Truck idles very high when starting

Hello. It seems one or more of your car's 'fuel injectors' is/are 'flooding' your cars engine. The excess fuel 'ignites'; making the engine 'race' at high engine speed yet it won't accelerate. Good luck and keep me informed; if you want to.

You may need check the spark plug. Cleaning or Replacing it could possibly fix the issue. Also clean or replace the battery terminals. Testing a different battery is another option to try.

old car, very old
this is easy, to find, but can be many things, my tests cut this to 2 reasons. mostly. (leaks and isc failure tests)
1: ISC system is dead, (stuck idle speed contr. valve)
2: throttle cable stuck or set wrong, (must have slack)
3: vacuum leaks, on all cars with map sensors, vacuum leaks make the ISC loose control and RACES fast with full engine power. all MAP based EFI SYSTEMS, "speed density systems:

In 85 Ford used a carb spacer that also had the EGR attached.

It could be that the gasket has broken and it has a large vacuum leak. Also the EGR could be stuck open. Look for other vacuum leaks like the PCV and brake booster vacuum systems. A 460 engine will run with huge vacuum leaks especially when the choke is on but the extra air will lean out the mixture and could cause damage.
Enclosed is a video about setting idle on a Holley carb which you may not need but others looking at this post may like to see.

Try cleaning the throttle body and check the gap on all the spark plugs also all electrical sensor plugs and battery terminals this could be related to engine temperature also if to hot rpms stay up longer to cool off but maybe your idle air control valve is bad when did it start?

Have them spray (lightly) starting fluid around the intake with the truck running. If there is a leak the engine will idle up even more. They may also just need to adjust the throttle linkage.

you didnt say if it was happening only during the initial warm up of the vehicle or all the time. if it is just during warm up this is not too unusual as long as the engine isnt racing. if it is just a "high idle", say arround 2,000 rpm's its normal. the idle would usually go down as the vehicle reaches operating temperature. when you put the vehicle in gear, you are actually loading the engine slightly, thats why the idle comes down then. when in park the engine has no load on it so it is free to rev a little higher at these times. if it a at a high idle constantly, then i would start looking for sticking throttle cable, binding throttle plates, ect and remedy the problem. this should not have anything to do with the dual exhaust.

check your idle air control valve.

Insufficient information

My gas petal used to stick on the jeep so i spray up in there on the petal to stop it from sticking ore the brake light woud stay on becuse petal got stuck try some WD40 just dont sray on your petal ok might work