zszabo

Water Injection

zszabo

Repost from link:

As some regular readers here may remember, I've been having problems with my throttle body for over a year now. The car drove without problems for a while, then the tach needle would start jumping up and down erratically, finally the EPC light came on and throttle control disappeared almost entirely. The first time around, the VAG program told me that the throttle body was malfunctioning (sensor readings out of range, motor non-functional, etc.). I replaced the TB last year in January, the car drove fine for about 2-3 weeks, then the same thing happened again. Last year I sent my ECU to APR and asked them to resolder their chip on the board (thinking it might be a loose solder joint). When I got it back from them, the car drove without any major problems for nine months. Then the problems started appearing again at the beginning of December. This time I bought a new ECU (thinking that perhaps my ECU was malfunctioning due to a defect in the main board - perhaps because it'd been worked on by APR and Autothority before them), sent it to APR, and had them modify it again. When I installed the new ECU, the car drove for one day and the problem appeared again.

So I was trying to troubleshoot the issue this weekend (with lots of useful advice from Mat Reid), mainly by following the factory manual procedure (test voltages, test continuity, etc.). All tests checked out OK and the manual's final advice was to replace the TB. But I refused to beleive that it was the TB, since I'd replaced it last year and it still failed.

So finally I decided to take out the current TB, put in the other one, and see whether it would work with both ECUs (the TB that was on there was failing with both ECUs). When I took off the TB I noticed rusty water dripping from the bolts/bolt holes. I put on the other TB and tried it with both ECUs - it worked fine.

So here's my current theory: I have an Aquamist water injection system built into the car that sprays water into the intake, right after the intercooler and I suspect that it's the water which was causing the TBs to fail. In the summer it was warm enough that the water evaporated before it could accumulate. In the winter, however, water mist probaly collected in the TB housing and caused a short in the electronics. This is most likely why the TBs would work for a while if they were left outside the car for days/weeks, but then failed after a few days of use.

Of course this theory could be false as well, but there's a good chance that I've finally found the culprit. If so, I advise anyone who has water injection built in to make sure that they're spraying the least amount of water into the intake; otherwise you might well face a problem similar to mine (if you have a car with an electronic throttle valve) unless you live in a region where it's always warm (but even in that case, water in the TB housing cannot possibly ever be good for it). The TB was of course bolted tightly onto the intake manifold, yet the water still managed to escape past the two metal plates.

I haven't decided yet whether I'm going to reactivate the water injection system again with a smaller nozzle (I think my current one is .7mm which is activated around 5 lbs of boost). But apparently there is an upper limit to how much water you can inject in a DBW car.


**NOTE** After I deactivated my water injection system over two months ago (1/08 - it's now 3/30), I did not have any further problems with the throttle in cold weather. I am going to put in a smaller nozzle (.6mm) and run that for a while. In the mean time, I would advise against using a .7mm (or larger) at low boost (6 PSI).<ul><li><a href="https://forums.audiworld.com/a4/msgs/2472382.phtml">https://forums.audiworld.com/a4/msgs/2472382.phtml</a</li></ul>

Joe Sixpack

<ul><li><a href="http://www.1010tires.com/WheelOffsetCalculator.asp">Wheels Offset Calculator</a></li></ul>

Ash A4

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jbrentd

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CURSH[silverbullet]

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2523541.phtml">Vac Line Link</a></li></ul>

A4SilverT

The good news is that the maintenance will likely have been performed on schedule or even more often. If parts are known to fail prematurely (such as the timing belt/tensioner), the tuner will likely have replaced it earlier than Audi recommends. The owner will probably have used top quality fluids and parts. The car will likely have been detailed more than a typical car, and the paint will probably be in better condition than average.

The bad news is that the vehicle may have been driven very hard, autocrossed, dragged, or tracked. While this can be true of any used car, it's somewhat more likely with a car that has significant performance modifications. One useful thing to check is the integrity of the fuel line. If it's been patched, that's a likely sign that the previous owner used a nitrous oxide injection system. That system has only one purpose.

Also, the vehicle may come with some mods that are illegal:

1) Sometimes tint that is too dark has been installed. If the tint level is illegal for your state, you'll have to remove it -- or be content being a magnet for police attention.

2) The catalytic converter (cat) may have been replaced by a straight pipe (test pipe) or been hollowed out. This makes the vehicle illegal for street use anywhere in the United States, and it is a violation of federal law to make such a modification. Depending on the state's inspection system, or lack thereof, this modification may not have been detected, and the vehicle may have passed inspection. However, if you're caught, at the very minimum you will be paying for an expensive new cat -- think about $1000 with installation. It is illegal for a salvage yard to sell used cats.

It's conventional wisdom among tuners that other modifications will not add value to the sale price of the car unless the owner is lucky enough to find a buyer who is also a tuner. As a result, owners will often remove their modifications prior to the sale and sell them to fellow tuners separately. While you'd like to think that the modified part is replaced with the original part, the part that gets put back on may be a used part from another tuner or from a salvage yard. So while your new-to-you vehicle may have only 50,000 miles on it, the springs and shocks might have 80,000 miles.

The best thing to do is get to the owner before the vehicle is de-modded and make an offer for those mods you want. A good offer is 30-50% of the original parts cost, which is what the tuner expects to get selling the part separately. The tuner saves the time needed to remove the mod and find a replacement. You get a mod at a greatly reduced price, already installed. Audi mods are usually high quality; many come with a lifetime warranty, at least to the original purchaser. And most manufacturers go to great lengths to ensure that their parts do not affect the legality of the vehicle for street use.

Also note that there are some really EVIL tuners out there, if only in the sense that they do modifications that ruin the car. If you're looking at an Audi that has a wing, or a hood scoop, or an engine compartment that was "simplified" by throwing out some engine components, or flame decals on the sides, or a coffee can exhaust, or a blow-off valve, these are signs of evil tuning. If you get a great deal on the car, all of these modifications can be removed, of course. The problem is that you don't know what else was done. Things such as hacked up electrical harnesses can be extremely difficult to troubleshoot, as can ECUs with amateur modifications, which may be why the car is for sale in the first place. Unless you have a lot of patience and a lot of money, you're better off avoiding cars like this.

<a href="https://forums.audiworld.com/midatlantic/msgs/166827.phtml">Problems from a modified wiring harness?</a>

Rather than list good mods, I'll suggest you take a look at the signatures of any 25 members of this forum and make a list of the mods you see in those sigs. Some may not be aesthetically pleasing to you, but they're all pretty much tried and true mods that improve the car.

Finally, even if the previous owner of the car is technically knowledgeable and completely honest, it's still a good idea to get an independent mechanic who knows Audi to inspect the car for you.

SpeedyDTP247 CQ+UrS4

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2532620.phtml">Torque Specs for Sway Bar Install</a></li></ul>

BSK

curtesy of BitJockey

Total cost: less than 50$ including P/S fluid<ul><li><a href="https://forums.audiworld.com/a4/msgs/2533140.phtml">https://forums.audiworld.com/a4/msgs/2533140.phtml</a</li></ul>

wasco1989

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