Missing under light to medium load and idle
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Freshman User
Joined: Mar 2005
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From: Brockville, Ontario
Missing under light to medium load and idle
My 93 F150 with 5.0 misses when going uphills and accelerating from a stop. It feels as though it shut down for a split second then goes again giving quite a jerk. It does this at random sometimes a few in a row sometimes just one or two up a grade. If you depress the throttle to pass all is fine. Also when it is doing it very often and you come to a stop the idle will be low and rough. The only other symptom is if you shut the truck down for 10 to 15 minutes and restart it, the idle sometimes will be very low (under 400 RPM) and rough. Truck is tuned up with all new Motorcraft parts and shows no codes. When it is idling rough you cannot hear it missing so I do't think it's an ignition problem. If anyone else has cured a problem like this I would love to hear about it.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Maybe a bad spot in the TP sensor. Check the voltage over the entire range (about .95V to 4.95V). It has a 5V supply from the PCM.
Check out this URL.
http://fordfuelinjection.com/index.php?p=30
Check out this URL.
http://fordfuelinjection.com/index.php?p=30
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Freshman User
Joined: Mar 2005
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From: Brockville, Ontario
The TPS is new and was checked for proper output. I will check it again. There is one other symptom that happens and that is when you put the truck in park the engine speeds up to 1100 RPM or so then slowly reduces down to normal of around 750 RPM.
It did not used to do this. The IAC has also been switched with a known good unit and the throttle body is clean and base idle is properly set. The EGR is also clean and has been leak tested.
The engine has been checked for vacuum leaks.
Thanks, Cleat
It did not used to do this. The IAC has also been switched with a known good unit and the throttle body is clean and base idle is properly set. The EGR is also clean and has been leak tested.
The engine has been checked for vacuum leaks.
Thanks, Cleat
Fleet Owner
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From: Easton,Ks
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Freshman User
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From: Brockville, Ontario
There are no codes just 111 for KOER and 111 for Key on engine not running and no codes in memory. Computer seems happy, truck starts right up in the worst of weather and runs great until it warms up then the missing starts or you might call it bucking. I wonder if I have a mechanical problem like a bad timing chain , valves, injectors ? there is no noise, truck is very quiet but it does have 206000 KM (128,000 Miles) so I guess anything could be worn out. Compression was also good I can't remember the numbers off the top of my head (I checked it in the summer) but it was good and even across all 8 cyl.
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Freshman User
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From: Brockville, Ontario
I'm not sure, it's an auto with the OD lockout on the end of the shifter. It also has the electric pushbutton 4x4 if that makes a difference.
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Fleet Owner
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From: Easton,Ks
Originally Posted by cleathumphrey
I'm not sure, it's an auto with the OD lockout on the end of the shifter. It also has the electric pushbutton 4x4 if that makes a difference.
If not, your distributor bushings may be wore and giving you distributor wobble that can give you this problem.
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Freshman User
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From: Brockville, Ontario
I would think possible but it has a rough missing idle as well and it does not sound it from the exhaust as you cannot hear the puts of a miss but you can feel it and see the engine rock around as well. If the trans is going I will probably junk the truck as it has some rust and high miles so it's value is very low.
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From: Easton,Ks
Originally Posted by cleathumphrey
I would think possible but it has a rough missing idle as well and it does not sound it from the exhaust as you cannot hear the puts of a miss but you can feel it and see the engine rock around as well. If the trans is going I will probably junk the truck as it has some rust and high miles so it's value is very low.
Another post on here had similar problems that nobody could figure out and after the PIP pulse was looked at with a scope he had wobble and a new distributor fixed it.
Here is the post.
https://www.ford-trucks.com/forums/s...=434356&page=2
Last edited by subford; Dec 12, 2005 at 11:13 AM.
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Heyy! i have a 5.8 with an automatic and mine does the exact same thing. My computer pulled up 02 sensor codes and a egr not opening code. I took out the 02 sensors when i changed the exaust and it doesnt seem to buck as much but it does miss almost everytime i start from stop. and i took it to a trans shop and they said the trans was perfect and they said the only codes they got were engine fuel related
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From: Brockville, Ontario
Found the problem. Truck was running terrible coming home from work 2 nights ago so when I got home I opened the hood right away with the engine running and the snap snap sound of high voltage was very clear. The front left spark plug boot has a tiny hole in it. Remember, these wires are practically brand new must be a defect. Replaced plug wire with an old one I had kicking around that seemed good and put in a new Motorcraft plug and all is well. I have driven it to work 2 days now (with temps at -24 degrees C or -10 degrees F I might add) and truck is running perfect, not a miss, silky smooth idle, and better power not that I push it too hard at these temps. I've owned this truck for 6 years and although the bucking just started a few weeks ago it has never idled right. Thanks for the input and I'm glad it finally runs right.
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Glad to hear u fix it without costing too much. For the past month or so mine was doing it very bad.. i thought it may have been the cold weather but all of a sudden i didnt start it for 2 days and i thought it was running wierd but it was running correct without hesitating. It ran perfect for 2 days and now it still runs good with the occasional bucking/hesitating
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Joined: Oct 2005
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well mines back to acting crappy again. ill check my plugs and stuff. i hear a small clicking in the engine area when its on. its not a ticking like the manifolds when their leaking but something else could it be the noise of electricity jumping from the spark plug out?