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My very own hesitation/bucking thread

Does it buck at the same throttle position all the time or is it different?

check your TPS again. this time use an analog gauge and slowly do a full sweep of the throttle with the key on engine off. watch closely. if the needle goes to Infinity at any time during the sweep then you have a dead spot in the TPS and it needs to be replaced.
 
striker2 said:
Does it buck at the same throttle position all the time or is it different?
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I think the bucking is more RPM dependent then throttle dependent. Because at 1500 RPM in 5th gear the car bucks whether it's idling or light throttle. Also, I did an experiment in 2nd gear, where I revved it up then let off the gas completely. As the engine was spooling down (still in gear), it would buck at 1500 rpm. It's weird though, it seems to buck the most during normal driving, but once I mash the gas at WOT it bucks the least. Or maybe the torque is overpowering whatever bucking is present...who knows.

striker2 said:
check your TPS again. this time use an analog gauge and slowly do a full sweep of the throttle with the key on engine off. watch closely. if the needle goes to Infinity at any time during the sweep then you have a dead spot in the TPS and it needs to be replaced.
Click to expand...

I'll see if I can fine an analog meter and check this tonight.

Thanks for the ideas!
 
You really need to replace the spark plugs AND spark plug wires all at the same time.

If you have bad wires, they will bake a new set of plugs in one trip. Likewise, if you have bad plugs, they will bake a new set of wires in one trip.

Also, you should give the insides of the plug wire boots a healthy coat of dielectric grease when you do that.
 
I replaced both the plugs and wires about 10k miles ago. Autolite double plat's and Motorcraft brand wires. It didn't change anything, didn't make it better, didn't make it worse.

If there's anyone in the Mass. area who wants to bring over some extra known working plugs/wires I will reward with beer and food.
 
Is it possible that this could be a PCV related issue? I have many of the same symptoms and have been researching them on the old forums and it seems my PCV valve/hoses may be the problem. I plan on replacing my PCV valve and related hoses by this weekend.
 
Let me know how that turns out.

I checked my TPS with an analog voltmeter with the car on and it went smoothly from ~.7Vdc to 4.8Vdc (ish). Like really really smooth. And I played with it for a few minutes.
 
Desiato: since your going to pull the PCV valve look inside the hose that goes from it to the intake manifold and see if there is any oil. iBrent you ought to check this as well.
 
striker2 said:
Desiato: since your going to pull the PCV valve look inside the hose that goes from it to the intake manifold and see if there is any oil. iBrent you ought to check this as well.
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I check my PCV valve, it had some carbon deposits, but not really any oil. What would that indicate? I take it its bad to have oil in there.

When I was pulling off the intake manifold a few weeks ago, there was another hose coming off the bottom of where the manifold meets the throttle body. That hose went somewhere, I'm not really sure where, but where it made a junction, there was lots of oil and crap in there. Plus, it just kinda set in there, wasn't really crimped down or anything. What does this hose feed and should there be crap in there? I can take pictures of it tomorrow while its light outside if you don't know what I'm talking about.
 
pictures please. i dont have a duratec so i i cant go look at one and see but if it goes into the intake manifold it should not have oil in it. if there is oil in those lines then the engine will be sucking in oil causing it to run rich. when you have lots of vacuum (low load and throttle) it is more likely to be sucking in the oil then. this could very easily cause the bucking.

follow the line and see what it goes to.
 
iBrent said:
I replaced both the plugs and wires about 10k miles ago. Autolite double plat's and Motorcraft brand wires. It didn't change anything, didn't make it better, didn't make it worse.

If there's anyone in the Mass. area who wants to bring over some extra known working plugs/wires I will reward with beer and food.
Click to expand...

I had a new set of wires and they were causing my hesitation. They were Autolite's (had the same problem with the Motorcraft set just before them). Drove me nuts until I found a set of used wires at a salvage yard for $10. My problem was solved and never resurfaced. I sold the car a few months ago so I'm not sure how it is now. I ran on those old wires for over a year.

Edit - sorry this was a double post from the first page.
 
striker2 said:
pictures please. i dont have a duratec so i i cant go look at one and see but if it goes into the intake manifold it should not have oil in it.
Click to expand...

As promised:

IMG_0239.jpg


Its right underneath the throttle cable and cruise control cable.
 
ooooh, that's the PCV valve. Okay i'm retarded. I'll replace that then, cause it's all gunked up.

Thanks! New project for tomorrow!
 
iBrent said:
So I have the same hesitation/bucking issue that many people have. [...] It started about a year ago, back then it was very slight and almost unnoticeable. It has since been getting progressively worse. Its so bad now that my whole body moves front to back in third gear while accelerating. Its worse around 1500 RPM. For example, i'll be cruising around ~35mph in 5th gear (1500 RPM) and it will buck with our without throttle. When the throttle is slightly opened, it will get worse. [...]

I've done lots of searching and replaced a lot of stuff. Its really bothering me. Help please!

Here's what I've done over the last year (in order).
Had a CEL, replaced fuel filter and pump. Fixed other problems, but the bucking was still there.

Replaced plugs/wires with APP764's and motorcraft wires - NO CHANGE (not better or worse)

Cleaned K&N and re-oiled - NO CHANGE

Tested coil pack, tested out of spec, thought i had something, replaced with autozone brand...- NO CHANGE

Checked spark plugs for carbon tracking and checked gap, all tested fine.

Rebuilt intake and cleaned IAC (yesterday) - NO CHANGE

I thought I had it with the intake rebuild...but 'twas not the case. Also, when the car is warm it seems my IMRC is malfunctioning and the bucking is worse. I bought a replacement transistor and will be replacing it this afternoon. That may fix the IMRC issue, but probably not the bucking.

Any help would be greatly appreciated...and if you successfully diagnose the problem, perhaps rewarded.
Click to expand...


I have same issues, and gone through the same laundry list. Everything seems to help either a little bit or for a short while.

HOWEVER, I recently talked with a mechanic friend of mine about this. He said stumble on acceleration means EGR issues.

Well, the codes say 335, 336, 337, all of which translate to "EGR voltage high," so I think I'm starting to get somewhere.

The DPFE measures exhaust pressure differential across a restrictor in the tube between the right bank exhaust manifold and the EGR valve. The higher the pressure differential, the higher the voltage output. Perhaps a clogged restrictor is the culprit?

Question:
Has anyone ever cleaned their "orifice tube assembly?"

(yeah, I know, but keep it clean please... :eek: )
 
Possibly. I have noticed a serious decrease in fuel economy since the problem started a long time ago.

How does one test for that? I've gotten them professionally cleaned before, where they smoke out the neighborhood and what not, but that was a long time ago as well.
 
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This thread has me scratching my head. I've always experienced some kind of hesitation/bucking and have pretty much gone through replacing everything the OP has, including IAC, IMRC, fuel pump/filter, plugs/wires, etc.
 
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