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Hey everyone, I have a '91 AWD 4EAT Legacy wagon that's making me crazy! long story short, it's got a miss/rough idle that I tried a few fixes for(checking/cleaning grounds, tune-up, switched coilpacks) all to no avail. I finally tried disconnecting the injectors and found that injector #4 was the only one not causing a stumble when disconnected. Figuring that I had identified the problem, I replaced the injector with a spare that I had kicking around the shop. Upon starting the car with the new injector everything seemed fixed and my rough idle was gone! unfortunately, after driving it for a day, my rough idle returned, and again it seems to be the #4 injector. Even after pulling the manifold and replacing the wiring harness, that injector doesn't seem to be working. Is the computer the only remaining culprit? Any insight would be greatly appreciated!

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Computer fault is unlikey,probably mechanical.

 

Got any trouble codes? Changed the plug wires?

 

Does it only miss at idle? If so,a vacuum leak is likely.Or poor valve seating.

 

Is #4 plug wet w/fuel? Can you hear the injector click through a hose?

 

I would check compression.

 

Plenty of other possibilities w/the computer at the bottom of the list.

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The computer would be the last thing I would suspect. What was the condition of the injector that you replaced the original failing one with? Was it used? It just could have been bad as well. Hard to tell.

 

Have you ohmed out the injector to see what it says? I would just try swapping out the injector again with a known good used one or a new one and see if that does anything. I would blame an old, used injector before a known working computer/wiring harness.

 

I ran into the same issues with my 1990 legacy a few weeks back, and I just swapped out the injectors, well the hole fuel rail actually, and haven't had a problem since. Hopefully your spare injector is just bad and it's nothing serious :)

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Well I just went outside to delve a little deeper into this injector issue, and the problem has mutated apparently. When I started the car, I noticed a vapor cloud behind me almost immediately. I turned her off and ran to the rear to check it out. I put my hand in the cloud and sure enough, it was gas! Actually enough gas to get my hand wet! :eek: Now I'm really frustrated/confused as to what's going on here. :banghead: The only positive thing to come out of this is the fact that my check engine light FINALLY came on and upon checking the code (17

) it decided it was time to tell me that injector #4 was bad(as if I hadn't already figured that out!

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:lol: same thing happened to me, well not the gas part :eek: Mine quit working 75 miles from home with no code, and then fixed itself. Then a few days later started back up and this time threw a code. Injector 4 I believe as well :lol: This seems like it's the "1st gen injector failure" year. You are the third, if not fourth person to have injector issues in the last 3 months :lol:

 

Just swap that bad boy out and you should be good to go!

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You may have pooched an o-ring installing that used injector - thats one of the major reasons I typically swap whole used rails from the junk yard - you get two good injectors and you don't have to touch any of the o-rings so very unlikely you will get a leak.

 

GD

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[...] I finally tried disconnecting the injectors and found that injector #4 was the only one not causing a stumble when disconnected.

That might happen from two possible scenarios:

 

1) You were only running on three cylinders. #4 was dead (due to any cause), so disabling any of the remaining three would make for a really rough engine. Possible, but not likely -- you'd probably have noticed a dead cylinder :).

 

2) The #4 injector was leaky, so it had output even when it was electrically disconnected. More likely.

 

 

Upon starting the car with the new injector everything seemed fixed and my rough idle was gone! unfortunately, after driving it for a day, my rough idle returned, and again it seems to be the #4 injector.

If I'm correct that the original injector was hanging open, since the replacement was initially okay and then developed the same symptom, there may be crud in the rail. Or, it was leaking for other reasons.

 

I'm with GD on getting a used rail with injectors already mounted. Be sure to protect the open ends from dirt until things are back together. The fuel filter does a good job of protecting the injectors, but it can't stop stuff from reaching the injectors that gets in the line after it.

 

You may now have gas dilution of the oil. You should probably change it as a precaution.

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I`m having trouble seeing how a stuck injector would set code 17 w/o any disruption in the electrical circuit.

 

An injector/ecu wire that grounded out to the chassis could give massive fuel and a code though.

 

I would unplug the ecu and measure resistance between #4 injector ground(at inj plug) and battery - while moving the harness around before trying another injector.Or just take the old injector out and try to blow through it.

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I`m having trouble seeing how a stuck injector would set code 17 w/o any disruption in the electrical circuit.

 

An injector/ecu wire that grounded out to the chassis could give massive fuel and a code though.

 

I would unplug the ecu and measure resistance between #4 injector ground(at inj plug) and battery - while moving the harness around before trying another injector.Or just take the old injector out and try to blow through it.

I missed the comment about the code 17, so what you said is something to look at.

 

In the first post of the thread, it was mentioned that the wiring harness was changed, but the problem persisted. The question is, exactly what "harness" was replaced? A short to ground on the #4 inj control line from the ECU could be anywhere along it, including the possibility of there being a problem in the ECU itself. If just a pigtail at the injector was used, maybe it wasn't insulated well enough.

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I`m thinking it more likely is an ecu fault after all.

 

If the signal wire isn`t shorted to ground and the miss/fuel dump persists at 4 after swapping injectors from 4 to 2 I`d start to suspect the ecu.

 

All provided the injector is not obviously stuck.

 

It woud be nice to check #4 injector signal w/a dwellmeter or scope.

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I'm seeing this as two separate issues. Initially, the #4 inj was stuck partially open, based on that it apparently still had output even when disconnected. (Otherwise, why would disconnecting #4 not cause "a stumble" while disconnecting the other three did?) After the swap and whatever else might have been done, there was an electrically-related problem, based on the code 17.

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OB99.. I suspect you were right earlier. I think that part of the fuel rail was contaminated. Recall that he diagnosed it and replaced that injector and it worked Fine. Then it went to crap. It's not like you didn't already caution about keeping the ends and lines clean for a reason.

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I'm seeing this as two separate issues. Initially, the #4 inj was stuck partially open, based on that it apparently still had output even when disconnected. (Otherwise, why would disconnecting #4 not cause "a stumble" while disconnecting the other three did?) After the swap and whatever else might have been done, there was an electrically-related problem, based on the code 17.

 

Maybe,or maybe #4 injector signal was bad enough to cause a misfire but not bad enough to trigger OBD1 dignostics.

 

Or,there is an unrelated problem on 4.

There were no fuel clouds w/the first injector.Could be residual,I suppose.

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Seeing as the earliest that I'll be able to get to the j/y is Sunday, I have a little time left to look at some things, just so long as it doesn't involve starting the car. Ideas/options on what I can look at?

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Seeing as the earliest that I'll be able to get to the j/y is Sunday, I have a little time left to look at some things, just so long as it doesn't involve starting the car. Ideas/options on what I can look at?

 

Remove the injector.See if you can blow through it.

 

Check to see if the injector wire has made contact w/the body w/an ohmmeter.

 

Could reset the codes,pull the fuel pump fuse,try to start,and see if code 17 comes back.

 

Measure the resistance of the injectors.

Edited by naru

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As far as wiring goes, it was the harness mounted under the intake plenum that was replaced. How exactly do I check to see if the injector wire has made contact with the body? :confused:

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A "noid" set might be useful here. Not too expensive to buy, and might be able to rent/borrow them from an auto parts store. Although that would not help with a mechanically leaking/stuck injector, it could give an idea of the electrical signal status.

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As far as wiring goes, it was the harness mounted under the intake plenum that was replaced. How exactly do I check to see if the injector wire has made contact with the body? :confused:

 

I would unplug the ecu and measure resistance between #4 injector ground(at inj plug) and battery - while moving the harness around.

Should be infinite.

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