I have a 95 with a 5.8, 133,000 miles. Start it up and runs great for 20-25 minutes then runs horrible almost like a miss or not getting enough fuel or something. Have already changed wires (twice), plugs (twice), cap & rotor (twice), o2 sensor, ignition module, fuel filter. Check Engine light is not on. Not sure what to do from here. When it runs good, it's great then after that terrible. Suggestions anybody?????

 

pull codes, www.fordfuelinjection.com has instructions using a paperclip. throwing parts at an unknown problem is silly. what brand/type of spark plug are you using. have you checked fuel pressure with a gauge at the fuel rail? what is your timing set at? should be 10*btdc with spout connector removed.

 

Motorcraft plugs, Bosch wires. Did have it to a mechanic who "claims" he checked the injectors and all is ok, checked pressure at rail but not with a gauge, I'll check timing tonight. Have you encountered something like this?

 

you need to know what the pressure is at the rail both with key on and with engine running. this will tell you if the fuel pump or fuel regulartor are causing your issue.

 

what type of gauge and where do I find what the pressure should be for both with key on and engine running?
really appreciate the advise.......

 

optimal pressure should be 39-45 max if it falls below 39 at anytime then you either have a bad fpr or fuel pump.

 

fpr? fuel pressure regulator right?
thanks Kemical!!

 

If that checks out using a can of keyboard duster held upside down so you get
the blast of frost and spraying the electric components with that to cool them
down and see if the problem goes away. You have to start with one component
and spray it down for say 10 seconds and give it a try and see if it still happens
if it does go onto the next and try, next so on and on. You will have to alter the
spray times to match the size and makeup of the part, ie the coil will take quite
a bit of spray time like 30 seconds+ but the TPS may only take 5 seconds.

There is a purpose made spray for doing this to mainframes and other electronic
transmitters and stuff but Keyboard duster is basically the same thing of course
you dojn't want to get the frost on your skin in your eyes or in your lungs but just
wear goggles and gloves and you should be okay. A digital multimeter can save
you a lot of money and if you take your time and post your problems we can tell
you what to look for and how to test it!! And I guarantee you will save a lot of
money!! Another thing to check is the big connectors on the drivers fender they
should have like 10 wires and there should be 2 pull them apart and check for crap
and a quick spray with CRC contact cleaner couldn't hurt, Connectors can sometimes
get hot and then just like a x-mas tree light flasher bend and lose contact and then
cool down and repeat the cycle over and over. A pin extractor comes in handy for
things like this so you can really clean and rebend them so they make good contact.
http://www.sherco-auto.com/cg.htm

 

OK, pulled codes and it came up EGR valve. Replaced, no difference. Still runs extremely rough, at time runs perfect, then bad, then perfect???????????? Can hear popping through exhaust, both sides. Does smell like it's running rich. No other codes (done by self test) are coming up.

 

Was egr real dirty? Have you ever cleaned your IAC? Your intake air temp sensor
could be all crudded up if the Iac was real dirty and that will prevent it from getting
a good reading on the air temp and it can screw with the mixture. Clean it with either
some denatured alcohol or a real quick carb cleaner blast and wipe off the build up.
Some gas line dryer wouldn't hurt I would triple dose it, especially if you hardly ever
fill it up.

 

Beast, cannot locate the IAC?

 

It's the diamond shaped mountingplate with the solenoid deal hanging on the side
of the throttle body. If it is dirty it will usually have idle problems and want to stall
but cleaning it isn't a bad idea if you are already in the cleaning mode. Hold the
solenoid deal up and spray the crap out of the Iac valve use a pick and move the
valve up and down and spin it. Make sure no carb cleaner runs into the solenoid or
it will fail down the road, let it dry and then a bit of Rtv silicone and silver antisieze
on the bolts. Clean the Iatemp sensor if there is a lot of carbon and crap from the
pcv inside the intake the Air fuel ratio depends on the IAt to get a idea on the density
of the incoming air!!

 

Hey d...I did a wright up on the whole Throttle Position Sensor (TPS) testing and replacement. Could be your issue. Testing will not cost you unless you do not have a multimeter. Check this out:
http://www.fullsizebronco.com/forum/...ad.php?t=53840

 

before I dig into the TPS, the problem seems to be changing each day. now it runs rough when I start it, then gets better for a very brief moment, then bad again. the issue is not staying consistent making it harder to pinpoint the cause. while its running rough its trying to get better, its coming in and out while just sitting there idleing.????