the very last post expains what my problem is now.

https://www.f150online.com/forums/sh...61#post2048361

i'm trying to fix this thing to be a reliable truck yet i keep getting pushed back 2 squares for every 1 i walk up to. it's driving me nuts.

here it is in short if you don't wanna read that whole thread:

thanks.

 

What happens if you take off the brake booster tube at the other end and block it with you finger? Did you check that tube for leaks at all?

By the way, I'm in S.E. Michigan and could probably help you out with some diagnostic tools if the problem continues. I've got my hands full redoing the brakes and other nonsense on my beater150.

 

Yeah, I would avoid the oiling of the plunger also. I use a cleaner and swab to clean all the black soot off, spinning and moving the plunger up and down swabbing it all. That should free it up. I also use a toothbrush when doing the throttle bore, opening the butterfly at different stages and scrubbing the crap out of it all. You can clean your IAC several times reusing the gasket at your own risk, but it will go bad(out of operating voltage range) and will need replaced. I would also check your fuel regulator. A quick check is popping the hose off and if it's wet, the regulator is bad. But you should check the fuel pressure at the shrader valve for operating pressure and bleed down pressure when you shut it off. You could have a weak fuel pump too. New filter lately? Someone also mentioned the throttle positioning sensor, which like the IAC, has a operating voltage range. Get a repair manual and a volt meter to check both. You can adjust the TPS(fine tune it), so check where it is. I had both the throttle positioning sensor and the ignition module go bad on my truck at different times. Both had the basic symptoms of running like crap one minute, sorta ok the next. But like someone said, be organized and eliminate one thing at a time and move on. But I never saw where you had reset the computer after any repair or I missed it. I always reset it after any maintainance. Hope this helps.

 

are you getting any codes?

you might have a bad pcv (replace it, and the seal around it..they usually leak after 4-5 years it will only cost 7.00 and works wonders for rough idles, IAC might be bad all together.. the plastic in the plunger breaks up after some time. how many miles do you have?

 

i've only checked the connections for leaks. i didn't think of actually checking the lines themselves. and i haven't checked the other end yet either but i know i gotta do it soon otherwise with these problems lingering in my mind it's gonna drive me nuts.

i was told tha the diaphram inside the brake booster might be leaking....and is causing the vacuum leak. i was also told;

with the engine idling higher than normal (NOTE: i do not have a tach nor one that is reliable to determine the exact RPMs the motor is actually spinning) there would be no vacuum in the manifold (since air is getting into the motor from another source), hence the absence of vacuum at the brake booster.

ok, i'll clean out the oil in the IAC. only thing is; it still idled like it did even before i cleaned it out. i used carb cleaner and sparyed and soaked the IAC and the TB too. i'll have to grab a fuel pressure gauge and check the fuel pressure. the fuel filter looks pretty brand new in the frame rail. i am unsure about the pump(s) (dual fuel tanks)

i have the 3 book set of factory service manuals for this truck and a multimeter so i'll be sure to check on the voltage conditions of the TPS and IAC if they're within spec.

i did not know i had to reset the computer after every mod/repair. i have never noticed the check engine light ever coming on or staying on. only whenever i start the truck.

i'll be sure to check the fuel regulator. as it kinda sounds like a fuel delivery problem as the truck actually RAN fine albeit with the normal 'high' idle BEFORE i tried looking for that elusive vacuum leak.

i have not checked for codes but i'm guessing i should regardless if the check engine light is on or not. they might be stored codes (assuming that these are OBDI/II or the like.) i'm new to these trucks so i don't really know much about them.

the pcv; my airbox does not seal correctly as the tabs that are used to bolt the top cover down around the filter has broken off. i don't think that should affect the vacuum system.

BUT when i start the truck after it's been sitting for a while, the idle is high(er) for about a minute or so and then the idle drops down supposedly after the motor has warmed up enough.....like in every other car that gets started after sitting a while and needs to warm up.

one of the guys at my work has said to check if the IAC is working is to start the truck, let it warm up and pop off the electrical connector to the IAC and see if this affects idle.

no change: IAC isn't working
with change: it is working

at the moment i don't really care about the higher than normal idle anymore ever since the motor craps out randomly. i don't want to get stranded at the side of the road again. i'll live with the high idle.

thanks.

 

and the mileage: i don't really know as i bought the truck at auction and the mileage may have exceeded the odometers mechanical limits. but i am pretty sure that the motor and trans have been rebuilt before as i was able to find the for sale sign which stated this by the seller. i have not spoken with the previous owner. and i know i should.

 

I've got a tach I can attach to a spark plug cable. Message me and let me know where you are. I can probably stop by one day.

I can probably find a vacuum gage too.

 

so i checked the voltage for the IAC and the TPS. the IAC is seeing 12 volts and the TPS is seeing .7-3.8 volts and changes whenever the TB is opened/closed.

the motor died on me when the electrical connector to the IAC was popped off. so i know it's working.

the vacuum line to the FPR is dry as a bone.

with the truck having dual fuel tanks i thought that maybe the pump in the current switched tank could have been the culprit. so i switched it to the rear tank and started it up. ran fine, then i switched to the front tank and it also ran fine.

the truck also has a really hard time starting after my quest for the lost vacuum leak. it never had such a hard time starting before. it used to start right up, but now i have to sit there cranking and cranking and hitting the gas to try and get it started. if it does start it doesn't wanna keep running and i'm having to keep giving it some gas.

popped off the PCV from the valve cover while the motor was running and i am getting vacuum there. i plugged the hole with my thumb and the idle kinda dropped a little and it sucked in my thumb. the valve itself still rattles when i shook it, so it's not gummed/stuck.

my buddy and i are totally confused because the motor actually ran fine and didn't die on us after we checked all of these things. BUT it does have a hard time starting.

after a while the upper radiator hose was really warm. but it was really hard. i was wondering why the thermostat wasn't opening up.

 

the KOEO codes i'm getting:

code 81, 82.
air management circuits 1 and 2 are malfunctioning. what do i fix for this?

continuous memory code 14
profile ignition sensor circuit malfunctioning.

fix?

where is the IAT sensor located at? and the MAF?

thanks.
since i'm not able to keep the truck running i am not able to check for the KOER codes. this does mean that i wasn't able to warm up the engine either.

 

You do not have a MAF on an 89.

 

Intermittant Code 14 is definatly one of your major problems.
Profile Ignition circuit is the small box on the distributor, it controls spark. Intermittantly failing will cause your engine to die, I had this same problem 2x on my 90 5.0 F150.
I would replace the module (cheap ones are around $40) check and clean the wiring harness on the PIP module and where it plugs into the main harness (white one if I remember correctly)
That should certainly fix your truck dying.
Although I would run a compression test and check your spark plugs for info on the condition of the motor first. I spent alot of time and money chasing a rough running problem through sensors (many which were bad) but there were also internal engine problems.

 

Don't worry about codes 81, 82 yet - they are thermactors dealing with smog / emissions. Get your engine running right first

 

ok, so which do i replace; the TFI module (at the side of the distributor) or the PIP (profile ignition pickup) inside the distributor? cuz i've allready bought a new PIP which means i'll have to tear apart the distributor to replace it.

if it's just the TFI module that'll be easier.

 

Sorry about the confusion
Replace TFI module, it will throw the same code, apparantly its a common problem in those trucks.

 

i just ran to the auto parts store and they were able to test the tfi module. the test came out as passing. so what now? maybe i'll just go ahead and replace the PIP inside the distributor.