I have a 1987 F150 2wd with the 300-6 engine. I will be driving down the road and just out of the clear blue sky, it starts to bucking--no back firing, then runs fine for 100 miles or so. Now it has starting doing this more often. The bucking will last anywhere from a second to maybe 5-10 seconds. It is as though you turn the key off then back on. No backfiring. It really doesn't cough when it does this, just bucks. Need help! Thanks in advance. ( Have put stuff in gas for water--no help)

 

Do you have dual gas tanks, and if so does the problem always occur on the same tank?? Maybe a fuel pump/clog related problem...

 

If it was like mine 2yrs ago & is starting to do it again I would check the distributor. After 575.00 of diagnostics and rebuilding the distributor, the problem was resolved. Watch your volt meter when this happens, mine would go completely to the left then come back to normal position afterwards and run fine. No amount of throttle would affect the problem. It's like just turning a light switch on & off. The shop rebuilt the distributor with a new stator resolving the problem. It was wearing out and basically cutting the electrical current on & off shutting down everything for a moment. I have a '93 F150 5.0 w/E40D auto. check my following post for replys on where to get a good replacement. good luck.

Wes

 

Has duals--I never use the second one.

 

I will watch the meter--sounds just like mine. Thanks

 

My '92 F150 did this for years before I took Nitro94's advice and made an EGR restrictor plate. Do a search on this list for complete details.

The basic problem with mine was that the fuel mix was too lean due to a high amount of EGR gasses being introduced into the intake manifold.

A quick test to see if this is the problem is to remove the vacumn hose from the EGR valve, and plug the vacumn hose, then see if the bucking goes away. If it does, make the restrictor plate.

My '92 now runs as smoothly as my brother's Olds Intrigue, which is a compliment ;-)

 

Well, so much for the gauge going backwards when it bucked. It did it again last night--a little longer than usual--and the gauage never moved the least bit. I'm really getting to feel like it is the fuel pump. I guess when it finally dies we will know for sure--just hope it happens soon--going on vacation in 2 weeks and don't want it to die then.

 

Try pulling the vacuum line off of your fuel pressure regulator. If it stalls or squirts fuel out of the vacuum port. You may have found the problem.

 

I suggest running off the second fuel tank for awhile to see if the problem still occurs. If it does, then you at least know it's not fuel tank related. If it doesn't re-occur, then the problem could be in the other fuel tank.

 

Delgan, As I mentioned previously my truck is starting to act up again. I ordered a new (with 12 mo./12,000 mi. warranty) distributor from Fordpartsonline.com for 140.00, it should be here on 10/22. In the mean time, based on info from this post I have been trying other senarios inorder to "create" the problem. So far no luck. Run one tank for a few days without a problem, then it does it. Switch to the other tank for a few days without a problem, then it does it. I don't think it is a fuel problem. The only thing that seems to be apparent is it does it most frequently while cruising aprox 40 MPH with very little throttle. Also, I noticed my volt gauge was not dropping to the left as it did the last time. Maybe it will do that when the problem gets so severe that I can't drive a couple of blocks without it shuttering every time. Next, I will try pulling the vacuum line off of the fuel pressure regulator as suggested in another post. Lastly, I will install the new distributor on Tues and post the results.

Wes

 

Your problem sounds like plugs or plug wires to me.
I have had it on several vehicles. Last one was 98 explorer 5.0, and it was one of the plug wires causing the problem.

Winford

 

Do the egr restrictor thing,or at least try it. You may be pleasantly surprised.

 

Hello everyone! I just joined this group today while researching a problem with my '90 F150. The bucking and jumping with mine is just as Wes described... most pronounced at about 40 mph with very little throttle. It will do it at other times as well, but this is the most frequent. My truck has 2 new fuel pumps (dual tanks), new plugs, plug wires, distributor cap and rotor, air filter, etc...But the problem is still there. I tried one of the suggestions in another posting on here... pulling the vacuum line to the EGR and capping it off... It seems to have helped, but hasn't eliminated the problem... I would appreciate any further advice anyone has to offer!

Thanks.

Doug

 

Well, I tried something. First thing I done was to switch places I buy gas---just thought maybe I was getting bad gas or water in it. Second thing I done was to put a bottle of Chevron Techron in it. I went about 3 tanks of gas before it done it again and that time was just like a miss. I put another bottle in just to help out. Now it is just wait and see.

 

Doug - You didn't say if your truck has EFI, but mine does and it had the same problem. I replaced the fuel pressure regulator (a reeeel job on fuel injected engines by the way) and the problem was solved. If you have EFI you CAN replace the regulator without removing the plenum and all that other stuff, but be ready for a real challenge. I had to fabricate a couple of long, angled and offset hex wrench tools to access the reulator.
I think the key is mileage... This stuff wasn't designed to last forever and periodically needs to be replaced. Even if it doesn't cure a problem, you know that you've eliminated one possibility and now have a new part. If it's like mine, pretty soon, you've replaced the whole truck! Hope this helps!