IML: Surge At Hiway Speeds

["Eric" <gearhead@xxxxxxxxxxx>]

Robin,
I had a '72 Newport that gave the same symptom. It had about 129K on the 
engine. After doing all the basics- plugs, wires, ignition control unit (it 
had the optional for '72 electronic ignition for Newports with the optional 
440), and a carb rebuild, it still would surge at highway speeds.

One night my timing chain's nylon cam sprocket lost the last bits of nylon 
coated teeth that were still holding on to dear life and let loose causing 
the engine to die and requiring the timing chain set to be replaced.

After I installed the new chain and sprockets, I noted the lack of the same 
surge that you mentioned. That was the word I was using to describe this 
trouble. Other symptoms that went away after I replaced the timing chain set 
were long cranking times, a resistance of the choke to come off of high 
idle, a lumpy idle, and relatively poor fuel economy.. I used to have to jab 
the throttle to the floor a couple or more times to get it off high idle 
when cold but afterwards, a normal fraction of an inch throttling took it 
off high idle. These symptoms were due to poor vacuum caused by out of time 
cam / valve operation

One way for you to check your timing chain set is to put a timing light down 
at the timing marker on the crankshaft. If it jumps around as the engine is 
idling, you have a worn nylon coated cam sprocket and chain. Do you know if 
your Imperial's cam sprocket has over 100K on it? If so, it's pretty much a 
given that it should be replaced.

There is another test is to see how much you can rotate the crank before the 
distributor rotor starts to rotate. Someone on the list was just mentioning 
this and maybe they can give the specifics.

My Newport ran smooth as silk after the replacment.

Eric
1964 Crown Coupe
_______________________________________________________________________
From: "Robin Giesbrecht" <robings@xxxxxxxxxxx>
Subject: IML: surging at highway speed
Any ideas on a surging that is slight but getting worse at highway speeds on
a 72 Imperial. I thought about a possible vacuum leak which I have to check
out with a gauge but what about coil or electronic control unit? Any
experience there? Everything else is great starts, idles, power you really
can't say if there is any difference when you step on it.
Robin Giesbrecht
1972 Imperial 


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