P0304 #4 cylinder misfire help

kevin25 · Post by **kevin25** » Thu Apr 09, 2009 7:22 am

Ok I just got the P0304 code which is a #4 cylinder misfire. I know there are things to check like the coil pack, wires, plugs, fuel injectors, and intake mani gasket.
I guess the cheapest place to start is plugs and wires. I already changed the wires and still getting code, plugs look good.
My idle in drive is at 600rpm, this cant be normal, I thought it is usually at 900rpm?
I know I might have to change the coil pack, but cost will add up quick. I also have to check the intake mani gasket around #4 cylinder to see if it pooped out in the corner, I have heard that could be it as well.
I want to know for those of you who had this problem what did you do that worked?
Thanks

Post by **racer12306** » Thu Apr 09, 2009 7:44 am

instead of just looking at the plugs, replace them. they are only ~$8 a set. misfire codes are generally plugs or wires.

what year is your car?

Post by **occasional demons** » Thu Apr 09, 2009 7:56 am

600 rpm while not moving wouldn't be out of the ordinary, unless they step up the rpm as soon as it is put in gear. (IDK, have MTX.)
OT/sort of:
My Raider does that. Annoying as hell. Especially since it has 4.625:1 gearing. Low range really sucks ass. Best have a good set on the brake pedal!

Sabersoul · Post by **Sabersoul** » Thu Apr 09, 2009 8:12 am

I'm with Racer, swap the plugs. As far as the idle speed goes, my '03 idles around 600 in gear when I have the AC off and around 750 with it on.

kevin25 · Post by **kevin25** » Thu Apr 09, 2009 8:15 am

Thanks I will try new plugs and see if that helps if not I will swap the number 4 injector with another to see if it is the injector.
I will keep you guys informed.

Post by **racer12306** » Thu Apr 09, 2009 8:43 am

So what year is the car?

Fill out your garage or sig, it may help us in the future.

kevin25 · Post by **kevin25** » Thu Apr 09, 2009 9:29 am

Ok thanks for the advice, my car is an 2004 sxt
Coil is stock, wires are stock, and I have irridium plugs.
I am first going to change the plugs to stock and gap them at .38
If I still get the code I might try swaping plug wires or try taking the #4 fuel injector and swaping it with the #1 to see if I get a #1 misfire, if so the problem is the fuel Injector.
I am also going to look at the intake mani gasket, I have heard that I might have a blow out at the bottom right causing the code.

Neon4Life · Post by **Neon4Life** » Thu Apr 09, 2009 9:33 am

kevin25 wrote:Ok thanks for the advice, my car is an 2004 sxt

hmm id idles at 600 u say. my 04 sxt idles at like 800 but diff cars will idle at diff rpm. like mine can sometimes go down to 500 rpm idling.

Post by **racer12306** » Thu Apr 09, 2009 9:34 am

In that case, I'd bet the plugs or wires have more to do with the problem than the injectors, but its always a possibility.

Post by **occasional demons** » Thu Apr 09, 2009 9:46 am

Unless you have removed the IM, There is no way the gasket can blow out. (unless the bolts are loose)
It is an o-ring style that sits deep in a groove. It would have to been out of the groove when installed.

I honestly think the manifold would burst from pressure long before the gasket came out on a properly installed IM.

Unless it is a Magnum manifold. They have a conventional gasket. then again it would need to be loose to leak.

kevin25 · Post by **kevin25** » Thu Apr 09, 2009 9:56 am

Thanks for the advice on the manifold, I have never took it out before. But I have heard of others on the srtforums say theres had blown out on the bottom right corner.
As far as the idle at 600rpm, I am not sure what it had idled at before but it just seems a little more rough at idle now than before.
I am quit sure it use to be around the 800 mark though.
Yeah like I said I will start with new plugs gapped at .35, than buy new wires. Than i will see what it does.
I will keep you guys posted, if this doesn't work we will work on the next step, which might be swapping the #4 fuel injector with another.
I have also heard if it was the coil pack there would be Two misfires, not sure it that is true or not.

ZeroChad · Post by **ZeroChad** » Thu Apr 09, 2009 10:23 am

^Let us know if that works.

My stock intake manifold failed on me. It was givin me a vaccuum leak though.

kevin25 · Post by **kevin25** » Thu Apr 09, 2009 11:04 am

Ok no problem I will keep checking this thread keeping you guys posted and in the meantime I will try what I said tonight and wait and see if the code comes back.

kevin25 · Post by **kevin25** » Thu Apr 09, 2009 7:55 pm

Update: I replace the plugs and wires. It is too early to tell if it has solved my problem, so far I have not gotten a cel code yet.
As far as my ideling I have noticed when at a stop if idles sometimes at 800rpm and when seems to get hot it idles at 600rpm?

Sabersoul · Post by **Sabersoul** » Thu Apr 09, 2009 8:08 pm

Mine does that. ~750 cold, 550 warm w/o AC on, stays @ 750 with it on

esteinmaier · Post by **esteinmaier** » Thu Apr 09, 2009 9:50 pm

kevin25 wrote:Thanks for the advice on the manifold, I have never took it out before. But I have heard of others on the srtforums say theres had blown out on the bottom right corner.
As far as the idle at 600rpm, I am not sure what it had idled at before but it just seems a little more rough at idle now than before.
I am quit sure it use to be around the 800 mark though.
Yeah like I said I will start with new plugs gapped at .35, than buy new wires. Than i will see what it does.
I will keep you guys posted, if this doesn't work we will work on the next step, which might be swapping the #4 fuel injector with another.
I have also heard if it was the coil pack there would be Two misfires, not sure it that is true or not.

Mine held with never a leak, until I blew it to pieces at 28psi.

SRT manifolds don't use the same type of gasket, as they are cast aluminum, not molded plastic.

The neon ECU aims for 800. If it's less, it opens up the IAC more, and vice versa. No, not every car is different in that way. Once IACs were introduced, that went out the window.

If the coil pack goes out all the way, yes. But usually when they go, they go a little at a time, like an old laptop battery. And pretty soon, it's just not strong enough to overcome the resistance. Small variances in resistance are enough to cause a misfire when the coil is dying.

kevin25 · Post by **kevin25** » Thu Apr 09, 2009 10:52 pm

esteinmaier wrote:
kevin25 wrote:Thanks for the advice on the manifold, I have never took it out before. But I have heard of others on the srtforums say theres had blown out on the bottom right corner.
As far as the idle at 600rpm, I am not sure what it had idled at before but it just seems a little more rough at idle now than before.
I am quit sure it use to be around the 800 mark though.
Yeah like I said I will start with new plugs gapped at .35, than buy new wires. Than i will see what it does.
I will keep you guys posted, if this doesn't work we will work on the next step, which might be swapping the #4 fuel injector with another.
I have also heard if it was the coil pack there would be Two misfires, not sure it that is true or not.
Mine held with never a leak, until I blew it to pieces at 28psi.

SRT manifolds don't use the same type of gasket, as they are cast aluminum, not molded plastic.

The neon ECU aims for 800. If it's less, it opens up the IAC more, and vice versa. No, not every car is different in that way. Once IACs were introduced, that went out the window.

If the coil pack goes out all the way, yes. But usually when they go, they go a little at a time, like an old laptop battery. And pretty soon, it's just not strong enough to overcome the resistance. Small variances in resistance are enough to cause a misfire when the coil is dying.

So I have a problem with the IAC? When cold it idles at 800rpm then when it gets hot and I come to a stop it idles down to 600rpm and I can feel it idle a little more than I used too.
So you are saying more than likely my coil pack is dying slowly?

Post by **occasional demons** » Fri Apr 10, 2009 11:07 am

Your IAC is fine. Everycar has it's own quirks. I think Eric meant that all the post eighties cars use the same method for controlling idle speed. If it was stalling at about every stop, or idling above 1200 or so RPM, then there may be an IAC problem.

Until the CEL returns I wouln't worry about the coil. The new wires may have cured it.

If there is a problem with the coil it will show up.

kevin25 · Post by **kevin25** » Fri Apr 10, 2009 11:13 am

Ok thanks, so far so good, I will keep you guys posted, it does seem a little stumbly during cold start up, but to early to tell yet, I will monitor everything and post here.
thanks