SUPER RICH idle/light throttle. Help.

[Florin1]

Hello all. I'm fresh out of ideas, and i need your help in hopefully diagnosing my troublesome rich idle. First my mods, then i will bring ya'll up to speed on what i have done and what i haven't.

Car: 91 Legacy SS Turbo
Mods: 96 wrx ej20g, "robtune" big tune, fmic, 3" TBE, 5 spd swap, COP conversion. I think that's about it for relevant mods.

So on to what the car is doing. Trouble started a few moths ago, and got worse, until finally, its unacceptable. What it started doing is running rich @ idle ~10.5-11:1 AFR, but then leaning out to 14.1 for a couple days, then going rich again, and also a little rich at VERY light throttle, or while just trying to maintain speed on level surface, or decline. I'd see dips of ~11:1. Car seemed to get a little richer as time passed, but only at idle and VERY light throttle. I had the battery disconnected while i replaced my transmission. When the car was up and running again, it would sometimes die at idle. I figured it was because the reset ecu. Rob thought that maybe i had a leaky injector and wanted me to get them cleaned and flow tested. I was hoping that maybe it was a pinched o-ring and replaced them, to no avail. I was now seeing a consistent 11:1 AFR at idle, and it seemed to take a hair more throttle while cruising, to get it to lean out to 14:1, but still at light throttle on level/decline (no load/light load). I ended up killing one WB sensor due to running so rich. So i replaced it. I also got a CEL for a knock sensor, which i replaced with another from a V3 STI 20k car. Car still ran rich, so i finally bit the $130 bullet and had the injectors cleaned and flow tested. They ended up checking out fine, and they opened up another 30cc's after cleaning. They went from 488cc to 512cc. (injectors are the 05 STI sidefeeds). Next we thought it was the FPR. So i had that tested, and also the rubber vacuum lines that go to the fpr from intake. They both checked out fine, and held vacuum. I was getting between 10-15 in-lbs at idle, depending on the rpm. I also applied vacuum directly to the FPR while car was idling (20 inHg) and it didnt change the AFR at all. It still idled at ~9.5:1.
Next i checked the injector wiring. Rob thought that maybe i flipped the Injector wiring somehow. So i switched the connectors from the injectors, 1 bank at a time, and it acted exactly the same, with the same AFR. Weird.
Also took out the spark plugs and disconnected the injector connectors and cranked the motor for like 30 seconds with paper towels shoved into the spark plug holes. No fuel was leaking, towels were dry.
Fast forward to mid may. Remember when i told you when im on the freeway, and im just getting on the throttle, or barely on the throttle while I'm cruising, and the a/f mixture drops to like 11:1? Well now it does it VERY noticeably, and it drops to 9:1. Even if im just putting up the street in 1st or 2nd, it starts flooding. I can hear the car fighting to run. Its actually bucking a little. Same with the freeway. If im on light throttle, it will be at 9:1. I actually have to push the throttle 1/3 down to get it to lean to like 13:1. So i thought maybe Rob gave me a ECU tuned for 440 cc injectors. So i swapped in some 480's off a v3 STI, and then, when that didn't change anything, i popped in some 440's. That didn't change much either. What it did change, was the time it takes to lean out under light throttle. So now it a little quicker to go to 14:1 under light throttle. Still at ~9.5 at cruise, light throttle, and idle.
FF to May 25th. Here is an email i sent Rob.
"I borrowed another maf and ecu from Mike. This is with car cold. I put in the maf first (he just pulled it off a car at a junk yard, so we will just assume it works) and fired the car up. Let it idle for like 30 sec. and nothing changed. Gave it a quick rev, and then it returned back to idle and like 9.1-9.4 AFR. So i swapped my old maf back. (oh, and car ran for like 45 seconds tops, before i turned back off. As you can tell I'm building up to what happened with the ecu) So next i unplugged my ecu, and brought the 4 connectors to the spare ecu. Plugged it in and fired it up again. I could tell immediately, it had a better idle, not as loopie/lopie sp.? Then my WB warmed up to where i could see afr's, and they were reading like 10.1. So after like 10 more seconds, i brought the revs up to like 3k for a few seconds, and let it return to idle. To my surprise, the car was idling at like 12, then got leaner all the way to like 14:1. So i was ecstatic. Car idled fine for a minute or so, and i gave it another rev, and then it got richer again, like in the 12's. So i went upstairs to get my wallet to go on a test drive, and when i got to the car, it was now reading mid 11's. SO i headed down the street, and tested my first, most annoying issue, maintaining a certain speed, say 5mph. Sure enough, it dropped the afr to high 9's. Maybe some mid 9's. So the rest of the drive what i did notice is that it leaned out sooner with less throttle. So i could get it to read 14's with light to light-moderate throttle, where to as with the other ecu it would take maybe twice the throttle to get it to lean out. As for idling, this ecu had a lot more trouble keeping the car running. It would lope like 4-5 times, and then die, every time.

One thing i forgot to mention is, a week ago iirc right after i got the car running again, i did see a nice idle and regular afr's for like 5 miles. So it started out running rich, as it does constantly, now, and then i saw those 5 miles of good afr's weather cruising or idling. So i figured, the car was learning and trimming. But after those 5 miles, on my way back it ran like poo again."

May 26th email (testing my NB o2 sensor & wiring)
"Well more bad news. I unplugged the o2 and reset the ecu, and went for a drive. Nothing changed. So i did the tests off that pdf file you sent me on page 49-50. Here are the results.

Test 1 (note that 22 pin connector on my ecu is called the b48 on my car)
1. check
2. .3 ohm
3. no reading on M ohm w/ ecu connected and o2 unplugged. I got .387 M ohm with b48 plugged back into the ecu and o2 still not connected. This was the only test i didnt get correct results?

Test 2
1. check
2. check
3. 11.89 v

Test 3
1. check
2. I did not have an oscilloscope, so i just did it with my multimeter. I got .4-.8v depending on the idle because like i said, it constantly fluctuates.
I also did a couple other tests while i was measuring these wires with the car idling. This was checking voltage to ground. Pin 2 had 13.75v at idle, and pin 1 didn't read anything.

And finally you've all been updated. Today i swapped in a NB o2 sensor from a bugeye (4 wire) mine is a 3 wire, so i just jumped the wires. I also reset the ecu. Car is acting the same So... What else can i check, or what suggestions do you all have?

ANY input is greatly appreciated.

[TurnNburn]

Holy smokes man, that was a lot to take in. While reading i was thinking leaking injectors... then FPR in the same order you diagnosed. But since your tests came back negative for both and since you didnt mention it, have you checked the timing?

[Florin1]

I have not checked the timing. And thanks for reading. lol :-p
How do i check timing? Do i gotta remove all 3 covers, or can i do it with a timing light and the center cover?

[TurnNburn]

Yeah no problem. Your better off just taking off all 3 covers. If you go down a couple of threads there is one that has a picture of the timing marks. Here is the link to save you the time. http://bbs.legacycentral.org/viewtopic.php?f=5&t=47070.
Just make sure you use the right marks because it can be kind of confusing if youv never looked at it before.

[Florin1]

^ That does me no good. I'm ej20g dohc

[TurnNburn]

oh... my bad. I wasnt thinking. I should have known that.

[wtdash]

deleted

[Legacy777]

My suggestion would be to also check the timing to ensure the belts are on properly.

The next step I'd highly recommend is going back to the stock ECU, injectors, & MAF for that engine. You mentioned you put in a spare ECU, but I'm assuming it was another ECU that was a Robtune. Swapping out the ECU, injectors, & MAF will let you know whether you have an issue with the tune in the Rob tune ECU, and/or whether you have an issue with the motor. If you swap in all the stock parts and the engine runs fine, you know the problem is likely with the tune. If you still have issues, then you know the problem is somewhere else, and in swapping those parts, you've help eliminate the ECU, MAF, and injectors as culprits.

[Florin1]

My suggestion would be to also check the timing to ensure the belts are on properly.

The next step I'd highly recommend is going back to the stock ECU, injectors, & MAF for that engine. You mentioned you put in a spare ECU, but I'm assuming it was another ECU that was a Robtune. Swapping out the ECU, injectors, & MAF will let you know whether you have an issue with the tune in the Rob tune ECU, and/or whether you have an issue with the motor. If you swap in all the stock parts and the engine runs fine, you know the problem is likely with the tune. If you still have issues, then you know the problem is somewhere else, and in swapping those parts, you've help eliminate the ECU, MAF, and injectors as culprits.

I did try a stock ecu, injectors (440's) and maf, not a robtune. No change.

So for the update, the car runs great. I think i figured it out, although it doesn't make any sense to me. Basically, if i disconnect the bpv vacuum hose, and cap off the nipple that feeds it on the intake manifold, the car runs great. As soon as i connect it, afr's drop to 9 again. Only problem is, if i dont connect the bpv, i get compressor surge between shifts. Also, i have tried a different bpv, and its doing the same thing...

[Legacy777]

Is this a stock BPV or an aftermarket setup? Is it full recirc or partial atmos? How is your intake piping setup? Have you pressure tested the intake piping?

[Florin1]

First bpv is a oem sti tmic one bolte to a 06 sti tmic. same issue. Second set up is a fmic kit with a hks ssqv 3. I tried both setups and had the same results. Car holds 17psi solid at wot.

[Legacy777]

Where does the tube for your IAC valve tie into?

Got any pictures of your engine bay?