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  #1  
Old 02-10-2011, 07:03 AM
04FX4LevelII 04FX4LevelII is offline
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Default Engine Bucks While Driving at Constant Speed or Cruise

I have noticed that when I am driving at a constant speed, foot barely on the pedal, the truck will sometimes "buck." It does not do this when I am accelerating or not pressing the pedal at all. It will do it sometimes while cruise control is engaged and is holding at a constant speed. My old Mazda MX6 did this same exact thing, however, when it did it the engine light would come on for problems with the EGR. The truck is NOT throwing the engine light.

Does anyone have any ideas? I am thinking it is either EGR related, or I need to clean the MAF and TB.

The truck is a 2004 FX4 Level II with 30,000 miles. No major maintenance has been completed that I know of.
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Last edited by 04FX4LevelII; 02-10-2011 at 07:07 AM.
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Old 02-11-2011, 04:57 AM
crowdpleazer crowdpleazer is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

what transmission is it?
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Old 02-11-2011, 06:08 AM
ranger024x4 ranger024x4 is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

I sent you a pm on ranger-forums.
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Old 02-11-2011, 08:04 AM
bluerang3r bluerang3r is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

many reasons for this. maybe a timing issue?? like a bad coil or something like that. but check the spark plugs in all cylinders cause usually when a engine bucks all cylinders arent affected except just a few. spark plugs can tell you alot about what is wrong with that cylinder. sounds like you have a misfire on a cylinder, which would cause the bucking. i know that the check engine light won't turn on if it misfires once.. it takes a certain number of misfires over a given amount of time to register and turn on the check engine light. I do know that the memory on the computer does store the misfire but dumps the code if it doesnt happen again over a certain time usually a couple miles. but question for you.. how many times does this happen cause it sounds like it only happens a few times and not often. so I would suggest checking the computer with a scan tool and see if a code comes up. if not then check the coil and see if it is cracked or something like that. if not then check the spark plugs.. see if they are wet(meaning they are covered in oil or gas) hopefully they arent. then if you had a olcilloscope i would check the spark of each cylinder and see how many volts are firing across the plugs. then check the resistance in the plug wires. it should be around 6 to 11 ohms. if its higher than 11 then you are not getting enough spark on the cylinder. and if all that doesn't seem to fix it then i would start checking the fuel injectors.
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Old 02-11-2011, 09:33 AM
04FX4LevelII 04FX4LevelII is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

Automatic transmission, and this happens only when cold and raining/snowing.
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  #6  
Old 02-11-2011, 09:56 AM
Clinton Clinton is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

Have you checked the accelleration cable?
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Old 02-11-2011, 10:01 AM
bluerang3r bluerang3r is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

well i would check the coil pack then to see if its cracked or a plug wire.. i know humidity can cause a rough patch like that if water gets into it sometimes
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  #8  
Old 02-12-2011, 07:55 AM
crowdpleazer crowdpleazer is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

i hate to disagree with everyone, but this sounds like a fuel related issue. especially since he said that its happens mainly when its cold and raining/snowing. could be injectors, or the fuel rail, or it might even be the throttle.
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  #9  
Old 02-12-2011, 08:09 AM
pooleo pooleo is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

I have noticed this in my ranger. usually only happens when in 5th gear and under hard acceleration up a good grade, almost feels like its to much for the motor to handle, so i usually drop to 4th and dont have the problem.
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Old 02-12-2011, 09:27 AM
cwaterboy1957 cwaterboy1957 is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

Might want to check the cam syncronizer I had the same problem and that fixed it I have 117000 on my 2003 and the cost is around 300 bucks but you waant to have a shop fix it it is very critical that it is installed properly
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  #11  
Old 02-12-2011, 06:40 PM
04FX4LevelII 04FX4LevelII is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

My problem happens when only under nearly NO load. I discovered today that the air filter box was secured by the two clips, but the 3 tabs were not inserted/lined up with the holes adjacent to them. I'm not sure if this was the problem, but here in NC there is no snow/cold weather in the forecast. They are calling for 80's by the end of next week.
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20% Front Tint | Sprayed In Bed Liner

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  #12  
Old 02-12-2011, 07:58 PM
ranger024x4 ranger024x4 is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

Quote:
Originally Posted by 04FX4LevelII View Post
My problem happens when only under nearly NO load. I discovered today that the air filter box was secured by the two clips, but the 3 tabs were not inserted/lined up with the holes adjacent to them. I'm not sure if this was the problem, but here in NC there is no snow/cold weather in the forecast. They are calling for 80's by the end of next week.
as long as you have a motorcraft air filter, you should have no more issues.
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  #13  
Old 02-13-2011, 06:43 AM
04FX4LevelII 04FX4LevelII is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

I do, the truck is stock and I checked the filter.
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2004 Ford Ranger FX4 Level II
Oxford White | Black Leather | 06 Emblems
20% Front Tint | Sprayed In Bed Liner

No major modifications planned as of now.
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  #14  
Old 02-13-2011, 06:51 AM
modelageek modelageek is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

Quote:
Originally Posted by 04FX4LevelII View Post
My problem happens when only under nearly NO load. I discovered today that the air filter box was secured by the two clips, but the 3 tabs were not inserted/lined up with the holes adjacent to them. I'm not sure if this was the problem, but here in NC there is no snow/cold weather in the forecast. They are calling for 80's by the end of next week.
Quote:
Originally Posted by ranger024x4 View Post
as long as you have a motorcraft air filter, you should have no more issues.
Quote:
Originally Posted by 04FX4LevelII View Post
I do, the truck is stock and I checked the filter.
+1.......I bet you are all set........there were a few threads going around with this issue..it seemed to mostly be solved by making sure you had a MC air filter and the intake was fit and secure........
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  #15  
Old 03-31-2011, 10:34 PM
Earlyboomer Earlyboomer is offline
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Default Re: Engine Bucks While Driving at Constant Speed or Cruise

You didn't say what engine it is. I would suspect a sensor. Do the auto parts stores in your area offer free scanner service? Lots of auto parts stores do scan vehicles for free now. A scanner should be a big help for your problem. I don't know what year that Ford quit using the Thick Film Ignition Control Module on the distributor, or even distributors in what engines, but that module can cause lots of bucking issues with the older engines like my 86 2.9L

Last edited by Earlyboomer; 03-31-2011 at 10:38 PM. Reason: added additonal information
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