740 turbo 86 intermittent miss

bdraht · Post by **bdraht** » 01 Jun 2009, 22:36

My volvo 740 with 290000K has a miss that shows up from time to time. The idle will tend to go a bit higher, and then I might get a hesitation. I installed new plug wires, and it seemed to cure it, but a month later I again had a miss. One was when I was idling, the other when I was going 30 kph, just picking up speed. I have had the miss when the car is under load, or not. The strange thing is that is that it will hesitate, then may not do anything for an hour, or a few days. When I push down on the spark plug wires my idle seems to go back to normal, and then it will be okay for a week or two. The temperature and dampness doesn't seem to make any difference. If the car is driven hard, it seems to run better for a few weeks. The only other thing I know is the previous owner, who is our local Volvo Mechanic, also had the miss, but it went away by itself a few years ago, after his bother who had the car drove it fairly hard for a while.

Thanks for any insight.

bdraht · Post by **bdraht** » 14 Jun 2009, 17:52

I think I figured it out. I noticed that one plug wire crossed over another, and it would settle down and they would touch. I put a plug wire separator in, and guess what-no more missfires.

Post by **billofdurham** » 15 Jun 2009, 12:39

Welcome to Matthew's Volvo Site.

Good that you found the problem and thank you for posting the result. It is one that most of us, including the previous Volvo tech owner, would have missed.

Bill.