Mine had a slight rough idle starting about 54k. Running Redline fuel system cleaner and cleaning the IAC keeps it at bay for the most part. The weird part is that the idle problem disappears completely when the a/c is turned on? Very puzzling. My idle is also low when the roughness is going on. About 63k the check engine light came on and I took it to Autozone to get the codes. It was PO171 if I remember correctly. I bought the 02 sensor for the indicated side, thinking it was fixed. About a month later the CE light came on again, and it ended up being the MAF. It has not turned on since, and I'm at 97k now.,,,,98

Redline really works well for the idle trouble on my truck. You can find it at Pep Boys usually, if there's one near you anywhere.

 

98 screamer,

what was wrong with the maf? did it just need cleaned? was it sticking? broke? was it a maf sensor or the actual maf valve?

 

I cleaned it, at the same time I replaced the 02 sensor. That seemed to hold it off a few weeks longer. The next time the light came on, nothing would help it, cleaning, resetting the battery, nothing. Came right back on within a mile or two. They replaced the whole assembly with a remanufactured MAF, which kind of made me a bit mad at first, seeing as it was a dealer? It was a sandblasted housing, with a new sensor screwed into it. They didn't give me a break on labor either, even though I had an aftermarket intake. I'd love to get paid for an hour and half of my time to R/R two hose clamps, a plug, and four 10mm nuts and bolts. ,,,,98

 

Well, I ran to Autozone, and no codes came up.

I also filled up the tank, put 89 in it this time (Citgo). Will try to use it for the next tank or two and see what happens, but Im not gonna bet on it :|

 

98screamer ........what did the remanufacture and labor cost? just researching incase thats my problem.

 

Well, the dealer charged me $268 parts and labor, which I thought should've at least got me a new MAF. At least they gave me the old one back, which I gutted and smoothed. I took the sensor out of the new housing, and put it in the gutted one. Got a nice throttle response and a slightly firmer downshift. ,,,,98

Not that I want to open the gutted MAF bag of worms in this thread. It's what I did though.

 

mahoney22e,
the O2 sensor didn't correct your rough idle? has it returned? i'm having the same exact problem as you. i've changed IAC, TPS, EGR, plugs and plug wires, fuel filter, EVAP hose, PCV valve and hose, and the DPFE sensor... hell, i'm tired of replacing stuff. the truck will not set a code. it will only rough idle when the truck has been warmed up, and it only does it when i come to a red light, rpm's drop to about 400, and the truck starts shaking bad. it doesn't do it everytime i stop... i need it to set a light. i'm starting to think its either the O2 sensors or the MAF sensor..

 

plug,


i have replaced everything you have except the egr and dpfe sensor. yes the o2 sensor has taken the edge off of the rough idle but it has recently dropped back down to 500rpms at a stop light (STILL IDLES FINE IN PARK OR NUETRAL). again it hasn't shaken to the point that i have had to rev the engine (like before the o2 change) but it does indicate to me that the problem is not completely sovled. thats why i was asking so many quetions about the MAF. i guess it is something to look into. let me know if you find a solution and i will keep you updated as well........take care and good luck

 

sure thing. my truck idles around 750 rpm's, but once in awhile it starts the shaking and rpm's drop.. its never died, but i sure thought it was going to... it'll shake violently, then all of sudden, its as if the IAC valve kicks in, and the rpm's shoot up to about 800, and the truck idles fine... its kind of crazy..

i've cleaned my MAF, but maybe its bad... hard to tell, i'm now waiting for a light, sense i've wasted so much money..

my truck use to have the rough idle several times a day, until i replace the PCV hose, the rubber elbow right at the PCV valve was worn and it would collaspe when the truck got hot. now i only get the rough idle once every 2 days or so...

my dad has a 99 4.6l F150 also, so i may put his MAF on my truck and run it for a few days, if this is the problem, then i'll know i'm buying the correct part... will keep you updated.

 

also, you may want to try to adust the throttle plate... some people will most likely disagree with this, but so long as the TPS is putting out a voltage between 0.5 and 1.0, you'll be fine...

look at the lever where it strikes the offset screw on the throttle body. you can either wrap some electrical tape around the plate on the lever, or take a pair of pliers and bend the lever plate inwards, towards the cab of the truck.... don't bend it very far, or if you use tape, just make about 3 wraps... be careful bending the lever, as you don't want to break it... a slight bend almost unnoticeable to eye will work...remember this will increase the idle speed of the truck. you should only adjust it enough to make the truck idle round 700 rpm's...

if you do use the tape trick, make sure to cut off all excess, and make sure it won't bind and hold the throttle open... the tape will basically just make a bumper to the set screw...

hope this helps..

 

thanks i will be sure to try that ......how has it worked for you? with you adjusting the idle does the rpms still drop on you with a load after it is warm? also did any of the items that you replaced or cleaned give you a temp fix. what i mean is did you think the problem was solved only to have it happen several days later? i am thinking of replacing the o2 sensor on the drivers side before the cat .con. and clean up the egr. i don't think the egr is all that dirty though. i cleaned the t/b, maf and none of them were that dirty. i have been told that when your egr is real dirty your truck has a tendency to ping, no pinging. i am also going to take it in to have a smoke machine hooked up to it to see if i have a small vacuum leak somewhere. i tell ya it is really getting to me. my wife thinks i am crazy. any how i will tell you how it plays out after this weekend.

 

when i 1st replaced the pcv hose, i thought the problem was fixed, but it showed up again last week. the tape trick that i spoke of doesn't really adjust your idle as in the computer mindset. it actually just holds the throttl open a tiny, tiny bit, thus reving the engine and holding the rpm's around 700...

my trucks rpm's will still drop when ever the mystery idle shows up... other then that, it purrs like a kitten at 700 rpm's... just once in awhile it decides to start acting up.... its about to drive me crazy, if that damn light would come on.... that's what i'm hoping for...

 

A friend of mine said that there was some kind of recall on radiator fluid that leaked to a bearing. Has anybody heard this or know about it. It would help If anybody could shed light on this

 

Red4.2XL,your questions are answered at this website;
www.leakingfords.com

Plug and Mahoney,what brand of plugs/wires are ya'll using presently?How many miles on them at this time?

 

i have the original plugs and wires w/ 52k on them. i plan on changing them in a couple of weeks. going to install motorcraft double plat. plugs and motorcraft wires. any suggestions??????