Weber 32/36 Rough Idle...then...

[manitou]

Okay folks--I understand how carburetors work, but I know little to nothing about diagnosing or fixing problems associated with them. I'm asking for some advice here simply to avoid getting screwed by a mechanic, when I take it in.

RE: '83 CJ5 - AMC 258 i6 / 4.2l - Authentic (made in Spain) Weber 32/36 carb w/electric choke - Mechanical Fuel Pump.

When I first start up and drive til it warms (195 degrees), it idles rough (stoplights & signs).

IF I park it for 15-30 minutes after its fully hot...when I re-start and drive, it runs like a dream. However, if I leave it parked for say--an hour, or more--then I'm back to square-one with the rough idle.

I recently installed a new EGR valve, and thermal switch (and connecting hose). That seemed to help...a little.

Thoughts? I do appreciate any help/advice you all might have. Thanks!!

 

[Lumpy Grits]

Sounds like the choke is way out of adjustment and need to be backed off some.
LG

 

[Hedgehog]

Sounds like your CJ is running cold to me. I'd replace my thermostat with something that allows your engine to run warmer.

 

[jdcaples]

You don't trust the temperature gauge reading he cited of 195F ?

-Jon

 

[Hedgehog]

Well, the stumbling is definitely heat related. An engines heat will spike shortly after shut down and a restart shortly after shutdown finds a smoother running engine. But if the engine sits for a period and is allowed to cool down some the engine runs rough again. It would be easier for me to follow the pack and blame the carbonator and the problem could very well be with the carb., but I'm attempting to follow the evidence as best I can.

 

[jdcaples]

Hedgehog, someday I'd like to meet you and shake your hand.

I agree with you. The engine's happiest when warm.

So which conditions are true when warm and, um "less true" when cold?

Could a worn gasket expand enough when warm to seal properly, but do a poor job when less than sufficiently heated?

My Jeep's PO installed a weber carb. I needed to adjust the two screws on the dirver and passenger side of the carb to keep it from spitting up when I accelerated too quickly with a cold engine.

On more than one occasion it spit so hard pulling into traffic that the choke plates locked closed and starved the engine for air. I think weber calls 'em "starting throttle valves," but they are the two plates over the opening to the carb, and they regulate air passing through the carb to the engine.

After adjusting those screws, it stopped misbehaving when cold and continued to run fine when warm.

-Jon

 

[Hedgehog]

As far as Weber carbs are concerned, I know practically nothing, but most carbs work in a similar way so most carb. theory still applies.

Could be a lot of different villains causing trouble when an engine is cold verses hot. I'm a big believer in the KISS system. If I believe there is an engine heat problem I start with a simple fix first and that's the thermostat. It could be running cold, it could be closing prematurely, it could be opening partially, one thing is for sure, it's easy to replace and I start there. Now it could be a sticky choke, again the choke might open properly when the engines heat spikes after shut down with the engine running properly after that. Remember a CJ's choke is a stupid thing, no computer involved, just a spring that responds to heat.

 

[Lumpy Grits]

OP-This could also be a jetting issue too.
Ramblings on what I've learned tuning a Weber 32/36 Progressive DGEV Carburetor - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Choke info here-
http://www.jeepforum.com/forum/f8/weber-32-36-how-test-electronic-choke-856339/


LG

 

[Neuner]

After adjusting those screws, it stopped misbehaving when cold and continued to run fine when warm.

-Jon

So you got your issue resolved?

I use to have the same carb. Got it all set up nice and tuned just right. Even graphed out the vacuums, port advance and centrifugal advance.

One morning out of the blue it started acting that same way and continued for some time. Was able to decrease the symptoms but never fully went away. Never figured it out but stopped trying after I knew I was going to do a swap anyways.

 

[jdcaples]

So you got your issue resolved?

I use to have the same carb. Got it all set up nice and tuned just right. Even graphed out the vacuums, port advance and centrifugal advance.

One morning out of the blue it started acting that same way and continued for some time. Was able to decrease the symptoms but never fully went away. Never figured it out but stopped trying after I knew I was going to do a swap anyways.

Yes, my issue was resolved.

-Jon

 

[Lumpy Grits]

LG