Firing On All Four
 

This seems strange:

I have a 74 2.O liter with a single weber carb. (I know, two are better--but if I want to stay married I need to wait a while--I just got the car.) Last week I posted about poor performance when it was in the ninties outside.

I adjusted the valves and the performance improved dramatically. (All of the clearances were tight before I did the adjustment. I don't know the maintainance history)

Now I get a very strong backfire at idle. And this is what I don't understand: If I pull the spark plug wire on the number 2 or 3 cylinder (individually), there is no change in engine rpm, or sound or anything. If I pull the wire on the number 1 or 4 cylinder, the engine dies. There is a spark firing on 2 and 3.

Any thoughts? The car is running good, and seems to have power, and I can't believe it's only running on 2 cylinders, but I don't understand why disconnecting number 2 or 3 doesn't cause any change, and 1 or 4 causes the engine to die?

Thanks for any suggestions

Richard

Some engines do this for no reason at all....and some are getting flat cams, and thats why the two opposing cylinders share the same condition...they share lobes.

do a compression check and see what you get.

2 and 3 are diagonal to each other. They don't share any cam lobes.

Compression, spark, and fuel are what are needed to make a cylinder fire. (That, and timing.) Sounds like you're missing one or more of them on two cylinders.

--DD

I don't understand?
 

I haven't had the chance to do the compression test but:

If I disconnect 2 or 3 (individually) nothing changes at idle, but if I drive the car--it runs terrible--no power, rough, etc.. So they must be firing--correct?

thanks

Richard

I had a similar problem... I had low compression on 2 cylinders... it was running, but rough! compression test should reveal a lot...