Won't idle

[sneakattak88]

Sled always ran like a top! Did low compression pistons, now it won't idle . Change plugs then it's fine for a few minutes, the thing won't start unless it hold throttle , and runs like poop, should I start with CO settings? I unplugged PCV5 and that didn't do anything. I have so many hours in this I'm pulling my hair!!!

 

[Northernboy]

Did you do the valve timing and check clearances? I just mine back together with a head shim which lower compression then pistons and idles fine. Try setting COs at 0. Also what the A/F readings?

 

[Northernboy]

Also check for a vacuum leak. I know mine won't idle if there is a leak.

 

[rxrider]

You may be off one tooth on the cam Chain.
Or a valve shim may out of position not allowing one of the valves to fully Close.

 

[nate007]

Have you tried new plugs at the same time as unplugging your control box?

CO settings would be a good place to start, and if you have an A/F gauge, let it cycle and ready itself before you start it, without the control box. I'm thinking you are too rich at idle, and it's simply fouling the plugs. Especially if you say it runs fine for a few minutes...
Make sure your plug gaps are set correctly for your application. Plug gaps are critical on most boosted stuff, especially when you start lowering compression. This can help fouling at idle somewhat.
Also (if you didn't already know) it's hard on the plugs if you don't let the engine get up to operating temp before you shut it off. Starting it multiple times for a few seconds or so will most likely leave the plugs "cold fouled" after a few times of doing this. Been there, learned that a long time ago the hard way...

Start with fresh plugs, no control box and afr gauge ready. You should be ok at idle or a few revs without the control box, but dont put any boost to it obviously (so no rips around the yard), and watch the gauge to see if it gets really rich before it dies.

If it does what I mentioned above, You'' have to start looking into the CO settings first, then fuel pressure regulator, possible stuck injector, etc, etc,

 

[FLYBYU]

Sounds like timing is off

 

[sneakattak88]

Ok if sled sits cools down will start, run like poop, but will run. Once hot the only way to start iis 1/8 throttle.and won't run with out throttle, Trimming was rechecked by a dealer and he claims dead on. I have New AFR gauge tonight coming in , to see what fuel I have on idle.