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93 Legacy Misfiring??????


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Yes, my car is an automatic and I will give your suggestion a try. I know it has me baffled, and I consider myself as someone who can usually reason out a problem. Is there testing equipment for coil packs? Thanks for the help.

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Have just read through the entire post, and would like to start by offering my sympathies!

 

I have a new suggestion: Since the problem often shows on inclines, perhaps your fuel tank is the place to look. I have witnessed to cars (Fiat Uno and Porsche 911) with a single tree leaf in the tank. When this gets sucked on the fuel pump intake the delivery stops. I know you said fuel pressure doesn't drop, but maybe the flow is disturbed in some twisted way that avoids a pressure loss?

 

Does the mis-fire occur even with a full tank?

 

 

Yes, it's a bit left-field, but seems like you have tried a number of things already :banghead:

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I have had past problems with the fuel gauge sending unit in the tank, but when I repaired that, there was no debris I could see in the tank. The prefilter screen was in place over the pump inlet, so I don't think debris could be causing a blockage. Keep on suggesting.....we'll figure it out sooner, or later. To keep things time related......the sending unit was repaired way after this other problem started.

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The plugs were replace early on, and checked recently. I can't say I saw any difference in their appearance. I wish I could try another coil pack, but I only own one Subaru. I did however try to simulate a coil pack under load. I would remove the plug wire from the coil while the motor idled, increasing the air gap between the coil and wire. I figured this would simulate an under load condition, and the coil would fail, but the gap was pretty large (3/8" maybe), and kept on firing. I don't know if this test told me anything, given that the test was at idle.

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Well, I used a timing light idea that was posted on this board to double check my Hitachi coil pack. It seems the cylinders 2, 4 and 1 fire great, but 3 fires at half the rate that the others fire. Since this ignition system wastes a spark on the exhaust stroke, the firing should be the same as the other adjoining side of the coil. It's not, or at least it's not strong enough for my induction timing light to pick up. Before I spend $100 on a new coil pack, is there any way this could be associated with the igniter? Also, a double check of the resistance did indicate a 1.0 & 1.7 ohms of secondary resistance for a spec of (I think) 0.67 - 0.75. Primary resistance was okay.

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You can pickup a new coil for like 60 bucks.

 

On your diagnosis, with the design of the coil pack, there is no way for one side of coil to go bad. There are two coils in there. The front coil handles the front two cylinders and the rear coil handles the rear two cylinders. If the coil went out, both front or rear cylinders would not work, or not work properly.

 

The only way I could see one side going bad was if there was a massive crack or something causing a disproportionate flow in current. If that was the case, I would think it would show up by measuring the resistance.

 

Just to verify the resistance values,

 

For testing the primary side, you meased from terminal No 2 on the connector of the coil pack to the Number 1 & 3 spots on the coil itself and got around 0.7 ohms.

 

The next test that the fsm gives is confusing, but the readings should be done solely on the coil pack female connectors. 1 & 2, and 3 & 4 according to the diagram.

 

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/coilpacktest.jpg

 

If anything is out of spec, replace the coil pack.

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Let me clarify the coil readings. I have checked the secondary winding resistance. They are 12.8 & 12.9 ohms for a range of 10.4 - 15.6. The Primary are 1.0 - 1.7 ohms for a range of 0.63 and 0.77. This reading is out of spec, and I'm looking into a new coil. The wires and plugs were replaced, with no improvement.

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  • 3 months later...

Well, let me begin by saying I took a step back, and reviewed some things. I have neglected the problem for some time now, but it’s still there. I have come to the conclusion that it must be related to a non-ECU monitored device, or it should have thrown a code. My rechecking of the coil pack showed it was within spec. However, that doesn't mean it's okay. I have used an inline pressure gauge to monitor fuel delivery while driving and that is okay. I have used timing light to monitor spark while driving. It too was okay on the wire I suspected of trouble. (Still three more to test) I am really leaning towards a plugged exhaust, or coil pack. I will purchase a vacuum gauge to try to rule out the exhaust. Besides, I can always use a new tool.

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Originally posted by 93leg

I will purchase a vacuum gauge to try to rule out the exhaust. Besides, I can always use a new tool.

 

Speaking of tool, add another one to your collection: Infrared Hand held thermometer. The cost is $70 and up. If you want to test the cat to see if it's doing its job, you can meas the temp at the inlet and outlet to see if there's a 200 deg temp rise at the outlet. An efficient cat is suppose to get very hot and burn up any unburned fuel in the exhaust. Of course there're other uses for this little handy tool.

 

Let us know how things check out. I'll be cleaning out the IAC, MAF and EGR valves today. I'll also be checking out the coil pack too.

 

Ali

'95

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  • 3 months later...

Well, a lot of time has passed since my last post, and I have decided to replace my coil pack tonight. I have purchased a new one with hopes of solving the problem, which is still around. I'll let you know what happens.

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I thought I give everyone an update as well. Let's see, '95 Legacy wagon, was experiencing P0303 (#3 cyl misfire) code and the engine was stalling right after popping up this code. I replaced the coil pack and for about two months all was well.:)

 

Now for the bad news :banghead:

Last week the car stalled and threw two codes:

P0420 - Catalyst System Efficiency Below Threshold Bank 1

P0301 - Cylinder 1 Misfire Detected

I'm open to suggestions!

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  • 2 weeks later...

I have to report that I have replaced my coil pack with a new coil pack from the dealer. The car has improved performance, shifts smoother and I'm sure as a result, I'll get better gas mileage. However, it did not fix the original problem. I am still glad I replaced the old one though. The improved overall performance was worth it.

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  • 5 months later...

I have same problem with my subaru liberty 92.I changed plugs ,leeds, knock sencer ,fuel and air filter, ignition coil still same problem. One subaru authorise service station charged Au$400 to fix this problem. It was ok for 3 months after so called upper engine de carbon soak/cleaning, but started again Iwent back to service station and they advised me to buy upper engine cleaner sprey cans and spray in side suction manifold wait for few minutes and start engine. It works for a while than goes back again.For sure it is carbon buil up in upper engine dont know why may be poor fuel quality or any other reason.I can say that because I had to replace this engine with second hand engine with low milage due to some other reason but after 5 months same problem .I am buying now and than upper engine carbon cleaner spray some time from subaru or some time from other stores similer kinds of cleaning sprays and upper engine lubricants, and they seems to be working untill next clean is due,but I dont trust this car now .

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  • 2 months later...

96 Legacy brighton 2.2 engine(140,000miles)-

with very similiar problems as those above ie: engine misfires under load (Throws a code which when read, says one or two cyl.misfire). It is inconsistant,happening at various times usually at high speed on hills, also with varying fuel levels, it lasts about half a minute and then seems fine. We have tried numerous solutions: de-carbonization treatment done professionally several times, it seems to help, but the problem returns, replaced: coil pack, plugs, wires, a bad cat. converter, fuel filter and had compression test that was judged fine. The latest suggestion was to try higher octane fuel and dry gas. Since using super it has happened once - just added dry gas and we'll see...

wondering if any one has any suggestions?

any suggestions...at all... we're desperate.

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There is another post that reports a similar problem and fix. I don't remember what the post is named, but it states he has had success replacing the Jidco (?) ignition relay. He had multiple cars with this problem, and they were repaired this way. I have not tried this, but I still have car problems. Try searching for Jidco, and post your results...please.

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An intermitant relay is possible, especially since you say the problem clears after restart. This would point to dirty contacts in the relay. You could try bypassing the leads of the relay to verify this. I think the relay has two set of leads that run through it.

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Here is the thread on the relay ttp://www.ultimatesubaru.org/forum/showthread.php?t=20291&highlight=sea%233

 

SEA#3

 

 

There is another post that reports a similar problem and fix. I don't remember what the post is named, but it states he has had success replacing the Jidco (?) ignition relay. He had multiple cars with this problem, and they were repaired this way. I have not tried this, but I still have car problems. Try searching for Jidco, and post your results...please.
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