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Old 06-02-2011, 01:17 AM   #1
Florin1
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Default SUPER RICH idle/light throttle. Help.

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.
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Old 06-02-2011, 03:19 AM   #2
pmugabi
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When adjusting/testing AFR, I always do it with the narrowband sensor disabled in software or physically disconnected. That way any corrections it would make will not affect what I'm seeing. It will run slightly richer with the NB disconnected but not more than 12 usually.

The AFR just after blipping the throttle will be slightly rich for a while (I see up to a full point richer sometimes for about 10 seconds) so concentrate on the steady state value.

I think you should also test the car only when it's warm so that you don't have to think about cold-start compensations (which maps AFAIK are still undiscovered).

Do you have a programmer to re-program the chip? If so, I would adjust the injector scaling to the point where you get a consistent AFR of between 13-14 at idle and then adjust the fuelling map to keep the on boost AFR safe. Once that is done, you should be able to reconnect your narrowband.
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Old 06-02-2011, 06:47 AM   #3
kimokalihi
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Rob is the programmer and I think it's the same tune I'm running with the same engine and setup so I don't think it's the tune. I think it's a problem with either the wiring, a sensor or fuel setup (not injectors since florin has tried others).
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Old 06-02-2011, 06:54 AM   #4
kimokalihi
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Did you ever replace the coolant temp sensor? I know they can mess with fueling if they send the wrong signal. Or maybe that's just cold start. Cheap part I think.
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Old 06-02-2011, 06:15 PM   #5
Florin1
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Haven't checked coolant sensor. Dont know what to look for when testing that. Kimo, that wrx knock sensor you have, is that from a 2.0 wrx?
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Old 06-02-2011, 06:25 PM   #6
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I've got no idea. I think its just off a 96 outback or something. I don't know how to test it but i have the fsm and I can look it up when I get home.
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Old 06-02-2011, 06:52 PM   #7
rob
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Hey Florin,

Thanks for bringing this to the forum for ideas. We have been banging our heads on this for a quite a while

Coolant sensor check was something I suggested when you had your car apart. It's a good thing to verify. Here are the testing specs.

-Rob

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Old 06-02-2011, 07:01 PM   #8
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Also I noted that if the NB is bouncing between 0.4-0.8 when the real AFR is around 9:1, then that points to problem with the sensor and/or the wiring back to the ECU.

Where exactly did you take those O2 voltage readings (between which two wires or pins)?

-Rob
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Old 06-03-2011, 12:28 AM   #9
Florin1
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I took the readings at the connector where the nb connects to the harness. I depinned the connector, and then plugged it on to the pins so i could read it live. I put my volt meter on pin 4, and body ground iirc.

Here's a vid from last night. At first, i was on a slight hill which is why it was reading 10. Then i floored it in 4th gear, doing about 30, which is why it leaned out nicely, and then finally, i was just cruising again.
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Old 06-03-2011, 09:22 PM   #10
kimokalihi
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Did you tell me before that you rewired the knock sensor in the past?
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Old 06-04-2011, 12:06 AM   #11
Florin1
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Yup. I may have figured out the issue. Kind of.
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Old 06-04-2011, 01:05 AM   #12
kimokalihi
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Do tell.
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Old 06-04-2011, 02:01 AM   #13
Florin1
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It ended up being the bpv vacuum hose. Its quite bizarre actually. Car runs fine with it unplugged, but as soon as i plug it in, it goes crazy. So i ended up plugging the nipple on the manifold. Now i get some compressor surge like so (not my car obviously)
, but it did fix my issue. I just don't know how it did.
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Old 06-04-2011, 06:43 AM   #14
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I have compressor surge as well but not nearly as bad as that 240 video. You don't really hear mine surge on low load shifts, mainly when you're gettin on it. That guy has it all the time no matter what the load or rpm is. He's got it real bad. Although Corky bell says compressor surge won't hurt your turbo as long as it's only doing it when you shift and not while in gear under load. So I don't worry about it. I was researching aftermarket BPVs but then I read that they can be finicky and if not set up properly can cause more problems than they're worth and so long as you're not pushing crazy amounts of boost it's best to stick with the stock BPV. That and aftermarket quality BPV is spendy.

Glad you fixed your car though. You should upload a video of how your compressor surge sounds. I'm curious to see if it's similar to mine.
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Old 06-04-2011, 04:37 PM   #15
Florin1
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Yeah, mine only does it between shifts. I will upload a video soon. I'm taking it drifting tomorrow at evergreen. We'll see if i can break it.
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Old 06-05-2011, 04:26 PM   #16
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Florin, so you're saying that with the BPV connection blocked off you're seeing AFRs of 14? Are you sure you didn't introduce a leak into the intake manifold e.g. not plugging up the nipple properly? The leak would definitely made a rich idle leaner which would appear to fix the issue.

The fix you discovered seems counter-intuitive since with the stock re-circulationg BPV no air is introduced into or leaked from the system so this part should make no difference on AFR.
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Old 06-05-2011, 04:35 PM   #17
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Hi Paul,

That is exactly the same concern I mentioned to Florin over email. I don't think he has tried a complete block off. That was my suggestion to make sure air isn't bleeding back through the bov and masking the real issue.

Honestly I think he is too happy with the way it is running right now to care

-Rob

Last edited by rob; 06-05-2011 at 04:41 PM.
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Old 06-05-2011, 04:57 PM   #18
kimokalihi
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Haha! I don't blame him. When you fix a problem that has been bugging you for ages (even if it's not really fixed) it can make you feel like a kid on christmas. I was thinking that fix sounded pretty peculiar myself.
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Old 11-29-2012, 02:12 AM   #19
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I had a similar problem, the issue was that the BPV outlet was not hooked up to recirculate. Thus, when I came into vacuum aka light throttle/idle/cruise it would open the BPV, I'd lose MAF measured air to atmosphere and go rich. It makes sense with the BPV disconnected you wouldn't have this issue.
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Old 06-10-2019, 05:11 PM   #20
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I have the same problem...Could the problem be that the BPV return is causing turbulence with the MAF sensor itself? Basically, I am very rich at very light throttle. Under just about any load (even not boost), it's fine. I haven't tried disconnecting the BPV vac hose.
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Old 06-14-2019, 02:02 PM   #21
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In my case it was the bpv disturbing maf flow. Fixed.
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