Since getting my licence back my A4 has developed an annoying fault. When any throttle is applied and you let the revs fall with the clutch depressed the revs bounce between 200rpm and tickover. When coming to a stop the car often stalls and needs to be restarted which is often hard. When started it will cough grey smoke. When my mate scanned it with VAG-com no codes were present and I was told this was symptomatic of the MAF dying. As I've had terrible experiences with pattern parts I went for a genuine Bosch replacement and.......... the fault is still there

Any ideas as I need to get this sorted before I bend the damn thing


CheeRS

 

There's alot if vacuum hoses going to and from the inlet, I'd be looking round that area for split pipes or pipes off.

 

My money would be on a vacuumed pipe as well. Had very similar fault on my Ibiza cupra. Was the vacuumed pipe coming of the end of the inlet to the DV

 

As above, check ALL vacuum and breather pipe work, also the non return valve on the breather. Also the dv itself if standard.

 

I'd only run standard dv's.

 

Vacume leak was what I thought of first so went over the system with a fine tooth comb and found nothing. Shall check again to be sure though. Dump valve is an HKS SQV (I know, I know a mate gave it to me for helping him out so figured I may as well fit it), it's been on the car for months previous to my disqualification without problems.

 

I'd never run the std one there shit and prone to leak.

Forge recirc is your best bet. Or blank it off and see if it cures it
?

 

Whys that then?

 

Standard bosch dump valves on the 1.8t's are one of the most common faults I changed mine as soon as I got mine. It might also be worth cleaning out the throttle body and getting your mate to do a re-alignment on Vag com if he can. Heard similar faults when the coolant temp sensor has been on its way out too mate. Failing all those its gotta be an airleak. Hose under the inlet with the pressure control valve is very common for perishing and leaking causing idling issues. Hope these point you in the right direction.

 

Ours never run right with a forge dv and they sound poo on the 1.8t's.
Ok you have to change the standard ones every 12-24 months.
But our A3 runs perfect all the time.

 

I'd deffo be trying a standard new dv.

 

Have a look on audi-sport.net a wealth of information on there !

 

It did have a forge dv on there! Surely that's better than the hks. When I scanned it on vagcom we did the throttle body alignment too but didn't fix it.

 

Could be a dirty throttle body, apparently that can cause a rough idle?

 

The Forge 007P is better than the HKS. But I was given a £200 DV for gratis so figured I might as well have a laugh and throw it on. Car was fine on it for a year before the ban.

Rhino mate when we scanned it we did throw a couple of codes, 1st, 3rd and 5th are apparently due to the battery dying, ignore the 4th Might be worth a rescan if you have time to see if the coolant has reappeared.

 

I remember when I has my Mk4 GTi (1.8T) not the weedy 2.0 lt I had a similar problem I ended up taking the throttle body off and cleaning (with something like brake/carb cleaner) the butterfly valve/flap and that sorted it ! It jsut wasnt sealing on idle.

 

+1.......

 

Steve, give me a ill bit of notice and come over whenever you want.

 

Can you not spray easy start around all the hoses 1 by 1 and see if it revs up

Also around any boost hoses etc
Will show an air leak at least

 

Legend mate

You about Saturday afternoon?

 

As said before Id look to the throttle body also I run an apr R1 dv and its mint better than the 720n.

 

Not happening mate. I've removed the original DV pipework and had a proper HKS takeoff welded to the cold side intercooler pipework.

Will have a proper poke about on Saturday as I'm working flat out at the moment. Got AutoCAD running in the background now sat here at home. I've inadvertantly become a workaholic

 

Run the engine at idle and take the oil filler cap off does it try to suck it back down?

 

Disconnect your MAF. If it is an air leak or MAF fault then the engine will run better in limp mode. Also perform a throttle body adaptation.

Rick

 

If all the vacuum hoses are ok, I'd put money on the throttle body needing cleaning and basic settings being carried out. Did a fair few like that when I worked at Seat dealer.

 

Right, gone through vacume hoses a 2nd time and everything is intact. MAF sensor is brand new genuine Bosch and hasn't cured fault . Rhino recalibrated throttle body so the only thing left is the coolant sensor.

Car keeps kicking back under light throttle and one minute I'll get 12psi then it drops back and won't boost above 5psi???