F-150 Bucking Occassionally
 

I have a 1992 F-150 - 4.9 FI, 5-spd manual, 124,000 miles

I notice "bucking" usually in 3rd or 4th gear if the gas pedal is lightly pressed. Sometimes you have to let off and reapply the gas pedal to make it stop.No check engine light. There are times when it is occasional and times when it seems to happen more often.

New plugs, cap, rotor, wires and coil which did not stop the bucking.

I have seen many articles related to this and many solutions from replacing the distributor, fooling the EGR valve, fuel injector cleaning, etc.

So I guess at this point I am collecting any ideas of what is causing this, what I might look for. I hate to just start throwing parts at it without some type of research and/or testing.

One other note, my state of MO no longer does emission tests so I am debating if removing all emission related parts would help. But would the computer then wack out.

Any suggestions very appreciated.

This is happening to me too. Almost exactly how you described it. I've replaced EGR, IC, Cap/Rotor/plugs/wires, cleaned throttle, cleaned MAF, replaced vacuum lines, PCV.

Someone else suggested the Distributor. Your problem sounds exactly like mine (5.0, 8cyl, auto). When he replaced distirbutor, before that, they did pretty much all the same things I did. And afterwards, it ran great so hoping that's it. Also I don't have any codes.

I'm planning on changing mine out this weekend. STill learning how to wrench and today, of all days, my balancer is at exactly TDC so I'll keep it parked where it is so I don't have to figure that part out.

I'm a little hesitant to put a new one in but I'll make as many marks as I can so I can get the rotor and distributor all lined up correctly. My new distributor happen to come with new rotor and cap.

I'll keep you updated.

I would put some fuel injector cleaner in the gas tank. Avoid the 10% ethanol if you have a choice.

Removing the emissions stuff won't help unless you would have a plugged cat converter.

Test the TPS

Oh yeah, I did that too. Replaced it with Motorcraft brand and dialed it in the correct voltage. Helped out my idling a lot.

thanks you all..........hey ericantonio.........will you ping back once you replace the distro and let me know how it goes?

My buddy at work used to race some dune buggies and I get a lot of automotive how-tos' from him. He's gonna help with the timing. I mentioned the problem you and I have and he said:

"maybe it wasn't a new dizzy, but maybe when installed the new one and did the timing correct, maybe it was the timing that corrected it?"

So he'll come by sometime and we'll check out the timing first. Frmo what I've read, it should say 10 BTDC.

But I have another problem with my timing gauge thingy. I'll post a pic and a new thread.

I think the piece that marks my timing is bent:

https://www.f150forum.com/f10/timing...lancer-329121/

I have to fix something before I check out the dizzy. I may have to replace this piece as soon as I find out what it is called. Or maybe bend it back. In the meantime, could you check your timing? My friend mentioned that it should be check cause yours and mine sound the same problem and he's thinking timing


https://cimg5.ibsrv.net/gimg/www.f15...a13a354eac.jpg

Checked timing this morning and it's right at 10 BDTC. So prolly change out the distributor this weekend. After that, I really don't know what else I can do. I've replaced both fuel pumps and 1 fuel tank.

My problem is just like yours. I ease off the gas when it happens or I can step on it harder.

If new distributor won't fix it I think I probably have bigger issues INSIDE the engine.