this may or may not be related but i can get my 95 4.9 to stumble just sitting still...if i lightly tap the gas itll drop 200-300 rpms and bounce back...its not as noticeable when accelerating, any ideas

 

Bob, I found my '93 300 to have a 1-1/16" sized nut, might have been metric actually but my old and worn 1-1/16" fit well enough!

 

I'm having the same problem with a 1987 F-150 L6 300. I plugged the EGR hose and it helped a little bit for a little while, but I still have the problem. I'm thinking the next step is the fuel injectors. Anyone else think that's my next step? Or should I try something else?

 

V8,
i am also dealing with the notrious bucking f-series. After reading posts on this for days, i have concluded that it is the fuel injectors clogging up. With the egr putting the normal amount of exhaust into the intake and the clogged fuel injectors puttiing in less gas, you get the bucking and stumbling. restricting the egr will solve the problem, but it is only compensating for the lack of fuel. The injectors need to be serviced. take it to a shop and have them cleaned. don't let them tell you you need new ones. Personally, i put half a quart of ATF into half a tank of gas and am going to run it out. ATF has some pretty hefty detergents in it that should do the trick. I'll post the results.

 

atf? as in tranny fluid?
i would be terrified to do this. wow.
enjoy the smoke show haha. does atf even burn?

 

yes. tranny fluid. No smoke so far and it does burn. this comes from multiple ASE's. This apparently is the poor man's octane boosting engine treatment. Again, this is what I am doing prior to a professional service and i will post the results. Wish me luck.

 

goodluck man! idk im weary off even seafoaming, something doesnt add up with me doin that. i might try it today though haha.not atf but seafoam.

 

smitty,

I believe that my injectors are causing my problems. Let me know what happens with the trans fluid.

My valve cover is leaking. And if I go that deep into the engine, I may go ahead and change out the injectors too. I found a guy on ebay that sells them pretty cheap compared to the part stores.

Set of 6 1992 Ford F150 F250 F350 4.9L Fuel Injectors - eBay (item 280636229938 end time Mar-28-11 12:28:30 PDT)

 

Why replace the injectors? Their an on/off solenoid and either work or don't. Take them off, remove the pintle caps, orings, and filters in the injector inlets and soak in ChemTool for a few days like you would jets from a carb. Then, remove from chemtool and use an injector test harness from the parts store and give each one 12 volts from the battery and blow them out with compressed air in the reversed direction. I.e. backflush them to blow any crud back out the injector inlets.

Buy this kit and rebuild them. I would only replace an injector if it doesn't "click" when you apply 12 volts to it or doesn't let air through when you energize it.

So $20 for the rebuild kit, $5 for the chemtool, and $5 for the upper plenum gasket and your done.

Doing this job got rid of the off idle stumble my 280K mile 95' 5.8L had. I reused my injectors with that much mileage without a problem.

 

I used to rebuild my own carbs. I never thought about rebuilding the injectors. I'll have to look into it a bit more.

 

well i fixed my issue. fuel filter properly gapped plugs and seafoam. that stuff does work. im amazed. i dont like pur in bandaids but it really cleaned the injectors really well. i didnt pull them out and put them on a flow bench but the truck sounds so much better has t-responce again and gets better mpgs. tranny even shifts better.!

 

So glad that I found this thread. I taped off the vacuum line and it solved the problem in my case! I will do a more permanent solution at some point, just had a few questions first.
1. Smitty, how did the ATF work for you? did that clean your injectors and solve the problem?
2. Has anyone tried crimping the inlet on the EGR valve instead of using the restrictor plate or the tin foil? This would allow it to not throw a code, and also restrict the airflow.

Truck has so much more power now. Before I had to give it a fair amount of gas when starting off in 2nd gear to prevent it from stalling out. Now I can give it a little and it will not drop revs at all in 2nd. I notice that I can go through 2nd and 3rd gear quicker now, which is nice - 1st gear is still too quick though

-dan

 

does someone have a pic of which hose to take off and plug? i looked in my engine bay and im pretty sure of the right one but i dont want to disconnect the wrong one.. thanks

 

Here is the picture of mine already taped off. This is the drivers side rear of my engine.

Don't feel bad, I had to call a friend to figure out where my EGR valve was.

-dan

 

haha thanks dan yeah i was too embarassed to ask where it was although that was my guess