Truck is bucking

boonewheeler

boonewheeler

New Member
Joined
Feb 22, 2007
Location
Boone
So yea the truck has been bucking now at light acceleration (approximately 1000-2000 rpms). All new filters all the way around, replaced the throttle positioning sensor and fuel pressure regulator. Fuel pressure checks out fine.

Posted this over on the ford truck site, but so far no luck so I figured I'd try it here.

Any ideas?
 
Assuming the vehicle in question is the one in your sig line, how about ignition parts ? Plugs? wires? cap , rotor ? How old, are they quality parts ?

Generally a buck is a result of a misfire, old wires, are real good for cross firing, especially on a nice wet dew covered morning.
 
Little more clarification: truck has a 302 ci V8, with the E4OD. The plugs and wires are under 6 months old, cap and rotor I'm not quite sure. Forgot to add before, truck throws no codes, terrain has no impact on the bucking happening. This occurs regardless of weather, hot/humid/wet/cold etc...

I'm pulling plugs and double checking Saturday
 
Ok, you need to diagnose before you just replace parts. Ford's are very very picky about plugs and wires. I would only put autolites and OEM wires. Second, you can't rely on the computer to tell you there is a misfire, I was at a seminar and the guy pulled 6 out of 8 plug wires and the crown vic never sat a misfire code.

Now whenever i get a misfire i do the following: smoke the intake(to check for intake leaks), run ignition scope, scope the fuel pump, fuel pressure AND volume check, ohm all the injectors, compression check, and then i scope the injectors if i'm not getting any other results. All of that stuff can cause a misfire, first I would try to have someone put an ignition scope on it to see if its a fuel or spark problem. Or you could try and replace cap and rotor and make sure you put autolite plugs and OEM wires

Another thing, why did you replace the TPS? Did you test it first?
 
How are you so sure this is even a misfire? Wouldn't a misfire happen regardless of throttle position?

Replaced the TPS after I found flat spots throughout the throttle range.
 
bucking usually means a misfire 95% of the time. And no it wouldn't misfire all the time, most of the time they(ford's) only misfire under load

I was just explaining how many things could effect the misfire, but first i would try autolite plugs and oem wires

Brendan
 
So OEM wires and the autolites went in this morning. Took it on a 20 minute test drive around conover, truck ran perfectly. Packed up everything and started heading back to Boone via 40-321.

Hit 75 on I40 no problem, took the exit, truck starts acting up BADLY. At idle, the truck shakes violently, and the bucking on acceleration is a lot worse.

I'm calling into work and checking my wiring job when the truck cools down.
 
EGR

Plug the vacuum line to it and go for another drive.

The high vacuum you experienced when exiting off the
interstate opened it and carbon probably prevented it from fully closing. Being hot made it more prone to sticking.
 
Update on the junk:

Problem solved (I think, will be further test driven and full results compiled)

The plugs and wiring installed originally solved the problem, however, being the first time I've changed those, I didn't pay close attention to exactly how the wires were run. So after much deliberation and pointers, I went to replace the distributer cap and rotor this morning and double check my wiring job.

Low and behold, the wire for #6 was caught underneath the corner of the engine and the heat from the engine had apparently melted the cable halfway through causing the misfire.

So lesson learned and truck fixed. Now all I need to do is find the wiring schematic for the radio and get this aftermarket one hooked up.

Appreciate all the help/advice
Jon
 
boonewheeler said:
. Now all I need to do is find the wiring schematic for the radio and get this aftermarket one hooked up.

Appreciate all the help/advice
Jon
Click to expand...
Battery LIGHT GREEN/YELLOW (+) RADIO HARNESS
Accesory YELLOW/BLACK (+) RADIO HARNESS
Ground BLACK (-) RADIO HARNESS
Illumination ORANGE/BLACK (+) RADIO HARNESS
Dimmer LIGHT BLUE/RED (+) RADIO HARNESS
Power Antenna AMP=BLUE
LF Speaker (+) ORANGE/LIGHT GREEN
LF Speaker (-) LIGHT BLUE/WHITE
RF Speaker (+) WHITE/LIGHT GREEN
RF Speaker (-) DARK GREEN/ORANGE
LR Speaker (+) PINK/LIGHT GREEN
LR Speaker (-) TAN/YELLOW
RR Speaker (+) ORANGE/RED
RR Speaker (-) BLACK/WHITE
Amp Location RIGHT REAR PANEL
Steering Cntrls NO
Speed Cntrl NO
Radio Security OPTIONAL
 
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