Missfire

[Metallman56]

well the miss is back. acutally it never went away. LIM gasket was changed, still have a miss. usually it only happens during a cold start, and goes away when I give it a little gas, and doesn't do it again unless its under a load.

this weekend it went exploring in hilly southern Indianan. up almost every freaking hill it missed. bad. like backfired a few times bad. which its never done before. I could power out of it, but I had to almost floor it, but once it downshifted it was fine.

I don't know wtf there is left to do to fix it. its really p*ssing me off, to the point of selling it and buying some POS that runs right until I can afford the car I want. I don't want to do that, but I'm really out of ideas. I cant just keep throwing money at the damn thing.

plus still no misfire code. how the hell is that possible?

also I checked the catalytic converter, it doesn't glow red at night so I think air is flowing through it fine, but I guess the only way to find out is get a new one, and hope it works like the rest of the parts I've replaced.

any help would be great as always. I'd like to brain storm it for a little while before I get any more parts for it.

thanks as always boys.

[sleepyalero]

Do the rpms jump up and down on hills?

[Metallman56]

no. no rpm jump the car acts like it wants/should down shift and doesn't but instead misses/backfires

[Metallman56]

took a vid this morning in my car of it missing. cold start about 60ish out, it doesn't miss until I put it in gear and reverse it out of my driveway. I kept the camera on the rpms so you guys can see no surge in rpms. missing starts around 25 seconds, stops around 34 seconds. its hard to hear so sorry for that. I couldn't hear the missing on my phone, had to listen on my pc

[Metallman56]

pulled the front plugs 2,4, and 6 irrc. took some pics let me know what you guys think/see, they all look like spark plugs to me

#2



#4



#6



yes there all e3. I replaced them from delco iridium plugs when the miss started. first thing I changed, still had a miss.

[mlog]

Sorry to bump an older thread, but did you ever find the source of the misfire?

[Metallman56]

Nope.

[Metallman56]

Well I ordered both a crank and cam position sensor. If neither of these work, ill try injectors, maybe. I might just say f*ck it, not sure yet.

[sleepyalero]

Id replace those plugs from your last pics posted. They look pretty nasty tbh. If it was my car i would

Maybe throw wires at it too.

[Metallman56]

Both done, neither fixed the issue

[Nick-G]

Originally Posted by Metallman56

Both done, neither fixed the issue

With the same style plug? Those E3 plugs are junk.

[Metallman56]

Sense the miss i went from e3 to ngk iridium, still have a miss

[datashifter]

Try some barstop leak pellets. Use the pellets, not the crap in a bottle with the floaters inside. My LIM was replaced and I later developed a misfire when the engine was cold, usually first thing in the morning. Dropped in all six pellets/tabs (about an inch in diameter each) and my misfire has been gone for over a year. Worst case scenario, it doesn't help and you haven't spent much...

EDITED - clarified about the engine being cold, not about it being cold outside.

[mlog]

Originally Posted by Metallman56

Nope.

I had a similar problem, and I threw a lot money buying parts. I'm too embarrassed to list all the parts I replaced. Needless to say there was no fix until I changed the fuel pump. I had long suspected the pump, but it's expensive. I probably had the cost of a fuel pump in the needless parts I replaced. After I replaced it with an OEM pump assembly, it fixed the misfire and hesitation, restored lost power, improved my MPG, and eliminated the frequent hard starting problem. My fuel pressure was only a couple of PSI low on the original pump, but apparently that's all it took. The check valve on the pump was leaky too, and that contributed to hard starts.

[Metallman56]

so i think i've finally got this miss figured out. there is some reading involved so bear with me.

in november i had to go back home for a funeral. we now live about 275 miles away from where we both grew up. my wife already had plans up there and was coming home monday. the funeral was on a friday and i wanted to drive back home that same day. so we left the night before, planning on getting to my cousins house around 10 pm to crash. about 30 miles into the trip my car started randomly missing. no rhyme or reason, the cruise was set and the RMPs would just spike from 2400 to around 4k just for half a second and go back down. it would only do it once every few mins. but then it started to do it all the time. and it wouldnt just jump to 4k it would jump anywhere from 800 rmps to about 4700 is the highest i saw. backfiring, and smelling like crap. so i pull over. my SES light was flashing (bout time) so i scanned it. misfire #3. sent my wife to the nearest autozone to buy a new plug, new wires, and tools. she came back, and i swapped out the parts. we continued on our trip and it got me to my cousins safely. it did however do an rpm jump 2x after that.

so i went to the funeral and came back to my cousins house. i decided to change all the plugs. i got all of them changed except 1 i couldnt get to with the tools i had, #1 the extension i had was too long or too short, i cant remember which. turned the car on, and it ran like sh*t. so i recheck all the plugs make sure everything is tight, fire it up again, same result, car runs like crap. so now i'm checking all the wires, well one of the wire connects came off of the plug wire. so i take it back to autozone get new wires, and ... still runs like crap. so i put the old plugs back in it, maybe the new plugs are bad. nope, still runs like crap. so i call my mechanic buddy, and limp the car over to his house. so he hooks it up to his crazy scanner. no SES lights, nothing. so he turns off the injectors 1 at a time. each one he turns off the car runs worse. then we get to #3. turns it off, no change. turns it back on, no change. bingo, its got to be injector #3. so the next day (saturday now) i get over there and take of the UIM and take out the injectors. i disconnect all of them except #3 and crank the motor. fuel goes everywhere. not a weak stream but a good working injector stream. so he suggests i take off the back valve cover to check the valve springs, and making sure thats all moving like it should. so i take that all off, and up nothing is loose all the rockers are moving just like they should. finally anther friend brings over a compression gage, and it reads 170 psi. so were good there. so now i dont know wtf to do, neither does anyone else. so i put everything back together thinking maybe something was lose, like an injector wire, and now that i have taken it all apart its like it should be. fire it up and.... still runs like crap. so my buddy hooks his scanner back up to it and turns off #3 injector again. this time the car runs worse. so then he tries #1, and no change. so we pull the plug, remember i never changed that plug, and there is quite a bit of carbon on it. we swap it out for a new plug, fire it up and it runs like new. i dindt know if i should be super p*ssed that was just a plug the whole time, or super happy that my car was running and i could finally go home. so i changed all the plugs, and drove it back home.

after a month i'm happy to report, that the miss is gone. and the car runs like it is supposed to again finally. it feels like a new car. the power i didnt realize had gone missing is back. so if you've got a miss here is what i recommend. NGK spark plugs. they are the only plug my engine seems to like. not E3 not denso, just NGK. ac delco is probably fine to, but from now on nothing but NGK goes into my car.

thanks to everyone for the help, and i hope this helps others figure out there miss.

[sleepyalero]

I suggested replacing the plugs, you said you did, and had no change?

I run NGK as well, and ac delco, just whatever im in the mood for.... Ac delcos are in both my 3400 aleros right now, neither have issues.


e3 plugs imo are junk, i would personally never run them

[bricooper78]

NGK makes the Delco plugs, or did as of a couple years ago

[Metallman56]

Sleepy plugs was the first thing i replaced. It made no difference between old and new plugs. Actually come to think of it now every time ive had a miss in this car its been the plugs. This would be the 3rd time.

[geldartb]

there's a plug that runs from the coil pack to the back of the engine block..iirc it's like two twisted wires. have you checked that. it sits pretty close to the exhaust manifold and can melt..

i went through this same shit with my Z26..

[sleepyalero]

That is the crank position wiring.