Runaway TDi Any assistance is appreciated!

Hi all, I am very new to this forum, allow me to introduce my MK4 TDI 2003 AHF 1.9.

I bought the car for relatively cheap and I'm in love, however the car felt sluggish, it wasn't too slow but definatelly didn't feel like 81 kw's, didn't even feel like 66kw's to be honest, it pulled away like a 1.3 but really lacked in the 3k+ Revs situations.

So I used VCDS and got the below error's:
17964 Charge Pressure Control Negative deviation
18057 Powertrain Data Bus: Missing Message from ABS Controller.
19561 Valve for Intake Manifold Flap (N239): Open or Short to Ground.
17957 Boost Pressure Controle Valve (N75): Open Circuit / Short to Ground. .

Yes A MOUTHFUL!, anyway I changed the vacuum hoses that were broken and reset the errors as per a friends advise, he advised that the errors would come back if they were still an issue
Okay so after resetting the errors she ran really well, definitely felt like 81kw's... maybe more so I pushed it a bit (Stupid), changing at about 3k's revs.
As I went from 4th to 5th the engine decided to max out on rev's, no noticeable smoke behind me, I panicked for a second as I was not aware what runaway was but a few seconds later I shut the car off and the revs went down and I rolled to a safe location with my hazards on.

I had to get tow'd but now there are no error codes at all on the VCDS.
The car now doesn't start, it turns but wont start properly.

The car has a full service history up to 190 000 k's (NOT AT A DEALER), It is currently on 230 000 k's, since owning the car I have put maybe 500 k's on, I recently had money to change the oil and oil filter, I'm quite sure I didn't over fill it.
I checked the dipstick, oil looks full still (No drop), I removed the glow plugs and turned the engine, nothing came out, definitely pressure though, but say five attempts at turning the engine the battery dies so I charged it and same issue, I've bled the fuel lines by loosening the injectors and cranking one by one they all give fuel.

If you have taken the time to read all that! THANK YOU SO MUCH!!!

Any way I have a few questions for any higher powered beings out there...

Firstly can roughly 3 or 4 seconds runaway at max rev's do damage to the engine?

Secondly where should I look next? Compression test would be my first guess, but does any one have any ideas why it would not start considering with plugs out no oil is evident?

From reading, it could be the turbo failure or a build up in the intercooler?

The shudder valve is present with Oil by the looks of it, thick and gunky but a bit wet.

Most of the time the car just clicks but I think that's the battery, after charging it it turns but wont start properly.
If someone could point me in the right direction that would be greeeaaat!

Sorry for babbling! Just wanted to give as much detail as possible
Thanks again.

Try a good battery and make sure your ash is open. Incorrect voltage can cause malfunctions as far as signals go. Start simple

Asv, sorry, auto spell

Might not be a bad idea to have someone ready to close that asv if it is tuning away

Hi jmodge, thanks for your reply, I put the battery on charge and it's got 13v standing and drops down to around 6v when cranking, then goes back up to 12v standing after a few turns, the ASV appears to move freely, how do I ensure its open? Can I start the car with the intercooler off the ASV?

Okay just realised I can get someone to push the lever open if it's not open.. will have a look when I'm home tomorrow thanks again for your help

What could be happening is that there was enough oil in the intercooler to fuel a
runaway and yes, the engine could have been damaged. It doesn't take a lot of
oil and it could have been there for a while while the engine was running more
slowly prior to you doing the the vacuum system repairs. It is not unusual for this
to happen after a repair that allows the engine to now have more performance.
You should make sure that the timing hasn't changed by verifying the cam, pump
and crank timing marks are all aligned. This isn't hard but requires some tools.
The AHF may actually be easier than the ALH in that regard.

Hi Flee, thanks for the input, will definitely check that out later on, so how else can I check if oil is where it shouldn't be besides taking it apart? Like i said nothing came from swinging with plugs out or am I being stupid, really want to avoid opening the engine :/ but this doesn't seem like it's one of those times...

If your battery is dropping to 6v while cranking that’s not near enough. It shouldn’t drop too much below 10.5-11v and recover quickly. I think I’d try a new battery first, low voltage can also cause a bunch of false codes.

The oil that causes a runaway usually collects in the bottom of the intercooler. Take care of the problem by installing a self tapping screw at the lowest point of the intercooler, remove the screw from time to time and let it drain then replace. It’s very likely that the runaway caused the timing belt to jump a tooth on the crank gear.



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@tdijarhead I hate to admit when my brother is right he says the battery is not up to par but I can't understand how when it was perfect before this happened but hes generally right okay will get on a new battery...this car is going to make me broke :/

@TLH_TDI thanks man yes I read that (the screw) will get on it, hmmm that's something I haven't been advised before so will check the timing too thank you!

3-4 seconds at redline doesn't sound like anything to me that should damage anything. but again I'm not an expert.

It only takes a fraction of a second being out of time for the piston to hit a valve and ruin your day.


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As these motors age the teeth on the pulleys become polish and rounded and when the teeth on the belt also become polished and if the tensioner is not as tight as it should be, there’s the possibility of the belt jumping teeth.


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Thanks guys will have to see what fate has in store..wish me luck!

leafs said:

3-4 seconds at redline doesn't sound like anything to me that should damage anything. but again I'm not an expert.

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No, it's an eternity with a runaway. There is a VG chance the engine went well above red line, jumped time and may have some hydro-lock damage.

@Ol'Rattler thanks for the confidence haha okay so I'm having a mechanic come have a look because I am stumped, I might just end up taking it to a workshop and have them fix/rebuild/replace whatever needs to be done and the timing belt aswell just while they're down there then I basically have a reliable car again, probably going to cost quite a bit but I don't have enough time to do it myself, if I had to do it would probably take forever and I'd probably end up with a few nuts&bolts left over after everything is back together :/ thanks everyone for the input I will let you guys know what the verdict is in a few days hopefully

Okay update. The timing belt looks good still tight and lined up, the battery was checked and is good, the car most of the time clicks and if I keep trying it turns but it sounds a bit sluggish and won't start, I've read a post where this happened to someone and it turned out to be the ecu, any input? Also the battery cables get hot after a few attempts to turn on. I don't want to replace the starter as it worked fine up until this never had an issue with it, I used vcds and I do get an ecu communication error which is why I am thinking ecu, I'm going to have to find a good diesel mechanic as I feel this issue may end up costing slot if I just replace blindly :/

Compression test and take the valve cover off and have a look to see if any damage on lifters and cam.

If its a 5 speed could try and push start it, but I suspect there's some major damage.

Seeing how it is a manual trans, it could be pushed or pulled and fired in 3rd or 4th gear. Considering the circumstances, maybe a compression check is due.

Sorry, I was a little slow with the button

Okay so lifters and cam look good no visible injuries I figured I would take the turbo off for a quick look, turbo looks perfect no visible oil no free play, there was oil in the intake though, haven't done a compression check yet I'm thinking I may just take the head off incase but I'm nakkerd now and have a million pieces, since turbo looks good any other ideas what could have cause this? Maybe an ecu issue?

Matty said:

the battery was checked and is good, the car most of the time clicks and if I keep trying it turns but it sounds a bit sluggish and won't start, I've read a post where this happened to someone and it turned out to be the ecu, any input? Also the battery cables get hot after a few attempts to turn on.

Click to expand...

When you say 'clicks' is it 1 click or fast clicks?
If it's fast clicks it could be a bad connection at the battery terminals or any where to the starter including the ground side.

If it's 1 click it could be the starter.
With the car in neutral take the smaller wire off the starter and jump the positive of the battery to the small terminal on the starter.
It should crank normal speed.

If the battery cables are getting hot the starter sounds like it's dragging or shorted.
Take it out to be checked.
There is a wire going from the solenoid on the starter to inside the starter.
Its known to corrode with time and does not pass enough power into the starter.

Last. 'I don't want to replace the starter as it worked fine up until this'
Everything works until it breaks.

Hi wonnerber, it will click a once a few times then it will turn over after say a few attempts then it will turn over every time until it is interrupted and then it clicks again and I have to try repeatedly till it turns again and repeat. Will check the starter when I am not working again. The starter wires get warm after a few turns, could the brief runaway have affected the starter? I tried to turn the motor and it seems stuck when using a wrench accidentally slipped a tooth on the IP when trying to turn it by the IP, I tried turning by all options lol, I think I've got it back to the original position but I might just take off the head to be safe, I read that I can take off the head without the timing locked then do the timing when putting back together is this true? Thanks for the input

It will click once a few time - I mean i turn the key and it clicks turn the key and it clicks and on and on till it decides to turn over (slowly) not too slow but not as fast as I've seen in videos

So you hold the key in the crank position and get click --- click --- click?
The battery was checked as OK and I am assuming they did a load test on it.

I can't rule out worn or sticking brushes inside the starter.

Have someone crank the car while you measure the voltage at the heavy positive stud on the starter solenoid and the case of the starter.
I'm thinking it will be bouncing up & down.

If so then measure from the battery positive post (not clamp) to the same positive post on the solenoid while cranking.

Same from the battery negative post to the case of the starter while cranking.
Post the results.

If I hold it in I only hear a single click, will only be able to do the test when the cars back together

Matty said:

If I hold it in I only hear a single click, will only be able to do the test when the cars back together

Click to expand...

OK. That sounds like the solenoid engaging but the starter not spinning.
Could be a bad solenoid, brushes, maybe the smaller wire from the solenoid going into the starter.

It's funny the wires get hot.
Can you try turning the engine with a socket and breaker bar on the center crankshaft bolt?
Might have to take some plastic off.
Do not turn it backwards, only like your tightening it.

With these interference engines be sure timing is right before forcing it to turn over.



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The odd thing is if I turn the key a few times then the starter engages and turns the engine, I tried turning with a breaker and it does not move, I'm going to Jack up the other side and see if I can move the wheel to check the timing is aligned it's a right hand drive so should the driver side wheel be turned clockwise?

Okay so when the car is jacked up and put in 5th I turn the wheels and the flywheel does not move at all. So I'm thinking head off time, I'm just wondering since it's not at TDC can anyone tell me if I take it apart will I be able to get it at TDC when I'm putting it back together or does it have to be TDC before I take off the head?