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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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  #1  
Old 12-29-2008
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Icon4 4.0 skip/misfire/bucking

i have heard afew of these engines have this problem. i just happen to have one that does it too. the guy i bought my truck from says the truck did it since it was almost new (idk why he didnt take it back to ford while it was still under warranty) but anyways in the lower rmps like anything under 2,000 it makes this sputtering noise while it idles. when i drive it it bucks alot until it either let off the gas or push it harder. i have replaced the plugs, wires, coil pack, cleaned the k&n. everything was stock on the truck when i got it by the way so whenever i added the k&n and throttle body spacer it didnt change anything. but i found on the ranger forums that i should clean the MAF. i did. it seemed better for a few minutes but maybe it was just me though. not sure. but what else could be the problem? should i get a new MAF? im stuck on this one. i hate not bein able to drive it with out it jerking at a steady speed.
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Old 12-29-2008
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I'm thinking it's electrical in nature. Usually a hard miss or stuble is.


I'd start off with two things.
1) Disconnect, clean with spray electrical contact cleaner, and apply some dilectric grease to the main wiring harness connections. Especially where the PCM connects to it. Might also do the MAF connector and the Crank position connection, as well as the cam position sensor connector.

2) Disconnect the battery, turn on the headlights, wait 3-5 minutes, turn off lights, and reconnect. Then put it through the idle learning process and see how it runs.

That will only cost you $5 and will rule out a whole lot of problem areas. (especially if it's not setting a code)

If those don't help... I'd next look into replacing the crank and cam position sensors.

Rich
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Old 12-29-2008
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for 1) what is the PCM and where is it and where is the wiring harness?

for 2) what is disconnecting the battery and turning on the light going to do or show me?
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Old 12-29-2008
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The PCM is on your firewall at the top.

Resetting the PCM (and KAM) will force the PCM to re-learn everything. Everything from idle, tranny functions, and adaptive learning stratagies.

Since you say its been doing it for a long time.. I suspect its a bad connectoion and/or the crank position sensor. But I also like to do the cheapest and easiest things first. Making sure the connections are good and the PCM is cleared will give you a solid base to start from.
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Old 12-29-2008
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so i just need to unplug it and spay the cleaner in it and let it dry then plug it back in? and disconnect the battery while i do it?
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Old 12-29-2008
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Yep.. battery first. (forgot to mention that)

Spray electrical cleaners don't leave a residue.

And don't put too much dilectric grease on them Just a very small dab of it on each little hole or plug. You don't want so much on there that electricity might flow between two circuts. Just a little dab with a toothpick.

Rich
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  #7  
Old 01-24-2009
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Same

Same crap happening tp my 4.0, just started doing it 2 weeks ago
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Old 01-24-2009
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Same here buckleing problem but i was told it is my EPC

https://www.ranger-forums.com/forum2...ht=trans+thump
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Old 01-24-2009
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My bucking was caused by a leak in my air-box lid. Zip-tie fixed it, to the tone of $300 from ford to find the problem.
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Old 01-24-2009
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could be a fuel delivery issue. did you try and change a fuel filter??
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Old 01-24-2009
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mine done that sometimes i replaced the intake gaskets and it fixed her right up
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Old 01-24-2009
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Have you ruled out an EGR problem?

Just pull the vaccum line of the egr valve, plug it and drive it like that for a few days.
Ignore the CEL (you WANT the PCM to see bad egr). I've seen a DPFE cause bucking at very light throttle pressure, just maintaining speed.
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Old 01-24-2009
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Try Changing your Fuel Filer. Where do you normally fill up?
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Old 01-24-2009
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Both of my trucks used to do this.
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Old 01-24-2009
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Quote:
Originally Posted by Earl43P View Post
Have you ruled out an EGR problem?

Just pull the vaccum line of the egr valve, plug it and drive it like that for a few days.
Ignore the CEL (you WANT the PCM to see bad egr). I've seen a DPFE cause bucking at very light throttle pressure, just maintaining speed.
i havent even messed with the thing lately. lets say i pull that (which i did before but only for a min. because i wasnt sure what it could mess up) what will happen if thats the issue? what am i looking for? the truck has always done if w/ me and the guy i bought it from so i pretty but am lost on the problem. but by the way it does do it at light throttle pressure and at idle.
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Old 01-24-2009
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Quote:
Originally Posted by Blackonblackfx4 View Post
Try Changing your Fuel Filer. Where do you normally fill up?
it was changed before i bought it. the guy i bought it from lives next door to me and he told me it never quit.
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Old 01-24-2009
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Quote:
Originally Posted by Crunchy View Post
My bucking was caused by a leak in my air-box lid. Zip-tie fixed it, to the tone of $300 from ford to find the problem.
no problem there. did it w/ the stock air box and does it w/ the K&N intake
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  #18  
Old 01-24-2009
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Filter

Quote:
Originally Posted by 07rangersport View Post
could be a fuel delivery issue. did you try and change a fuel filter??

Fuel filter here on my desk., gonna do the change in the morning, also bought the little tool to remove clips from Auto Zone.
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Old 01-25-2009
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Quote:
Originally Posted by yfzman450 View Post
i havent even messed with the thing lately. lets say i pull that (which i did before but only for a min. because i wasnt sure what it could mess up) what will happen if thats the issue? what am i looking for? the truck has always done if w/ me and the guy i bought it from so i pretty but am lost on the problem. but by the way it does do it at light throttle pressure and at idle.

http://free-auto-repair-advice.blogs...gr-system.html

http://www.tomco-inc.com/Tech_Tips/ttt36.pdf


What'll hapen is the PCM SHOULD see a problem with EGR. The CEL will illuminate, a code will set and the truck will run without the EGR vavle opening (Because you disconnected it- it CAN'T open).

If it runs without the surging, you have an EGR problem.

You can reset the CEL by disconnecting the battery and turning on the headlights.
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Old 01-25-2009
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Quote:
Originally Posted by Earl43P View Post
http://free-auto-repair-advice.blogs...gr-system.html

http://www.tomco-inc.com/Tech_Tips/ttt36.pdf


What'll hapen is the PCM SHOULD see a problem with EGR. The CEL will illuminate, a code will set and the truck will run without the EGR vavle opening (Because you disconnected it- it CAN'T open).

If it runs without the surging, you have an EGR problem.

You can reset the CEL by disconnecting the battery and turning on the headlights.

CEL isnt a problem, i got access to a scaner. already got A CEL anyway so it wouldnt make a difference to me. well im bout to go to advance for my ball joints. ill pull it off and see how it does.
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  #21  
Old 01-25-2009
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that fixed it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!
so what do i need to replace now?
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  #22  
Old 01-25-2009
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Wait what fixed it??
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  #23  
Old 01-25-2009
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Quote:
Originally Posted by Ford04Ranger4.0 View Post
Wait what fixed it??


i'd like to know that as well
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  #24  
Old 01-25-2009
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Icon13 EGR Valve-Just exactly where is it located????

I put on the new fuel filter, Cleaned the MAF and I still have the Bucking/skip stuff., From what I am reading here I need to deal with the EGR. I looked and looked but could not find it. The Delta valve is on the LH Fender is see the hoses from that point. There was a 9.5mm vacuum hose that goes to the air intake just behind the TPS and it was in preety bad shape(9 years old), so that has been replaced. I know what an egr looks like and am very familiar with them but i cant seem to find it. could it be under that coil pack thing?
Am i blind???
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  #25  
Old 01-26-2009
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the EGR thing fixed it. i unpluged it and it dont do it now. so what do i need to replace?
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