NYTooCooL

iTrader: (1)

So let me say the whole story, just to see if one thing could have caused another. So I replaced my 200k engine with a used engine that had about 70k on it. My old one blew because my cats clogged up. Replaced the front main precat with the engine, then eventually replaced the main. Then after, I finally got my cattman headers on, no cats. So my max started misfiring about 2 months ago and a major oil leak.. I decided to get, valve cover w/ gaskets, NWP Spacers, NWP B.O.P, and replaced the Spark Plugs. The old spark plugs were TOAST. We also realized that Cylinder 5 spark plug and coils were covered in oil. So we do all that stuff. Still misfiring. Better, but misfiring. So a few weeks go by and i finally replace all the coil packs with used ones from someone on the org. Drives way better. However the idle is still low, and unsteady, but for the most part is good. Then we realize the primary o2's are not getting signal. We replace that and FINALLY NO CODES. Got my emissions done, an hour later(today) Cylinder 2 Misfire. I replaced it with one of my old working ones and cleared CEL, and now its gone again for now. Now i kept driving it within all the gaps of getting it done, i don't know if that had something to do with it. however why would that pop up again? Im worried another Misfire will pop up again. The idle has yet to be steady within all of this, even no CEL. It stays around 550-650. When I come to neutral out of gear it drops to like 550 then maybe to 600. BTW could it be because I never did the Idle relearn? I know this is SUPER LONG but i just wanted to be accurate so if anyone commented they know EXACTLY what I did. Thanks in advance .ORG!

Also, my alternator died in between replacing the sensors and coils. So I replaced the Alternator, then we did the coils/o2s a week or so later.

nsnrider

iTrader: (59)

i would check the two grounds on the engine timing cover. if those two grounds do not have good connection, they might set a cel for primary o2 sensors along with making a rich fuel/air mixture which in turn might contribute to misfire/rough idle. I went through hell until I ended up back at those two ground points. cleaned them, solved all of my problems. that was also after an engine swap.

good luck. do the idle relearn procedure.

NYTooCooL

iTrader: (1)

Would driving around on the misfire for a couple weeks after replacing the plugs mess the new plugs up that quick? My thing is I figured if it was something non coil, plug related, it would through P0300 which is just multiple/random misfire. Not a specific cylinder. Right?

foodmanry

iTrader: (15)

Do idle relearn and I would also suggest pulling plugs to inspect them. At least cylinder 2 plug.

NYTooCooL

iTrader: (1)

I was thinking about that, but that would be strange since the plugs are only like a month and some change old. However im wondering if driving with the misfire could have messed them up. Anyway today ill see if another misfire comes back, as of yesterday there was no codes after i swapped that coil.

2003MaximaMan

Also check your throttle body. Clean or replace. I replaced mine with the new NWP one and it cleared up a similar issue with the idle.

foodmanry

iTrader: (15)

Yes it could and you can have a misfire without showing any codes. At a minimum pull plug from cylinder 2 since that has been problematic.

ACee

I am having a very similar problem with my 03 and I am convinced it is a fuel issue. Maybe clogging or dirty injectors.

NYTooCooL

iTrader: (1)

Well I put some Chevron Techron injector cleaner in the gas tank after replacing the coils. Next is going to be seafoam the car though the brake booster.

Slamrod

iTrader: (11)

May be silly but make sure none of the wires that go into the coil pigtails are lose - give them a good push into the connector.

SSJRICH

I would do the Idle re learn. Might fix your idle problem. It takes literally 2 min to do. Did you replace your plugs with the right ones???


Also, my boss's 5.5 was having misfire problems for the longest time, it turned out to be the coil boot/spring/resistor part. It would random misfire so with was hard to find, but I suggest checking them too. Basically the spring worn out and wouldn't make good contact onto the plug.

ACee

I've done the injector cleaner and seafoam and it helped but not for long. Through the brake booster is the only way to seafoam imo.

NYTooCooL

iTrader: (1)

Drove it to work today and still no CEL light. I guess replacing the used replacement coil pack with my old working one helped. For now... Anyway i'm still not sure about the low idle. I'm going to seafoam this weekend check the cam sensors connection.

ACee

I replaced the cam sensors too. No improvement. I also replaced the rear cps wiring harness because the wire sheathing showed exposed copper wire and doing that helped but did not fix it.

NYTooCooL

iTrader: (1)

just figured id chime in again. Been driving all week, even aggressively. No CEL. Hopefully it stays off. Still idles low @ 600 though

alanfury75

Hey there TooCool!

Just wondering how your misfire has been treating you. I recently installed new plugs, and 1,3,5 coil packs. It solved the initial P0303 misfire that caused the CEL. But now it's back and back with a fury!

It is likely, rather obvious, that the mechanic did not use OEM coils, but it is odd that it is still cylinder #3 that is misfiring.

I've cleaned my MAF and checked my throttle body... though I do not believe that to be an issue since it is a specific cylinder misfiring.

My next step would be to swap out a front coil with the #3 coil to see if that solves it. I doubt it though. I'm just wondering, while I have the Intake Manifold off, is there anything else I should check while in there? Fuel injector? Maybe the wire harnesses?

Any update/advice you can offer would be awesome. Thanks!

tosheto

iTrader: (5)

Did you put NGK plugs? Did you get OEM coils? You can check your rear valve cover for leaks (not related to misfire). With the info you provided I am going wit bad coil.

alanfury75

No, they are not oem coils and yes that cpuld be the issue. However, the mechanic put 3 new coils in and new plugs, so there is probably something else going on.

Im going to get in there and swap out of the fronts with cylinder 3 to see if the misfire jumps.

But other than that.. I may look at the injectors next.

abg124

Check the connections on the coils sometime the prong on the coil can bend and this will stop it from making a connection... Hence the misfire

alanfury75

Yeah, this weekend I just took the IM off, swapped out the rear aftermarket with the oem fronts, checked harnesses, checked injectors, cleaned throttle body... and whatya know... no more misfire.

tosheto

iTrader: (5)

Good news. Thanks for posting up how you fixed your problem.