Hi all,

A quick question about a service engine soon light activation. The other day when I started the LR it ran rough for a few moments and the light came on. Its run fine since then. This also happened a few years ago and it was my intro to the 1500.00 LR major tune up, LOL. I had the same service done locally for 700, w/o the coils. I subsequently picked up a new set on ebay and have them ready to go in if necessary.

I just picked up an OBD II scanner and used it for the first time, thats where I got the cyl 4 misfire. I saved all the readings and cleared the code. I then checked the wires, all looks good.

My intention is to let things be and see if the code comes back, any downside to this approach? If it does, I plan on breaking out the FSM and doing the coils, wires (I know magnacore) and plugs myself.

Just a thought I also like to run by you guys, any chance this could be caused by humidity/moisture. Its been raining heavily and humid as hell lately and IIRC the last time this happened the same conditions existed. The LR was sitting for a few days when it happened.

Thanks



Oops, 04 Discovery with 65K

 

Not sure if humidity/moisture could cause it, but I just found out the hard way that misfires can be caused in a hurry by crappy wires.

I replaced my wires with some off-brand about a year ago (only put about 7,000-8,000 miles on the car since then, if that), and just last weekend, I started running really rough (the term "running" used very loosely). Flashing SES light, etc. The truck started by a little rough idling the day before to being barely driveable the following day.

I decided to try replacing the wires with something better first. I replaced my "Allmakes" 7mm's with some Kingsborne 8's. Problem solved. The whole thing cost me $48 and about 2 hours. Would have been much faster if I hadn't taken so many breaks (it was hot out).

When I removed the old wires, they looked fine. Didn't see much wear on them. I was worried when I saw that, because I thought the problem might be elsewhere... like the coil packs. But the new wires did the trick. Did the job yesterday. Drove the truck 30 miles to the hospital where I work (I'm a 2nd-year med student) this morning. It runs beautifully.

 

If the plug wires are going south then with all the excess moisture in the air they can short out and cause a mis fire.
I would leave well enough alone and start studying up on how to do a tune up yourself as one is in your future.

 

Oh, also, I think sometimes, you can just get a random misfire from the truck. When I first got it (used '02 disco II, with about the same mileage as is on yours), that happened. It sputtered and the light flashed and I freaked out. At the time, I was a poor student who had just flushed his credit down the toilet to return to school to do my med school pre-requisites, and I knew nothing about working on engines either. The problem went away on its own and no problems until last summer when I had to do my tune-up.

 

Thank you guys, The wires used by the shop last time weren't anything special so this looks like the plan, I'll pick up the magnacores and plugs and once fall arrives I spend some quality time under the hood.

 

Sounds like a good plan.

 

Before I changed my wires my truck would misfire terribly on wet rainy mornings. I bet the new wires will cure your situation. Magnacors are $85 from Apex Performance best price you will find anywhere. If the is too rich for your blood people have reported to have god luck with kingsborne 8mm wires.

 

My truck likes to throw a misfire once every few months. It threw a #4 misfire code a few days ago actually. I reset it and it doesn't come back again. It has been very humid and rainy here too.

 

Engines, if tuned properly and running good gas won't shut throw a misfire cause it feels like it.