Troubleshoot: Runs poorly/wont't when Damp

[SumpChump]

General Sunday educational question to help build the BITOG knowledge database....

Subject: modern fully computerized car, perhaps 2001 or newer (fuel injected, coil packs at or near spark plugs, fuel pumps in gas tank, etc) the average 4 or six banger.. Honda Civic, Chevy Cobalt... Ya get my drift.

Condition: Runs poorly, idles poorly when damp, foggy, misty or raining outside, Runs smoother and better when dry outside
Knowns: battery is good, gas tank is full, ignition is in working order and no fuses blown... An average car that "ran fine all last month".

Your troubleshooting steps are?
Your likely culprits are?

 

[SZR48207]

Have you hooked up an OBD reader to it when it runs poorly?

 

[Run]

I had this issue on my caravan. Rain and mist always gave it a rough start. So far I changed out the spark plugs and wires. It smoothed out the engine by a wide margin. However heavy rain still brings a bit of roughness on startup. The issue in my case appears to be water leaking from a drainage line. In my case this bugger leaks over plug 1 and the serpentine belt.

With the amount of electronics in today's vehicles its important to keep the engine bay as dry as possible. Any small leak should be dealt with quickly. I cringe when I see someone take the power washer to their engine bay. My neighbor blew the alternator in his S-10 by being careless with the power washer.

 

[SumpChump]

Originally Posted By: Reddy45
Have you hooked up an OBD reader to it when it runs poorly?


This is just a textbook type question to grow the knowledge base, no vehicle in service bay.

So that'd mean you suggest:

Step 1: Hook up to OBD reader and looks for codes

---------------------
Any other data you would focus upon if on the OBD reader as part of your troubleshooting step #1?

Thanks!

 

[SumpChump]

Aha! Thanks BITOG member Run.

Proposed Step 2: Look for engine bay specific leaks or dampness.

 

[RooflessVW]

If it's a VW:

Step 1: replace all 4 coil packs.

Step 2: buy 4 more new coil packs and keep in trunk.

 

[Warstud]

Remove the Distributor Cap and spray down the inside with WD-40 and wipe it clean.

 

[mk378]

Systems with spark plug wires or even distributors are really prone to losing sparks from cracks and deteriorated insulation. Coil over plug designs are much better but still not completely immune.

1. Idle car in the dark look under hood for any sparking or glowing around ignition parts.

2. Fill up a spray bottle with plain water. Get engine running good in dry conditions. Then put water on parts and see if it gets worse.

3. Never power wash.

 

[Leo99]

Originally Posted By: Warstud
Remove the Distributor Cap and spray down the inside with WD-40 and wipe it clean.


And check the cap is integral.

 

[user52165]

Originally Posted By: Warstud
Remove the Distributor Cap and spray down the inside with WD-40 and wipe it clean.


You did read the original post?

 

[Warstud]

Originally Posted By: user52165
Originally Posted By: Warstud
Remove the Distributor Cap and spray down the inside with WD-40 and wipe it clean.


You did read the original post?


I missed something?

 

[bullwinkle]

Wonder if the boots that are between the coil packs & plugs could be cracking & losing spark somehow?

 

[SumpChump]

Originally Posted By: bullwinkle
Wonder if the boots that are between the coil packs & plugs could be cracking & losing spark somehow?



I've always wondered about that but have never seen it in person. Always curious though.

 

[beanoil]

I had a Rendezvous that exhibited this issue. Damp conditions would cause hard start, rough run, cutting out while driving accompanied by gauges acting odd, and dash lights flickering. Bad ground under the hood near the trans speed sensor was my problem. Agree with Reddy though. Any codes stored can help get you started in a direction. Let the computer help you if it can.

 

[Tosh]

Dodgy electrical wires (esp. grounds) and connectors.

 

[toneydoc]

Check for corrosion at the coil/distributor and spark plug wires to plug connections. Caused much hesitation and bad running in vehicle I had. Of course more moisture in air did not help any

 

[Eddie]

+1 for electrical. Start with all chassis grounds (remove clean & reinstall). Next is to check high tension wires if you don't have coil over plugs. (open hood at night, start engine and use a spray bottle to spray engine with water while watching for corona)

 

[RooflessVW]

Originally Posted By: SumpChump
Originally Posted By: bullwinkle
Wonder if the boots that are between the coil packs & plugs could be cracking & losing spark somehow?



I've always wondered about that but have never seen it in person. Always curious though.


Hence my VW comment. See spark leaks from them all the time. The OEM coils, even after 55,916,737 revisions, are still horrible. BERU makes some that last.

 

[user52165]

Originally Posted By: Warstud
Originally Posted By: user52165
Originally Posted By: Warstud
Remove the Distributor Cap and spray down the inside with WD-40 and wipe it clean.


You did read the original post?


I missed something?


"Subject: modern fully computerized car, perhaps 2001 or newer (fuel injected, coil packs at or near spark plugs"

On the profile car from the OP - there would be no distributor on a car like this.