Jerky at low rpm / small throttle angles and down on power

[RS4RAB]

Definately change the injectors.

Did you log Low pressure fuel and High pressure in the pulls?

For reference I see a peak of 162grs maf read at ~7800, give it a clean first to see, I assume the air filter is new or at least recently cleaned?

The lowest I get at WOT with lpfp is 3.8 and hpfp specified and actual at around ~120


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High pressure was logged and at 7000rpm to 8000 car was specifying 114.99, actual readings were anywhere from 113-119

At this pull i was reading 150grs on the MAF

Didn't have low pressure logged but had group 106 which is electrical fuel pump and between 7-8k this was between 49 and 52, think that is a percentage

It does start to pull timing at around 5k rpm? and other times randomly at low RPM?

Have taken the air filter out this afternoon and it was filthy, cleaned now and once dry i will re oil with the spray from the cleaning kit, will clean the MAF also as looks a bit dirty

The readings you mention seem ok, adaptation is something you could to do but honestly I would not underestimate the injectors specially with the mileage you have, flap screws and faulty injectors are the main reasons behind these engines getting blown. A faulty TB would give a code and you would notice in some cases sudden jumps in idle moving, you could also peep down the hose between the MAF and TB and see if the TB flap has any dirt buildup. As someone else mentioned hpfp could be a possibility but you haven’t mentioned anything about misfires

You mentioned AMD tuned so are you in the US? AMD tunes here as I recall are done by UM, about the air filter just clean it but don’t oil it, theres different views but most of the owners I know including myself will go with a non-oiled filter.


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TB was cleaned when I had the IM off for carbon clean, (should of done the injectors at the same time) 1 way valve under intake was changed and new IM gaskets used

When doing this I found a split in the vacuum line that runs across the front of the engine bay that goes to the air box flap, thought at this point that was my issue! Also one of the arms that actuate the flap rods had a fair amount of slack in it, I was removing the flaps and screws but the actuators were going to be left in so they didn’t need mapping out so I replaced the worn part

As far as misfires go VCDS shows nothing as the mapping seems to disable this data, not sure if getting the car flashed back to stock is the first thing to do or change injectors!

I’m in the UK, AMD are in Essex and believe this is where the car was mapped by the previous owner

[rs user]

in all honesty i would be looking for evidence that one of the injectors are faulty before changing them-i realise in the states fuel is different and there are a good few failures but here in the uk there are not so many injector failures-many sill on originals and fine heading to 200k

the mapping should not have disabled the fault finding data-for anything that can still go faulty that is,so should still show relevant code and show missfires,issues with individual cylinders etc

also are you 100% sure you do not have an air leak in the intake somewhere? does the new one way valve you fitted deffo work fine?

pulling timing at 5k plus is also typical of high inlet temps-if fitted lower airbox flap stuck[just sorted this on mine will go to caf in spring]

my car was holding no vacuum at the front at all-the solenoid for the lower airbox flap was leaking badly-had no flap code errors but as the ecu shows a flash and the car has all the signs of a deflap[still pending a physical check]

[RS4RAB]

in all honesty i would be looking for evidence that one of the injectors are faulty before changing them-i realise in the states fuel is different and there are a good few failures but here in the uk there are not so many injector failures-many sill on originals and fine heading to 200k

the mapping should not have disabled the fault finding data-for anything that can still go faulty that is,so should still show relevant code and show missfires,issues with individual cylinders etc

also are you 100% sure you do not have an air leak in the intake somewhere? does the new one way valve you fitted deffo work fine?

pulling timing at 5k plus is also typical of high inlet temps-if fitted lower airbox flap stuck[just sorted this on mine will go to caf in spring]

my car was holding no vacuum at the front at all-the solenoid for the lower airbox flap was leaking badly-had no flap code errors but as the ecu shows a flash and the car has all the signs of a deflap[still pending a physical check]

New 1 way valve was only fitted as recommended to do when you have the inlet off, the problem was there before and still is now so this seemed to make no difference

Air box flap has been removed and CAF fitted, IAT temps I think were around 16 at the time of the pull I think, will need to check the logged data on the laptop

All of the mods were done years ago so it’s not down to a change recently

Will do some checks to see if I can find any vac leaks

[RS4RAB]

Definately change the injectors.

Did you log Low pressure fuel and High pressure in the pulls?

For reference I see a peak of 162grs maf read at ~7800, give it a clean first to see, I assume the air filter is new or at least recently cleaned?

The lowest I get at WOT with lpfp is 3.8 and hpfp specified and actual at around ~120


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Cleaned the MAF and filter, filter was very dirty, looks like new now, MAF cleaned with MAF spray, however the car is now even worse, very slow to respond so ordering a new MAF

[coffey555]

When I cleaned my MAF all it did was kill it! I leave it well alone now as they seem very sensitive.

[rs user]

When I cleaned my MAF all it did was kill it! I leave it well alone now as they seem very sensitive.

same here-never had any sucess cleaning them-...

[AA_954]

When I cleaned my MAF all it did was kill it! I leave it well alone now as they seem very sensitive.

Yes they are although I’ve never had an issue cleaning mine but I do try to spray from a distance and not put too much pressure on it, theres always something that comes up with these


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[RB1]

is it worthwhile trying a throttle reset?
viewtopic.php?t=124222

Mike

This made a big difference on drivability for me. I did the throttle body alignment procedure first with VCDS (http://wiki.ross-tech.com/wiki/index.ph ... ment_(TBA)), and this helped a little, but it was small.

The procedure in the car that was a massive difference on the overall drivability after a carbon clean and de-flap. I still think some of my problem is maybe the dual mass flywheel, or the rear diff mounts (or both), but this certainly helped to drive smoothly around the potential other issues.

[RS4RAB]

Ok so quick update

Original problem was slight surging at low throttle / rpm so was initially investigating that, took the air filter out and it was full of dust / debris

Its a BMC aftermarket filter, at the same time i took the MAF out to clean with some MAF spray, filter was cleaned with the proper spray and re-oiled after with the correct filter oil

Anyway, once all was put back in the car ran horribly, no power sounds like it is miss firing so i thought i had damaged the MAF using the spray.

New MAF fitted today and its no different, cant see that i could of disturbed anything to make this much of a problem as the car is pretty much un drivable now where as before i had a light surging issue.

Unplugged the MAF and the car runs pretty much the same

Car still has VAC pressure after running etc, throttle body VCDS alignment carried out all ok

Is there anything that i could of disturbed around the air filter to make this much of a problem as i cant see anything and have checked a few times

[RB1]

How much filter oil did you apply after cleaning the air filter?

If its too much, maybe its passing by the MAF and distorting the readings? You could briefly run without a filter to check, but obviously you need to take care that no dust or debris passes in to the inlet manifold while idling.

[Kenny147]

Maybe a bit of a red herring but when I swapped over from the VAG air filter to a new BMC filter, my car was not happy about it. On startup it would run very roughly and misfire for a few moments before it settled down. I didn’t do anything other than swap filters. Here’s the interesting part though, If I left the codes in the system it would start without the roughness and misfires. As soon as I cleared the codes, misfires.

This carried on a for a few days before the car settled down and it started normally after the codes were cleared. My feeling and this is just a personal opinion, is that when you put a high flow filter in, there’s such a big change in the air/flow mixture that some cars’ ECU’s think “WTF” and can’t re-calibrate quickly enough. When you reset the ECU’s by clearing the codes, they revert to a baseline air/fuel mixture and you keep getting the misfires on startup.

I know plenty of owners have fitted a BMC filter without any issues but you might want to swap in a standard air filter just to see what happens.

[rs user]

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[RS4RAB]

Quick update for anyone that gave some input or suffers similar problems

Basically the original problem was very jerky at low speed / small throttle angles, car seemed a little down on power sometimes but fine others

The last drive home from work just as i was nearing home it started to run rougher than normal, exhaust note changed (went quieter), anyway i shut the car off and didn't think too much of it at the time as i was literally a few hundred yards from home when it happened

I then didn't use the car all weekend and on the Sunday evening i cleaned the air filter out and the MAF, after this i took the car for a drive and when cold it was even worse, at this point i thought the air filter clean and re-oil plus MAF clean had caused a problem

Fast forward a few weeks and all is now sorted, took the car to a local garage (owner has a B7 RS4 avant) as the clutch needing replacing soon anyway he advised that the dual mass flywheel could be the cause of the jerky feeling and the crank position sensor may be the reason for the running issues i was experiencing

Ordered all parts for the clutch change from rock auto including flywheel, all other parts inside the bell housing including stainless hose and slave cylinder ordered from Robnic and new crank position sensor supplied by the garage

What a difference, as soon as we started the car the exhaust note was back to normal, during the test drive all the jerky low rpm surge had gone and the car was back to full power

The old dual mass had a lot of play and was out of tolerance, and the crank position sensor end had actually broken off, now i believe the engine will not start if this sensor is defective so it must of been still giving a single but was definitely causing an issue, i also had no fault codes relating to this

Anyway thanks for the help, just wanted to update people as there is nothing worse than a thread without a conclusion

[mikep99]

Good work!!

Do you have the part number of the crankshaft position sensor?

ta
Mike

[rs user]

glad you got it fixed and thanks for the feedback