i have a 91 f250 and when i drive it for a while and turn it off and try to drive it again a few minutes later it misses out really bad. when i drive it a few blocks it straitens out. i have replaced fuel filter, plugs, wires, distributor cap, and roater. i think that i might have a leaky fuel injector and it drips down into the cylinder and it misses out until i burn the gas out of it, but i am not sure

i am at witts end any input will be appreciated

offroadguy

 

My 88 300-6 does that sometimes and I theorized that the motor is getting mixed signals from the computer that it just has to straighten out. For instance the temp sensor may think the motor is warmer than it really is and sends a signal that makes the computer deliver a rich fuel mixture. I've found that letting my truck run 30-40 seconds before going anywhere helps the computer get the right settings. So I don't think its a true ignition or fuel delivery problem.

 

It may be boiling the fuel out of the rail and injectors. Does the little blower motor on the fender on your truck run at all? It's supposed to run for a bit after the engine is shut off. This may be bad.

Jared

 

i didn't know that they have a fender blower, so i guess that it doesn't come on, but i have had the truck for like 4 months and it just started doing it like 2 weeks ago

someone told me today that i may have burnt up my valves because i don't have enough compression. my converters are cut off and i have glasspacks so it is virtually free flow

 

if my fuel injector is bad how do i go about finding which one is the leaky one?

offroad guy

 

[updated:LAST EDITED ON 03-Jan-03 AT 11:49 PM (EST)]The injector cooling fan was only used on '87-88 4.9Ls. Cutting off the cats & muffler reduces "backpressure", not "compression" which is what the pistons do.

Pull your codes http://www.broncodata.com/tech/codes.htm
Do a vacuum test http://www.users.bigpond.com/ergoff/vac1.htm
And do a compression test using a screw-in tester; not a push-in. Be sure to pull ALL the spark plugs AND block the throttle open for the whole compression test. Sears sells a good compression tester for less than $20.
Identifying a single leaky injector will be tough, but you should first test your fuel pressure and see how fast it bleeds down after the engine is shut off. Sears sells a good FP tester, too.