1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Dismiss Notice

Hesitation / Jerking & Cruise Control Issue

Rob-Quattro Jan 8, 2018

  1. Rob-Quattro

    Rob-Quattro Registered User

    226
    13
    18
    Hello all,

    I have an odd hesitation or jerking from my 2007 A3 170 quattro diesel. The car has only done 50k miles and has a full service history, everything replaced when it should, including the fuel filter. I run it on Shell V-Power most of the time and the occasional Tesco's. The hesitation only seems to appear when the engine is warm but It may do it all the time but I will only drive the car hard once the oil is up to temperature.

    Once the car is up to temperature, if I accelerate hard off a roundabout for example, in 3rd up to 4th, 5th and then 6th, when engaging the clutch after changing gear there is a jerking/hesitation as soon as the clutch is released, the first jerk is very noticeable the second about 1 second later is less noticeable. I have seen other describe it like the turbo is being cut on and off, on and off very quickly. The revs don't increase when changing gear like a slipping clutch can cause.

    Also, when in 4th, 5th and 6th is the higher rev range on full throttle I can feel the car pulling back again like it is hesitating which is limiting the top end power, this can almost feel like a bouncing backwards and forwards. I have recently had the car on a power run on a rolling road and the power is down with the graph showing a dip high in the revs which in a previous graph a few years previous it is smooth all the way through.

    Last night during a 50 mile drive on a dual carriageway with multiple roundabouts the car was constantly hesitating and jerking exiting the roundabouts. I got fed up and ended up putting the cruise control on 70.

    I then noticed another issue I hadn't seen before. If I go up above 70 and then turn the cruise control back on, as I do the car jerks forwards slightly and the revs drop about 100rpm before the car slows down to 70 and keeps it there. I wondered if this has anything to do with the other problem.

    After 15 miles at 70 I came to a stop at a roundabout, after the lights changed and I set off the car felt very responsive like it used to, I left the roundabout again in 3rd and powered it into 4th, 5th and 6th with no hesitation or jerking at all. I drove another 10 hard miles without fault with the car feeling like it had much more power and grunt than before.

    There are no faults logged, error messages or lights displayed. I have use of Vag-Com from a friend with live data but I am unsure what to look at and if I am looking at the live data, how would I know if the read out is incorrect.

    I came up with some ideas which might be causing the problem. I have no problem in replacing the part at fault, but I would prefer to single out the other possible causes before spending a £1000s on parts.

    Possibly faults I came up with are:

    The Dual mass flywheel or clutch. I don't have any slipping from the clutch or any noise from the flywheel but as the fault can appear when changing gear I thought it could be an option. I also have a oil leak from rear of the engine which I want addressing and guessed it could be the main oil seal possibly leaking onto the dual mass and clutch which could cause slipping.

    I have also seen on a forum that the fuel pick up in the tank on the 140 and 170 models get very blocked which can cause this hesitation I have described. Being a quattro the tank is in two sections with a pump on either side. Does this mean to check if the pump is blocked I would need to check both, or does one feed the engine and the other pump the fuel over to the other side of the tank?

    The turbo actuator sticking.

    Veins on turbo sticking.

    The Throttle body/throttle pedal at fault.

    As the issue seems to come and go I am finding it hard to diagnose.

    I can get video's to show the cruise control fault and hopefully the hesitation/jerking.

    Any help would be much appreciated.
     

Share This Page

Do Not Sell My Personal Information