99 F-150 doens't run right when it rains.

Tiny
LECLERCD
  • MEMBER
  • 1999 ALL OTHER MAKES ALL OTHER MODELS
Whenever it is humid or raining out my truck runs really "rough". It's like it isn't running on all cylinders. The check engine light comes on and bad gas mileage and lack of power are other symptoms. I have a pretty good feeling that the problem lies with the ignition system (such as a bad spark plug wire. Etc) but i'm not a mechanic. I just wondering if someone could give any tips on how to locate the problem. Thanks in advance
Monday, March 26th, 2007 AT 11:05 AM

8 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
It's kinda like my back! Try spraying the enginge with a mist from a hose. It will help you locate the bad part! If you do it at night you will see the "arc"
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Monday, March 26th, 2007 AT 4:58 PM
Tiny
SIRGIBBY
  • MEMBER
  • 32 POSTS
I know I had a problem like that. I went to wash the engine one day. The ting just cranked and cranked and didn't start. Let it sit for awhile and tried again. Finally started ran BAD tho. Soooo started checkin stuff. Found that there was a LOT of condensation inside the distributor cap. Dried it out. Ran like a champ. Sooo problem could lie in there.
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Monday, March 26th, 2007 AT 11:34 PM
Tiny
STEELWEELS
  • MEMBER
  • 60 POSTS
Just like sirgibby said, this is the best place to start, there is moisture in the cap, if it is old, replace it and the rotor, make sure it is on tight, if this doesnt help, start looking at spark plug wires, there may be cracks in them or just corroded on the inside of the casings, but this should take care of the problem, and for less than $20.00 you cant go wrong.
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Tuesday, March 27th, 2007 AT 11:27 AM
Tiny
STEELWEELS
  • MEMBER
  • 60 POSTS
Let me know the results
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Tuesday, March 27th, 2007 AT 11:28 AM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Kinda hard to find one of those on a 99.
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+1
Tuesday, March 27th, 2007 AT 2:10 PM
Tiny
FROZENGY
  • MEMBER
  • 1 POST
Check the back coil on plugs. When it gets wet, the hood drains some of the water right on the back 2 plugs. This can also short them out. They run good most of the time. But every once in a while, they run like crap. I have replaced 5 coil on plugs on my triton v8.
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Tuesday, March 27th, 2007 AT 3:44 PM
Tiny
STEELWEELS
  • MEMBER
  • 60 POSTS
Sorry merlin. Read the description wrong, my bad
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Tuesday, March 27th, 2007 AT 4:14 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Leclercd
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Monday, April 2nd, 2007 AT 2:59 PM

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