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Misfires and intermittent power loss

Old 09-28-2013, 05:55 PM
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Misfires and intermittent power loss

Hey guys, I started seeing a misfire CEL (P0302) a couple weeks ago, with the only evident engine symptom being that my idle had been a little erratic lately. This is an '05 6-speed with about 85K miles. BHR coils, wires and plugs are just under 10K miles old. I pulled the plugs to replace them last week, and they looked really fouled for that mileage (see pic below). So, I have brand new NGK plugs in there now and the idle actually did smooth out quite a bit. However, a couple days later, I ran into a new problem.

I was on my way to work, after only driving for about 5 minutes, and the engine suddenly lost power and I got a flashing CEL while in motion. Engine was somewhere under 5000 RPMs. I thought it went into limp mode, but it didn't seem like RPMs were limited. However, the engine would only rev very slowly even while flooring it and it ran very rough. After about 30 seconds, power was suddenly restored and the CEL went away. No other issues that day. The next morning, I started the car, and I immediately got a flashing CEL with loss of power and extremely rough idle. The car would barely move. After a few minutes, things went back to normal again and no more CEL. The drive to work was uneventful. But then after work I started the car up again to the same situation. And again after several minutes, I got power back. This time, the CEL stayed on, but read as a random/multiple misfire (P0300).

No problems after starting up this morning, but since that CEL has been on solid, there has been a noticeable exhaust odor that I can't identify. I'm aware of the misfire checklist and I will check the coils and wires first. But since I replaced these not long ago, I was hoping to get some ideas about what else may be causing the problem. Keep in mind I have no problems starting the car and it does not stall. I've gone through many misfire posts and I can't seem to find this exact issue. A couple weeks before all this started I'd cleaned the ESS and MAF as part of routine maintenance. Neither of those were dirty though. Performed a NVRAM reset as well. I did have a little oil in the accordion tube, but none on the MAF sensor or filter. Oil and coolant levels are good.

Please let me know if I missed anything that could be helpful in diagnosing the problem. I run DashCommand but i haven't noticed anything out of the ordinary yet. Although, I'm not 100% sure what acceptable levels are for some of the readings. I did notice that when I started the car the other day, the engine was running quite lean. It went back to normal after a minute or so though. Maybe a fuel pump issue? I thought the exhaust smell could be the cat dying (or dead), and that's another thing I need to check. I've been on the fence about getting rid of the cat for a midpipe, and maybe this is the time to replace it if it's involved in all this. Any suggestions are greatly appreciated.
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Old 09-28-2013, 05:58 PM
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This sounds exactly like an issue I just got done with. Talk to Charles at BHR. He's going to tell you to check each coil with timing light.

I had the identical issue and it turns out I had a failing BHR coil.
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Old 09-28-2013, 06:16 PM
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Thanks for the really quick reply. I definitely intended to talk to Charles. I just haven't heard about too many failing BHR coils.
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Old 10-01-2013, 08:27 AM
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Originally Posted by Olorin2 View Post
Thanks for the really quick reply. I definitely intended to talk to Charles. I just haven't heard about too many failing BHR coils.
I just started having this same problem yesterday. Normal driving at low acceleration, but when I start to get on it the engine sounds like it's drowning and I get a flashing CEL (haven't checked the code yet).

I replaced coils/plugs/wires with stock parts, did a MAF clean as well as the "20 brake stomp" procedure two months ago, but haven't seen any issues until now. Also have been getting terrible gas mileage (13mpg instead of my normal 18-20mpg).

I'd love to hear what you find out - I was going to take her in for a compression test. If nothing else, I'll get some peace of mind out of it.

Last edited by cschoeps; 10-01-2013 at 08:33 AM.
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Old 10-01-2013, 08:35 AM
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Originally Posted by cschoeps View Post
I just started having this same problem yesterday. Normal driving at low acceleration, but when I start to get on it the engine sounds like it's drowning and I get a flashing CEL (haven't checked the code yet).

I replaced coils/plugs/wires with stock parts, did a MAF clean as well as the "20 brake stomp" procedure two months ago, but haven't seen any issues until now. Also have been getting terrible gas mileage (13mpg instead of my normal 18-20mpg).

I'd love to hear what you find out - I was going to take her in for a compression test. If nothing else, I'll get some peace of mind out of it.
Get codes scanned, check your cat, if you have one.
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Old 10-01-2013, 09:10 AM
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Originally Posted by BigCajun View Post
Get codes scanned, check your cat, if you have one.
Yup, sure do. I'm borrowing a scanner from a co-worker, so I'll check codes after work. There's just the flashing CEL while the engine is stuttering; no remaining light after.

A friend across the state borrowed my jack/jack-stands, so I'm considering letting the dealer do a compression test and check the Cat all at once.
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Old 10-01-2013, 09:51 AM
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A little update...

I removed the plugs again (only a couple weeks old), cleaned them up a little and reinstalled. Now I have no CEL and the car seems to be running okay. Wires were all connected properly. No idea. Still need to verify coil performance.

However, after driving home the other night, I checked under the car and saw that the cat internals were glowing red. My catalyst temps are around 1600 deg during normal driving. I'm not sure what the normal operating temp is, but the glowing cat has me thinking it's time to replace it. I've been meaning to ask Charles at BHR this question, but has anyone been running with their newer ceramic cat for a while? How has it held up? I'd like to go with their midpipe/cat combo.

Also, I attached a pic of one of the leading plugs. This is what it looked like after about two weeks (there's another pic in my original post of the older leading plug). Can I get some input about the condition? The trailing plugs were practically unblemished, but these looked very fouled already for such a short period of time.

cschoeps: Your issue sounds a little different. I had power loss at all speeds and at idle, and the engine ran extremely rough. I agree you should check your cat and get that compression test. I may do the same. Good luck diagnosing the issue!

Thanks again...
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Old 10-01-2013, 11:26 AM
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Originally Posted by Olorin2 View Post

cschoeps: Your issue sounds a little different. I had power loss at all speeds and at idle, and the engine ran extremely rough. I agree you should check your cat and get that compression test. I may do the same. Good luck diagnosing the issue!

Thanks again...

Thanks! Likewise.
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