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  #16  
Old 12-21-2016, 12:40 PM
cowboybilly9mile cowboybilly9mile is offline
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Default Re: Running extremely rough after being driven.

Quote:
Originally Posted by Laidout98 View Post
Howdy folks,

My 1994 4.0L runs great from cold crank to my destination ...... ...... I turn the truck off for about 5-10 minutes and go to crank it up again, it runs EXTREMELY rough as if someone pulled a spark plug off. If I feather the throttle and hold it around 2500 rpm (I know I will be scolded for that) for a matter of about 5-10 seconds, it smooths out as if no problem existed.
^^^ This is indicative of flooding, and right at the top of the list of common causes on engines of your vintage would be caused by failure of the FPR.

Quote:
Originally Posted by cowboybilly9mile View Post
Knowing the history on causes of the problem, first thing I would do would be to check the FPR to make sure the diaphragm hasn't ruptured. To do this takes less 60 seconds.
^^^ See the word, "history" and the words "check the FPR to make sure the diaphragm hasn't ruptured" up there?

Quote:
Originally Posted by cowboybilly9mile View Post
The regulator, your symptom is consistent with a failing FPR. A failing FPR DIAPHRAGM can/will produce the problem you've got, yet it runs great as you described and it will pass a pressure test. A leak causes fuel to bleed into the vac line and then the intake, and they act flooded when trying to start a warm engine. The only thing needed to test for this is your nose.
There is the explanation as to what failure of this part does. Flooding normally = hard start, but the BIG clue/hint/observation to take note of on yours is that it only happens on a warm engine, not a cold start (per your first post).

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Originally Posted by Laidout98 View Post
Update -
I replaced the FPR with the motorcraft replacement part. When in with ease. Drove the truck for a couple of days and no change. I have not smelled fuel as of yet though.
Any other ideas out there? The symptoms are the same since the part has been replaced.
Never did hear if you TESTED this part BEFORE replacing. If it tested good, I'd have pointed you on to another quick way to check for suspected flooding on a warm engine. With very few exceptions, never buy parts without knowing that the part you are replacing will take care of the concern; it's both a waste of money and time.
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Last edited by cowboybilly9mile; 12-21-2016 at 12:47 PM.
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  #17  
Old 12-21-2016, 08:07 PM
smif smif is offline
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Default Re: Running extremely rough after being driven.

I have a similar problem, only my 04 Ranger runs rough when in neutral with the throttle fully pressed it will only turn 3200 RPM and surges. The exhaust smells like it is running rich. The CEL is on and the code says there is a misfire on cyl 4. When on the highway it seems to accelerate well with no surging or missing. I forgot to mention this is a 3 L engine 2WD auto trans. Could this be a MAF sensor problem?
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  #18  
Old 12-21-2016, 08:13 PM
Jswifto Jswifto is offline
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Quote:
Originally Posted by smif View Post
I have a similar problem, only my 04 Ranger runs rough when in neutral with the throttle fully pressed it will only turn 3200 RPM and surges. The exhaust smells like it is running rich. The CEL is on and the code says there is a misfire on cyl 4. When on the highway it seems to accelerate well with no surging or missing. I forgot to mention this is a 3 L engine 2WD auto trans. Could this be a MAF sensor problem?
The computer is not allowing to over rev it in neutral
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Last edited by Jswifto; 12-21-2016 at 08:16 PM.
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  #19  
Old 12-27-2016, 08:48 AM
txoutback txoutback is offline
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Default Re: Running extremely rough after being driven.

I have the same exact same issue on my 96 4.0L. I have replaced the fuel filter, and also cleaned the plug harness at the MAP sensor with de-oxidiser. No improvements so far. I'm going to try the FPR next.
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  #20  
Old 12-27-2016, 09:38 AM
cowboybilly9mile cowboybilly9mile is offline
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Default Re: Running extremely rough after being driven.

^^^ Suggestion RE FPR....before replacing, after driving, let the vehicle sit for 5-15 minutes and pull offf the vacuum line leading to the FPR. Now smell that line for the presence of gas as well as look for dampness. There should be no fuel odor or dampness/wet, ever. If there is, you've found the reason for hard starts on a warm engine.
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  #21  
Old 12-28-2016, 08:43 AM
txoutback txoutback is offline
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Default Re: Running extremely rough after being driven.

Quote:
Originally Posted by cowboybilly9mile View Post
^^^ Suggestion RE FPR....before replacing, after driving, let the vehicle sit for 5-15 minutes and pull offf the vacuum line leading to the FPR. Now smell that line for the presence of gas as well as look for dampness. There should be no fuel odor or dampness/wet, ever. If there is, you've found the reason for hard starts on a warm engine.
Nice, thanks for the tip. I'll check it out.
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  #22  
Old 12-28-2016, 03:33 PM
matthewavogt matthewavogt is offline
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Default Re: Running extremely rough after being driven.

my truck did this exact same thing a few years ago. It would run great cold or hot but if you let it sit for a few min it ran like turd till it warmed back up. After wasting hours upon hours fixing not broken parts I discovered that I had a vac leak. Ended up pulling the intake and replacing the gasket. I also did a bunch of other stuff while I was in there but the new gasket fixed my old truck
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  #23  
Old 12-28-2016, 04:00 PM
txoutback txoutback is offline
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Default Re: Running extremely rough after being driven.

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Originally Posted by matthewavogt View Post
my truck did this exact same thing a few years ago. It would run great cold or hot but if you let it sit for a few min it ran like turd till it warmed back up. After wasting hours upon hours fixing not broken parts I discovered that I had a vac leak. Ended up pulling the intake and replacing the gasket. I also did a bunch of other stuff while I was in there but the new gasket fixed my old truck
The gasket at the manifold or at the TB?
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  #24  
Old 12-28-2016, 08:54 PM
matthewavogt matthewavogt is offline
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Default Re: Running extremely rough after being driven.

Upper and lower intake manifold gaskets. I also changed the valve cover gaskets because why not and replaced the o rings on the injectors and cleaned them again because I was in there but that ultimately was the resolution to my problem. I had tried everything to resolve this problem and finally this fixed it. It took a good day to do it all but I also cleaned in the intake and tb as well as replaced a bunch of other stuff it didn't need simply because I was in there. Spark plugs are way easier to do with the friggen intake out of the way
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  #25  
Old 12-30-2016, 01:05 PM
txoutback txoutback is offline
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Default Re: Running extremely rough after being driven.

I've tried to smell around on the FPR hose, but no luck. The conditions weren't warm though. I also found one hose that was a little loose and pushed it on. I then checked around for a vac leak with carb cleaner but no luck. I'm going to carry some carb cleaner in the truck and try it out on the spot next time I have the issue occur...and I'll sniff the FPR hose too.
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  #26  
Old 12-30-2016, 10:20 PM
matthewavogt matthewavogt is offline
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Default Re: Running extremely rough after being driven.

I know with mine the carb cleaner didn't work. I knew it has to be a vac leak but couldn't find it. I don't remember how we came to the conclusion it was intake gaskets but it was the correct conclusion. Oh and by the way... 2 year it took me to figure it out. Drove me Fricken nuts
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Last edited by matthewavogt; 01-01-2017 at 06:59 AM.
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  #27  
Old 12-31-2016, 09:10 AM
txoutback txoutback is offline
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Default Re: Running extremely rough after being driven.

I was looking at how to do the upper intake gasket. Seems pretty straightforward, and like you did, there's plenty of "while you are at it" stuff that can be done.
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  #28  
Old 12-31-2016, 09:15 PM
matthewavogt matthewavogt is offline
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Default Re: Running extremely rough after being driven.

Yeah I replaced a bunch of crap simply because the parts were cheap and it was much easier with the intake off.
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  #29  
Old 01-12-2017, 10:50 PM
Laidout98 Laidout98 is offline
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Default Re: Running extremely rough after being driven.

Pulled the IAC, used carb cleaner and cleaned it out, let it dry, reinstalled it and let the truck run and warm up. Shut it off for about ten minutes and cranked it up. Still ran rough.
DangerRanger37 - what should I expect the truck to do if I pull the plug on the IAC?
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  #30  
Old 01-13-2017, 08:25 AM
mxpxpunkrock1987 mxpxpunkrock1987 is offline
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Default Re: Running extremely rough after being driven.

i had the same issue recently vacuum lines cracking and replaced intake gaskets. but in all the mis fire was do to the cam and crank sensor usually starts with one cylinder and then to the next. but i went though changing plugs fuel filter oil iac valve clean the mas flow sensor and it came down to them two sensor cam and crank. these 6 cyl are fun aren't they
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