Steering Wheel vibrate at certain RPM between 1200 - 1400

I recently bought an Audi A4 1.8T quattro 2002. It runs good at hight speed. But I can clearly feel the vibration from steering wheel during acceleration and deceleration when RPM hits the range from 1200 to
1400. Below or above this range, the vibration is gone. And there is a not loud but noticeable humming noise coming with the vibration. The vibration can barely be felt from the seat or clutch, only from steering wheel.
Sometimes it is really annoying so I went to 2 dealers. The first one changed my catalytic converter and an oil valve. The other one changed 4 engine mounts for me. But none of this treatment solved the problem. I have my car checked thoroughly by them both. There is no leak in my car.
I just wonder could it be some problems with my engine or transimission? Does it sound like a serious problem? What could it be? I have doen some internet research. There are 3 major opinions on that: [1] The timing belt may be loose. I had it checked by dealer. No loose timing belt is found. But I heard timing belt is really hard to check. Maybe he didn't check carefully for me. Is there any way that I can check the timing belt by myself? [2] Front-end balance, steering balance or motor mounts. I had all 4 engine mounts changed by the second dealer. Nothing improved. Is there anyway that I can check the balance by myself? [3] Power steering problem, power steering muffle or something else. I don't know yet. I got my car checked by the dealer but no specifically on the steering system. No problem was mentioned by dealer. Could that really be the problem for my situation?
Every time I went to dealer, I have to take at least half day off. I don't want to waste my time any more. I am planning to go there one more time. But this time I would like to bring some knowledge with me. So I need your help to give me some share of your experience or technical knowledge. Any share will be warmly appreciated.
Michael Wei
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Michael, I fail to see how a vibration in the steering wheel could be caused by a "loose timing belt" - vibration from a slipped belt is usually of the form......"BOOM!" as the pistons hit the valves, break them off and destroy the engine. The RPM connection could be verified by sitting still and holding the engine revs in that range - is the steering wheel vibrating when you're sitting still? If the vibration is felt only when you're moving, chances are you have a broken belt on one of your tires, uneven tire wear (possibly caused by/or) worn suspension links. I would suggest rotating your tires and then take the car for a drive and see if the vibration has changed. As far as checking the alignment, I have talked to people that have measured their own alignment, checking caster, camber, toe out, etc. on all 4 corners - they made their own alignment rig using a flat floor, protractors, and even used vinyl floor tiles under the tires to allow the wheel to pivot on the floor. I prefer the laser rigs that shops use - provided that the kid operating the rig knows how to use it on an A4 (any piece of high-tech equipment is only as good as the dummy running it.....which might explain why the strut-top adjustment was not tightened on my 5ktq, almost causing a wreck....) There is the ol' "Screwdriver Stethoscope" trick - in which you press the end of a long screwdriver against something (say, the body of the steering pump), and then hold the handle end against your temple(head in front of your ear) to hear any noises or vibrations being transmitted through that piece of equipment. Of course, "standard disclaimers apply" - be careful of moving equipment and loose clothing/screwdriver/friend who shifts car in gear while you're under the hood/etc. , electrical contact with a metal screwdriver and your head, etc. etc. etc. It's an old mechanics trick - maybe you should have an old mechanic do it for you..... Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Yes, I do feel the same vibration when the gear is in Neutral (sitting still). So I guess this vibration is nothing with tire or transmission since transmission system is not involved while gear is in Neutral. I prefer the opinion on steering system. How do you think?
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Michael, If you're sitting still and you can still feel the vibration, then it doesn't sound like transmission/wheel problems - it could be the power steering pump, or even the clutch flywheel. How well do you know the history of the car - are there any telltale signs of accident damage (dents/bent mounts, paint overspray, rust, welding)? Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Hi Steve,
Thanks for your reply.
Actually, I have no idea about the history of this car. I bought from a dealer. They said there is no title with this car and I trusted them. If, I mean if, I found any title with this car, can I return the car?
I didn't find any dents or damage of my car. Oppositely, it is very nice for a 4 yrs old car. A little bit too nice. That's the main reason that I bought this car. How to check the damage? Is there any easy way to check other than "checking every part carefully"?
Best Regards,
Michael Wei
Steve Sears wrote:

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Michael, Whoa, the (Audi?) "dealer" said there was no title? How do you register it then? Here in Ontario, Canada (no idea where you are), you need to buy a Used Vehicle Information Package if you're selling a car - it's the law. The package includes important information about a vehicle's Ontario registration, lien record and odometer reading, etc. There's also Carfax - (if you ask around on the vehicle newsgroups, there may be someone with an account open that can run the VIN for you). As far as returning the car - you didn't exactly buy it from Wal-Mart, so the "dealer" may say that they have no idea who you are. As far as checking for damage - collision damage and repairs are fairly easy to spot - bent mounts, scratches on adjacent parts, paint overspray on trim/windshield, etc. Damage from, say, a broken timing belt will be much harder to see - you'd have to pull the plugs and check for piston damage, compression, leakdown, etc. I believe that the clutch is even harder to check - it may have been replaced and not aligned properly causing a vibration (although the clutch and engine vibration should be isolated from the body and steering wheel by the motor and tranny mounts). The screwdriver stethoscope trick is what I would use to isolate the vibration, and then go from there. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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