misfiring, but without a misfire trouble code?

[NovaPath]

So my pathfinder has been very rarely missing at idle for a couple of weeks now. It started so infrequently that by the time I thought I felt it the time had passed and I'd forget about it for a week until I was at a stop light and the same thing happened....until today.

 

Now it is misfiring multiple times in a row, for as long as 15 seconds at a time. Typically at idle, but it has happened under light acceleration and cruising at 2k RPM or so. Under heavy load such as WOT it runs just fine. Obviously, something has gone badly. I checked the trouble codes, and they are the same two that I've been riding with(I know, I'll take my lashings) which are a rear 02 sensor and the driver's side intake cam sensor code P1145. Neither of these will typically cause a misfire.

 

I'm going to go ahead and replace the 02 and cam sensor so that I can rule those out, but suffice to say I am less than optimistic about those solving it.

 

Any ideas? I'd think a coil would throw a misfire code and a vacuum leak would cause a lean code, the only thing I can think of is a fuel pump on the fritz, but under load at WOT it still runs great.

 

Open to ideas!

[Manik]

It sounds like a coil intermittently breaking down. Possibly a plug wire. Check you plug boots for "tracing". It will look like a white line on the boot. This is a carbon track that conducts electrical current from your ignition system. Off idle it's not as noticeable due to the ignition being able to compensate and provide sufficient voltage to fire the plugs. You can look at the spark plugs for this too. Hope this helps. That's the most common thing I've seen for what you are describing.

 

 

Bubba.....

[Manik]

It will look like a pencil mark on the spark plug porcelain.

 

 

Bubba.....

[NovaPath]

Thanks for the response! I will take a look at that on Saturday. I've got the other two parts now so at least while i'm at this I can get the CEL fixed finally.

 

If I don't see anything, I think i'm going to buy 3 coil packs(can be found for 30.00 each), and swap one bank of cylinders, if that doesn't solve it I will then take the original ones and swap the other side.

 

Also, I forget what kind of plugs I bought when I swapped them 10k miles ago. Are these engines incredibly sensitive to a certain type of plug? I doubt I splurged on the "good stuff"

 

Thanks!

[Rebelord]

Sensitivity to plugs. Yes. Stick with NGK brand. If you run other brands, you tend to have misfires etc. Its just one of them things. Remember, if you get the cheap NGK which is fine, they dont last 100k like the IR OE ones. 25-30k is a good change point.

 

Check your oil level too. If your oil level gets low, likes to create havoc. As the cam phase timing runs off oil pressure. So if your low on oil, less pressure cam shafts dont run what they are commanded to. Some funky idle and weird off throttle issues.

[NovaPath]

Based on that, it also seems plausible that the code for the intake timing solenoid could in fact cause a misfire as well then right? I already have that part, just need to install. That code has been around for over 6 months, though......

[rc_cola_j]

This sounds exactly like the trouble I was having. Thought it was a misfire with no code....replaced plugs, wires and distributor. No luck.

 

Turns out it's the EGR. I disconnected vacuum line to the EGR valve and plugged the line with a roofing nail. Problem went away.

 

Hooked it back up, problem came back.

 

Try it and let me know what happens.

 

 

Sent from my iPhone using Tapatalk

[NovaPath]

The old girl threw me a bone today in the form of a p0305 code. I've ordered the coil and will be installing tomorrow, hopefully that fixes it. It is a 80.00 gamble but I can't keep driving the thing like this...

Edited January 15, 2016 by NovaPath