Sputters and rough idle when there is heavy condensation or wet weather

ROCKINSD

MEMBER
1998 DODGE DAKOTA
2.5L
4 CYL
2WD
MANUAL
180,500 MILES

My truck will run very rough when there is moisture in the air overnight. If I can keep it idling it warms up if it is not idling too hard I let it because I do not want to stress the engine. It seems too dry out and run perfectly after it warms up or I wait until later in the day and it is warm put again. If I run it every day it usually is a mild issue. If I let it sit a day or two and it is wet out it will run so rough it will stall or choke itself out. I have replaced everything in the engine including the computer. Have had master mechanics sit in the engine and trace every wire? I think it is the fuel pump or related because I now smell it running rich and recently the check engine light revealed a vacuum leak. How do I know if it is a clogged screen in gas tank or regulator or fuel pump? Cheapest to most expensive fix would be appreciated.

1 Reply

HARRY P

MECHANIC
2,293 POSTS

Actually, this is usually a really simple and cheap (sometimes free) thing to fix. On just about any vehicle with a distributor, moisture can start getting in under the cap and cause the rough idle that you are experiencing. What you need to do is pull off the distributor cap (pictured below) by first labeling and then unhooking all of the plug wires from the cap. Be sure to label the wires and where they go, otherwise you will have a great time figuring out what goes where. Then you will unscrew the two screws that hold the cap down. Then all you have to do is inspect the cap (closely) for hairline cracks and also look at the seal for any cracks or general stiffness. Also look at the contact points inside the cap for corrosion (greenish white-ish crud) and, if it has rained recently, moisture. If your problem is simply dirty corroded contacts, clean them up with some sand paper and put it back together. If you have got moisture under there, then replace the cap and gasket/seal.

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