Skyfire

I know I've posted this before, but after searching and reading through past posts on similar topics, I'm still not clear what the cause of these problems are, so I'll start from the beginning, please bear with me.

The car is a 2000 A4 2.8QMS 30V. Oil/Anti-freeze leve is normal. It currently has ~49k miles on it, and is now out of warrantee. The water pump was changed under warrantee about 3 months ago (dealer said it was making some weird noises and is on it's way out, so they changed it)

About 1.5 months ago, the engine started to behave "strange". During cold startups (after it's been cooled for a good 6+ hrs), the car will "rock" and "jerk" for about 1 second before finally starting up. It's as if some of the cylinders have a hard time firing up. Before it used to go instantly. During winter times, I usually start the car up and leave it idle for ~3-5 minutes before driving it, don't know if this had anything to do with it.

Also, after driving for a while, and when it's stopped at a stop sign or light, I can sometimes feel the car rock slightly. It's completely random, and not as severe, but I can feel it when it's sitting idle.

I took some suggestions and gave the car two Techron treatments. The cold startup problem still didn't go away, either did the random "rocking" idle problem. Now I've got spark plugs and is preparing to change them (as soon as I can find a touque wrench). I've heard everything from cylinder alignment, to spark plug wires, to MAF sensors. So what I'm asking is: is there a step by step elimination process to isolate the root of the problem instead of me blindly change the spark plug wires or the coil packs etc? Either the spark plugs nor the coil packs are cheap, even from discount distributors like clairparts If I indeed need to change these parts, what's a cheap place to get OEM replacement parts? (besides junk yards..)

mau

Any DTC's?

Skyfire

what's DTC?

mau

Diagnostic trouble code. Is your check engine light on? Do you have a VAG?

Mau

Skyfire

No, the check engine light isn't on (come to think of it, it was never on) and I don't have a VAG

JWG

Before doing anything, VAG the car. Someone near you certainly has a VAG/COM on their computer. If not, pay any independent garage a few bucks to pull the engine error codes.
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If you discover a misfire problem, start from the plugs and work backward.

First, make sure the plugs appear in good condition. If you do not know how to "read" the plugs go to the major plug manufacturer websites to find out. If they appear okay, go to step two. (Note: when you pull them, make sure the plug hole is clean so no debris gets into the chamber or under the plug when you reinstall it)

Second, as you have about 50k on the plug wires, I would replace them. Luckily, Neuspeed has some nice aftermarket performance plug wires. However, you can get good wires at a lot of places. Bosch has its ultra premiums, for example. Since you will need to eventually replace them anyway, I would do it now.

Third, coils and coil amplifier may have problems; however, these should last a long time. Check the amplifier first since its much cheaper to replace. Look for tech articles on this issue. If the amplifier checks out okay, I can suggest only a weak coil as the culprit.

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If you do not suffer from misfires, feel fortunate, because the following remedies cost far less than trouble shooting misfires. I would bet that you have carbon deposits and/or still dirty fuel injectors. Forget Techron, it's baby stuff.

First, go to a reputable garage and get some BG 44k--its professional strength stuff! Pricey ($20) but it really works; none of the stuff you get at PepBoys or Autozone will do even 25% of what the BG 44k does. Dilute it in about 1.5 tank fulls by filling up after using 1/2 tank or fill up after using 1/4 and then another 1/4.

Second, If that does not smooth things out, go to a dealership or similar large repair shop that has a BG, Bilstein, or similar fuel system cleaning machine that plugs in place of the fuel line and runs the car on a combustible cleaning solution. This does wonders for carbon deposits on valves and in combustion chambers. So-so, for fuel injectors. Cost: varies drastically but usually $50+.

Third, the only thing left is fuel injectors--sometimes, even a fuel system cleaning will not dislodge or dissolve the deposits on the inside of the injector. For this, you need to send them to a lab for ultrasonic cleaning and testing. Cost: around $20 per injector; again this varies. For cheap solution, hit-up UrS4 on these forums, as he has such a machine and will clean your injectors for a much cheaper fee.

Good luck to you.

mxp

what is really going on.

Also, a common mistake is for people to add the techron but NOT drive it around hard. This renders the techron useless in the tank.

I usually do a "clean" when i know I am going on a long drive (say SF to LA) and drove it pretty hard.

Anyway, here's the url to check ur plugs condition. And, u may wish to try BG 44K. It's the best out there.<ul><li><a href="http://www.gnttype.org/techarea/engine/plugs.html">click here to check your plugs condition</a></li></ul>