4.0 odd idle not iac

[faron021]

here goes, this is my girls cars 01 4.0 sohc 2door, this is the older motor like the 99-00 had. she brought it with 102XXX miles. didnt think it was in to bad of shape for the price so she got it. had to replace a few parts, first thing i did was a tune up, org fuel filter (black) rusted plugs also org, org wires, and coil. well i changed everything i started just with the plugs i put e3's in it, while i was changing it the boot end of one wires broke i believe it was #2 was so old it shrink to the plug so i went ahead and replace the wires. few weeks ago she was saying it was shaking real bad, with the luck i was having with e3's at the time, i changed them to ngk while i was doing that i said i would go ahead and change the coil, so i put a accel coil #140035.

i was told if you unplug the IAC at idle it should almost or complately kill the engine so i did this and it didnt even seem like it did anything, so later on a put a new IAC on it, as well as cleaned the Throttle body and some of the intake, still shakes, no change with unpluging the IAC, but something new has devoloped over doing this. now if i rev it at idle to any rpm in stead of returning to the 500-600, it hangs at 1000rpm for a little to goes on down.

my only guess is theres a vac leak somewhere. my best guess would be the intake gaskets, every ford i have owned at around 100k they seem to go out.

any help or advice on this thanks.

 

[sport97]

I have similar issues, but my bad idle is hit or miss. Mine also will drop idle to 300rpm and stumble back up randomly. I think I have an intake gasket leak. I can hear the sucking sound from that area and Ive gotten lean o2 code as well.

That is odd that unplugging the IAC had no effect. Mine died instantly...

 

[faron021]

mine hasnt dropped that low, and it only does it one time, its like the computer tell the idle to hesitate, it dont matter what rpm i rev it to in the return to its set idle speed it likes to stop at 1000 then heads on down, but it never did this until i change the iac and clean part of the intake.

if you have a running to lean bank 1, ect i would almost tell you it was the intake gaskets for sure. i had a 01 f150 4.2 and had the same code and finally gave up and to it to a shop the guy there had worked on them before, and said right off the bat thats what it was, a few days later when i got it back worked like new, a few months after that my moms 99 ohv explorer did the same thing, the gaskets are not that much so i took hers apart and replaced those gaskets i run into a problem with the egr tube o-ring, in got stuck and ended up breaking when i was putting everything back together, and that was a $10 o-ring, other then that hers worked fine as well. if you think about doing this watch out for that o-ring, some oil and lube help getting it back in.

back to mine, it also has a weird air sound, but i dont have a check engine light, maybe its not enough to throw it off yet, but enough to keep it running with the iac unpluged, its my girls car and only get to play with it on the weekends ill see what i can find tomorrow.

thanks for the input, hope you get yours fixed as well

 

[faron021]

replacing all the intake gaskets tomorrow, i will try to take pics, im sure there is a how to aready, but i mainly mint of what i found, hopefully this will fix the problem, the set come as upper and lower together might as well change them all.


edit: i feel like pretty dumb now, i have complately forgot about the pcv vavle, im sure that needs replacing at over 100k, that also could be the reason for the odd idle, but none the less i will be changing all tomorrow. i even have a spare MAF. basically it should run like new tomorrow no matter what.

 

[faron021]

alright replaced all gaskets today upper and lower, i have never seen an intake so dirty i went through two can of cleaner and turned my grass black and it still had some left in it. i also took the pcv vavle out and cleaned that still heard the bell so left it on there. everyone who has had problems with getting these pcv's out i pulled the tee right off of it no problems, getting the vavle itself out was another story didnt want to give i took a small flat screwdriver and kinda peeled the hose off of it giving it same air as well and pop it come out no problems, and cuts, cracks, nothing. put everything back together i got so happy it went so smooth i put the upper back on, looked down and forgot the tighten the lower bolts lol. alls back on and starts right up like new, still has the 4.0 shake there could be a motor mount going to not sure yet. but anyways its good for another 80-100k.

however just randomly thout i should unplug the iac just to see, and it did die same it sped back up when i pluged it back in however, it still did seem to have much effect. dead stop floor it almost acts like it dies for a sec then takes off. i sparyed everything before and after the gasket install, and nothing kicked the motor up, im about 95% sure i dont have a vac leak, still doesnt explain the iac issue. unless the throttle body isnt closing all the way that would do it. hmmm. i'll fix it yet, if anything im fixing stuff that needs to be replaced or will be soon.

next im going to try a bigger air filter the one a had is a universal, and i made my own CAI kinda. that would almost make sense with above, floor it computer is dumping gas in by the tps however a split sec the MAF say it doesnt have enough air flow, and kicks it back down that would explain the surge and fall. ill keep yall updated.