overnight rain = runs rough in morning - Maintenance and Repair Forum

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overnight rain = runs rough in morning
Tuesday, May 29, 2018 6:31 AM

So I was going to post this morning asking about how to solve the loose visors that swing wildly and won't stay put, but now there's a new log on the fire.

We've had the wettest last month or so ever around here - and every time it has rained for a long period of time overnight - that is, - after I have parked for the night and the car just sits there in the pouring rain - when I go to start in the morning, it runs REALLY rough but eventually gets better through the day when I make many frequent small trips. NO CEL until this morning. This just happened within the last month and it has been really hot and humid - otherwise if it had been the winter I would have guessed the IAT sensor. Anyway, had the codes read and the girl didn't seem to know what she was going and just said, "Spark Plug" without any specific code.

Anyone had this happen? Was it moisture getting into some place around the ignition coil? Ideas?

Re: overnight rain = runs rough in morning
Tuesday, May 29, 2018 8:36 AM
What year and motor?



"In Oldskool we trust"
Re: overnight rain = runs rough in morning
Tuesday, May 29, 2018 9:31 AM

2001 Cavalier 2.2 5-speed manual 231K.

I'll try to go to another place to see if there's a more specific code. I doubt it is the plugs. I guess the water could be coming from driving on wet roads. So many potential causes. The place I took to replace the power steering pump didn't put the right front wheel plastic black cover back correctly so I am a little worried that the computer is gonna get soaking wet. Just got new tires - I suppose they could be kicking up more water onto everything.

I had initially thought it was a "running rough until it warmed-up" thing, but now I see that it is actually more likely to be a "running rough until more dry" thing. *sigh*
Re: overnight rain = runs rough in morning
Tuesday, May 29, 2018 10:54 AM
Dean Johnson wrote:

didn't put the right front wheel plastic black cover back correctly so I am a little worried that the computer is gonna get soaking wet.


This is almost 100% what is causing the issue. If you pull those plugs off you'll probably find water and/or corrosion. In addition, the main harness runs from that stupidly placed PCM in the passenger fender down and across the lower rad support before coming back up to the driver side fuse box. That area across the rad support is known to see damage from debris or collision with things like concrete parking lot markers. When that happens, the wires get damaged and things either stop working altogether or short out when there is water present.



"In Oldskool we trust"
Re: overnight rain = runs rough in morning
Thursday, October 25, 2018 8:50 AM

Ok, so an update to this. This problem started for the first time back in May and I have just been dealing with it since then, but it has gradually - over the last few weeks - got much worse so that it isn't just when it rains or when there is moisture/water around the car. Now it pretty much happens every single morning for sure - that is when it is the worst by far - and also even after just sitting parked during the day for more than 20 minutes or so after the engine cools off. The low temps have dropped to the 30s most nights now, so now I don't know if water/moisture was or is the problem or if it is just a cold engine that causes the issue. I had become so sure that it was bad plug wires, that I went and bought a new set figuring that they would be the first thing to try - but I haven't had the chance to change them. While they've been sitting in my car, I have had more time to research - it it seems like it could be a long list of things including the ignition coils, the ICM, the plugs themselves, or the air temperature sensor.......and then of course all of the fuel injector related stuff on down the line.

But over the past few days, another problem that I thought was unrelated has started, and now I am wondering if they are actually symptoms of the same problem. The car stumbles and lurches - as if the clutch is slipping (but it isn't) when I am accelerating, particularly at low rpms and/or when the car is under load. It doesn't happen at high rpms, at sustained speeds. I just hopped on the interstate and as long as I keep it in gear longer than usual and keep the rpms up, it runs great and at 75-80+ mph, no issues at all, runs perfect.

So I guess what I am really hoping for is the order of things you would start replacing. Obviously the plug wires - since I already have them - are going to be first and I hope that takes care of it But given my description what would your next things on the list be?
Re: overnight rain = runs rough in morning
Monday, December 03, 2018 7:00 PM
It sounds like your coil packs are arcing off the motor. These happens when rain and dirt cause electrolysis and eat away at the insulation around the secondary windings. Use some Spray 9 and see if you can see physical arcing.


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