5.7 misfire but no codes

[croaker567]

Hey guys, I'm stumped.... I've got a 2003 dodge ram 1500 with the 5.7 hemi that I just put a new engine in. I got it as a short block and had my heads worked and put them on and then put the engine in. It is running good except it has a misfire in one of the cylinders. Its not throwing any codes and I went and paid to have it put on a computer at a shop. Everything is good and isn't saying there's any misfires electrical wise. What could be my problem? Any help would be greatly appreciated I've put way to much money and time in this truck and I'm ready for it to be perfect. Thanks guys

 

[KGBIGCOUNTRY]

Is it a dead miss or just missing every once in awhile? Have y'all tried to identify which cylinder is the issue? Could be an unseated push rod, cam gear out of time by a tooth, coil pack not seated on the plug, cracked plug, injector not seated, injector harness at the back of the motor not fully clamped. That's just a few quick checks.

 

[croaker567]

I'll check all that and no not had the time to figure out which cylinder it is. And I'll check all that to make sure. It's seems.constant but sometimes I don't notice it being as bad as othertimes. Sometimes it'll have a good surge to where you can feel it and othertimes it doesnt. You can hear it on the outside and you can see the rpms play around just a touch. Wjats a good way to clean injectors out with if you pull them? Brake or carb cleaner? I'm fixing to replace all the spark plugs.

 

[croaker567]

How can I tell which cylinder is misfiring?

 

[SyrenSkywolf]

Old school method that I have seen is to disconnect the spark plug cables and see what happens. If you unplug them and nothing really changes, that is the one that is misfiring. If you unplug them and the engine changes, then move on to the next ones.

Just remember, that from what I have seen, the 5.7 has two plugs per cylinder. That is from what I have seen on here, though, as I haven't had my truck long enough to deal with them yet. So you would have to unplug both.

 

[JPT]

Old school method that I have seen is to disconnect the spark plug cables and see what happens. If you unplug them and nothing really changes, that is the one that is misfiring. If you unplug them and the engine changes, then move on to the next ones.

Just remember, that from what I have seen, the 5.7 has two plugs per cylinder. That is from what I have seen on here, though, as I haven't had my truck long enough to deal with them yet. So you would have to unplug both.

I've done this on my 93 maxima to find a misfire (no ODBII). It works great. Just remember that the plugs are sending a charge that can jump... I got a nice wake you up shock as the plug arced to the block while my hand was resting on the top of the engine...

 

[croaker567]

Yeah haha I'll watch out for that and try to figure out which cylinder it is. Thanks guys!

 

[KGBIGCOUNTRY]

Unplug the coil pack and pull the boot on that cylinder that will make sure that hole is cold. The coil pack does the ig spark and the second plug is a wasted spark for emmisions. If you have access to a temp gun you can check the manifold and look for the cold hole. If all are within 20-50* of each other you have something else going on. The reason for the wide # is because you will get some cross over heat soak from the other holes with the stock manifolds. You could also take a pressure check of each cylinder to see if its something mechanical like a valve leaking, seat that was not done right ect.

 

[croaker567]

Is there a certain way the coil packs should be on? On the drive side the coil packs are on 2,4,6,8 on the passenger its 1,3,5,7

 

[RonJon '06]

Other way around. Driver's side are odd, passenger's side are even.

 

[croaker567]

Thats what I thought but I can't get it to be the other way around. I tried to do it different but I couldn't get it any other way....

 

[RonJon '06]

You mean the wires won't reach?

 

[croaker567]

No you can't turn or switch or rotate the valve covers, or the coils to make it the way its supposed to be

 

[croaker567]

No matter how I turn or switch the valve covers to the otherside it stays driverside even passenger odd.

 

[RonJon '06]

It should look like this.

 

[croaker567]

Right but instead its backwards. And to what I see theres no way to flip anything around to get it to be the right way. My buddy is fixing to be home so I'll have another set of eyes see if I'm not seeing anything. But it being wrong would cause a misfire, high idle then low idle right? Pretty much all over the place

 

[RonJon '06]

Just disconnect the wires from the coil packs and switch them to the other side. You shouldn't have to remove the valve covers and the coilpacks are all the same just the wires have to be in the right order.

 

[croaker567]

But then I cant bolt them down. My coil packs are in the wrong places. My wiring is perfect. Just on the driver side the coil packs are in number 2,4,6,8 hole and the passenger is odds. Does that matter?

 

[RonJon '06]

Are the coil packs installed upside down?

 

[croaker567]

There installed pointing inwards towards the middle of the motor. Let me try to post pictures