Alfa Romeo Forums banner
1 - 4 of 4 Posts

·
Registered
Joined
·
40 Posts
Discussion Starter · #1 ·
My 1976 2000 Spider has developed an intermittent misfire with an associated sharp cracking noise which sounds like an ignition arc grounding, or could also be described as a sudden compressed gas escaping noise. It mainly happens during warm up and low RPM but I occasionally also noticed it with normal diving load and RPMs.

I thought I would do the easiest fix first, so I changed the complete ignition harness which was another story, upon which I shall elaborate in a separate post. Needless to say this did not fix the problem.

On further examination, the sound did seem to come from the rear carburetor area, so I am now suspecting a rubber flange leak, but I could not reproduce any misfires by flexing the carburetor mounts.

The single misfire and its seemingly completely random nature mainly at low RPM still has me suspecting ignition, so I was wondering if the forum brains trust would have any suggestions on where to proceed next with the diagnosis.
 

·
Registered
Joined
·
10 Posts
Hi, dirty carb jets that make its misfire through the choke mechanism. Usually lack of use and fuel gums up. If it was mounts would happen more often. Ultra sonic cleaning is an easy way to clean jets.
 

·
Premium Member
Joined
·
24,164 Posts
Agreed, and perhaps the mixture is off on that throat. The choke misfire sounds like a big snort or sneeze, very sudden, and a little puff comes out of the choke (starting circuit) breather.
Test for leaky rubbers by spraying something, WD40, water, that will cause the rpm to drop if it's getting sucked in. And if they're leaking they idle normally will suffer, so that's a clue.
Andrew
 

·
Registered
Joined
·
40 Posts
Discussion Starter · #4 ·
Does this advice also apply to Dellorto carbs?

I don't ever use the choke, and have not seen any little puffs.

The carbs were just cleaned/overhauled properly less than a year ago. The result was that the car drove better that I can ever recall in the past.

Come to think of it, the car was just back with the same guru for another matter, and he did say he made a carburetor adjustment ...
 
1 - 4 of 4 Posts
Top