Getting a P1416 with a strange set of circumstances.

If I start and drive, I get a rough idle (the misfire on #6) and the code.

If I start and drive in Tow/Haul, no rough idle misfire, no code.
If I start and drive in Tow/Haul and drive until engine is completely warmed up, I can turn off Tow/Haul and run fine with no misfire or codes.
If I stop, start and drive while engine is warm/normal operating temp, no Tow/Haul, there is no misfire, no codes.
If I forget to turn on Tow/Haul before I start driving it may or may not stop misfiring when it warms up.
If I remove battery cables and touch together (the hard reset), it will run maybe 3 times without Tow/Haul before the misfire comes back.

What I've done:
Checked the plugs multiple times.
Changed all plugs. Rechecked plugs in #6 and compared to #4 plugs. They look identical.
Replaced all four MDS solenoids. TWICE!
Run Rislone for 2000 miles before oil changes, twice, hoping to clear out gunk in MDS lifters.

What I've not done:
Swapped coils, injectors or plug boots as it runs fine in Tow/Haul and after warm up.

Is this a PCM problem?
Is there another module in play with the MDS getting/sending a bad signal?

Why would it be fine once it warms up?

2007 Grand Cherokee Limited, 5.7L

186,000 miles

K&N CAI
Over time (9 years), I've replaced radiator, water pump, power steering pump, starter, rear bearings on front propeller shaft, assorted sensors, catalytic converter (one week after purchasing- done by dealership). I may be forgetting a few things.

Any ideas, plesase?

Thanks!
Todd

It sounds like you are getting a P0306 with the P1416 ? Is that all the codes?

P1416-CYLINDER 6 REACTIVATION CONTROL PERFORMANCE

I wouldn't look at misfire as the cause . P1416 will cause a missfire but not the other way around . Also, the reason tow/haul works is because it disables MDS operation. You could also try starting then drive in 5 or 4 as that should also disable MDS and allow normal shifting. Or turn MDS off if you have a tuner.

Are you running 5w20 synthetic oil ?

Have you changed or tested the MDS solenoid?

 

I'm with yzjwk; you're disabling MDS, so you don't get an error which for some reason causes a misfire. It sounds like keeping it out of MDS is one answer, but you seem like you'd like to just fix it so you can have MDS at times.



Are you running exactly the oil they say, and only the oil they say (5W-20 synthetic, I think)? I know there are safe, proven additives, but I take the easy way out and use only what the engine designers said they designed it for. Some people have magic stuff to put in, but then you need to turn to them for advice when it doesn't work as designed.



Just walking through your questions/observations, I can speculate along with you, claiming no more reason I would be right.



Once warmed up, MDS is operating as expected and the computer is happy. Before it's warmed up, if MDS activates, something the computer gets as feedback is causing the computer to react by throwing a code and running bad.



What works better when warm? I assume the oil is thinner and gets around that supposedly complex MDS system quicker, but I think MDS wouldn't try to activate until your oil is up to a temperature where I'm not sure there's much difference. That shouldn't be it, but maybe it takes an already weak mechanical response and makes it just weak enough to throw an error.



Electrical connections can be different warm versus cold, but probably not unless they're corroded, wet, or ?. Your battery voltage might be different warm versus cold, but not unless something's wrong. I'm guessing you've already checked with a meter. If you have a computer connection expecting a certain voltage signal back, and there's a bad connection, then a little more voltage drop can put you over the line for an error, when you otherwise wouldn't.



How are your engine grounds and battery connections?



It doesn't sound like a crazy PCM to me. It's awfully repeatable. I will tell you I've come across a couple different times a circuit board was physically cracked, but would expand and change connections when hot. I had a brand new Evinrude OceanPro that would go nuts when hot, then cool off and be fine. They told me it was a cracked PCB. I saw it one other time in an industrial setting. I don't think that's happening to you.

 

yzjwk and azzkicker,

I have had the P0306 code along with the P1416 but lately, it's only been the latter. It behaves like it's a misfire, which it actually is because of the reactivation control issue (logically in my mind, it's reading the MDS on, hence the call to reactivate it to off, that is all 8 cylinders/valves/spark running normally. I have changed the MDS solenoids twice. Running 5W20 Mobile 1 Synthetic and did another oil change on Saturday 4/11/20 - same behavior.



It's almost as if the MDS was left on (4 cylinder operation) and when I start it, the engine tries to shift to MDS off (all 8 cylinders running) but can't. Turning on Tow/Haul tells a computer that MDS should be off and seems to override the initial call to reactivate the lifter and associated electronics. I understand doing the shifter trick but I've tried that and it's misfiring terribly all the way through the gears. I don't want to take a chance and damage the engine or *** unburnt fuel to the converters.



Thank you for your suggestions, gentleman. I'll take into account all you give me!

 

I found an ECU reset method in another post that is, pull positive cable off battery and ground it to frame for 30 seconds, reconnect, turn ignition to ON, push gas pedal to floor 5 times to reset Wide Open Throttle, turn off. Aside from resetting WOT, I'm not sure what this does differently than pulling off both battery cables and touching them together for 10 minutes which I've done ad nauseam.

It didn't help. Within 5 minutes of driving, #6 started missing.

Anything?
Buehler?
Buehler?