Cylinder misfires or bad injectors, please post here.

http://img.tapatalk.com/d/12/11/12/upadubev.jpgWell that's what number 4 is putting out. And I just put in a brand new plug. Lets see what's up with the valve adj

My shortblock looked great when I pulled it at 160K. Mine started misfiring and it ended up being the valve seats not sealing anymore.

My valves were sealing too tight, there was no clearance at all. 140PSI on the compression test in all 4.

 

I guess when the valves heated up they didn't seal and that was causing the misfire. I wish I knew how to prevent it from happening again. I spent all my Christmas money on fixing the car and I'd like to not do that again.

 

The cylinder walls looked good, original crosshatching still looked intact. I'm not sure if the pistons were pulled to look at the rings. But it was barely burning a drop of oil.

Ya if she throws the code again this week she'll going for heart surgery. Ill pull the heads and check the cylinders and get the heads cleaned up

Man all this talk about internal motor issues causing misfires is starting to scare me a bit. Im having issues like alot of you and have been considering a compression test for the hell of it. What would a good pressure range be for these motors? Maybe next weekend ill be borrowing a kit.

subaru loves to set the valves on the tighter side from the factory, unfortunately, as time goes on and wear happens, the valves tighten up which- guess what, lands you out of spec. a tighter valve lash is quieter than loose, and thats why i think subaru does it.

Man all this talk about internal motor issues causing misfires is starting to scare me a bit. Im having issues like alot of you and have been considering a compression test for the hell of it. What would a good pressure range be for these motors? Maybe next weekend ill be borrowing a kit.

 

142-171 PSI I think with less than a 5PSI difference between cylinders.

Has anyone had injectors as the culprit for AF Learning #1 A being off the scale at 15, but the others being within tolerable limits?

Well I ran a compression test on mine this weekend. Although im not sure how accurate it was. It has been awhile since I have done a test and when I did it was on an old 70's v-8 so I imagine its a little different. The tester's instructions indicate that the motor needs to be warmed up and throttle needs to be wide open. Not sure how im supposed to leave the throttle wide open being fly by wire. I just floored it while cranking, i assume that opens the throttle. Also how important is it to have the motor warmed up? Seems kinda tough to do considering how hard it is to get to everything. By the time I get everything ready it would cool down quite a bit. I plugged in my block heater and got coolant temp up to 120 deg, but it only increased pressure 5 psi. I basically was seeing 100- 105 on three cylinders and 98 on cylinder #2 which is the cylinder im mis firing on. Any suggestions or advice would be great!! The difference between cylinders isnt all that bad, but i just cant except that all cylinders are this low. Thanks again for any help.

My guess would be either all of your rings are worn or your gauge is inaccurate.

 

My test with a Craftsman tester was 135/135/134/132. When I had it done professionally, it was 140 on all 4 approximately 2 years ago.

I was thinking the guage to, so i rented a brand new tester and it basically matched my older one. It could very well be the rings for all I know since I bought it with 45,000 mi on it and it was modfied already. Who knows how it was treated. I think at this point ill have my tuner look at it and worst case I take it in to a shop to verify. Just seems so odd being it still runs like a champ.

Well I performed one final test to verify my findings. This time I made sure the block was as warm as I could get it 120 deg. Topped the oil off and when doing the test cranked the motor a few more times. My findings were Cylinder #1 114, 114, 114. Cylinder #2 104, 104, 104. Cylinder #3 110, 110, 112. Cylinder #4 110, 109, 112. Still alot lower then I was hoping. I cant see how it would make any difference but being up in elevation, could that make a difference? I think I'll be taking her in to the shop to verify my readings:icon_sad:

Elevation will make a difference due to less compact air molecules at altitude vs sea level, so less molecular content to compress.

Makes sense to me. One of my buddies was saying the same thing but he is normally the last one to take advice from . Do you think elevation would make enough of a difference to account for my low readings?

I'm sure there's a formula to figure pressure coversions at a given altitude (check with our resident respiration therapists), but possible 10% or more reduction, maybe more.

 

Cyl #2 delta concerns me at any altitude though. Probably worth a professional check-down.

Use the US standard atmosphere chart to find density at altitude.

not sure what your relation to Denver is, but they are 12.1psi atmosphere, whereas 14.7 is sea level. What I think you should do to be accurate is to do a leakdown test

Multiply your pressure test numbers by the ratio of sea level / altitude Patm (1.1 for Denver).

Looks like your multiplier would be ~1.22. With NMT 10% variance between cylinder averages, still am concerned about Cyl #2 and still recommend a leak-down test to rule-out internal (valves or piston/ring-land) issues.

Ya I was thinking the same thing about #2 as well. 10 psi delta isnt very cool. That also happens to be the same cylinder im getting a misfire on. Looks like it will going to see the doc.

I recently experience an episode of cel comes on with cruise control flashing and rough idle. The codes were misfire with cylinders 3 & 4. I first changed spark plugs, which didn't help. Then changed coils, which didn't help. Didn't really want to change my injectors because they were quite expensive. Bought a bottle of BG44K from local autoshop. Took care of rough idle and misfire codes. Engine running smooth again.

Thought I would add to this thread. 2000 Outback 73,000 miles all stock. Developed a stumble under load but light throttle plus backfire into the intake. Wouldn't set a code but got the light to flash a couple times. Car had new T belt, plugs, head gaskets at 58,000 mi due to collision damage.

 

Anyway, did some research on the I-net and was getting frustrated with all the possibilities. Decided to try a new set of plug wires. When I pulled # 3 from the coil pack the terminal was green. Cleaned it with scotchbrite, installed new wires and it runs perfect. BTW, and strangely, after this the engine light was on. Said misfire cyl 2 even though the bad wire was #3. Cleared it and it hasn't come back.

 

Hope this may help someone. Sometimes it's so simple and right under your nose.

I recently experience an episode of cel comes on with cruise control flashing and rough idle. The codes were misfire with cylinders 3 & 4. I first changed spark plugs, which didn't help. Then changed coils, which didn't help. Didn't really want to change my injectors because they were quite expensive. Bought a bottle of BG44K from local autoshop. Took care of rough idle and misfire codes. Engine running smooth again.

 

I did the same thing with my car and the misfire ended being a burnt valve. I had used BG 44K after replacing injectors, plugs and coils and it worked for about a month or so and the CEL came back again and ran worse than ever. I hope for your sake the 44K is a permanent solution because a burnt valve is a friggin' large expense.

Cylinders 1 & 3 are fine at start up but after running for 5 minutes or so they misfire

sounds like a valve problem. valve seals expand as they warm. sounds like they're too tight.