MAF or IAC -which to replace?

[djsk8r33]

most deffinately when my truck is cold on startup, the RPMS at idle jump up and down. not bya lot. maybe from 600-800 and back down. it keeps doing that. you can hear it

sometimes even when its warm.. it will do that.. i cleaned my MAF and IAC, my MAF looks new and was clean. IAC on the other hand was dirty, but i cleaned it pretty good. nei ther helped

the IAC for ALL my other trucks was around 40 bucks. this one for some reason is 72? is the IAC deffinately my problem? an MAF sensor is over 100 bucks

edit: no surging or anything at acceleration

 

[aldive]

Have you cleaned the MAF and IAC?

 

[fordnut71]

check your rubber hose as they could be crack an will cause a rough idle till it warms up an swells the cracks shut.

 

[Lt.Jim]

When my MAF took a dump it would surge all the time making the truck very difficult to drive. A good test would be when you start the truck and the idle surges unplug the maf and see if it evens out. If so then it's probably a maf problem. Are you getting a cel?

 

[little x]

If you unplug the MAF the truck will stall out immediately, won't it? When I cleaned my IAC it didn't really do any good, but a new one sure did. It's an expensive guess, but if you can't find any air leaks, that very well could be it. How many miles are on the truck? It's a 91, so it's probably time to be replaced.

 

[djsk8r33]

Have you cleaned the MAF and IAC?

... you ddint read my post did you?

When my MAF took a dump it would surge all the time making the truck very difficult to drive. A good test would be when you start the truck and the idle surges unplug the maf and see if it evens out. If so then it's probably a maf problem. Are you getting a cel?

no CEL. i recently got the truck and i got one for a few minutes about a month ago, but havent had one since

If you unplug the MAF the truck will stall out immediately, won't it? When I cleaned my IAC it didn't really do any good, but a new one sure did. It's an expensive guess, but if you can't find any air leaks, that very well could be it. How many miles are on the truck? It's a 91, so it's probably time to be replaced.

truck wont stall if i unplug MAF, nor will it if i unplug tps on IAC. 50k on the motor, but who knows if either have bene replaced

 

[aldive]

... you ddint read my post did you?

Sorry, I missed it somehow.

 

[little x]

I'm guessing the truck has more then 50K original miles, and that the motor was either rebuilt or a short/long block was ordered and swapped in. And if I'm not mistake neither the IAC nor the MAF would be replaced in any of those situations (maybe if it was a long block the IAC, but I can't remember for sure). So those parts are most likely 17 years old, even if the engine only has 50K.

 

[djsk8r33]

I'm guessing the truck has more then 50K original miles, and that the motor was either rebuilt or a short/long block was ordered and swapped in. And if I'm not mistake neither the IAC nor the MAF would be replaced in any of those situations (maybe if it was a long block the IAC, but I can't remember for sure). So those parts are most likely 17 years old, even if the engine only has 50K.

oh yeah.. i know. they LOOK like 17 year old parts..
i think im going to go ahead and replace it. if anything autozoo will take their crappy part back and gimme my money if it doesnt help

 

[djsk8r33]

i was hoping(maybe not so much) there may be something else that'd fix this. but ill replace the IAC today and see what happens

 

[manaen]

did you check for vacuum leaks? there are other things that can cause this other than the IAC and MAF.

 

[djsk8r33]

did you check for vacuum leaks? there are other things that can cause this other than the IAC and MAF.

there are no leaks of any sort, all hoses were replaced and checked recently.

i just finsihed putting in the new IAC and fired her up. idles a bit lower and smoother. not sure what harm it was doing before.. but its gone

70 dollars well spent......... i guess

 

[aldive]

Did you reset the PCM after the IAC install?

 

[djsk8r33]

yes i did reset the PCM by unhooked negtive cable for abotu an hour