rough idle 86 f150 straight 6

[napoleankjj2006]

my truck, when you put in in gear it shakes while ur in gear at a idle.
i just rebilult the carb., fuel filter, cap, rotor, plugs, retimed it at tdc
and it still shakes. any other sugestions on what it could be.the carb does have have electronics on it that arent hooked up also.

[mudslinger88]

Is the fuel pump electric or mechanical?

Why are the electronics disconnected from the carb? Are you able to re-connect them? I'm not real great when it comes to troubleshooting electronic issues but I do know that if they are supposed to be hooked up and they aren't it wont run right.

All the emissions equipment working correctly? EGR, and(I don't know when they started putting O2 sensors in) are the O2 sensors in working order?

Is the cat plugged?

Do you have any power loss when your driving?

What is your fuel pressure at?

[carguyzack34]

i would also check vacuum lines for the carb and distributor.

[napoleankjj2006]

two of the plugs on the carb is still open. actually, the electronic choke wire is not plugged in any where and the thing on the side of the carb isnt connected.

all vaccum lines are either plugged in or blocked off as far as i know.

how would i know if the cat is plugged?
my truck has a 02 sensor

if i hit the gas as in flooring it, sometimes the air breather shakes.

i do smell gas exhaust fumes sometime when i get out of the truck and around the engine so its possible the cat is plugged.

when i start the truck, it dont shake but i put it in gear, it shakes until i hit the gas and it stops.

but when the truck is in drive, the idle is rough but if im idling in park or nuetral its ok.

would it be a good idea to clean the 02 sensor as well.

and as far as all emissions, im not sure.

[Davescort97]

To check the cat to see if it is plugged, put a vacuum gauge on a port. If it is plugged you will get a reading of less than 17 inches.

[napoleankjj2006]

sorry the fuel pump is on the engine. thats all i know

[mudslinger88]

If the pump is on the engine then it's mechanical. Check for leaks on or near the pump.

It won't hurt to clean your O2 sensor.

The carb 300 4.9L is infamous for vacuum leaks. Even the smallest of leaks will cause hesitation, rough idle, etc. Check all vacuum line from one end to the other for any dry rotted, cracked, or pinched vacuum lines. I would take a look at you vacuum diagram (located under the hood or in a good repair manual), and make sure that all the vacuum lines are connected. If you have any doubt in a vacuum line's integrity, then replace it. Vacuum line cracks are easy to miss so you have to inspect them very closely. Any more questions feel free to ask.
~JD~

[napoleankjj2006]

i also just dsicovered that the tranny mount was bad, replaced it, and i have no tailpipe, i have a cat and muffler losely attached to the manifold. should i just take off the cat and muffler for now r try to tighen them them up until i can get it fixed?

so is what ur teklling me pretty much is that is it most likely a vaccum leak or fuel pump is leaking that would cause the shaking once its in gear.?

[napoleankjj2006]

autozone told me its not the wires, but the carb is bad and it will cause the shaking and loss of power.

[mudslinger88]

I would make sure that the cat and muffler are secured tightly. If you have any doubt that the cat is plugged, either replace it or pull it out and put a straight pipe in it to replace it but only if your local emissions laws permit you to do so. Verify before removing the cat. You shouldn't run a street vehicle without at least the muffler. It needs the back-pressure to help the exhaust valves open. If not it will cause premature valve train wear.

Yes I would say that it is most likely a vacuum leak. The other things I mentioned are things that I would suggest inspecting to be sure that they are in good working order.

With the carb being bad (according to AutoZone) and you saying that it has been rebuilt, I would check the price for a remanufactured carb and a new one in your area. The reman will be cheaper almost guaranteed. The bad thing is that even a reman will run about $400 from NAPA. A rebuild kit will run about $30 to $40 from NAPA. I would rebuild the carb from top to bottom if it were me. I don't have the money for a reman carb.

[napoleankjj2006]

i rebuilt the carb my self
about a week ago top to bottom
they had the egr valve blocked off, i unblocked it

i found out also that the tranny and motor mounts were bad.
i replace them and it still shakes but it runs better than it did before.

also my tail pipe was never on there ,but the cat and muffler are still attached to the exhaust manifold but there is a gap between the manifold and where the exhasut pipe attaches to. they are just sitting there shaking with the engine when i put it in gear and its at a idle

also. i notcie it shifts hard into reverse and drive. i slowly now shift in reverse and drive but it still shifts hard when i shift from park or nuetral to reverse and drive. its gotten so what smoother now but still does it. what could cause that?