Fuel cut after 25% throttle??

Heads, valves, pistons, rods, crankshaft, etc...

Moderators: Helpinators, Moderators

Post Reply
subieroo
In Neutral
Posts: 8
Joined: Fri Oct 13, 2017 2:15 am

Fuel cut after 25% throttle??

Post by subieroo » Mon Jan 29, 2018 3:22 am

Hey everyone, I am having some tricky issues with my 93 touring wagon that had a 5spd from an 07 legacy swapped in by a previous owner.

The issue I am experiencing involves what I've determined to be a fuel cut if I open the throttle too aggressively past about 25% when the engine is warmed up. I checked both the stored CEL codes and ran the self diagnosis and pulled codes from that to find a few different things going on.

The stored codes I got with just the black connectors hooked up and the engine off were 22, 45, and 49. The first is a knock sensor code and the other two seem to be MAF related or some other intake related sensor. The knock sensor code could've come from a bad misfire or stalling out when the fuel was cut, I assume, so the other codes are probably where the culprit lies is my guess.

The codes I got while running the self diagnostic setting with the green plugs hooked up seem to tell a similar story. They were code 45 again and, this time, code 51. The reoccurrence of code 45 leads me to think the problem is almost definitely sensor related and code 51 makes sense because the auto to manual swap involved tricking/disabling the neutral safety switch.

So, does anyone have any pointers on where to start looking for this faulty sensor? Or maybe some insight as to what is actually causing this fuel cut issue?

wtdash
Fifth Gear
Posts: 2283
Joined: Fri May 04, 2007 4:09 pm
Location: N. ID

Re: Fuel cut after 25% throttle??

Post by wtdash » Mon Jan 29, 2018 5:22 am

codes = http://legacycentral.org/library/literature/codes.htm
22 = knock sensor / KS
45 = Press. Sensor
49 = MAF

51 = Neutral switch
The KS needs replaced. It's causing your car to go into LIMP mode.

99% of Legacys from '90-'95 will have cracked KS by now (and years ago). Get a new one - supposedly the cheap ones online are OK.

Reset the codes and check again. MANY peeps on here have the same codes related to a bad KS.

Make sure you have the SILVER metal MAF sensor. The black plastic are for NON-turbo / NA. (the '90-'91 manuals NA used the same MAF as the turbos).

Tangent:
'07 Legacy didn't have the mechanical speed sensor, AFAIK. How is your Speedo getting a signal?
Turbo Subies:
'87 GL-10 Turbo 4WD Wagon (pre-Loyale) - SOLD
'90 BJ, EJ22T/DOHC and 5-speed swap - SOLD
'04 FXT, Forged internals, VF39, STI TMIC, Cobb AP- SOLD
'93 Legacy SS - 5-speed, SOLD :-(
'02 WRX GG-SOLD
'96 BD - turbo'd-SOLD

subieroo
In Neutral
Posts: 8
Joined: Fri Oct 13, 2017 2:15 am

Re: Fuel cut after 25% throttle??

Post by subieroo » Mon Jan 29, 2018 6:51 am

I'll pick up a knock sensor tomorrow, it's cheap enough. I do wonder then why I didn't get the knock codes while I was driving it in d-check mode and experiencing the same fuel cut scenario as usual.

Legacy777
Site Admin
Site Admin
Posts: 27536
Joined: Tue Oct 15, 2002 11:37 am
Location: Houston, Tx
Contact:

Re: Fuel cut after 25% throttle??

Post by Legacy777 » Mon Jan 29, 2018 7:07 pm

If you clear the codes, are the same ones still there? Are you able to clear the codes?
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm

subieroo
In Neutral
Posts: 8
Joined: Fri Oct 13, 2017 2:15 am

Re: Fuel cut after 25% throttle??

Post by subieroo » Mon Jan 29, 2018 7:46 pm

Legacy777 wrote:If you clear the codes, are the same ones still there? Are you able to clear the codes?
Clearing the codes is the same procedure as the d-check mode just with both the black and the green test connectors hooked up, right?

I'll give it a shot when I get home tonight, if so.

Legacy777
Site Admin
Site Admin
Posts: 27536
Joined: Tue Oct 15, 2002 11:37 am
Location: Houston, Tx
Contact:

Re: Fuel cut after 25% throttle??

Post by Legacy777 » Mon Jan 29, 2018 7:53 pm

D-check is only with the green connectors connected and the clear procedure is with both black and green connected. Sometimes codes won't clear if there is an active code. You can also try pulling the EGI/TCM fuse (No 14) for an hour.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm

cj91legss
Fifth Gear
Posts: 6307
Joined: Fri Jun 20, 2008 8:17 am
Location: Lakewood, Wa 98439
Contact:

Re: Fuel cut after 25% throttle??

Post by cj91legss » Tue Jan 30, 2018 1:44 pm

Code 45 - Pressure sensor. that'll do it too.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT

impostor
First Gear
Posts: 60
Joined: Sat Mar 29, 2003 5:57 am
Location: Omaha, NE

Re: Fuel cut after 25% throttle??

Post by impostor » Thu Feb 01, 2018 1:52 am

As far as a replacement knock sensor goes, personally I'd stay away from ones that aren't marked with the factory markings. I installed a Standard Motor Parts one on my wagon a little over a year ago. Recently it went back to the lack of power thing it was doing before. No codes. Pulled the sensor and found it cracked badly, just as bad as the 20 year old one I replaced it with.

You can still get less expensive than dealer supplied ones that are just OE repackaged. I believe they say "JECS" and a bunch of numbers. I just checked rock auto. The SMP one is OE in the picture, but that's not what they're shipping out currently. The Bosch one is probably legit. Even though it is the priciest of the bunch, its still half the cost of a subaru packaged one.

jamal
Vendor
Vendor
Posts: 2484
Joined: Thu Dec 11, 2003 11:34 am
Location: Missoula
Contact:

Re: Fuel cut after 25% throttle??

Post by jamal » Thu Feb 01, 2018 3:34 am

Does the speedometer work?

Have you figured out why the MAF and MAP codes are on?
peter@functionauto.com

dankberries
Second Gear
Posts: 482
Joined: Thu Oct 27, 2011 5:09 am
Location: Dirt Roads, Colorado

Re: Fuel cut after 25% throttle??

Post by dankberries » Sat Feb 03, 2018 12:08 am

Generally​ diagnosing codes I always start with the lowest number code and work up. It's very likely the knock sensor is the only problem and causing a multi code fault. It maybe the knock sensor wiring is the culprit causing intermittent readings in check mode.
93 impreza rally muffin
93 legacy ss Tarmac Terminator
89 Nissan 240sx sr20
90 Nissan 240sx 2jz
killajamal wrote:Dank is actually German for "silly term which the kids have come up with to describe exceptionally choice marijuana.''

subieroo
In Neutral
Posts: 8
Joined: Fri Oct 13, 2017 2:15 am

Re: Fuel cut after 25% throttle??

Post by subieroo » Sat Feb 03, 2018 9:36 pm

Thanks everyone for your input!

A few things; firstly I'm picking up a knock sensor in a few minutes and will replace it before I retry running the engine since attempting to reset the codes by disconnecting the battery for more than an hour.

Also, I will clean the maf and try to find this pressure sensor I'm getting the code about, but I haven't seen anything online that seems to be the part it speaks of. Does anyone have a part number or where I can find it in the car so I can look for a replacement?

subieroo
In Neutral
Posts: 8
Joined: Fri Oct 13, 2017 2:15 am

Re: Fuel cut after 25% throttle??

Post by subieroo » Sat Feb 03, 2018 9:40 pm

jamal wrote:Does the speedometer work?
The speedometer does work. I don't know what that means in terms of what transmission it must have in it to give a mechanical speedometer signal, but it does appear to work.

jefferson
Third Gear
Posts: 740
Joined: Sat Dec 16, 2006 4:41 am
Location: Parkville, Mo.

Re: Fuel cut after 25% throttle??

Post by jefferson » Sun Feb 04, 2018 1:23 am

My car did pretty much what you are describing and I found the hose off the boost solenoid if I remember right. It was on the passenger strut tower with oll those other electronic devices. You couldn't give it much throttle at all or it would just die.
91 Black SS 5spd. Edm lights, wrx gauges in dash, 45 degree airbox, cryoed drilled and slotted brakes. Invidia divorced downpipe with custom stainless exhaust. To be installed, aluminum a-arms, manual belts, awic.

dankberries
Second Gear
Posts: 482
Joined: Thu Oct 27, 2011 5:09 am
Location: Dirt Roads, Colorado

Re: Fuel cut after 25% throttle??

Post by dankberries » Sun Feb 04, 2018 1:30 am

subieroo wrote:Thanks everyone for your input!

A few things; firstly I'm picking up a knock sensor in a few minutes and will replace it before I retry running the engine since attempting to reset the codes by disconnecting the battery for more than an hour.

Also, I will clean the maf and try to find this pressure sensor I'm getting the code about, but I haven't seen anything online that seems to be the part it speaks of. Does anyone have a part number or where I can find it in the car so I can look for a replacement?
First replace the knock sensor, then go from there, the code for the pressure sensor is likely because of the knock sensor.
The part # for the map seonsor is : 22012AA020
Part # for pressure exchange solenoid valve : 14774AA341
93 impreza rally muffin
93 legacy ss Tarmac Terminator
89 Nissan 240sx sr20
90 Nissan 240sx 2jz
killajamal wrote:Dank is actually German for "silly term which the kids have come up with to describe exceptionally choice marijuana.''

subieroo
In Neutral
Posts: 8
Joined: Fri Oct 13, 2017 2:15 am

Re: Fuel cut after 25% throttle??

Post by subieroo » Mon Feb 05, 2018 2:44 am

Well, I replaced the knock sensor with no luck in fixing the problem. I am still getting the fuel cut and a CEL. The harness wiring was cracked and broke while pulling the old sensor. I depinned the old male end of the plug and soldered it to the intact end of the old wiring and sealed it all up with heat shrink. Hooked it all back up and reinstalled everything I had to pull to access the knock sensor, started it up, let it get up to temp and drove it around. I didn't get a CEL until I drove it and experienced the same symptoms as before.

I have yet to check what codes it was throwing and I haven't had any luck in clearing the old codes. I've tried disconnecting the battery as well as pulling the ECU fuse for more than an hour each and was unable to get the old codes to go away. I'll go read the codes its throwing now and report back later tonight. Any input you may have as to how I may have fixed the old wiring wrong or messed anything up in the process of replacing the old sensor would be appreciated!

cj91legss
Fifth Gear
Posts: 6307
Joined: Fri Jun 20, 2008 8:17 am
Location: Lakewood, Wa 98439
Contact:

Re: Fuel cut after 25% throttle??

Post by cj91legss » Mon Feb 05, 2018 3:29 am

To reset the ecu the proper way you need to connect both the black and green diagnostic plugs together and drive it 1st through 4th staying out of BOOST and getting up to 35mph.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT

jamal
Vendor
Vendor
Posts: 2484
Joined: Thu Dec 11, 2003 11:34 am
Location: Missoula
Contact:

Re: Fuel cut after 25% throttle??

Post by jamal » Fri Feb 09, 2018 7:45 pm

If your wiring to the knock sensor was messed up I would take a close look at the maf and map sensor wiring as well.
peter@functionauto.com

subieroo
In Neutral
Posts: 8
Joined: Fri Oct 13, 2017 2:15 am

Re: Fuel cut after 25% throttle??

Post by subieroo » Sat Feb 10, 2018 11:52 pm

jefferson wrote:My car did pretty much what you are describing and I found the hose off the boost solenoid if I remember right. It was on the passenger strut tower with oll those other electronic devices. You couldn't give it much throttle at all or it would just die.

I just went out to give troubleshooting this issue another shot and noticed a hanging vacuum line, lo and behold it went to the boost solenoid! The car seems to run fine with it attached and immediately started sputtering out after 20% throttle. Thanks for saving the day!

cj91legss
Fifth Gear
Posts: 6307
Joined: Fri Jun 20, 2008 8:17 am
Location: Lakewood, Wa 98439
Contact:

Re: Fuel cut after 25% throttle??

Post by cj91legss » Sun Feb 11, 2018 12:01 am

Nice!!!
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT

jefferson
Third Gear
Posts: 740
Joined: Sat Dec 16, 2006 4:41 am
Location: Parkville, Mo.

Re: Fuel cut after 25% throttle??

Post by jefferson » Sun Feb 11, 2018 3:06 am

Glad I could help.
91 Black SS 5spd. Edm lights, wrx gauges in dash, 45 degree airbox, cryoed drilled and slotted brakes. Invidia divorced downpipe with custom stainless exhaust. To be installed, aluminum a-arms, manual belts, awic.

Omega79
Second Gear
Posts: 279
Joined: Mon Feb 28, 2011 6:08 am
Location: 86406

Re: Fuel cut after 25% throttle??

Post by Omega79 » Sat Feb 17, 2018 4:13 am

Congrats! I had nearly the same issue, just the vacuum line came off a different location :)
lucas wrote:There were multiple Legacys with 300k+ miles. Jesus will return on a Turbo Lego.

Post Reply