87 LXi Won't Start When Damp Out

It starts and seems to run just fine when the weather is nice. But this morning it was foggy and damp out and it would not fire at all. Fortunately in Colorado we do not have a lot of these days so I bet she will run tomorrow but if I lived in Oregon I would be screwed.

I did some searching but did not find a exact match. My guess from searching would be maybe the main relay or a coolant temp sensor. When it does start it will idle at 2K for awhile then drop to 1500 after warmed up it will idle in gear (auto trans) at about 700 but will stumble and go a little lower then correct and bump up to 1K idle. I think that the idle I see when it does start may not be related to my damp no start problem. I think the idle might be idle air control instead. It has already had a new Dizzy, Timing belt, and plugs installed. The dizzy and timing belt were done 3K miles ago by PO and I did the plugs. The plugs I pulled out had a .079 gap I put the new plugs to .044 which seemed to be a big gap still but that is what the parts store said the spec was.

So I am not sure what part I want to throw at it or how best to test it after I think I have fixed it. Like I said damp foggy days are few and far between here and I would like to be sure that it is fixed so it doesn't strand me. I am a real noob when it comes to these cars. I have worked on a lot of cars and EFI systems but they are usually American cars like Mustangs or pickups. The concepts are the same but all the parts are different.

My car would idle high after warmed up (1200 rpm) and I have to adjust the fast idle valve to get it to idle at speed. It sits on the intake manifold close to the throttle body on the side pointing to the cabin. It has two screws on the flat top... search here b/c there are threads that explain how to adjust it

As for the no-firing, I have not heard anything close. Did you check if there is spark?
In a normal startup sequence, when you turn the key on, the PGM-FI light comes on and you will hear a faint buzz from the back (it is the fuel pump pressuring the fuel line).
When the light turns off, you can hear the starter relay clicking too, and the buzzing stops. Did you notice any difference?

is it misfiring when it's damp? start with simple, how old are the plugs,wires cap? if they are old you will get a misfire or no start condition in bad weather

sound like bad plug wires to me. run it at night in the dark and look for arcing under the hood

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Originally Posted by POS carb

sound like bad plug wires to me. run it at night in the dark and look for arcing under the hood

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if the plugs are old and the gaps have gotten wider, they will also misfire in damp conditions

Not bad plug wires. I got home from work this afternoon and it started just fine. It had nothing done to it except for sit in the sun after the fog burned off. It is not like a miss or a skip. It is just a plain crank with no fire it doesn't even try to fire just turns over. Battery is strong and spinning the engine at a good speed.

I would check for fuel and spark on cold days first. That's an unusual failure, so it's probably going to be something interesting that we want to learn about when you get it fixed.

I swapped out the EGR valve because it was not holding vacuum and I replaced the main relay earlier this week. Today we had a high humidity day and even some snow/sleet and rain (yes all within about 2 hours I love Colorado) and the car performed perfectly today. Is it fixed? I have no idea but it is looking good so far. Only time will tell if the main relay was the problem. I will update this thread from time to time.