Misfire under load. No codes thrown. Under acceleration, there is a notable misfire, the tire alert symbol comes on, yet there are no codes thrown.

[DAKMAN]

While towing a small camper yesterday, the truck developed a misfire under acceleration, along with the tire alert symbol coming on. When I come out of the throttle, the misfire goes away, and the tire alert light goes off. There are no codes thrown. Without the camper today, it is still having the same symptoms. ECM, PCM poss.? Thanks for any direction. 2012 1500 Laramie Quad Cab. 5.7,

 

[Jeepwalker]

IDK. It's wierd both would occur at the same time. You're saying it idles fine and drives nice as long as you don't step on it hard, right? I guess the place to start if it were my truck ...and just like they say in the service manuals, is to start with a good visual inspection under the hood of various components, and then basic troubleshooting.

Start with the most un-obvious thing of making sure the electrical is good: Batt connections are solid-good (redo them). I'd leave them disconnected a while (to reset the computer) while you do the other things on this list. In the meantime ensure the engine and body grounds are good by loosening the bolts/nuts and wiggling the cables and re-tightening. And that the battery itself is good (go to a parts store and have it load-tested). There are (on my tk) major grounds under a plastic panel above the L front tire. Mine were super rusty, I bet yours could be too. They should be cleaned so you know there's good grounds. Theres also a major ground back by the tank filler neck on mine ..that were also rusty. Grounds are how the electrical path gets back to the computer. Wiggle fuses, etc. The reason is, often semi-good electrical can cause "wonky" TIPM behavior (like a drunk salior who can't think straight, lol). And therefore odd truck behavior. It's well-known that these trucks (and any modern vehicle) can act 'funny' when the electrical is compromised (I've seen it!). It just takes a short while to look at the above and cross those basic things off your list.

Remove the engine cover & hose, Inspect the throttle bore for "dirtiness" and carbon build-up. Clean if necessary with throttle body cleaner and a solvent-safe brush.

Inspect the PCV valve. Or just change it if your truck has a lot of miles on it. Also inspect the hose for cracks, etc. The reason is, when you floor it, the PCV valve spring allows the valve to open for maximum air flow. If it were 'sticking'.... ?

5.7 Hemi PCV valve replacement

Please use the following link when ever using Amazon.com. Any purchases you make on Amazon will help support this channel.http://amzn.to/2mALgqSEveryone love...

www.youtube.com

Inspect the air filter. Make sure there isn't anything (like a mouse nest) in the air box.

I'd probably wiggle the TIPM wire bundle just a little ...under the fuse box. These have been known to get rusty at the pins in heavy salt areas ...but for now just wiggle them...come back to them later if nothing else does the trick.

It would be a real good idea to inspect each of the plugs and the coil packs (ohm them out). But you might wait until after a test drive for that. It might just be weird electrical. When you do, inspect the ends of each coil for cracks or spark traces. Cracks could allow the spark to be jumping which you might feel under heavy load. But if you don't want to do it just yet, then take it for a drive and see if the problem persists. Fuel pressure and vacuum would be good to know too if you have to dig into things a little deeper.

Does your scan tool allow you to get real-time readings?

.

 

[Wild one]

If none of things posted above show any improvement,your next step might be to do a compression test.Almost sounds like you could have a lifter chewing up a cam lobe

 

[Dodge 1500 4X4]

Put some seafoam in the fuel tank, you may have an injector being partially clogged causing a misfire or stumble, how many miles on your truck?

 

[Jeepwalker]

With your scan tool, if you have 'real-time' readings, check the temp gauge when the truck is cold, and again after warm-up. To verify that the temp sensor hasn't 'drifted'. That can screw up things. Same with manifold pressure and even the throttle position. If your scanner doesn't give real-time readings, and you go to like Autozone to get a battery load tester ....see if their scanner can give real-time readings and at least look at the TPS, the manifold pressure readings, and for the heck of it press the brake pedal on/off 20 or 30 times and see if the brake switch works like it should each time. The accelerator is actually a rheostat, so I wonder if that could be a source of problems? You might check that as well on the scan tool.

I'm thinking out loud here.

Edit: I agree: if you remove the spark plugs for any reason, perform a compression test. You can rent for free a compression tester at Autozone/OReilly's, etc. Watch some videos how to perform

.

 

[jws123]

Recently had a issue on a 2011 that I did a camshaft on the bank 1 sensor 1 02 sensor would cause it to randomly missfire under load would be a good idea to check those out aswell read the live data if you find someone with a scan tool

 

[Jeepwalker]

You're right. It's possible the computer has already registered a high number of misfire counts ...but just under the number which would activate the Check Engine light.

 

[ramffml]

Do you hear any ticking while it's idling when hot?

 

[DAKMAN]

Truck has 365K. It has no tick. Recent oil change, and road test w/ a Snap -On diagnostic which showed no misfires, or sensor issues. This was 2 weeks ago when she was running well. Will have to do another diagnostic to see what is detected.

 

[DAKMAN]

Update on the misfire under load/tire alert. I installed 16 new plugs yesterday. The plugs I removed looked toasted, as if the load of towing the Camper had somehow called for a lot of fuel, and it chewed up the plugs internally, and browned them externally. Speculating, since I had not previously towed such a load weight wise. Anyway, the issue has been cleared. No more misfire/tire alert under acceleration. I will run 93 when I next put any weight on it, as opposed to the 89 I normally run. Thanks for all your insights, and replies.

 

[Jeepwalker]

Yaaaay! Congrats. Cheap fix. No bad lifter...

Relavent Story: I once (yrs ago), had an engine miss that was a bugger to track down. It seemed like ignition, so I installed new plugs, wires, cap, etc (classic car). The miss still there. Did carb work a couple times. New engine, so I chased around all kind of intake leak possibilities for a while. Couldn't find it the problem. Ended up taking it to a dealer to hook up on their machine (remember those big 6' tall Bear "Analyzers" back then with tons of hook-up wires?). Guy found it right away. Guess what? One of the new plugs I put in was faulty. I had checked them for continuity, but something internally was wrong. New $1 plug (back then) and problem solved. Doesn't happen often, but sometimes those can really get ya!