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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 01-29-2007
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4.0 ohv headaches

I've got a 2000 Ranger X-cab 4x4, 4.0 ohv, auto w/ 63k miles I about ready to drive off a cliff. Perrformance is decent, but gas mileage is bad and all over the place. It idles rough and occasionally wants to die when idling and sometimes won't start. It's always idled rough, but the dying is new. Seems on average its around 12-14, 60% town, 40% highway. It's dropped as much as 11-12 and gone as good as 15-16. Worst I've got out of it was 10mpg, best was about 20 (drove to Detroit one weekend and back). I've put new plugs, wires & air filter in it. Had new cv joint and u-joints put in last summer. At the time, it would miss hard every now and then when the A/C is on. Garage looked at it and couldn't duplicate the problems. My driving style is moderate, not always jamming the gas to the floor, but usually one of the first off a light. No towing or junk in the back. My wife can do better by maybe 1mpg when she drives it. My only other refernce is our '99 Explorer (4x4, 4.0 sohc, auto) which usually does about 15-16mpg in town and about 18-20 highway. Its fairly constant.
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Old 01-29-2007
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check the IAC (Idle Air Control).....it is attached to the side of the upper intake on the driverside.........that is most likely your problem.......if you have a repair manual you can look in there to find were it is located......when you find it, you can unplug it and if the truck doens't change the way it is running (really if it doesn't quite running) then that is the problem.....they run about $100 from an auto parts house....
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Old 01-29-2007
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but that is idle only maurice.

have you changed the fuel filter? cleaned the MAF? You can clean the IAC as well.

new air filter? might try one of those new coil packs as well.

on a side note when is the last time the battery has been disconnected?
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Old 01-29-2007
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Quote:
Originally Posted by zabeard
but that is idle only maurice.

have you changed the fuel filter? cleaned the MAF? You can clean the IAC as well.

new air filter? might try one of those new coil packs as well.

on a side note when is the last time the battery has been disconnected?
ahhhhh yes......but seems that 95% of his problems are at idle.........

check your plugs and make sure that you dont have a "dead" plug....it is possible even though they are new plugs (speaking from experience, just had that happen to me), then check your compression....if you have even a slight loss in compression, you lose power, which inturn means a loss in fuel milage...
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Old 01-29-2007
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new air filter. Doubt its the plugs. It didn't change the way it idles at all when we swapped them and the wires out last fall. I've had 2 other 4.0 ohv (both '94 2wd 5spd) and remember them idling a little rough, but not this bad. The tach doesn't jump around, but you can feel the truck shake and the motor twitches like fresh roadkill that's not quite dead...

Haven't unhooked the battery recently. I did when I bought it 6 moths ago to swap out the radio and again about a month later to pull the radio (cd player died). Actually, we may or at least should have unhooked it in Sept. when we changed the plugs.

Haven't cleaned the MAF or changed the fuel filter (too cold now). If I pound on the accelerator, it takes off happily without hesitation. The engine under load seems ok. I did have trouble last summer with it missing and bucking a bit at highway speeds with the A/C on, but haven't noticed it lately. Granted, you don't run the A/C in 15 degree weather, but it runs ok witrh the defrost on (kicks on the A/C w/ defrost, right?) What about a vacuum leak somewhere?

Last edited by sams dad; 01-29-2007 at 09:33 AM.
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Old 01-29-2007
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Had the same problems with mine.....Changed the EGR, IAC, all upper intake gaskets, fuel filter, injector O-rings, Cleaned MAF, changed plugs,wires, and another sensor I can't remeber what it was called it's on the intake next to the IAC. Now my truck runs great and I get about 17-19mpg.
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Old 01-29-2007
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Quote:
Originally Posted by sams dad
new air filter. Doubt its the plugs. It didn't change the way it idles at all when we swapped them and the wires out last fall. I've had 2 other 4.0 ohv (both '94 2wd 5spd) and remember them idling a little rough, but not this bad. The tach doesn't jump around, but you can feel the truck shake and the motor twitches like fresh roadkill that's not quite dead...

Haven't unhooked the battery recently. I did when I bought it 6 moths ago to swap out the radio and again about a month later to pull the radio (cd player died). Actually, we may or at least should have unhooked it in Sept. when we changed the plugs.

Haven't cleaned the MAF or changed the fuel filter (too cold now). If I pound on the accelerator, it takes off happily without hesitation. The engine under load seems ok. I did have trouble last summer with it missing and bucking a bit at highway speeds with the A/C on, but haven't noticed it lately. Granted, you don't run the A/C in 15 degree weather, but it runs ok witrh the defrost on (kicks on the A/C w/ defrost, right?) What about a vacuum leak somewhere?
i had the EXACT same problem you are stating.....DON'T DOUBT THAT IT IS THE PLUGS!!! trust me on that I am speaking of experience within the last month.......had 6,000 miles on my plugs i changed....

doubt it is a vaccum leak, but there is a diagram on the header panel that you can trace all of the maybe 8 vaccum lines and see if there is a leak.....


let me tell you what was done to fix mine:
- changed plugs (only had 6,000 miles on the plugs that were removed, but the ones removed were the wrong ones)
- installed new Screamin' Demon coil pack (it is cheaper than a stock Motorcraft or any other brand that an auto parts place will sell by about $50)( http://www.stuffforyourranger.com/st...roducts_id=162 )
- gapped new plugs out to .065"

The coil pack and larger gap plugs smoothed out my 4.0 OHV....had better throttle pick up and so far i am getting a slight better fuel economy....

if you want the A/C compressor to stay off in the winter time whenever you turn on the defroster or any other setting that the A/C compressor comes on with (the mix setting also runs the A/C compressor), take out the temp controlls and find a SOLID PURPLE wire, cut it, and put in a SPST (simple on/off) switch.....in the on position, the A/C compressor will work as normal, and in the off position the A/C compressor WILL NOT come on whenever you select the defrost or any other setting that the compressor runs on.......HOWEVER you will need to turn it on atleast 1 time a month to lubericat the o-rings and seals in the A/C compressor....

I am serious though, you could have a dead plug or a fouled plug, even though the plugs don't have that many miles on them. Like I said above, the plugs I removed from my truck only had 6,000 miles on them and 1 was dead and 1 was fouled...
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  #8  
Old 01-29-2007
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next warm day I get I'll check the plugs. If they are bad, what is recommended? I don't remember what we put in, but I think they were some kind of platinum tips.
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  #9  
Old 01-29-2007
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get Motorcraft plugs and put in it.....REPLACE ALL 6 PLUGS!!!.....and double check in your owners manual to see if they sold you the correct plugs if you have Motorcraft plugs in it now....if not, take the part# in the owners manual and go to a dealership and tell them that is what you want......they will run you about $7-$8 a plug for the correct ones.....
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Old 01-29-2007
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i get ****ty gas milage too.. i hate it
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  #11  
Old 01-29-2007
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I would also try buying gas from a different place OR stick with only 1 place.

I HAVE to run 93 or higher in my truck ( Program and compression ). Mobil's 93 pings like a popcorn machine, Citgo's causes all sorts of bad detonation, Sunoco 93 runs beautifully.

You might want to toss in a bottle of STP fuel system treatment/cleaner ther next time you top off the tank. It can't hurt.
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  #12  
Old 01-29-2007
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I run a upper cylinder lubricant made by lucas, it helps smooth the idle a bit. Put it in the fuel to lube the upper cylinders.
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