1988 F250 idles - but runs like crap

lavcheech · #1 (**permalink**) 07-04-2009, 12:58 PM

Please - I'm at my wits end.
I have a 300 4.9 engine, that I changed the wires, plugs, the fuel filter, checked the fuel relays. Now - I have two problems - it revs high then low at idle -

and when I go to drive the truck, it sputters like crazy in all gears. It has been sputtering in gear only. But in idle it either seems to idle fine -or- it idles up to 2000 on it's own, then either I have to kick the throttle down to lower it (takes a few times) or it does it on it's own.

Vacuuam line seems to be Ok.
This is driving me crazy - along with it raining almost every day in June and July and getting soaked working on this. I know today is July 4th, but maybe someone can help me out. I have no other vehicle but this.
Thanks guys - I really appreciate it,
Anthony - 718-931-6381

BRay09 · #2 (**permalink**) 07-04-2009, 02:01 PM

Not really sure on this year motor, but did you try and remove the IAC and clean it? maybe its shot and in need of a replacement.... Just a thought.

lavcheech · #3 (**permalink**) 07-04-2009, 10:43 PM

Thanks, but I just replaced the IAC.

Now the damn thing doesn't even want to start.
All relays are working.

I do NOT have a Fuel Pressur Guage, but I did open the schrader valve, and fuel was spraying out pretty well. (but I do not know how many lbs.)
Today is 4th of July and the stores closed early, so I would not have gotten there in time.

The fuel filter was changed.

I had someone turn the key on, while I was under the tank - and I did hear the pump (as well as the external pump).

I have a brand new (in tank) Fuel Pump and filter here - and tomorrow I will drop the tank.

I really wanted to avoid dropping the tank - and I tried every possible process of elimination that I can think of.

I have spark to the wires.

When I spray a burst of Ether - it wants to start.

I did not check the injectors (and I do not know how - unless I read the Hanyes Manual)

I'm pulling my hair out.
Any other suggestions?
Thank you - I appreciate it.

BRay09 · #4 (**permalink**) 07-09-2009, 11:48 AM

Maybe the motor is way out of timing here... have you messed with the distributor lately and maybe accidently tightened it back down out of time?

BRay09 · #5 (**permalink**) 07-09-2009, 11:51 AM

IDk if this year motor has an ignition module. That could be bad. That what happened to mine. The module was over heating and the truck began running horribly and all of a sudden it shut down and didnt start again. Have you checked all of your vacuum lines around the motor? This also could be a cause