I have a 2011 f250 with a 6.2 gas with roughly 110,000 miles on it. It's taken on a rough idle issue on cold startup when the temperature is below freezing. It will start, then stumble on idle anywhere from 2 seconds to 30 seconds, then either smooth out or stall. If you turn the ignition off immediately and start again, it acts like there was no issue. Also to note, it never throws codes. I had it at the local dealership for the past week and they can't figure it out. The mechanic says it's acting like it's running lean and has verified that the fuel pump, pressure and flow are all within parameter. They did change the MAF, which Didn't help. Any ideas? Thanks.

 

Moved to the 6.2L forum.

Could be ignition related. If it's misfiring the tech should be able to see cylinder misfire counts with Mode 6 data. That would be telling, if it's isolated to a specific cylinder you'd look at the fuel injector, COP, or plug before digging deeper.

 

Plugs have been changed, and was experiencing the same issue before that. I'll quiz them on the misfire, but sounds like they had scanned for quite a few things in the 10 days they had it. Would a misfire throw a code? Thanks

 

After a point it would, but if it's not happening enough to exceed that threshold you'll not see a code. The PCM can recognize a misfire event without setting a code, and they can watch that with their IDS scan tool.

 

Sounds good, thanks. I'll check if that was looked at tomorrow. These are the same guys that misdiagnosed a dead cooling fan motor on my flex, and they kept throwing control modules at it. I finally got time to look at it myself and found a dead spot on one of the Motors.

 

Talk to the tech and there were no misfire's present on multiple starts.

 

I would run your fuel down and fill up at somewhere else before you get to involved with finding a problem that may not be there.

Denny

 

Tried that. I run premium all the time, and tried switching to regular for a couple tanks with no change.

 

So dealership had my truck for couple weeks. Checked pretty much everything without tearing into the motor and found nothing wrong. Supposedly they are now In contact with Ford engineering. Is there any chance that the plugged catalytic converter could cause this issue?

 

Don't think so. A plugged converter will make the engine run much worse at high engine loads and RPMs. At idle your engine isn't breathing much air, so an exhaust restriction wouldn't be as big of deal unless totally obstructed.

 

not the catalytic... its would act like a potato is stuck in the tail pipe... OK idle. bad at speed.

throttle body need cleaning? bad PCV valve aka sticking when cold...

 

Did you ever find out what was causing it to stall at cold start. My 2011 f-350 6.2l has been doing the same thing for a long time. I have replaced the canister purge valve, I have done a full tune up-all factory plugs, I have replaced my cats, I have got a custom tune from 5 star. All with no change to how it starts. Mine cranks forever before it fires, sometimes it cycles 2 times before it will fire. Then it might stall it might not or I put it in reverse to leave and then it will stall. My next step is a Pcv valve, I have one coming from ford today. But if you have fixed yours please let me know

 

Come to the conclusion that mine won't run right on premium 91 octane fuel.

 

I replaced my Pcv valve and it didn't change anything. The one I replaced was probably just fine. Since that didn't work I decided to clean all my injectors. It took me all day but it seemed to help. Starts right up but time will tell. I had one injector that was completely clogged up, I don't see how it could have possibly been working at all! The sediment looked like tiny white crystals, and after I drained the rail, there was more rattling around inside the fuel rail so I had to clean that out too. I made a cool setup with a 6v lantern battery and a momentary switch with pin connectors to hook to the electrical plug points on the injector and a piece of 3/8" fuel hose and hose clamps to a syringe. I pushed cleaner through the injector with the syringe as I pulsated the injector via the momentary switch. I used about a half gallon of berrymans chem-dip carb and parts cleaner. Then I pushed compressed air through the injectors to remove all the cleaner and reinstalled after clean. All my parts were less than $75.00. Anyway, you might try and manually clean your injectors if you or anyone else is having this problem. My truck didn't have any set codes and I know for a fact that at least one of my injectors were clogged!

 

Have you determined if the fuel injector cleaning solved your issues? I have about 58K miles and had an idle throttle control failure. The dealership fixed that, but once winter arrived, Ive noticed the same sympton you have. Once the engine is warm, the problem does not happen. further when the temps are above 55F or so, it does not occur. Dealership has had it several times and cant find the problem, two catalytic converters and all O2 sensors later, no help.