2004 A3 2.0 TDI juddering and struggling to start?

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gizm0

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hi guys i have a 2004 A3 2.0TDI on about 100k, the car sounds like its struggling to start and sometimes taking a couple of attempts to start, also when sitting on idle the car is juddering really bad, iv had a new fuel filter as the old one was really blocked up and a new throttle body, had it checked for faults but none were showing, has anyone had this problem or any suggestions for me to try to fix it.

thanks in advance

Dan
 
EGR could be blocked with crap plus you could try a good dose of injector cleaner.
 
ok cheers ill try the injector cleaner and get someone to look at the egr valve, im usually good with cars but dont know my way round these engines lol

anything else worth checking guys?
 
If you search this forum for threads regarding juddering and rough idle you will eventually find that in a large number of cases the injector wiring loom is at fault. Apparently some of the looms were subject to intermittent failure for some reason or other and I believe Audi introduced a revised version at some stage.

It is not that expensive to buy and, from all accounts, is relatively easy to fit although I am in the fortunate position of not having had to do this job.

Hope this helps
 
How old is the cam belt on it?
My car was quite lumpy on start up until I changed the cambelt.
If you do a serch for Torsion value you should find posts on lumpy idle.
The cambelt can stretch a little over time which can push the timing out slightly.
Or it wasnt set up properly when the new belt was fitted.
Vagcom (VCDS) or the like can measure the value and adjustments can be made as the cams on this car can be slackend off to
1. Help fit the belt in the first place
2. Allow a slight adjustment to get the "Torsion value" correct.

Best watch my spelling of Torsion as well - Audi may spell it different to me!
 
I did search the forum but wanted to know if there was anything more simple that could be causing it.

Off the top of my head I can't remember how old the cam belt is but would this cause the car not to start first time?

It Took a couple of attempts to start again last night :'(
 
Does it start really well on a stone cold engine?
but warm or hot it takes two goes?
There are two starter related problems (but not lumpy idle)
1. heat damaged starters makes them weak
2. Audi have a hot and cold map in the ecu for starting
When the engine is in the hot map it can be tricky to start most of them.
I stripped mine and cleaned and greased it - that helped but didnt elimate totaly as compared to other make starters there pretty clean on the inside.
some people have had the map adjusted by audi or when getting a aftermarket remap
On a warm engine just try the starter once - they may be a pause followed by a climb to idle revs - works for me.

Rough idle is a different fault though
you have had all the right suggestions for that - there wont be anything simpler.
 
And when you say throttle body what do you really mean as diesels dont have a throttle body as such.
they do have the valve that closes in the air intake when the engine is shut off - do you mean this?
 
Ok cheers for the suggestions, it does struggle to start alot when hot. But it does also struggle sometimes when cold? Could it be something to do with glow plugs? I'll be filling up in a couple of days so I'll put some injector cleaner iv got.

Yeah sorry it was a valve at the front of the engine?? (I didn't change that myself someone done it for me n I watched lol) but it was full of gunk!! This didn't really make much difference though...

Thanks for the advice so far guys :)
 
Ok cheers for the suggestions, it does struggle to start alot when hot. But it does also struggle sometimes when cold? Could it be something to do with glow plugs? I'll be filling up in a couple of days so I'll put some injector cleaner iv got.

Yeah sorry it was a valve at the front of the engine?? (I didn't change that myself someone done it for me n I watched lol) but it was full of gunk!! This didn't really make much difference though...

Thanks for the advice so far guys :)
 
devonmikeyboy said:
you could try a good dose of injector cleaner.
Click to expand...

Which did you use on your bkd's Mike?

gizm0 said:
Ok cheers for the suggestions, it does struggle to start alot when hot. But it does also struggle sometimes when cold? Could it be something to do with glow plugs? I'll be filling up in a couple of days so I'll put some injector cleaner iv got.

Yeah sorry it was a valve at the front of the engine?? (I didn't change that myself someone done it for me n I watched lol) but it was full of gunk!! This didn't really make much difference though...
Click to expand...

Intake manifold flap you're referring to, although they may have swapped this, did they remove the egr & clean this fully & test ok, did they also check the egr cooler actuator at rear of engine, check glow plugs functions with vagcom?

Starting crap when hot is usually 1 of 2 issues, coolant sensors or starter, the starters suffer from heatsoak given its strapped to the gearbox which gets fairly hot from use, thus the starter is almost a heatsink & affects possibly the coil/solenoid, I have fitted new starters to some bkd's & the new starters were a hell of a difference, also a DIY swap aswell, somethings to consider aswell as injector problems which have affected these cars too.

Glowplugs wont affect a warm engine as they're just used on cold blocks to heat the cylinders as such, so wont be used all the time, for me its not this your problem mate, probably one of above to check.
 
im going to be gettng the alternator and injector wiring loom off someone i know, but hes saying theres two looms available? could anyone help me out with chich one i need or possibly give me a part number?

cheers

Dan
 
im going to be gettng the alternator and injector wiring loom off someone i know, but hes saying theres two looms available? could anyone help me out with chich one i need or possibly give me a part number?

cheers

Dan
 
also i heard someone mention about a sensor at the back of the engine to try unplugging and seeing if it starts ok then? could anyone tell me where abouts its located and if its accessible from just opening the bonnet?

thanks guys :)
 
thanks :) what does BKD mean? sorry lol (newbie here) lol
 
Dan
As suggested by James above.
If the cam belt has stretched a little, the cam/injector timing will be out. This will cause a poor start, without fault codes.
If the belt has been changed without using the correct crank tool and cam pins, the timing references will be from the old belt.
I guess at 100k it has had a belt and water pump change? Check under the covers to see if there is any tipex marks on the pulleys, if there is it would suggest the belt has been changes without the correct tools?

Also have the garage do a block test to check if you have any CO2 in your coolant, this could indicate the onset of a cracked cylinder head. This would give a poor idle quality when started.

Faulty heater plugs will throw up a fault code.
 
Last edited:
All engines have a code and if you look inside the front cover of your service book you will see against engine code the letters BKD.
 
If you unplug your coolant sensor and try and start the car. This defaults the car to -2°c and kicks the glowplugs in as if freezing cold. The glowplug light will stay on for approx 5 secs and if the car starts OK then you can eliminate most things like fuel delivery issue including air and the fuel pumps and probably timing as well. I believe there is an issue with the cold map in the ECU on mine as I have changed both fuel pumps ..new timing belt with correct aligning tools and timed with torsion value in VCDS reading 0.0 as per manual. To bypass this issue I cut one of the temp sensor wires and run the wires under the ecu and to a small switch under my parcel shelf. This means that when cold I flick the switch which forces the car into freezing cold mode and glows the plugs to start..Result it works! Might not be perfect but much cheaper fix for someone. Be warned if left on for more than about 10 secs will throw the MIL on the dash as power is cut from the sensor and you will need to turn off with a scanner.
 
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