I will gladly paypal $100 to the first person who can diagnose my problem. I have no dealer in my side of South Dakota and am desperate. I am good for it, it would be the best $100 I could spend. VW dealer won’t even look at it which makes me mad.

My car, 2001 1.8t Audi TT 225hp, 130k mile, runs rough. Perfect idle, doesn’t waver, but it is just rough. Revs up rough. Very predictable. I can set the cruise at 80mph and it seems to be perfect. Fuel economy seems normal, plugs look good, 300 miles of this and no CEL. Problems came on all it once, not subtle over time. All stock, not a mod car.

Is running on all 4 cylinders

This is very embarrassing, but I will go through what I have done. Try not to laugh too loud.

New front two motor mounts. Made the problem less noticeable but the underlying cause it still there.
New plugs
New ignition coil packs
New MAF
Replaced timing belt
Took cylinder head off, had it rebuilt. Needed valve guides, all 20 were out of spec
As long as I was in there, had turbo city look at the turbo.
All new intake and exhaust gaskets
New cam sensor
Checked vacuum lines. Replaced one on fuel pressure regulator.

Seems to run rougher when cold. When the “warm” circuit kicks in it runs better.

May not be as powerful as it once was, but it has been so long I may have forgot.

Please PM me or email if you have any thoughts or want me to check anything to help you diagnose.

Thanks! I am a desperate man.

Peter S

 

We need more details on "runs rough". At what rpms/all gears/mph?/noise? (if so, where?)

 

Could be plug gap, blown turbo or dp gasket, or even just a vac leak. Long shot is a dying n75. Best start looking at some of those parts yourself

 

maybe its your turbo inlet pipe (TIP) collapsing?

 

Not likely on a bone stock car. I would start with basic stuff. Pull off the Throttle body and clean it up really good with carb cleaner (could be sticking, friend had same issue) also clean the MAF sensor with denaturated alcohol (found in paint isle at home depot). Just pull of the MAF sensor with housing attached and soak in a large ziplock bag and agitate. Let dry completely before reinstalling. Also you could run a boost leak test. Do a search on google or other place to find easy way to make the tool. You could also do a throttle body alignment at the time of cleaning the throttle body (vagcom necessary for proper alignment but other methods work as well)...run some injector cleaner...I like lucas brand. Check things like fuel filter. All this stuff can easily be done for less than 100 bux.

There are write ups for all these things. IM me if you need links.

 

Use your money and buy a vag com cable and download the software. www.ross-tech.com i can diagnose it in less than an hour if you give me the needed data blocks.

 

sounds like a evap problem.

EDIT: I was just thinking about it more it could be SAI related. You have a heater that heats the cats when you turn it on. Have you have the cats checked out? It could be stuffed from carbon. That causes the two o2 sensors to go bad & cause crazy missfires.

 

thanks for the input, I'll have the CAT's looked at and throttle body cleaned. I'll also have a fuel pressure check done. The throttle body on my montero was dirty once and acted like it wanted to stall, which my TT isn't doing.

I pray for a check engine light that can point me in the right direction. but after about 300 miles it hasn't come on.

When I say it runs rough, that pretty much sums it up. Almost like it needs a "tune up." the idle is not eratic, never stalls or wants to die, doesn't chug. You will fee the vibration in the steering wheel at idle and when accelerating. not cruising at highway speed.

I have a 4cyl turbo saab 9-3 as well and the difference between the two cars is night and day. the saab reminds me of what the audi was and should be like again someday!

Peter S

 

what does a "dying n75" mean?

 

The N75 electronically controls your Boost. If it goes bad than you may have some Boost issues. So you are saying the car overall runs GREAT only rough? Could it be suspension related? CV joints, A Arms, Ball joints? If it is engine related a Vag Com will tell you a lot of things even if you don't show a CEL. You don't need a CEL to show fault codes. Do you have someone close to you that has a Vag com? It would be worth a try. Also do a SeaFoam treatment. Buy a can of Seafoam and put half a can in a shallow bowl then take off the vacuum line to your FPR and let it slowly suck in the Seafoam. It will clean your intake track and fuel system. Then put the rest of the can in your gas tank. That stuff works wonders and will clean your injectors which also could be the culprit. Good luck with your diagnosis.