1993 Pathfinder runs rough (missing) in morning till warmed up


#1

I have a 1993 Pathfinder that runs rough in the morning for about 5 minutes. It feels like a cylinder is not firing and this is intermittent (sometimes it runs smooth but mostly like it misses. I thought it might be the distributor since it had a crack and replaced but its still doing it. I figured if its plug wires, it would continue doing it which it doesn’t. Someone suggested it could be a cracked plug or temp sensor. Once the car runs for about 5 minutes, the missing stops. The other thing I wonder is if it could be leaking oil onto the plug overnight and drys out after running a while??? Any ideas what it might be? Thanks.


#2

A faulty coolant temperature sensor or a vacuum leak (that seals up a bit when things warm up) might account for the problem.


#3

I hadn’t thought of a vacuum leak. I have replaced a couple vacuum hoses a couple months ago that were cracked/not connected anymore. I will check it out this weekend along with replacing the plugs next. Thanks.


#4

It could be the spark plug wires. When the engine is warm, spray silicone on the coil and spark plug wires. See how it starts next morning.


#5

Will do. Thanks.


#6

Well I replaced the plugs and it didn’t help. However I think I’ve figured out the problem. Yesterday it rained and I took it out that evening when it was really humid. I noticed that it was running rougher than ever and the usual sort of intermittent missing was continuous (like a bad plug). Since it was getting dark I thought I might try opening the hood and see if I could see if the plug wires were arching. Sure enough I had two plug wires that were continuously arcing to each other in several places. If you think you might have bad plug wires, try looking under the hood while the engine is running at night.