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Old 05-18-2017, 12:19 PM   #1
MantisTobbogan
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Default No injector pulse on Number 1 cylinder at idle. 1999 ej25

1999 Subaru Legacy Outback. There is no injector pulse at the number 1 injector at idle. When you rev up to about 2000 or 2500 rpm a pulse comes in but it is not normal. So I have redone the timing belt and the timing is absolutely perfect. Tone rings are ok on crank and the pickups on the cam seem to be ok as well. I am absolutely stumped on this problem can someone please point me in the right direction?
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Old 05-18-2017, 06:13 PM   #2
yarrgh
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could be in the wiring. how does the signal look at the ECU?
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Old 05-18-2017, 07:23 PM   #3
Charlie-III
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I would think if it was timing or a sensor, all cylinders would have issues, since it's only 1, I would check connection to the injector, injector wiring, then ECU/MPFI control unit.
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Old 05-18-2017, 11:31 PM   #4
MantisTobbogan
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Well I don't fully understand how the ecu grounds the injectors. I have a wiring diagram and I guess they all have a common 12v which is the yellow wire I think but don't remember. Then for the number 1 injector it is a brown wire that goes back to the ecu and this wire has 12v coming out of the ecu. I would think that the ecu would ground this brown wire this giving it its pulse but am unsure. The timing had jumped due to a bad tensioner and I thought this was the problem but after installing new tensioner and timing belt the timing is exact. Not even off a half tooth anywhere. I used the marks but also counted the teeth and it is exact. If it was a bad cam or crank sensor I would think that it would have no spark or at least effect other cylinders. So where do I go from here? The only code I'm having is p0505 and that is because I loosened the screws and adjusted the top part of the iacv. This problem existed before I did that and got that code so I am pretty sure it's unrelated I could be wrong though. I am a lead technician in a shop and this problem is embarrassing me so any help is greatly appreciated. Thanks.
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Old 05-18-2017, 11:33 PM   #5
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And like I said the weird part is when I rev it up the misfire smooths out and the injector gets a pulse.... so wtf is that about????
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Old 05-19-2017, 12:55 AM   #6
Charlie-III
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Last diagram I have is a 96, but I believe yours is the same (other than maybe colors).
Key on feeds power through the ignition relay 12VDC), then to the injectors (common power) and then to the MPFI control unit. This unit then completes the circuit for each injector as needed by connecting to ground. Thus yes, you should have constant power TO each injector, but they won't fire until they are grounded.

So if you have consistent power to the injectors, then check the connections at the injector and then follow along back to the MPFI. A bad connection may get better with the additional vibration of higher revs.
I reLly don't think it's a "brain problem". I think wiring is more likely.

When did this issue start? Was it before or after the jumped timing? Has any other work been done?
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Old 05-19-2017, 03:48 AM   #7
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Ehhhh.

If you've got good battery voltage at the injector wire at the ECU, I'd wager the harness is OK. Sounds like it's ECU internal to me.

Easy enough to test, though. Take your NOID light and run a power wire to a known good B+, then pull the #1 injector wire from the ECU and run a wire from the NOID light to the ECU pin. If you've got a good steady flash, then yes, it's an issue with the wiring or injector. If there's no flash, you've eliminated everything but the ECU as your issue.
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Old 05-19-2017, 03:58 AM   #8
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Quote:
Originally Posted by MantisTobbogan View Post
Well I don't fully understand how the ecu grounds the injectors. I have a wiring diagram and I guess they all have a common 12v which is the yellow wire I think but don't remember. Then for the number 1 injector it is a brown wire that goes back to the ecu and this wire has 12v coming out of the ecu. I would think that the ecu would ground this brown wire this giving it its pulse but am unsure.
Sounds like you understand it to me, you're 100% correct. All 4 injectors have a common battery power, and the ECU has internal switches that connect the individual injectors to ground.

The 12v you measured at the ECU isn't coming from the ECU, it's coming from the injector. Until the ECU grounds the circuit, it's an incomplete circuit and there will be battery voltage present from one end to the other, generally speaking.

If you were to unplug the injector, and measure at the ECU again, it should have no voltage, and no continuity to ground (unless the engine were spinning, then you would ideally see intermittent continuity to ground).
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Old 05-19-2017, 09:41 AM   #9
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Well then I think I have found the problem and that being the ECU. The car was running ok and then parked for a long time and when it was started up after the long sit down the timing jumped. So no other work done. I can take my probe right at the ecu and no ground comes. Solid 12v. So being as the ECU is supposed to be sending my ground to complete the circuit and it is not sending anything, directly at the ECU connector, that has to be the problem then? Charlie-III like I said Im working in the shop I have napa prolink which is similar to alldata so any and all diagrams are available to me so if you or anyone else ever needs one shoot me a PM or something. And thanks for all the help and suggestions. So being as how my ecu is not sending my ground, directly out of the ECU that pretty much eliminates everything as the problem then?
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Old 05-19-2017, 09:50 AM   #10
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Ok just to verify I clipped the wire that is supposed to be the ground for number 1 injector directly at the ECU and there is no pulse at idle. The strange thing is when I give it some gas a pulse comes. So is ECU the consensus or what? I also just realized that it is the same story for the number 2 injector. No pulse at idle, give it some gas, and the pulse comes.
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Old 05-19-2017, 09:53 AM   #11
Charlie-III
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Thanks Cosmo for he additional info, I figured wiring would be similar.
Question, the MPFI I see in my diagram, is that the ECU, part of the ECU or a separate box?

Mantis, sounds like you got it. By chance, is the interior damp or wet? High humidity could make an issue with the ECU.

As to Alldata, I work PT at a local shop and they have Identifix I can access, but thanks for the offer.

Curious why is would just die like that........
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Old 05-19-2017, 10:01 AM   #12
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No moisture at all... I just took out the ECU and took the cover off, I cant see anything burnt but it does have a bad burnt electrical smell to it...
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Old 05-19-2017, 12:05 PM   #13
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ok so heres a funny thing. update. i notice the temperature sensor is pegged all the way hot even though the engine is not hot. So I notice in my wiring diagram the throttle position sensor and the coolant temp sensor share a common ground. so i unplugged the throttle position sensor and the pulse comes back and it runs fine...
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Old 05-19-2017, 04:28 PM   #14
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temperature sensor was unplugged plugged it in makes no difference on the misfire. if i unplug TPS runs great once i plug it in back to misfiring.
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Old 05-19-2017, 04:48 PM   #15
Charlie-III
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Quote:
Originally Posted by MantisTobbogan View Post
ok so heres a funny thing. update. i notice the temperature sensor is pegged all the way hot even though the engine is not hot. So I notice in my wiring diagram the throttle position sensor and the coolant temp sensor share a common ground. so i unplugged the throttle position sensor and the pulse comes back and it runs fine...
Quote:
Originally Posted by MantisTobbogan View Post
temperature sensor was unplugged plugged it in makes no difference on the misfire. if i unplug TPS runs great once i plug it in back to misfiring.
Looks like another common wire feeds the temp, TPS and MAF. This wire comes from the MPFI control unit.
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Old 05-22-2017, 09:32 AM   #16
MantisTobbogan
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Ok so why does it misfire all over the place and run like crap until I unplug the TPS? If I unplug the MAF it dies. And the temperature gauge and fans are working properly.
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Old 05-22-2017, 09:41 AM   #17
Charlie-III
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Quote:
Originally Posted by MantisTobbogan View Post
Ok so why does it misfire all over the place and run like crap until I unplug the TPS? If I unplug the MAF it dies. And the temperature gauge and fans are working properly.
I don't have a good answer for you, sorry.

BTW, since it sat a while, are there signs of chipmunks or mice? Things like acorn shells, balls of insulation, droppings, etc?

When I get a chance, I will look up the diagrams to see if something makes sense.
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Old 05-22-2017, 10:38 AM   #18
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No, no signs of mice. Thank you.
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Old 05-25-2017, 09:16 PM   #19
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>>>>and NO codes (CEL)? Or did I miss that?
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Old 05-26-2017, 05:06 PM   #20
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idle air control valve p0505 but that didnt come up until i took the motor off of the valve. it is adjustable and i guess i just didnt put it back in the same position as it was before. so the problem existed before and after the code.
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Old 05-26-2017, 05:07 PM   #21
MantisTobbogan
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and it is an lj25 not ej25 my mistake...
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Old 06-01-2017, 11:50 AM   #22
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so everyone is stumped huh
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Old 06-04-2017, 01:19 AM   #23
jsully1130
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having the same issue. research tells me its going into a fail safe mode. because of a high idle issue. when in fail safe #1 and #2 injector shut off. Im still researching the issue as we speak.
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Old 06-08-2017, 11:16 AM   #24
MantisTobbogan
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interesting. thank you very much i will be interested to hear what you find out
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Old 06-08-2017, 01:28 PM   #25
Charlie-III
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Quote:
Originally Posted by MantisTobbogan View Post
so everyone is stumped huh
Yep, you got me on this one.

Quote:
Originally Posted by jsully1130 View Post
having the same issue. research tells me its going into a fail safe mode. because of a high idle issue. when in fail safe #1 and #2 injector shut off. Im still researching the issue as we speak.
Quote:
Originally Posted by MantisTobbogan View Post
interesting. thank you very much i will be interested to hear what you find out
You and me both. I've never heard of a failsafe like that.
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