Cylinder misfires or bad injectors, please post here.

Yeah, makes sense.

 

Next question, I finally got around to pulling the code and it doesn't seem to be one running around on this thread- P0171 System Too Lean. Its idling rough with the AC on or off right now (worse with it on of course). I'm going to pull and clean the MAF, I installed a reusable AVO filter element about a year ago and I've heard if they are over oiled it can dirty the MAF sensor. I've looked for vacuum leaks, can't find anything.

 

Car has less than 50k miles on it.

Clean MAF, look for intake leaks (torn inlet tube), blown intercooler tabs, check front o2 sensor. Pressure test system if you can. Apparently you can use a tire hose to a vacuum/pressure line that goes to BOV and block off the inlet by the MAF with a pipe.

Subscribed

Oops.. I didn't mention, we did pull/swap the #3 plug with a new one before swapping coils. Looked fine.

 

So today, mechanic pulled & cleaned #1 and 3 injectors, replaced (in reverse position) and everything is now running smoothly, doesn't seem to be missing anymore, for now..

 

Update -- yesterday car threw a P0301 - so the misfire has followed the injector to cyl. 1. New injector on the way...

Good diagnosis!

Clean MAF, look for intake leaks (torn inlet tube), blown intercooler tabs, check front o2 sensor. Pressure test system if you can. Apparently you can use a tire hose to a vacuum/pressure line that goes to BOV and block off the inlet by the MAF with a pipe.

 

1. How can you tell if the O2 sensor is bad?

 

2. Intercooler tabs? are you referring to the end tanks?

 

3. When you say put a pipe in the inlet, do you mean something capped (like PVC) to make a seal?

Edited September 29, 2011 by 2.5GT_dude

1. 02 sensor will not put out good readings and will be all kinds of haywire. You'd probably get a CEL for it.

 

2. I am referring to the intercooler tabs on end tanks, yes. Mine blew on a stage 1 tune!

 

3. I meant [paint] can not pipe Anything to create a seal will work.

my car threw the same P0301 last week, i went to schucks and reset the code and it hasnt come back on....

Good diagnosis!

 

Good mechanic

 

I picked up a new injector today ($242 cdn.. ow.) and installed it tonight. No misfires so far, running strong.

 

Any use for the bum one? I know Deatschwerks takes them in sets if you're buying their injectors, but I suppose that's for working injectors. It's just.. painful to toss something that costs $242.

how did you know it was misfiring besides the obvious check engine light?

Engine will shake, driving will be jerky, odd exhaust noises can be heard. In my case, I had all of the previous and I could hear a "puff" every so often. Turns out the spark plug in cylinder #1 was cracked through and replacing the plug solved all of my issues including the mystery "puff" misfire that had been occurring for 9 months!

oh well lol that would definitely throw a couple red flags. My car isnt throwing anymore check engine lights ever since i reset it. Either way im gonna check out my spark plugs and injectors tomorrow just to be safe.

Any use for the bum one? I know Deatschwerks takes them in sets if you're buying their injectors, but I suppose that's for working injectors. It's just.. painful to toss something that costs $242.

 

You could send the fouled injector to Witchhunter and have them recondition it as a spare (nice to have in the spare parts locker). Or you could recondition it and sell it to someone else for a spare.

I am looking at getting a set of deatchworks to cure this problem. I was just told that there is a service bulletin on our injectors. Might as well upgrade and replace em all, cheaper than buying OEM

Subscribed. 75,000 mile 5MT. Car originally threw P0304 after idling roughly for a few weeks. Before P0304 I replaced plugs with OEM NGKs. Compression test done at the same time (all good). After P0304 I replaced intake manifold O rings and BPV gasket. This all in the past 2 months.

 

Car continues to idle very rough but no CEL. Pulls strong and no issues at speed.

 

Time to replace #4 injector?

First check spark plug - look for hairline fracture in porcelain, then swap coil pack on another cylinder and see if it follows. Then swap injector.

check the o2 sensor too. i was misfiring on 3 cylinders, new o2 and im gtg

@85,000 miles with stock everything until 72k when I did 3 revisions of Infamous (remote) tuning. As a big plus from that is that the Tactrix cable has saved me hundreds of dollars during this misfire problem.

 

Leakdown and pressure test showed 25% leakage in Cyl#3 and 30% in Cyl#2. Exhaust valves in Cyl#2 needed to be replaced and resurfaced in Cyl#3. Got the car back and was shocked at how smooth the idle is now. I guess that crept up on me over time so I didn't notice how rough it had gotten.

 

Sadly in <30mi I got a P0011 and now I've lost my car again though my mechanic says that there is a bulletin on this code having to do with a banjo bolt filter going into the turbo. Hopefully he's right about the cause and this is an "easy" fix...

 

to be continued...

Update: Cleaned MAF with contact cleaner and shop towels, wiped down clean-side of the airbox with shop towels, reassembled.

 

Idles smooth as buttermilk with AC on, no codes present.

check the o2 sensor too. i was misfiring on 3 cylinders, new o2 and im gtg

 

Were you getting a CEL with the bad o2 or just rough idle? I haven't had a CEL since the original P0304, but it's idling the same.

No check engine lights, but misfires at idle on cyl 2,3 and 4 in logger. I've been going nuts trying to find a vac leak because of a/f learning #1 0-5.6 in learning view being high (occasionally 15), but smoke test found nada.

 

I'm due for plugs, maybe 50k on them... MAF sensor was cleaned with electrical parts cleaner very lightly... car does sound noisier under the hood than ever before since my woes began a couple months ago, I hope it isn't valves!

 

I'll be pulling out my two front plugs, cyl 1 has shown no misfire so I'll compare it to any other easily accessible plugs since the rest are misfiring. If they're good, I'll swap cyl 1 injector to anywhere else and see if cyl 1 starts misfiring, or the swapped cyl stops misfiring.

 

Leakdown and compression test hopefully done next wednesday. If it's anything more than plugs and injectors I'm getting an f'n new KIA and washing my hands clean of LGT/defeat.

Do check on your plugs. I had misfire caused by slow crack propagation in the porcelain on a brand new NGK plug.

Really - first I'd heard of that, especially with the NGKs. Probably a million miles on my Subes over the years on NGKs and never had one issue. Do you think there's an underlying cause, i.e., cylinder leaned too much, over-torqued, etc.?

I dropped the box (they didn't look damaged, but I bet that was enough)

 

FWIW I noticed an ever-so-slight misfire for the entire time (it's gone now). You could hear it if paying attention, but it never showed on the logs or triggered a CEL for 9 months.

OIC - that could likely do it.