While driving home last night from work in Seattle after about 25 miles when I let off the accelerator the Tach went to zero when I stepped on the gas back to 3000 rpm no hesitations this went on for another 25 miles when I got of the highway and came to a stop so did the engine. I was able to restart with the accelerator depressed I made it home the engine won’t Idle. This morning it started right up and Idled just fine until it warmed up and the cold start valve shut. It will restart and run with the accelerator depressed. Just no Idle. I checked the throttle position switch it is OK. This is a 2056 with 1974 Djet with mostly new components and a new Bowlsby Harness

Vacuum leaks. Point dwell and timing. Valve adjustment. Mixture, both at idle and at operating speeds. Idle bypass adjustment. MPS. The Cap'n

Did you test the CSV? It shouldn't be activating at all in our temps, and shouldn't be suspect in your symptoms. Need to methodically work through the things the Cap'n listed before making any assumptions.


Although, I have to say, a vacuum leak on Djet usually causes high idle issues. So don't spend a lot of time looking for vacuum leaks just yet - except for the line to the MPS - which could cause low idle because insufficient vacuum to the MPS makes it run overly rich.

Let me get this straight. As you were crusing along the freeway, in gear, the tach dropped to zero when you let off the accelerator, and then jumped back up to the right rpms when you put your foot back on the gas? And I am assuming you don't have an automatic...

The tach doing wacky things usually means a problem with the points. I would start there. The tach combined with bad idle screams points at me.

If not, maybe the battery is tipping against something when you decelerate and shorting out? Grasping at straws now...

Yes in gear at speed tach goes to zero when the throttle is closed, open throttle rpms jump back. with throttle closed if I put in the clutch the engine is off, let the clutch out engine on. come to a stop throttle closed engine is off. open throttle turn ignition on engine starts let out clutch and go. the engine runs fine. started at first attemped this morning and idled at 1100 rpm until theAuxiliary Air Regulator shut then the engine stopped. This in not a case of poor idle this no idle. this happened suddenly. It has petronix no points.

you answered it.
Get points.

Rich

My understanding is if the petronix goes bad it would not run at all?

Maybe your ground strap fell off and it's getting ground through the clutch/throttle cables or something else goofy?

I took out the pertronix and put points back in. runs perfect thanks for the help.