Maybe there are some smarter people out there than my local Audi dealer who has tried numerous things to fix this problem which I have had for the last 18 months;

I am a UK owner. The car is a 1998 Audi TT 180 imported from Germany. She has been displaying the following symptoms:

1. Starts fine in hot or cold, as soon as you move off, the engine goes all 'lumpy' and misfires, very limited response when pressing accelerator. Almost cuts out when in neutral and you can literally feel the engine wobbling where it's trying to stay on. This happens more so in Winter when it's cold but is still there in the summer and warmer weather. Problem goes after a couple of miles or 3 or 4 minutes.

2. At very high speeds (110mph +) the car starts 'lurching', a surge of speed than momentarily loses it's power, then surges again etc...

3. The car doesn't seem as powerful in general as it was but that might just be me...

Not sure if these problems are connected. Audi dealers have run diagnostics on it 3 times and can't find problem. I have even left the car with them for 3 days so they could do a cold start. They recommended the following:
a) Change Air Mass meter - have done so with no difference whatsoever
b) unplug air mass meter so engine management isn't connected - have done so - no difference whatsoever
c) Change the coolent temperature sensor (which was coming on even when I topped up the antifreeze, it still thought the water was too cold) Have changed sensor, no difference whatsoever but the warning light does come on every now and again even now and I know the coolant mix is fine.

Audi now don't have a clue what could be causing it and say that I will have to book it in for 'intensive diagnostics' which is their language for 'we don't have a clue but you can pay an extortinate rate of $170 per hour (95 english pounds). This problem is proving extremely expensive in terms of time and money and I can't afford to go on throwing money at the problem.

Is there anybody who can shed some light on this before I finally give up and put my beloved TT through a car auction?

Yours pleadingly,

Jason Harris

 

Welcome to the forum.

What kind of gas have you been using?

 

changed the vacuum lines?

 

Correct me if I'm wrong but maybe the second problem (engine cutting out at 110mph+) could be because of the governor kicking in. It usually cuts out the engine about the same speed or does it?

 

My Jetta had the same symptoms, finally traced it back to the wiring harness to the ecu...there was a bad ground. The troubleshooting flowchart has you measuring all of the voltages of various sensors bit neve has you chase the ground resistance. This was an intermittent problem I had but was eventually solved by a independent mechanic near me for $65 bucks.

 

Thanks guys for your suggestions...

The gas (or petrol!) I'm using is the standard 95 octane unleaded. It's rare that you can get anything else in UK. You do sometimes see 98 octane which could improve the problem but don't know if this is the cause of it. Will try the higher octane though. Thanks BaconBait

Not sure the high speed problem is the governor kicking in, I thought it was 155mph but will check. Thanks Kianoosh

The Vacuum lines - not sure what this is as not too technically minded, I just like driving them! But it is worth mentioning to my local friendly mechanic. What is the cost of this -expensive? Thanks Jestomen

The wiring harness to ecu is an interesting one, although I'm not so sure it's electrical. It seems more like a fuel problem to me as it happens every time the car is cold. Could it be the automatic choke? Thankyou for your suggestion though 400HP A4!

You seem a good bunch on this forum. I will post back here if I ever get to the bottom of the problem! Any other suggestions are also welcome...

 

A friend of mine had the same symptoms and it turned out to be a bad ground also. I would check that out.

 

When you say the coolant light is soming on I presume the coolant dispaly on the dash, this isn't testing the anti-freeze mix and it isn't generated by the temp sender it's showing the coolant bottle level if it comes on while the bottle is full it means that the sensor in the bottle is nakerd and you need a new coolant bottle to stop the light flashing on the dash. How ever if it's the engine managment light this should mean that there are some faults logged in the ECU that can be read by the diagnostics even if the light has gone out as they will be logged as sparadic faults.

I must say it sounds like an intreasting problem (proberly a complete nightmere for you though). The air mass does sound like a first guess but as you have already tried this it's obversly not, I think if my memory serves me correctly when the ECU is looking accross the map the three main input parameters are;
airmass
knock sensor
throttle position
The other inputs like
lambda probes
MAP senor
are triming sensors, meaning that if they are faulty they don't have such a big effect (still noticable)
If there was a major fault with the knok sensor or the throttle body I would expect faults to be logged in the ECU and easly detectable with diagnostics pluged in (all though they could still be checked in measured value blocks).

Just a couple of random idear's what's the fuel pressure like while the engine is having such running problems? The fuel pump could be braking down

Is the EGR (secondary air)valve braking down on the side of the cylinder head above the gearbox. This will be working overtime when starting up from cold to help lower the emissions due to the extra fuel demand with the engine being cold. (I think that I might seen one of these valves cause a similer proberlom before causeing the TT to kangaroo down the road)

Keep us posted