WI is great! However, I have had throttle body problems on two different DBW cars using WI. The first was my '03 GTI and now with my '01 Audi A4.

Here are the symptoms. The car starts idling erratically. You may or may not get a CEL, and may get an EPC light, but you will certainly get some stored DTCs associated with the throttle body (or throttle valve).

Here's what happens. When the water jets are installed ahead of the TB, the pressure of boost eventually forces water past the throttle plate shaft into the electronic part of the TB. This causes electrical malfunctions confusing the ECU into thinking there is a mechanical failure or some other nonsense.

The fix is dry out the inside of the compartment where the gears and electronics are. That's under the black cover. Pop off the six clips (carefully) and blow dry the inside with high pressure air. You could also use some quick dry (QD) electrical contact cleaner, but you want to get all moisture out of the compartment.

Next is to move the jets AFTER the TB (see my photos below). This seems to have fixed the problem for me (for now).

Third, replace the throttle body. Eventually it will fail at the most inopportune time. (At least get a good working used one as a spare incase my "fix" doesn't work.)

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Here is the original location, right after the IC, but before the throttle body.

Here is the new location, after the throttle body.
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I have the pump located right under the coolant reservoir.

I got a standard fuel filter and used it as a water filter and a buffer to catch air bubbles in the line. You can also see that I have a tube running into the washer fluid, which is what I use.

 

what are you injecting?

also i have never heard anyone complain about those issues with snow performace or devils own kits. Plus with you injecting behind the TB, you elimate the extra cooling effect of the water/meth and just mainly get the knock resistence.

Closer to TB = more knock resistance and less cooling
Further from TB = lower iat's and less knock resistance

This is why you use 2 nozzles or compromise and run one nozzle about 12-18" from the TB.

 

I use washer fluid, which is approximately 25% methanol.

Other folks have experienced this problem, though not many. I don't know if they were using Aquamist or another brand, or what percent methanol.

I only post this so people who may experience a similar problem will be able to fix it more quickly. The first time it happened with my ’03 GTI, I had to take the car to the dealer (after removing a lot of stuff) because I had no idea what was going on. They had it for three days and were about to replace the ECM because of the bizarre codes that were being thrown. Finally, they tried replacing the throttle body and that worked. The mechanic working on the car was cool enough to “overlook� some things and told me later that they opened the throttle body electronics and the inside was corroded. Perhaps that was because I was running a 50% solution at the time.

If you consider what you are trying to do with WI (which is to gain power by advancing timing and suppressing knock), lowering IATs is one way. But if you can do the same thing by controlling detonation through water mist, then that should determine where to place the jets. In this case, IATs are not a problem for me because my RaceTec FMIC is sufficiently effective. So, suppressing detonation is my goal. If placing the jet close (after) the throttle body is the best location, then that works for me.

 

Nice post! I think with all the WI inquiries lately this would be a good one to put in the DIY section or sticky. For now ill just put the link in my favs.

 

the dye in some ww fluids have been known to mess up TB's and even cause them to stick. If you switched to distilled water and Heat, you should have 0, thats ZEROissues before the TB.

Also NO air to air ic is 100% effiecint, thats crazy talk. The iat's can still be droped 15-30*C lower by plancing it back about 18" from the TB and you will keep knock protection. That would make a HUGE differnce in timing pull and you should see in increse of a few degrees equating to another 10+hp

 

I didn’t say the FMIC was 100% efficient, only sufficiently efficient. The output side of the IC is consistently cool to the touch. However, you may be right about the dye in the washer fluid, so I may try distilled water and HEAT. Still, my throttle plate wasn’t sticking from what I could tell. It moved freely when I pushed it open by hand. There was still the spring resistance that keeps it closed, but it moved smoothly.
When I removed the cover from the electronics, there was moisture (condensation) on the inside of the cover. All I did was dry it out with an air hose and reinstall it. I moved the jet from before to after the throttle body and have had no problems in the last 200 miles. So while it may have been the dye, I am certain that the moisture was the primary cause.

 

by injecting it further back you can lower iat to below abient temps.

 

haha. i had no idea what u guys were taling abotu at first. my dad used to have straight water injecting into our 68 mustang becuase it was tuned for 100 octain

 

it works great and has been around forever. not to many people seem to get the point that it is a great mod and only cost about $300 and you can run far more timing/boost, even race programing made for 100+ octane

 

Is there any point of getting a fmic if you plan on doing water injection? I've been wondering this for a while and i'm going toward its pointless.. water injection is the only mod left I can think to do to my car and keep it a DD