'82 CIS cold start issue

[groovydude]

I rebuilt my CIS a few months ago. I replaced the airbox and plugged up all the air leaks! The engine runs beautifully, except that since the rebuild I've been having a cold start issue. Once out of 10 times, the car starts perfectly when cold. The other times it doesn't turn over immediately, after a few seconds on the starter it sounds like it's barely engaged, and if I let go of the key it gets going. It runs rough at first, like its too rich, and after about 20 seconds or so the idle ramps up to where it's supposed to be.

I've checked the pressures and everything is up to spec. There's no vacuum leak, idle drops as it should when I remove the oil cap. I'm sure the CSV is doing its thing.

Here's the rub. I've figured out that if I sharply tap and release the gas pedal BEFORE I turn the key it fires right up. I'm thinking slightly sticky throttle plate (is that what it's called)? Any other ideas?

[gazzerr]

Hey Groovy. I have a similar problem - grumpy when cold with oscillating low idle but once it warms up it runs great. I don't need to touch the pedal to start it. Normally it starts just fine.

One morning I did give it a stab of throttle and low and behold it rev'ed up to 1200 and settled nicely to 950 over a few minutes like it should!

I plan to run another pressure test as Tony recommended (now that the weather is warm). I also found more air leaks - specifically the brake booster venturi y pipe that comes off the side of the airbox and plugs in the brake booster hose. There's an o-ring in there. John Walker recommends covering the joins with heat shrink so I plan to try that too.

I also plan to replace the plugs and wires. My timing seems spot on.

[groovydude]

It sounds like we might be facing different issues. I checked my brake vac line pretty closely when I had my CIS out. I didn't see any signs of possible leaking. The line looked pretty new, a PO may have had it replaced. Have you tried the pedal tap? It's like a miracle cure for mine, or at least a miracle work around!

[gazzerr]

I haven't tried the pedal tap. I'll try that. The venturi is the bit to check it actually come apart. There's a little rubber o-ring in there. I sprayed carb cleaner on it and she revved up so I've got a leak there. The other thing I was wondering about was the throttle body where the shaft the butter fly rides on. Air must be getting sucked into there.

[Reiver]

I had rough cold starting...weak and a slight backfire on occasion on my '83 (euro).
It was the thermo time switch that controls the cold start valve opening when the block is below 113 degrees....page 240-23 Bentleys.
Easy electrical check for op.

[gazzerr]

Cool thanks will check that too. I never actually checked that.