foru2nv4

How do you know when your aftermarket throttlebody which mine is 75mm BBK has gone bad and what would cause that?

zero2005

define "gone bad"? you mean the throttle position sensor? what other problems are you having?

95SHO

Can you be descriptive.

cliffyk

There's not a whole lot to "go bad" with a TB, other than the TPS--it's just a hole in a block of cast aluminum with a "flapper" valve in it.

As others have said, be more specific...

foru2nv4

Car idles at 1500 rpms when being drivin down the street. but when i start the car from a cold start or a warm start or a hot start it idles fine as soon as I drive the car it stays at 1500 rpms at a light then it drops like its gonna die but car adjusts and brings it up past idle then its idling high again, is it a bad TB if so why its a mechanical device controlled by a spring and a foot pedal?

cliffyk

Other than the preset amount of air allowed to bleed through the TB (here's the procedure for making that setting) the TB has nothing to do with controlling the idle speed. That is done by the PCM.

The PCM controls the Idle Air Control (IAC) valve to allow additional metered air into the engine, and thus control the idle. What you describe sounds as though it may be an incorrect initial setup of the throttle stop screw and perhaps a sticking IAC.

I would recommend first checking the throttle stop screw setting, make sure you disconnect the battery for 5-7 minutes while doing so.

You can check the IAC by unplugging the electrical connection while the engine is hot and idling--the idle should drop immediately and perhaps stall, if it does not the IAC is bad; replace it...

foru2nv4

I did unplug the IAC and the car stop running. I changed the IAC a week ago with a new one from autozone because car was idling to low but the new one did not fix that problem it has opened up a whole new can of warms. Now when you drive the car it idles up around 1500 rpms while driving then one you come to a stop the idle jumps up to 2000 rpms immediatly then drops all the way down to 200 rpms almost gonna die but the car compensates and gets the idle back up before the car stalls out and resumes idling at 700 rpms which is alittle low thats why a replaced the IAC. You start driving it again from light or stop sign it starts the same thing all over. Any more ideas possibly the TB sticking open while air is rushing in and then slowly closing while at a stop? I wipe the TB down no change at all.

zero2005

you would know if the TB is sticking... its all mechanical so you would feel it in the pedal.
there's only a couple problems. i would say take the IAC back to autozone and swap it out for a new one, its very possible that it could be a bad one. really thats the only thing that would make most sense.

also, make sure you disconnected the battery for 5-7 minutes like cliffy said, as it clears the memory.

foru2nv4

But what are the chances of the IAC stock being bad and buying a new one from autozone doing the same thing? I am hopin changing my throttlebody and my MAF and a new cold air induction kit works. I am installing all this 2nite since Im on vacation and let you all know if this helps my high idle.

cliffyk

You never before told us that you had a 90 mm MAF housing, loaded with the stock sensor (as revealed in your other thread)--this completely changes the MAFs transfer function, effectively increasing the output voltage to air flow mapping by 35% or so.

The car runs like crap because doing that without modifying the tune to reflect the new transfer function leaves the PCM thinking the airflow is the same as that of the 80 mm housing--it does not inject enough fuel and the engine run lean. In closed loop the short term fuel trim will make up some of that but not all.