really started to misbehave so i thought i was almost out of gas (gauge was very low and i was on the way to the gas station anyway) filled up the tank and still the car wasn't acting right, it got worse and worse on the way home, actually so bad i had to do 35mph on the highway just to get the car home.

Symptoms:

Idles great when cold, but idle is a bit unstable when worm.

As soon as trying to build boost it just coughs,misfires, refuses to build boost over 0.3-0.4 and acts all strange

No fault codes from Vag-Com

So i'm thinking boost leakage, (but shouldn't vag-com then show the "Maximum Boost Preasure exceed" ?

Low fuelpreasure?

Would a stuck Bypassvalve lead to any of these symptoms?

Coils,sparkplugs and all that is almost new.


Thanks in advance for any opinion.

Jan

[avants2turbo]

try unplugging the mfts? Is it any better?

[quattrojan]

Thanks, will check that today

[quattrojan]

Did a boostleak test today and no leakage at 1.5 bar of preasure in the system, So next up is the mfts.

Anyone with other ideas while i wait for the stealership to get that new mfts?

[S2central.net]

Do NOT buy a new MFTS yet - they are stupidly expensive and don't appear to have anything to do with your misfire. If boost hoses are all airtight - and bypass valve is leak free - and also WG diaphragm... I would have to suggest coil packs or HT boots would be most likely cause of misfire, but you say those are new... Have you also changed the POS units.

Boost leaks often don't trigger a fault code BTW - very annoying I know.

Anyway - have you tried resetting the ECU - unplug it for a minute or so to force a cold start - it might have some bad history stored in there.

When MFTS triggers the temp alarm to ECU - it disables high boost levels... would not cause misfire though. Just unplug MFTS (you lose water temp guage as well) to see if that changes anything.

The other thing to consider is that 'new' MAF may not be healthy - I'm assumed it was a 2nd hand one.

Have you checked timing is perfect - or imperfect I should say for RS2 with its oddball half-tooth out to the left.

[shark_90]

Last time I had this problem a new set of coil packs were the order of the day. I know you say they were changed not long back but it sounds exactly the same.

[quattrojan]

Tanks for all the replies

The "new" MAF is from my S6 so i know it works.
I did unplug the mfts when the car was idling today and that did do some changes to the idle(rised a bit on rpm's) did not go for a test run with it unplug thow.

I have 2 spare sets of coilpacks and pos units so next will be to throw one of them on and see if that makes her smile again

Will also try to reset the ecu as suggested

Timing is already checked and is spot on!


And i bought this RS2 just cause the S6 project isn't completely finished yet and wanted the S/RS feeling untill it was back on the road and i also promissed my self not to spend money on it before the S6 was done I Hate myself

[S2central.net]

Timing on RS2 is NOT 'spot on' the marks - you know that right ?

[quattrojan]

S2Central: Yes.. but its spot on in "RS2 Style"

[S2central.net]

OK - just checkin...

[AUDIS2avant]

How do you reset the ecu again???
Cause my car keep´s acting strange, so want to try this

[UrS4boy]

How do you reset the ecu again???
Cause my car keep´s acting strange, so want to try this

Disconnect the battery for 10 minutes (have your radio code handy for unlocking) or pull the ECU fuse (sorry, I don't know where that is for an S2/RS2 since I have an UrS4).

[quattrojan]

Did reset the ECU yesterday with no luck, Changed both POS and still the same.
Took off the coil cover just to see and the coil 1-4 looks spanking new but nr 5 was a bit blackish looking, like at had had been exposed to exhaust or something so i pulled out the sparkplugs and they all looke like they get the same and right amount of air/fuel. Was gonna try out with a new complete coil set, but i guess that when my ex-gf told me to organize my garage last year i must have put those coils in a very special place cause i sure as h** couldn't find them So gotta continue that search today


The boots are all as new.

Also changed back to stock airfilterbox and bypassvalve just in case.

But still when the car is cold it almost runs great... havent floored it since the engine is cold but no problem getting 1 bar without misfire, but at working temp it acts like a freak

Might do a compression test today just to be sure.

[UrS4boy]

Suspect: No 5 spark plug or coil

I don't know if you know this BUT...

Recent batches of Bosch F5DPOR plugs have been showing signs of the ceramic separating from the hex. In fact, the ceramic can often spin free of the threaded metal hex. As a result, there can be gas leakage around the plug, into the sparkplug well. This would not do the coil good.

Here is an example of that problem:

http://forums.quattroworld.com/s4s6/msgs/3660.phtml

[EspenW]

I'd VAGCOM log some of the values that the MTFS generates and check if they are out of whack at operating temps.
Also, check the resistance of the coil to plug connecting boots, no matter how new they are.