Unintended acceleration
 

Hello everyone, new to joining this forum however have scanned through tons of info on the forum throughout my build. Hoping someone can guide me in the right direction.

Yesterday while pulling out of the drive way i had a wild little ride once putting truck into gear. I put truck in low gear and literally tapped the gas giving no more than 50-100 rpm and the truck violently tried to launch like I had floored it. Threw it in neutral and shut her down. Luckily I didn’t smash the front of my other vehicle park in the street. First thought was the throttle cable had gotten stuck so I popped the hood to check and throttle cable was returning freely. Stumped. So I fired it back up gave it some revs in park to see if the cable is hanging and nothing.. rpms come back down freely No hanging up. Put it in drive and touch the throttle and the same thing as before... violently tried to launch. Turned it off, pulled air cleaner to check carb and noticed the secondary sight glass was way to full and there was fuel dripping from secondary Venturi... fuel level was set to correct level before. Could this dripping cause the truck to rapidly accelerate unintended? Could a vacuum leak cause this? If anyone’s got any ideas before I start to tear into this that would be awesome.

specs:
1982 dodge d150
1990 318 block
stock bottom end balanced
bored over .30
KB pistons
arp rod bolts
72 360 heads milled and ported
comp cam 274h
compression around 10.5 1
Quickfuel hot rod series 650
rpm air gap intake
msd 6al- pro billet distributor.
timing 18 initial 36 total. No vacuum advance
a999 trans with turbo cheetah RVMB
2200-2500 stall
4.10 gears 8.25 rear end
longtubes with H-pipe.

This happened to me for a while in my '68 until i finally caught the issue--busted driver side motor mount. The torque would lift the engine up a few inches, which pulled throttle cable taut. wouldnt let go til i hit 3rd gear. scared the hell out of me for a while, tbh lol! thought the rig was haunted. :D

i replaced and it broke again almost immediately, so i replaced once more then locked it onto the k-member with 1/4" chain and a big ass bolt. :P

I’ll definitely take a look at that this week. Could be the culprit. It’s definitely a quick scare of a situation lol. I’ll post an update once checking everything over. Thanks for that info! I’m assuming the reason it wouldn’t do it in park is that there’s no load twisting the motor like there is when in gear?

Right! Mine locked up too. :D I hope it's as easy as that. I can't imagine what else it would be.

Also Make sure both float levels are correct... And make sure your throttle return spring is tight enough to return the throttle to idle.
And yes.. if the carb id dribbling it can cause that issue...

Appreciate it! Actually getting ready to work out the issue today. I’ll report back after tinkering with it

woot woot good luck, man! :)

Late update. Been very busy the past two months. But finally did find the culprit. Throttle cable was hanging up on a wire loom clamp on the fire wall yanking the throttle under load. Motor mounts were in great shape. But did do a full run through and found that a brand new trans Mount rubber was shrunk and wobbling In is support. (Cheap a** mount). Replaced with a prothane poly mount. Much better fit. Appreciate all the help!

woooohooo! At least ya found it. :)

Yea! Such a simple thing to over look! While I was looking it over decided to go ahead relocate a new fuel tank and ran all new AN fuel lines and electric pump and return No more vapor lock issues! Running super good now!

Glad you found your issues....
Also Hope you added in a Fuel Pump Relay for the use of the pump?
https://www.enginebasics.com/Advance...p%20relay.html

Relay installed. Going to install an inertia switch aswell soon

Unintended acceleration, I've clammed that a time or two...

Me also.... One for an "Exhibition of Speed" Citation..... lol