i have a 4.6 with coil on plugs and the motor started idleing funny and if i cruise at a consistant speed it runs unusual. the rpms just jump up and down while i drive or idle for a while. i just changed the spark plugs and i wonder if it could be a coil or if its better to replace all of them??

 

How many miles on it? Did you use dielectric grease when you changed the plugs?

 

did you change the boots when you changed the plugs?

I just change my plugs and a week later it stormed really bad and the next morning I had a bad mis. Come to find out the boot on #7 was bad and the sparkplug hole was full of water. When I talk to napa they said it was very common for the boots to go bad and do this or cause the the spark to go to the walls of the hole instead of the plug because of small cracks.

Changed #7 boot and ran great. Going to get the of seven and do them now.

 

How many miles on it? Did you use dielectric grease when you changed the plugs?


i have 101000 on it and never changed the plugs since i bought it at 78000. i just touched the plug threads with white lithium grease to make them go in smooth

 

did you change the boots when you changed the plugs?

no i might need t do that because i may have of gotten water in there but it still ran funny right after i changed them. how did you find out that it was that certain boot?

 

Sounds like th eTPS sensor is going out.

 

Sounds like th eTPS sensor is going out.




what is the tps sensor?? never heard of it and how much would it cost to replace.

 

TPS= Throttle Position Sensor

The coils are common to go bad not just the boots,also pull the plugs and check the condition of them.

 

If you use anything on the threads, you use antisieze compound, not white lithium grease.

You are required to use silicone dielectric ignition grease inside the boots when you replace the plugs. It's not like the old days, there are procedures that must be followed these days.

 

could this make it run like crap??

 

Well, I asked you if you used dielectric grease, and you didn't answer my question. I then told you that you have to use it - now answer your own question.

 

When the RPMS jump up and down - that's not a coil problem - it'sa TPS one. Been there done that . Unless your not describing the problem incorrectly - I would suspect the TPS sensor.

 

jbrew may very well have nailed it, but the absence of grease COULD make it run like crap. Why else would the use be required? I've been using it on ALL vehicles I've ever owned with electronic ignition. Back in the days of points it really didn't matter, but it matters a LOT now. There's a lot of voltage jumping around in there, no grease along with moisture = intermittent spark.

 

I know - I've seen the carbon trails on an un-greased boot before. He doesn't have those symtoms IMO.

He said the RPMS are jumping up and down - not misfireing.

 

i believe the rpms are jumping because its not getting the spark, at an idle after its been drivven it bogs down then revs up and bogs down and revs up without me touching it. i will put grease on it and i need to replace my egr valve and o2 sensors then ill try it.