Guys, I've talked to several people who are quite knowledgable about subarus and no one can work out what could be ailing my 2k4 Sti. Here are the details:

After a very nasty storm here in NJ (6 inches of rain) the car will start but idles VERY rough after 10 seconds of being started. The rpm's will surge then fall below idle then surge again which will then repeat over and over. The afr's, as read from my wideband 02 shoot from 12-15 to 12 and back up again in tune with the rpm surge. Before the 10 second point it idles dead balls perfect which leads me to believe it's a sensor failure as the cold start mechanism should disable the sensors until this point.

First thing I did was see if it was throwing any codes by use of a deltadash but it was not. I then tried a new maf sensor from a 2k2 wrx which the part number matched identically yet with the same exact results. At this point I removed the utec but same results. Next I unplugged the map sensor and tried starting. I do not have one available to me to test with so unpluggin it was all I could do. This seemed to keep the idle much more steady for 30 seconds or more but began to stall soon after. At this point, I am ready to either buy a new map sensor and try my luck or take the car back to stock and have subaru look at it which I do not really want to do for obvious reasons.

Mods are turboxs shortram, turboxs utec, joe p or similar mbc, turboxs tuner and turboxs stealthback exaust w/ cat. I was running the shipped stage2 map with great results minus the documented stumble at the crossover point which I hadn't gotten a chance to tune out.

There was no visible water in the engine bay when this first began the day after this storm and we had no flooding although the rain was torrential and I was assume angled at times. Any help would be greatly appreciated so I do not have to stock the car and take it back to suby. The situation is so odd because the car ran just fine the night before the storm when I parked it. This is a cross post.

-Seneca

Check all your negative ground cables, see if anythings fried. Maybe it was struck by lightning?!?

I will check for any visible damage once again on the hot side. As for lightning I thouhgt it possible but I was in the house sleeping not 10 feet from it so I'd think I would notice. Otherwise I am running out options.

How deep was the water you drove through? If you don't slow down to cross standing water it can be forced into areas you wouldn't think possible. Check all your ECU connections, open the air box and see if the filter is wet. You will have to check about every electrical connection on the car. Also check your MAF and it's conection.

I DID NOT DRIVE IT THROUGH ANY WATER. As stated above, I am running a turboxs shortram and I have looked over the car as best as the nakedeye can. The maf has been replaced with same results. I am leaning towards map sensor but I am having a hard time locating one to test with. Can anyone confirm that a wrx map sensor might work on an sti. I know the part number are different. Any more help would be appreciated but please read the post first.

brand new car = warranty.


take it to the dealer.........

you have free towing.

oh I know... but brand new car + tbe/mbc/tuna/utec/intake/pulley has to be stock to take to dealer.

unplug the front 02 sensor from the harness, see if it still sputters. It may still run pig rich when you do this... but it should start and idle.

If that doesn't seem to make any difference, try the same thing with the MAF sensor.

The car has the ability to run in a "safe" mode with those sensors unplugged, just in case they should fry.

Have you tried giving it some throttle after it's started up? If it wasn't running in a puddle or driven through water, and it's just been sitting through the rain, it's very doubtful that it can be hydrolocked... so I would say revving it up won't hurt. It just might give whatever sensor got waterlogged the chance to dry off.

oh I know... but brand new car + tbe/mbc/tuna/utec/intake/pulley has to be stock to take to dealer.


lol, understood. :lol: :cool:

Reading is Fundamental

seems as though you would be getting some sort of code for this type of condition. can you let the car idle for around 5 minutes? i bet something would show up by then.

i would start removing mods one at a time (starting with the easiest one to remove of course) and turning it back to stock. reset the computer after each removal and see where it's at. you may isolate the problem and if not, it will be back to stock to return to the dealer.

it's weird that it just quit...

i would start with the utec, mbc and intake as those are 5 minute jobs and most likely part of the issue. i can't imagine a tbe causing such a problem.

Start drying out electrical. Start with ignition related stuff.

I'd be shocked if the rain were the cause.

Down here in good 'ole Georgia, we get unbelievable downpours pretty regularly with no ill effects. It's not unusual at all to get 2-4 inches of rain in 30-60 minutes coupled with gusts up to 50mph. And this happens around once a month during the summer. It causes all kinds of bad street flooding (when you are at sea level, there aren't many places it can go) and standing water to drive through. I drove through such a storm on June 22nd in my STi, including the resultant standing water (see other post on subject). Rain gauge at home reported 4 inches of water. Power was out for nearly 5 hours.

But I've never noticed any ill effects to my STi, with the possible exception of momentarily wet brake rotors.

If it was water entry causing problems with a sensor, there may be a problem with the sealing of that sensor as well. Other, less severe, storms might cause the same problem in the future.

Good Luck!

-Michael

It's been two weeks so I would think anything that got wet would be dry by now. As for removing mods, the utec is out and the mbc and intake will come off tonight. Looks like a trip to dealer might be in my future.

Try getting a loaner ECU to test.

Im having a hard enough time getting a loaner map sensor. Suby wants 290 for it and it isnt in stock. =\

ONE ON EBAY LOOKS LIKE!
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7912140893&category=42604&sspagename=WDVW

did you by chance unhook your exhaust to attempt to drain it? after the hurricane here last summer, my exhaust had quite a bit of water in it. The car ran but like crap for about 30-40 minutes.. very rich and sputtering..

map not maf.... I was able to borrow a maf sensro and rules that out as the cause.

ah my bad, i cant read.

ah my bad, i cant read.


Me either. :lol:

maybe uoy are dislexic like em? =P