Safe mode?

[marie]

I have had my A4 Avant auto for 3 years and covered 40+K, love the car however I have had this issue since buying - Intermittently the car will not respond to the accellerator. ie the car will rev ok but not accellerate, other than really slowly. Happens at all sorts of times, on overtaking, from cold and hot, mid long run, doesn't seeem to have any regularity or common trigger point. I have had the EGR valve replaced soon after I bought it, I have cleaned the Air Mass filter also. thinking of getting rid because it is becoming more regular, once or twice a week.

Any comments are appreciated.

[kite]

Scan the car for fault codes.

[MrBigglesworth]

That sounds like limp mode and best first course of action is to get it scanned like kite says.

Is your engine management light on?

[Rob69]

I have had my A4 Avant auto for 3 years and covered 40+K, love the car however I have had this issue since buying - Intermittently the car will not respond to the accellerator. ie the car will rev ok but not accellerate, other than really slowly. Happens at all sorts of times, on overtaking, from cold and hot, mid long run, doesn't seeem to have any regularity or common trigger point. I have had the EGR valve replaced soon after I bought it, I have cleaned the Air Mass filter also. thinking of getting rid because it is becoming more regular, once or twice a week.

Any comments are appreciated.
So the engine revs up but the car does not accelerate - if this is what you mean, with an automatic box this sounds like torque converter issue, maybe gearbox oil level low?

[marie]

Safe mode does not come on the dash, there are no fault codes present, gear box oil changed last service. When I stop the car, turn off and turn back on it the fault always goes away!

[MrBigglesworth]

What tool did you use to scan for codes?

[zollaf]

limp mode doesn't always make the eml come on, and there more than likely is a code, you just havn't used a good enough computer to find it. it won't be in obd though, you need a proper computer.

[SKnibbs]

its definitely limp mode if the ignition cycle clears it.

will usually happen on an incline when the turbo is called for more so, and usually effect the higher gears more than the lower gears. ie. 4th/5th/6th gears on a manual.

are you a gentle driver? if so, soot etc and other particles can clog up a turbo and it wont spool correctly causing limp mode. generally a really good thrashing in the lower gears helps heat things up, burn up the carbon deposits and can help the turbo work more like it should and will reduce the limp mode. diesles are not good when driven too gently too much of the time. they work best when given a good thrashing every so often.

I have had the same issue on my car.

I suggest you buy some "forte" turbo cleaner for £13 on amazon, stick that in with a 1/4 tank of fuel and take the car out for a good aggressive drive . you need to keep revs up high , a motorway is good for this as you can keep the revs up in the range for extended period of time more easily. if you have an auto box try to put it in sport mode or whatever you can to hold revs higher for longer. you MUST warm the engine / oil first before driving it hard. give it 10 mins driving about and you should be warm.

when I did it I took time to warm the engine oil first (10mins normal driving) then went down motorway shifting from 3rd gear to 4th gear and back down to 3rd and kept gunning it . you ultimately want about 15 hard pulls from 2500 RPM to red line combined with some driving remaining at high revs (ie. keep it just below red line for 10-15 secs then ease off - and repeat this 4,5,6 times or so).

after all this combined it can really, really help. I have done this on multiple cars (diesel turbos) and it works well.

even if you try it first without buying the "forte" stuff.

ofcourse this helps with a turbo that is a bit clogged. if your issue is something else it may not help - but it usually is clogged turbo internals.

try it.