here is what i've replaced within the past 3 weeks. distributor cap&rotor new wires plugs ignition coil fuel pressure regulator new fuel pump new t.p.s. and a new o2 sensor on my driver side manifold and i fixed the horrific exhaust leak. its STILL missing occasionaly. my injectors are less then a year old. my only thought is that there is a vacuum leak somewhere or i need to replace my other o2 sensor in the passanger side manifold and clean my M.A.F. cause im sure its dirty. (late night drives down some back country roads) i farted around with it and when i take the vacuum line that goes from my throttle body to the black can lookin thing close to my firewall (not sure what it is) it idles higher and healthier.

any help would be greatly appreciated. its a 96 with the 5.0.

 

you say you changed your fuel pump did you change your filter also try testing your ignition module???

 

Have you pulled the computer codes to see if anything has been flagged? You should have the OBD-II system, and many chain auto parts stores will read these for you as a free service.

If you choose to clean the MAF sensor, be sure to use the proper cleaner - carb cleaner will damage it. The stuff I bought was about $7 for the can. Many members report significantly improvements after a cleaning.

I hope you used good quality parts on your ignition system changes - the bargain stuff often times creates more problems than they solve.

Perhaps inspect your Idle Air Control (IAC) solenoid. The 87-91 model years were notorious for gunking up, causing idle speed issues. If for nothing else, this will eliminate one of the things not causing the problem.

Check for vacuum leaks by carefully spritzing carb cleaner around the vacuum lines and intake manifold & plenum gasket lines. With the MAF system - any air going into the engine that is not metered by the MAF sensor will cause fuel mixture irregularities that the O2 sensor must work to remove. Since the O2 is a feedback system - it will not be as responsive to fuel / air changes.

As a WAG, you may wish to verify that your timing is where it should be.
Good luck, and keep us posted.

 

Hey - I just solved a bad misfiring problem on my truck by plugging in the wiring connectors to the engine wiring harness. It's just a shot in the dark, but if that is the problem, there's nothing else that will fix it... (I felt like I was having deja vu when I read your list of fixes - my post was here: https://www.f150forum.com/f10/bad-engine-trouble-32458/)

Good luck - let us know what you find out...

 

ill check the connectors in the morning but it only happens a little higher then idle. when i get on it it doesnt miss a beat and can still get the truck sideways with 33" remington mud brutes. so im thinkin it might be a vacuum leak so ill check the chilton tonight and see what the "black can looking thing" is and see if i can get a new one. and as far as quality parts. motor craft plugs borg warner cap and rotor. borg warner ignition coil. oe replacement wires bosch o2 sensor and the new fuel pump came with the filter that goes on it. i dont skimp on parts unless i need a quick fix to last me till i get paid. and whats the name of the cleaner i should use on my MAF???

 

the codes all came up with o2 sensor related problems. which doesnt surprise me cause the sensor i pulled out had a big chunk missing out of it. a few had stuff that was either o2 sensor or vacuum leak related stuff. also a random cylinder miss fire. it seems like its only missing on my driver side. may be because thats the side thats right in front of me and the one i can't hear??? idk. but its drivin me up the friggin wall

 

I had that problem. Turned out the last two plug wires (new) on the driver side were laying across each other, causing sporadic misfires at low rpm. The problem negates itself at higher RPM's. This was the subject of a Ford Tech Bulletin. P.S. Under most circumstances, change your O2's as a pair. Aside from contamination, their switching speed tends to slow w/age. So you'll have one haullin ***, and the other one draggin ***. This will provide less than best accuracy for air to fuel modifications. Kinda like wearin two different shoes. they work, but.....................!

 

It was a CRC product, specifically labelled as "Mass Air Flow Sensor Cleaner".

For those scratching their heads as to why I would be needing this, given my signature info - it was for another vehicle in my beater fleet which actually had the MAF system. :-)

 

wires seemed okay. pickin up the other o2 sensor tomorrow. was going to to take my maf sensor out of the housing to clean it but one of those torx head screws had solder over it so i took the whole housing off took that back plate off and sprayed it with that cleaner. i think im going to get some kind of wire protector to keep it from jumping cause the more and more i think about it the more i think thats what it is. and i need to clean the IAC..... again

 

changed the other o2 sensor. aaaaaaaaaaand i was going to warranty out my iac cause i figured it was under a year sence i got it so i didnt have to screw with cleaning it out. well called orielly..... missed it by TWO days. what kind of crap is that??? so i bit the bullet pulled it off went through a little bit of carb cleaner and ended up with 4 completely black q tips caked with all kinds of trail dust. it idles like a champ now though. found out my wires are grounding out to my valve cover cause my spacer things that came stock broke.

solution? http://www.summitracing.com/parts/RN...B/?image=large
and while im at it http://www.summitracing.com/parts/TA...8/?image=large

have to wait till the check hits the bank though