Hey one and all,
I just recently replaced spark plugs and cables on my 740 GL and now it idles very heavy as if one of the spark plugs isn't firing. I once encountered this symptom when and plug wire came off. I checked all of them to be sure and all seem on. What is causing this? Can anyone help. I'm a novice to the do it yourself thing and I'm stumped. Any input would be much appreciated.
Thanks

Make sure one of the new wires are not bad.
Take one of the old ones you just took of and install it back on the cylinders one at a time and see if it gets better.
If not the leave one plug wire off one at a time and start and see if it runs the same as with the wire on if it does then you might have a bad plug.

Just beacuse they are new doesn't mean they aren't bad.

Thanks, I'll give it a try.

Let me know how it goes!!!

Hey Tech,

After about an hour of farting with the wires it occured to me that I might be failing to take into consideration the obvious. My alternator belt recently broke and I have not replaced the belt yet. Could my dead alternator possibly cause this rough idle due to lack of current to the spark plugs? I know these questions may seem obvious to anyone who has ever worked on a car but understand that my brother is a mechanic and until as of late he always just took care of my cars for me. Unfortunately, moving out of state has forced me to try to learn to fix simple stuff myself or go bankrupt paying others. Thanks much for answering my questions even if some seem quite stupid.

Usually it wont cause the low idle but is possible.
It might cause it from really low voltage.So low that it would not crank it to start it up but would stay running if it had already been running.

well with no alternator you are about to have more problems than bad idle

like no car :mellow:

Just an update on my idle problem. I replaced the alt. belt. Then I began to check for the reason for the rough idle. I reinstalled the old plugs and seemed to have the same response. Then I tried pulling each individual plug and found that it increased the rough idle each time I removed an individual plug wire. It then occured to me I might be interpreting a change in idle from the pre-tune up idle as rough idle. So I gave it a test drive to see how it responded on the road. It sounded very good. In fact it was much stronger, I'm assuming because of the platinum spark plugs. Also the plugs I replaced appeared to have been in the cylinder a long time by virtue of the huge gap they had come to have. I guess all is well. Let me know what you think.