Does changing plugs & wires effect mixture
 

Does changing your plugs and wires change fuel mixture?

I have 82 'SC with disconnected 02 sensor. My car was running fine but as a part of routine mainentance I changed my plugs and wires (magnecores). After the change the car started up normal cold, but after the WUR seems to shut off it idles very rough. Further, on warm start it still idles rough. The old plugs were copper and the new are platinum. The old plugs appeared white (too lean) and the gap was too large (.8mm).

I suspect I need to have the mixture readjusted. But would the new plugs and wires require a different mixture? Further six months ago I had my mixtures adjusted with an analyzer, so why are my plugs whitish?

My worry is that I accidentally pulled a vacuum hose or disconnected something when I was changing the plug/wires.

thanks

Other guys are more qualified to answer this but my thoughts are, if the mixture was ok before the plug and wire change don't touch the mixture, and follow your thoughts on the vacume leak.

Maybe do a resitance check from the distributor cap to the end of the spark plug. It may be a case of a bad connection with your new wires or a bad plug.

Look at the engine bay in the dark and see if a current is leaping accross from a sprak plug lead to an earth.

Good luck, Bill.

Possible you might have cracked the insulator on one of your spark plugs during installation. Find out if a plug is missfiring, if so, change it out with another new one.
Hope it helps,
Gary

I suggest copper plugs for your car, properly gapped. A number of German car mechanics I know routinely remove platinum plugs when they find them and replace with copper. Make sure your ignition is working perfectly and your valves are adjusted, then adjust mixture or have it adjusted with a gas analyzer. I don't think your rough idle is caused by the fuel mixture.

I really think it is a vacuum leak and the plug/wire change may be coincidental. The car ran exactly like it is now a few months ago when I accidentally did not have the oil cap on correctly.

This morning I checked my airbox and vacuum lines and could not find an obvious leak. I think I hear a sucking sound from the left side of the engine. I pulled the vacuum lines that go to the distributor advance/retard? and didn't feel any vacuum and there was no change in the idle.

The problem actually did not start after the plug change. Initially I changed the wires on Sunday. However the old plugs did not have the cap on the end - that is how they fit into my old wires. The new wires were a little loose but the car seemed to run great. I took the kids for a short errand and that is when the car starting running rough on the way home. I initially thought it was because of the loose connection. The next day I changed the plugs but the problem persisted despite the tight plug to wire connections. I now think my plugs were white from running lean secondary to a vacuum leak and not the mixture settings.

Anybody have any ideas about where to check for an air leak. I know it is not the oil cap again - when removed makes the car stall. My engine is getting too much air???? P.S. I check the frequency valve and relay.