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Old 11-09-2021, 10:13 PM   #1
StreetForged
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Default New F+T Swap, Lean AFRs

Just finished a grueling solo F+T swap last night with an OE 940 Garrett setup and threw an AEM wideband on it to be safe, and I'm seeing pretty concerning AFRs from idle and cruising/light accel.

Last night it idled around 14.5-15 until it started to warm up, then began to run around 16 with a lot of spikes up to 18-19. I had to drive it home which was about 5 mins, in which case it ran around 14-15 most of the ride home. I gave it another test drive today and when I took it up my road it was staying between 15-18 the whole drive, so I turned around half a mile up and came back. Haven't gone even close to WOT yet since idle and light throttle AFRs have been so sketchy.

My O2 sensor is only a few inches away from the turbo since I had to shave a bit off the downpipe to fit a 240 so I'm not sure if that's causing any issues. Open downpipe currently until I find the motivation to fabricate another exhaust.

I have 850t injectors, a fresh pcv setup into a catch can, and a janky intake setup, but everything else is OE turbo parts for a 1995 940se. Turbo seems to be leaking oil which wasn't disclosed in sale to me, as the intercooler and hoses had a decent oil film and I'm seeing fresh oil on the intake side of the housing that isnt coming from the feed or drain.

I just put in new NGK copper plugs which I gapped somewhere around .29-.30, all my ignition stuff is new, 3 bar FPR, shouldn't be any vacuum leaks, fairly new fuel filter and sock, have tried a few MAFs..

I've been waiting 2 months on my manifold gaskets, so I'm thinking this could probably play a big role. Is there anything else to consider? This is my daily and it's been out of commission for a week. Save the judgement, I am aware this probably wasn't smart but it was necessary.
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Old 11-09-2021, 10:24 PM   #2
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Using turbo computers?
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Old 11-09-2021, 10:54 PM   #3
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Using turbo computers?
Yeah as far as I'm aware I didn't cut any corners on it other than having a pretty rough intake hose and my coolant hoses are weird since they're for a 940. I figured I'd have a few issues doing my first +t and doing it by myself, but I didn't expect to have such scary AFRs for having a completely stock setup
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Old 11-10-2021, 07:35 AM   #4
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are your manifold gaskets leaking? Grab a four foot section of vacuum tubing and with the engine running, shove one end in your ear and the other probe the exhaust manifold.

If you're running lean all the time and not just during transients then you have an issue, but expect every time you let off the gas for the AFR to spike into the 16-20 range.
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Old 11-10-2021, 10:05 AM   #5
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Where is the maf located?
Any check engine light or codes?
Where in the downpipe is the wideband probe? with it being open you could just be seeing ambient air making it up there
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Old 11-10-2021, 10:10 AM   #6
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Narrowband working? Do you actually have one or are you using the simulated NB wire off the wideband?
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Old 11-10-2021, 10:58 AM   #7
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I've been waiting 2 months on my manifold gaskets, so I'm thinking this could probably play a big role.

If the gaskets you are waiting are the intake gaskets and condition is unknown I would start there, that's some pretty lean numbers and possibly an intake gasket leak.

My b230 +T runs rich on cold start up and settles at 14.7 ish when up to operating temp on LH2.4.
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Old 11-10-2021, 12:08 PM   #8
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Definitely do any questionable or unknowns to get a proper stage zero - so intake gasket & injector orings, for example)

Pics of where you placed things helps - I put the AEM WBO2 just before the downturn (740 install) it only lasted maybe 1K miles. The sensor is supposed to be 18" or so from the turbo, if you read their install directions. The sensor must be installed above horizontal or moisture will kill it. Where is yours exactly? If there is an exhaust leak around /near it, that will throw off readings.



With that said, many factory (Volvo) WBO2 installs are within 6-8" of the hotside, and hold up just fine.

If everything you swapped over is stock Volvo turbo LH2.4 components, it should run stock values for AFR readings. Did you use all new Bosch components (FPR, etc.,)? Aftermarket replacements may not be giving correct values, esp. if you used sensors that are meant for LH2.2, for example....
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Old 11-10-2021, 12:36 PM   #9
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Where is the maf located?
Any check engine light or codes?
Where in the downpipe is the wideband probe? with it being open you could just be seeing ambient air making it up there
There's a 3 inch intake hose and PCV off the turbo, then to maf, then filter right now. No check engine yet. The probe is probably only 2 inches from open air so I wouldn't be surprised if it's leaning my numbers a bit but it doesn't seem to run all that great either so I doubt it's just the probe misreading

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Old 11-10-2021, 12:40 PM   #10
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Definitely do any questionable or unknowns to get a proper stage zero - so intake gasket & injector orings, for example)

Pics of where you placed things helps - I put the AEM WBO2 just before the downturn (740 install) it only lasted maybe 1K miles. The sensor is supposed to be 18" or so from the turbo, if you read their install directions. The sensor must be installed above horizontal or moisture will kill it. Where is yours exactly? If there is an exhaust leak around /near it, that will throw off readings.



With that said, many factory (Volvo) WBO2 installs are within 6-8" of the hotside, and hold up just fine.

If everything you swapped over is stock Volvo turbo LH2.4 components, it should run stock values for AFR readings. Did you use all new Bosch components (FPR, etc.,)? Aftermarket replacements may not be giving correct values, esp. if you used sensors that are meant for LH2.2, for example....
The wideband is on the second bung of the dp, so probably far enough downstream. Probably more than 15 inches. Oe sensor is the one on the first bend
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Old 11-10-2021, 12:43 PM   #11
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If the gaskets you are waiting are the intake gaskets and condition is unknown I would start there, that's some pretty lean numbers and possibly an intake gasket leak.

My b230 +T runs rich on cold start up and settles at 14.7 ish when up to operating temp on LH2.4.
I did the intake manifold gasket, replaced all my PCV stuff, and cleaned out and replaced gaskets on my throttle body less than a month ago. I'm pretty anal about the maintenance on the car. Exhaust gaskets are what I'm waiting on since I've had the manifold off a few times on these gaskets and they're probably about 2 years old now
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Old 11-10-2021, 12:48 PM   #12
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are your manifold gaskets leaking? Grab a four foot section of vacuum tubing and with the engine running, shove one end in your ear and the other probe the exhaust manifold.

If you're running lean all the time and not just during transients then you have an issue, but expect every time you let off the gas for the AFR to spike into the 16-20 range.
I'll check the manifold tightness today and look for a leak. It was lean all the way through accel 1st gear to 4th riding around 16-17:1 and never really came back down. Seemed to run a healthier ratio when I had just plugged the battery back in
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Old 11-10-2021, 12:52 PM   #13
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Narrowband working? Do you actually have one or are you using the simulated NB wire off the wideband?
That means my ECU would be reading off the wideband, right? Its using the o2 sensor I got with the turbo Downpipe, wideband is standalone
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Old 11-10-2021, 01:11 PM   #14
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so you have a 3 inch maf? i thought you need bigger injectors with it or did i remember it wrong
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Old 11-10-2021, 02:35 PM   #15
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If you're only concerned about what the AEM gauge is reading based on the AEM wideband, I would not sweat it. We have one in our race car that reads good at cold idle at about 14.5:1, and progressively reads leaner as the car approaches and then achieves closed loop. It gets to the point where the gauge shows three dashes, or "undetectable". At full chat, however, the gauge reads where it's tuned to: about 13:1. There are lots of reviews/comments/etc. about this. It would appear that the sensor needs a somewhat healthy volume of gases to read accurately. Sometimes a new sensor fixes it, sometimes it doesn't.

If everything TRULY IS a direct swap from a 940, and you've been over it all to make sure nothing is obviously wrong, and the car runs well, I would not worry about what that AEM gauge reads at low throttle angles.
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Old 11-10-2021, 03:05 PM   #16
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Was the wideband new when you put it on? I’ve already been through three O2 sensors and two wideband controllers since getting my car together. Those UEGOs are kinda garbage.
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Old 11-10-2021, 04:33 PM   #17
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The probe is probably only 2 inches from open air so
meaning the exhaust ends 2 inches past where your wideband sensor is located?
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Old 11-10-2021, 09:57 PM   #18
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so you have a 3 inch maf? i thought you need bigger injectors with it or did i remember it wrong
No 3 inch maf, had to step down off my intake pipe with a coupler.
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Old 11-10-2021, 09:58 PM   #19
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meaning the exhaust ends 2 inches past where your wideband sensor is located?
Yeah, haven't had the ambition to make a full exhaust work yet, it's already cutting it super close to my frame rails and there's not much room to begin with. Just open downpipe under the car
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Old 11-10-2021, 09:59 PM   #20
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Was the wideband new when you put it on? I’ve already been through three O2 sensors and two wideband controllers since getting my car together. Those UEGOs are kinda garbage.
Brand new
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Old 11-10-2021, 10:01 PM   #21
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If you're only concerned about what the AEM gauge is reading based on the AEM wideband, I would not sweat it. We have one in our race car that reads good at cold idle at about 14.5:1, and progressively reads leaner as the car approaches and then achieves closed loop. It gets to the point where the gauge shows three dashes, or "undetectable". At full chat, however, the gauge reads where it's tuned to: about 13:1. There are lots of reviews/comments/etc. about this. It would appear that the sensor needs a somewhat healthy volume of gases to read accurately. Sometimes a new sensor fixes it, sometimes it doesn't.

If everything TRULY IS a direct swap from a 940, and you've been over it all to make sure nothing is obviously wrong, and the car runs well, I would not worry about what that AEM gauge reads at low throttle angles.
The thing is that it does seem to idle fine but it didn't seem particularly healthy when I last took it out. It seemed like there may have been some misses or something else going on. Didn't spend nearly enough time driving it to get an accurate understanding of what felt off though.
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Old 11-11-2021, 10:10 AM   #22
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Yeah, haven't had the ambition to make a full exhaust work yet, it's already cutting it super close to my frame rails and there's not much room to begin with. Just open downpipe under the car
the wideband reading cannot be trusted with it that close to the end of the pipe. It is seeing ambient air which will read as lean
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Old 11-14-2021, 04:55 PM   #23
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the wideband reading cannot be trusted with it that close to the end of the pipe. It is seeing ambient air which will read as lean
I welded another few feet of pipe onto the dp and moved the o2 bung about 1-1.5 feet down the pipe and the AFRs are good under normal driving, but I got into boost and it didn't drop below high 13s. Normal cruising stays between 13-15, rev match downshifts drop it to about 10.9 for a second. I guess I should be good to use it as my daily again, but will be driving like a grandma and staying off boost until I figure out why it's still running lean. I've never replaced my primary fuel pump, would it be a good idea to ditch the double pumps and run a walbro 255 or something?
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Old 11-14-2021, 08:22 PM   #24
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Not necessary for your power level. Right now the more variables you introduce deviating further from stock, the harder this is going to be to figure out. What do you know about the injectors and fuel pressure regulator?
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Old 11-15-2021, 04:04 AM   #25
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Not necessary for your power level. Right now the more variables you introduce deviating further from stock, the harder this is going to be to figure out. What do you know about the injectors and fuel pressure regulator?
I put a 3 bar fpu in it about 2 years ago, bought some refurb 850t injectors and replaced the baskets and o rings. I ordered a part number I found on these forums so I'm hoping I didn't end up with some Toyota Yaris injectors or something on accident.

I figured moving to a single fuel pump would be nice for the sake of simplicity and diagnosis if I have to replace it anyway, though my power goals are staying below 250. iPd turbo cam should be in tomorrow, have an MSD 6a and will probably leave it somewhere around 10psi once it's all dialed in, but that should leave me somewhere around 200 I'd imagine.
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