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94 Ranger 4.0 shakes under a load

  #1  
Old 04-28-2011, 08:17 PM
JimmyDoodle
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94 Ranger 4.0 shakes under a load

I have changed the fuel filter, new plugs and wires, cleaned the MAF sensor, cleaned the throttle body with spray, I am open to hear from anyone who has experience this symptoms and fixed it, the engine idles and revs up fine but when I put it in gear and take off it doesn't feel like it hitting on all cylinders, and if you shift before the rpms are up to snuff it feels like and sounds like a diesel and shakes like a U joint is bad, but its not I replaced those a year ago. It just plain runs like crap when you mash the throttle under a load. Any help would be greatly appreciated, thank you in advance. Jimmy
 
  #2  
Old 04-28-2011, 10:02 PM
kev03
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try cleaning the idle air control valve

the idle air control valve is located on the top left side of the intake, my 94 4.0 was running rough and I changed it out with a used one I cleaned and it runs great now.
 
  #3  
Old 04-28-2011, 10:50 PM
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Originally Posted by kev03 View Post
the idle air control valve is located on the top left side of the intake, my 94 4.0 was running rough and I changed it out with a used one I cleaned and it runs great now.
I removed the IACV cleaned it and its still the same, it doesn't run rough when it idles only runs crappy under a load, like if you lug it a little it shakes and shutters and feels like its running on 3 cylinders. Thanks anyways.
 
  #4  
Old 04-28-2011, 10:55 PM
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have you checked for spark on all 6 cylinders. and whats your MPG like i get about 17 or 18 and i got the same truck but extra cab and 4x4. becasue if your geting really bad mpg then you motor is running to rich will make it bog and shutter like that, but its EFI so it shouldnt make it that bad, but check for spark
 
  #5  
Old 04-28-2011, 10:58 PM
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Originally Posted by Dutter View Post
have you checked for spark on all 6 cylinders. and whats your MPG like i get about 17 or 18 and i got the same truck but extra cab and 4x4. becasue if your geting really bad mpg then you motor is running to rich will make it bog and shutter like that, but its EFI so it shouldnt make it that bad, but check for spark
Yes Dutter I check for spark when I put new plugs and wires on it, pulled each wire off the coil and saw a good blue spark out of each one. I think my MPG is sucking.
Jimmy
 
  #6  
Old 04-28-2011, 11:12 PM
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Alright, well then the only thing i can think of is the motor is running really rich, try to get the numbers ran and see what turns up,, but is you temp gage barley gos past cold then you need a new thermostat, and that will give alot better mpg, and if the motor is running cold it will run rich but no so much that youd feel it bogging, but its something to check and may help the problem
 
  #7  
Old 04-28-2011, 11:45 PM
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Have you pulled any codes? There are stored and pending codes in the computer.

Josh
 
  #8  
Old 04-29-2011, 03:33 AM
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Originally Posted by Bullitt390 View Post
Have you pulled any codes? There are stored and pending codes in the computer.

Josh
Yes, Autozone put there little hand held that fits in the connector under the hood and it pulled a #11 code, which he said it says everything is fine. This is frustrating.
Jimmy
 
  #9  
Old 04-29-2011, 03:33 AM
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I put a new thermostat in it 2 months ago.
Jimmy
 
  #10  
Old 04-29-2011, 09:27 AM
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Welcome to FTE.

If it's missing, you should have a blinking CEL when it does this & misfire codes should be set in the computer for the cylinder/s that have the problem, so any trouble codes can provide good clues & shorten your trouble shoot.

A miss under load is usually a sign of a weak spark problem. Like a loose plug wire, bad plug wire internally, cracked or chipped internal or external plug ceramics, excessive plug spark gap, a bad coil pack, or low B+ voltage to the coilpack, from bad wiring, connector, bad battery, or alternator.
The coil packs of that era were known to crack underneath, out of sight & cause mischief.

SO, seeing as how this is a 94 & it's OBD-1, the DLC is under hood, so the results the AZ guy had are suspect, if he wasn't under hood with his code reader!!!!

You can pull the codes yourself, using a jumper wire, 12 volt test lamp, analog multimeter, or watching the in dash CEL blink or the meter wave the codes.
Where to place the jumper wire & how to hook up the meter or test lamp & read the codes, is outlined in a thread link in the "Tech Info" thread atop this forums thread listing page.

So, maybe begin with scanning for codes yourself, if the AZ guys results are suspect.

OR, raising the hood at night & look for plug, wire & coilpack arcs & sparks & maybe consider doing a "wet down" test of each plug, wire & the coilpack, with a spray bottle of water & look for arcs & sparks, or a rougher running engine.

Did the miss come about After the plugs & wires were replaced???? If so, concentrate your trouble shoot there. I once had an intermittent under load miss, that was worse in wet/damp, or rainy weather, on my then new 99 Ranger, that was traced to a cracked #6 plug ceramic, when the Dealer did the wet down test.

Just because the plugs & wires are new, doesn't automatically earn em a pass, make them earn that good label. If the wet down test proves naught, pull each plug wire & make sure it's end to end internal resistance is within spec using your multimeter & the readings don't change when you flex the connectors on each end. The resistance should be about 1000 ohms/inch of length, 30,000 ohms max, no matter the lenght. Make sure the wires are snapped on good & tight on both ends, and are routed to the correct plug & coilpack terminal, using the factory routing & All of the wire looms.

If that doesn't do it, pull each plug & closely inspect each plugs internal & external ceramics for chips & cracks. In my case, the Dealers lead Tech had cracked the #6 plug when he installed it after a head change.

If that doesn't do it, maybe consider pulling the coilpack for a bench test. Most autoparts stores can do it & at no charge. Maybe take your spray bottle along, to wet it down on the bench test, if need be.

Other things can also cause an under load miss, like a lean mixture from a vacuum leak, low fuel pressure, acting out EGR system, ect, ect, so the trouble shoot scenario can be lengthly in stubborn cases, so don't get discouraged if you don't get joy right away. Be thorough in your trouble shoot & put everything on your suspct list to begin with!!!!

A bunch more thoughts for pondering, let us know how it goes.
 
  #11  
Old 04-29-2011, 09:42 AM
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Originally Posted by pawpaw View Post
Welcome to FTE.

If it's missing, you should have a blinking CEL when it does this & misfire codes should be set in the computer for the cylinder/s that have the problem, so any trouble codes can provide good clues & shorten your trouble shoot.

A miss under load is usually a sign of a weak spark problem. Like a loose plug wire, bad plug wire internally, cracked or chipped internal or external plug ceramics, excessive plug spark gap, a bad coil pack, or low B+ voltage to the coilpack, from bad wiring, connector, bad battery, or alternator.
The coil packs of that era were known to crack underneath, out of sight & cause mischief.

SO, seeing as how this is a 94 & it's OBD-1, the DLC is under hood, so the results the AZ guy had are suspect, if he wasn't under hood with his code reader!!!!

You can pull the codes yourself, using a jumper wire, 12 volt test lamp, analog multimeter, or watching the in dash CEL blink or the meter wave the codes.
Where to place the jumper wire & how to hook up the meter or test lamp & read the codes, is outlined in a thread link in the "Tech Info" thread atop this forums thread listing page.

So, maybe begin with scanning for codes yourself, if the AZ guys results are suspect.

OR, raising the hood at night & look for plug, wire & coilpack arcs & sparks & maybe consider doing a "wet down" test of each plug, wire & the coilpack, with a spray bottle of water & look for arcs & sparks, or a rougher running engine.

Did the miss come about After the plugs & wires were replaced???? If so, concentrate your trouble shoot there. I once had an intermittent under load miss, that was worse in wet/damp, or rainy weather, on my then new 99 Ranger, that was traced to a cracked #6 plug ceramic, when the Dealer did the wet down test.

Just because the plugs & wires are new, doesn't automatically earn em a pass, make them earn that good label. If the wet down test proves naught, pull each plug wire & make sure it's end to end internal resistance is within spec using your multimeter & the readings don't change when you flex the connectors on each end. The resistance should be about 1000 ohms/inch of length, 30,000 ohms max, no matter the lenght. Make sure the wires are snapped on good & tight on both ends, and are routed to the correct plug & coilpack terminal, using the factory routing & All of the wire looms.

If that doesn't do it, pull each plug & closely inspect each plugs internal & external ceramics for chips & cracks. In my case, the Dealers lead Tech had cracked the #6 plug when he installed it after a head change.

If that doesn't do it, maybe consider pulling the coilpack for a bench test. Most autoparts stores can do it & at no charge. Maybe take your spray bottle along, to wet it down on the bench test, if need be.

Other things can also cause an under load miss, like a lean mixture from a vacuum leak, low fuel pressure, acting out EGR system, ect, ect, so the trouble shoot scenario can be lengthly in stubborn cases, so don't get discouraged if you don't get joy right away. Be thorough in your trouble shoot & put everything on your suspct list to begin with!!!!

A bunch more thoughts for pondering, let us know how it goes.
PawPaw
Thank you for taking the time to write that lengthy explanation, much appreciated. It missed before the wire and plug change that's why I did the change out. I will work on this. Thanks again.
Jimmy
 
  #12  
Old 04-29-2011, 10:59 AM
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Yep thats pawpaw for ya
 
  #13  
Old 04-29-2011, 11:10 AM
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OK, so the problem was there before the new plugs & wires, well maybe begin with suspecting the coilpack if you don't have any trouble codes. Remember that "Murphy's Law" is still in effect, so don't take the new plugs & wires off your suspect list just yet!!

Then maybe progress to looking for vacuum leaks & the intake manafold gaskets belong on your suspect list for vacuum leaks & fuel delivery, EGR system, or compression problems.

If you can come by a scantool, like an Actron CP9145, ect, that has a hook up cable for your OBD-1 system, that can read & display live sensor PID's to the computer & look at fuel trim numbers, MAF sensor & TPS sensor PID's to the computer, O2 sensor switching & any pending or set codes, those too may help shorten your trouble shoot. For instance, if the TPS doesn't signal the computer that the throttle is opening, the fuel mixture will go dead lean & can cause the engine to stumble.
Same for the MAF sensor or O2 sensors if they are lazy to react, so a scantool that'll read sensor output PID's to the computer can be a Big help in a trouble shoot.

You've been busy on this one & have covered a lot of the usual suspects, keep looking, you'll likely find the culprit.
 
  #14  
Old 05-01-2011, 12:12 PM
JimmyDoodle
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I located a 94 ranger just like mine 4.0 and the vacuum lines are all good. I guess the next thing to do is locate a coil pack at the local salvage yard and swap it out.
Jimmy
 
  #15  
Old 05-01-2011, 09:21 PM
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Auto Zone pulled some codes and got a 158, 181, think one is a EGR code, so I pulled it off and cleaned it, pulled my TPS sensor out and they showed me how to check the resistance on that with my OHM meter and it checked ok. Still looking for answers, everything's still the same I think if I can find a coil pack cheap enough I'll change it out.
Jimmy
 

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