Anyone? " Bucking " at low speed.....

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I am reposting this from my original post on 12-28-05 at 3,000 miles. '04 SCAB.

I am still having this problem, now after 9,500 miles. “Bucking”, as if you were tapping on the gas pedal. However, it only happens when the engine is HOT, then turned off for a few minutes (I run into a store or something) then start it up again and proceed slowly. It is more noticeable if going up a slight incline, either foreword or backward. It lasts for about 5 seconds and then everything is OK.

I now can get this to happen regularly. At first I thought this happened when the engine was cold, but it never happens on a cold start. I’ve had it in 3 times for this and I’m going to take it in again, so if you’ve had this fixed, please let me know what they did so I can tell me dealer. Thanks!

 

sounds like mine when one of my coil packs started to go bad....

 

My 04 did this when going slow in a parking lot. It would surge as you describe. The dealership reflashed my PCM with a later calibration after calling the Ford tech line and that fixed it.

 

Mine would rapidly shift through the gears into OD at low speed (especially up an incline) causing it to buck because of the load on the engine.

A PCM reflash cured mine as well.

 

Mine does it too occasionally. I have the edge programmer so I am not sure if that is the cause of it or not. It does seem to be getting worse lately. Hopefully someone has an idea what it is.

 

how hard is the bucking? becuase we have an astro van.. and on acceleration it would buck very hard.. just changed the distributor cap , rotor , plugs and wires and seems to be running perfect after 70 kms

 

I took it in this morning and after 4 hours of diagnostics, test driving, and fuel pressure tests, the tech found two leaking fuel injectors. Apparently, when the engine was hot, they would leak gas into the cylinder after being off for about five minutes. Enough gas would leak and cause erratic low speed acceleration and produce the "bucking" acceleration until burned up. Good technician, Morris!

 

I was sure it was fixed. I guess I didn't let it get hot enough. Appointment 9am tomorrow.

 

if you can get me your vin i may be able to look into it

 

..... the tech is off until Wednesday. We will try again then. VIN 1FTPX14524N.

 

i still need 6 more characters to your vin

 

Mine did and does this as well. Only when i first start it up and take off with slight acceleration. Once i get over 15 or so it stops. I added the xcal2 and it still does it occasionally. Im at 40,000 miles now. It just seems like a really sensitive gas pedal at first.

 

Sorry, Adam, those last six #'s were larger; I got them off my window sticker. VIN 1FTPX14524N A71232 and thanks for taking time to look this up.

 

I've had this same thing happen whenever I make a short shopping trip, then
restart and try to drive at a low speed across the parking lot. The truck
surges unless you let off the gas or accelerate. i took it to the dealer and
they were unable to duplicate and heard from several others on another
site that had the same thing happen. I have yet to hear of any fixes, as I
did have my pcm reflashed and it went away for a while, then returned.
I have an 04 Scab Lariat 5.4.

 

I've found that if I get it Hot (mid temp mark on the dash) then park on a slight incline and wait up to one hour (5 minutes is sometimes not enough), I can get this to happen every time. When backing up it is more noticable for some reason.

I would be interested if some of you would try this and post back here. BTW, my build date is 10/2003 at the Newark plant. THANKS!