Starts very rough then smooths out nicely - F-Series & SuperDuty Diesel Forums

BigRedWeather · 01-15-2012, 01:17 PM

WHEN IT HAPPENS: sometimes in cold weather, but many times in cold weather it does not happen. It just seems to happen when it wants to, not because of any set of confitions.

WHAT HAPPENS: The truck will start and run kind of rough, like it is missing 2 cylinders, or very rough, like it is missing 5 cylinders. The amount of power it has corresponds to how many cyliners (imagine that!) it seems to be running on. When it is very rough, I have to put it in 4 wheel Lo to back it out of my gently sloping driveway.

WHEN IT STOPS: After I have driven for about 5 minutes at up to 2000 RMP it will run smooth as silk with all the power it normally has. It will do 90 on the interstate easily.

My injectors have 150k to 200k miles on them. I can't understand why they would operate so poorly and then run so smoothly.

It only runs rough for 5 minutes after I have started it.

Any ideas?

Thanks,

BigRedWeather

Tim4R · 01-15-2012, 04:10 PM

I have an idea that your oil is too old/too cold/too thick. Rotella T6 5w-40 cured that in mine. Yeah, it stinks to pay $25.00/gallon for motor oil but my truck is happier.

BigRedWeather · 01-15-2012, 05:01 PM

Hmmm. I run Rotella 15W40 (certainly thicker), and it is at 3500 miles. I change it every 5000. Since cold weather would make it thicker, I would think I would have this problem every time it gets cold, but I don't.

I have thought like you did, that this problem sounds like the fuel or oil (and hence the fuel) not getting to the injectors at the right pressure or volume. That could make it put only 20% of the fuel in the cylinders that was needed and cause the very rough running. But I don't know what would cause that under the conditions I mentioned. If this is the scenario when the engine heats up, or oil thins out or the stars line up, it runs smoothly with full power again.

Thanks for your post.

BigRedWeather

94f450sd · 01-27-2012, 07:47 AM

Your oil is fine.shouldn't being running anymore but 15/40.try cleaning the fpr screen if you haven't already.

BJS · 01-31-2012, 07:05 AM

I'm going to hazard that you have some poor connections at either the VC gasket or in the UVC Harnesses going to some glow plugs or possibly the injectors and once it warms up those poor connections make contact

01-15-2012, 01:17 PM	#1
BigRedWeather SDD Member Join Date: Sep 2006 Location: Richmond, KY Posts: 62 Thanks: 0 Thanked 0 Times in 0 Posts	Starts very rough then smooths out nicely WHEN IT HAPPENS: sometimes in cold weather, but many times in cold weather it does not happen. It just seems to happen when it wants to, not because of any set of confitions. WHAT HAPPENS: The truck will start and run kind of rough, like it is missing 2 cylinders, or very rough, like it is missing 5 cylinders. The amount of power it has corresponds to how many cyliners (imagine that!) it seems to be running on. When it is very rough, I have to put it in 4 wheel Lo to back it out of my gently sloping driveway. WHEN IT STOPS: After I have driven for about 5 minutes at up to 2000 RMP it will run smooth as silk with all the power it normally has. It will do 90 on the interstate easily. My injectors have 150k to 200k miles on them. I can't understand why they would operate so poorly and then run so smoothly. It only runs rough for 5 minutes after I have started it. Any ideas? Thanks, BigRedWeather __________________ 97 F350, 7.3L diesel, 5 speed, 4 X 4, crew cab, 226,000 miles. No mods.

01-15-2012, 05:01 PM	#3
BigRedWeather SDD Member Join Date: Sep 2006 Location: Richmond, KY Posts: 62 Thanks: 0 Thanked 0 Times in 0 Posts	Hmmm. I run Rotella 15W40 (certainly thicker), and it is at 3500 miles. I change it every 5000. Since cold weather would make it thicker, I would think I would have this problem every time it gets cold, but I don't. I have thought like you did, that this problem sounds like the fuel or oil (and hence the fuel) not getting to the injectors at the right pressure or volume. That could make it put only 20% of the fuel in the cylinders that was needed and cause the very rough running. But I don't know what would cause that under the conditions I mentioned. If this is the scenario when the engine heats up, or oil thins out or the stars line up, it runs smoothly with full power again. Thanks for your post. BigRedWeather __________________ 97 F350, 7.3L diesel, 5 speed, 4 X 4, crew cab, 226,000 miles. No mods.

01-27-2012, 07:47 AM	#4
94f450sd certified nutjob Join Date: Oct 2005 Location: plymouth,ma Posts: 2,275 Thanks: 23 Thanked 27 Times in 26 Posts View Photos By: 94f450sd	Your oil is fine.shouldn't being running anymore but 15/40.try cleaning the fpr screen if you haven't already. __________________ RICH my pictures 95 F350 XLT,automatic,CC,dually 2WD,fully loaded.,328,000miles.Dana HD70 rear with 4.10 gears,trans temp,pyro,and boost gauges on the pillar.3" down pipe.TS 6 pos.chip with the crazy TWILDMAN programs!!,.intercooled,DIY tymar,monsterbox E4OD, BDP stage 2s,BDP fuel system,stealth HPOP from BDP powered by,Beans diesel performance old best,15.340@86.93MPH new best,15.079@91.53MPH 367HP,not running 100% poor mans onboard air,wannabe train horns and hadleys on the roof 72 pontiac lemans GT37

01-31-2012, 07:05 AM	#5
BJS SDD Senior Member Join Date: Apr 2005 Location: Jacksonville, FL Posts: 1,498 Thanks: 4 Thanked 141 Times in 134 Posts	I'm going to hazard that you have some poor connections at either the VC gasket or in the UVC Harnesses going to some glow plugs or possibly the injectors and once it warms up those poor connections make contact __________________ Brandon 95 F350 Centurion Conversion Bronco (Crew Cab SRW) 4X4 4.10, Isspro Performax Boost, Pyro, & trans temp on the A-pillar, BDP Stage 1 injectors, Open air intake, Dpp Downpipe, Self built E4OD with parts from Racer-X, Tony Wildman Chip, Early '99 Intercooler.

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01-15-2012, 04:10 PM	#2
Tim4R SDD Junior Member Join Date: Dec 2011 Location: Hub City, MD Posts: 4 Thanks: 1 Thanked 1 Time in 1 Post	I have an idea that your oil is too old/too cold/too thick. Rotella T6 5w-40 cured that in mine. Yeah, it stinks to pay $25.00/gallon for motor oil but my truck is happier.