Multiple Misfire

[bluwarguy]

My truck misfires at WOT (going up hills and things like that). The check engine light flashes then it'll stop when I ease off the gas and coast downhill. I checked the codes with an OBD reader and got Random/Multiple cylinder misfire, misfire on cylinders 1, 6, and 8. Now normally whenever this happens i'll check the plugs and replace them if they need to be replaced. Well, I replaced them and it still does it, flashing check engine light and all with no change in codes. It shakes/shudders in overdrive and overall the exhaust sounds a bit off.

 

[SYKRAMMAN]

Test your coil and injectors, seems like it’s only happens under load, could be bad injectors but probably something simple, just do some basic diagnostics.

 

[dudeman2009]

Have you replaced the coil recently. I don't remember what you did to it a few years ago, but you'd done some stuff with the ignition system.

Recently another guy on here had a similar issue and everyone forgot that ignition coils can fail intermittently, and it took the guy weeks to get back to replacing the ignition coil.

Ohm it out, but it might be worth replacing it if you haven't already.

 

[bluwarguy]

Over a month later, the problems are still persisting. I've noticed a couple different things however. The engine won't shake/misfire as bad when it's cold but as soon as it hits 180 it shakes bad. I've also noticed that at higher speeds, when I let off the gas there's a rapid ticking noise coming from what sounds like the right side of the engine. It corresponds with the RPM's and slows down as the engine does. I don't notice the noise at 25 and below. There's also slight sputtering going up hills. Putting it out of overdrive solves the problem unless I'm slightly pressing on the gas or going up a hill. I'm honestly at my wits end here.

 

[14RAM1500BG]

Have you checked the fuel pressure. Maybe the pump is taking a crap.

 

[bluwarguy]

Just replaced that not too long ago

 

[Yeret]

Plenum repair?

 

[MarshRam]

I'm going to he honest with you and tell you that a multiple misfire is a headache. You can throw parts at it until your wallet turns to ashes. I cringe every time I see these posts. Don't ask me why!

It could be a very simple fix that costs more to diagnose than to repair. It could be the other way around. It could be diagnosed quickly and fixed inexpensively, it could not.... If you want to track it down yourself, know what to do,have the tools or can rent them, then go through all the procedures.

If you don't know all those procedures and don't want to spend countless hours figuring them out, then try to find a shop that knows Ram trucks and hope for the best. I am not recommending the dealership in any way.

I don't mean to come across as pessimistic, but the reality is multiple misfires suck and you are going to get many more good recommendations on what to check than you have seen thus far on this thread.

 

[ouch1011]

Have you replaced anything else in the ignition system? Like the wires, cap and rotor? The symptoms you are describing sound like a text book ignition misfire to me.

 

[EvilSpirit]

You didn't answer to the plenium repair. Can in itself cause a random misfire.

More food for thought, which can be tied to a plenuim repair. While the distributor doesn't set timing, it must be phased correctly, so that the rotor is aligned properly with the contacts in the cap when the coil fires. Sometimes during plenium repair the distributor doesn't get put back correctly, and while it starts and idles fine, as timing advances and cylinder pressure goes up, the rotor is too far from the contacts in the cap for the spark to jump. Try turning the distributor a few degrees CCW to see if it helps or cures the issue.

 

[Yeret]

When my plenum was blown, I had absolutely every problem you just described. Random misfires, flashing CEL, shaking in overdrive. It actually got to the point where I couldn't hardly use my overdrive because the engine shook so bad. I went through countless spark plugs, rerouted the plug wires, dumped more Seafoam into the tank than I care to admit and it was all just a temporary fix.

Here's the deal. If your plenum is leaking, you are going to have incessant running/driving problems. Fiddle with everything else all you want, if the plenum is leaking, NOTHING is going to help.

Here's another thing to consider. If your plenum has been leaking for some time, burning oil will have left significant carbon deposits on the pistons and combustion chambers. This crud is very insulating and gets very hot while running and these "hot spots" will cause detonation which, left to go for too long, can cause blown head gaskets, excessive bearing wear and destroyed pistons. Someone posted here recently about an engine that had running problems, tore it apart and discovered a piston with a huge chunk blown off which basically trashed the entire cylinder. Detonation was likely to blame. So, you have two options here. Pull the heads and clean everything or simply replace the heads, which isn't a bad idea anyway since your factory ones have a 95% probability of being cracked.

In my case, I had the heads replaced (yes, mine were cracked to hell), the pistons cleaned and had the plenum repair done. Ever since, no spark knock, no misfires, no weirdness. Since then, I've flashed the ECU with a tune that actually made the timing curve more aggressive, something which will exacerbate detonation issues (hence why Ryan will not provide a tune for an engine without the plenum repair). Still no problems.