RS4 B7 Slight misfire and jerky at low revs

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Kingdv8
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RS4 B7 Slight misfire and jerky at low revs

Post by Kingdv8 » Thu Mar 08, 2018 11:56 am

Hi has anyone got any ideas on resolving a problem I've got my RS4 B7 has been running with a misfire and at low revs is 1500 to 2500 it's very jerkyand is down on power a bit.. I've had it serviced including new plugs and was still doing it. so I've changed the ignition coils and still the same, someone said a carbon clean would maybe sort but it was done a couple of years ago so only covered about 9000 miles since . If anyone reads this and has had the same problem or maybe have a idea what could be the problem give us a shout pls it's starting to drive me mad. Thanks in advanced David 😀

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Re: RS4 B7 Slight misfire and jerky at low revs

Post by marc1 » Thu Mar 08, 2018 12:17 pm

Could be carbon build up / flap position movement / fuel system / injectors / vac leaks and probably other things. Do you have VCDS or access to anyone that does? If not, get it in to a specialist that know these cars.

Kingdv8
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by Kingdv8 » Thu Mar 08, 2018 12:19 pm

Ok cheers I'll make a few phone calls

Rw@@dy
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by Rw@@dy » Thu Mar 08, 2018 12:29 pm

Maf I would say is on its way out, any epc lights yet?

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Re: RS4 B7 Slight misfire and jerky at low revs

Post by marc1 » Thu Mar 08, 2018 12:32 pm

Yep good point on the MAF too.

Kingdv8
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by Kingdv8 » Thu Mar 08, 2018 12:37 pm

No lights yet and no fault codes either when checked the other day.

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Re: RS4 B7 Slight misfire and jerky at low revs

Post by Pistolpete2543 » Thu Mar 08, 2018 12:55 pm

I have something quite similar at the minute. Car has just had service & new plugs fitted at main dealers. Car was driving perfectly before but now it is stuttering very badly on very light throttle, worse when cold but still detectable when warmed up. I’ve scanned VCDS but there is no misfire fault code showing. I’m thinking they may have disturbed MAF doing the plugs? Car starts & idles perfectly.

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12th
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by 12th » Thu Mar 08, 2018 1:03 pm

My post seems not to have made it.

If it goes away when cold it may well be flaps in manifold, if not maybe one of the fuel pumps. Both issues I have had.

Everyone loves MRC - use them if you can.
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FaisalJ
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by FaisalJ » Thu Mar 08, 2018 1:35 pm

Any car that has had the manifold tumble flaps removed will be lumpy until warmed up - as is mine. Any history of that being done, perhaps at the same time as the carbon clean?

Alternatively, the flaps could be stuck. 9k miles is plenty to have carbon issues again.


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12th
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by 12th » Thu Mar 08, 2018 2:07 pm

Removing the flaps won't make it 'very jerky' though. Mine isn't.
Sprint Blue B7 RS4 Saloon with MRC tweakery.

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MIDZ
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by MIDZ » Thu Mar 08, 2018 2:13 pm

Using VCDS carry out function test of I-Man flaps, Exhaust flaps, and Airbox flap. All tests are done with the engine off and can prove if something is sticking or losing vac pressure.
I had similar issue when cold and ran this test, it turned out my airbox flap was faulty and losing vac pressure through it. Good write up on here under FAQ's

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Re: RS4 B7 Slight misfire and jerky at low revs

Post by coffey555 » Fri Mar 09, 2018 12:22 am

I would pull the spark plugs out and check the condition of them. My car had a similar issue a few years ago which turned out to be a weeping injector.

Car would misfire on start up and if it was driven down a long hill with no throttle. The plug gets wet which causes a weak or no spark, effectively making it only run on 7 cylinders.

Sometimes I got a MIL light, sometimes not.
Misano Red RS4 B7 Avant

mcox42
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Re: RS4 B7 Slight misfire and jerky at low revs

Post by mcox42 » Mon Mar 26, 2018 9:00 am

I Had similar, lumpy/labouring at tick over and missing on 5 and 8 cylinders. I also had EPC light come on and error codes "Cam Position Sensor and Crank shaft Position Sensor Correlation error". Took it to 2 recommended VAG independent "Specialists", one who didn't have a clue and another who didn't have a clue but decided the timing chain was stretched and required engine out and all bits replaced for (quoted) £7.5K!!!!!

Put engineering hat on a thought about the problem logically and also knowing the car was running fine at higher revs (fueling, misfire lumpiness disappeared) decided timing chain was fine. Replaced both camshaft sensors on Bank B, no difference but only £40 lighter in the pocket. Replaced one of the oil pressure solenoid (£39 from stealer) on Bank B (the easiest one to get to on top) and everything went back to normal. I seems the solenoid was stuck open on Bank B and letting more oil through changing the cam profile on Bank B at Idle, thus running a lot richer etc and giving the correlation error.

I also spent £4.95 on an OBD2 reader and downloaded "Torque" on Android to get the codes...in my book the best £4.95 I've spent and a must have for this car if you don't want to fork out for a Vagcom wotsit!

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Re: RS4 B7 Slight misfire and jerky at low revs

Post by K08psy » Mon Jun 27, 2022 11:14 am

[interesting about the oil pressure switch. I’ve been through everything on mine that has similar symptoms, running rich, slightly lumpy, lost the 6k power surge.
Replaced PcV, Evap sensor, plugs, coil packs and still the same. Just about to change out injectors but might try the oil pressure solenoid first. Hope it’s not the back one!

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Re: RS4 B7 Slight misfire and jerky at low revs

Post by slowcoach » Mon Jun 27, 2022 12:32 pm

Have you tried with the AC turned off?

I had a mystery rough running issue that I threw everything at, MAF , plugs etc.

Turned out an AC pressure switch and a re-gas sorted it.
Audi RS4 B7 Saloon - Avus - SS+ Suspension - Tubi Exhausts (once i get round to fitting them...)

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