what would cause a 5.0 to rev uncontrollably?

[Asha'man]

On my way home today I saw a blue-on-silver fox GT on the side of the road with his hazards on, so I ducked in in front of him. Was a mexican guy who works at the IHOP by my house, I've seen the car there before; it's really ragged out. Anyway, he said the RPM's just started to skyrocket uncontrollably, so he pulled over. I started it up and it did just that....tached up to about 4k in a second or two and showed no signs of coming down, so I shut it off immediately. Now, being a 2.3 guy with no real experience with 5.0's, what could cause this? Due to the slack on his gas pedal, I'm thinking it was a stuck throttle cable, but I looked around by the TB and didn't see a cable. Anyone ever had this happen? It was an automatic, btw.

Some *******s shouted "hahaaaaa" out their window as they drove past, I don't know which car it was. Guess they thought it was funny to see two Foxes on the side of the road. Flipped them the birdy as an afterthought....let's see another Sunbird or whatever owner pull over next time they're in trouble, shall we....

Ash

 

[IndyBlk5.0]

stuck throttle cable more than likely. The throttle cable is underneigth the throttle body on these cars.
That or a blown intake gasket, which is unlikely.

 

[DirtyD916]

i say throttle cable. find it get some carb cleaner on a rag and just clean it and rub it real good.

 

[MustangPunk302]

Like they said throttle cable, or a major vaccum/intake leak...

 

[HISSIN50]

the cable and linkage for the throttle is under the TB. you can see the cable sheath from the back side of the TB and the linkage from the front.

as said, have him check for a big vac line cracked or that has come off. on a stockish 5.0, vac at idle should be 15-20 inches (if it helps with determining if it is a vac leak).

good luck, and good on ya for helping him out.

 

[Asha'man]

Under the TB, got it. I'll see if I can swing by in a day or two when the car's at IHOP and see if he got it fixed and what it was. Thanks guys!

Ash

 

[riceater89-5.0]

mine was revving up to about 2 or so by itself, i jus unplugged the TPS and left it for a minute, plugged it back up, and wallah!!! but in this case it does sound like throttle cable.

 

[TheUser]

if not the throttle cable, maybe his tps is off/bad.

 

[89MustangGX]

I say more than likely it's the IAB on the side of the TB. As they get used they get gunked up with oil/carbon/whatever from the breather and incoming air. You can take it off and clean it out good with carb/brake cleaner and a screwdriver -- try and get it as clean as possible. You may end up having to replace it though if it's really bad.