Still having ignition problems - 79 280SE

[kalpol]

I keep thinking I have fixed the missing problems on my 280SE but i haven't.

...I found a bad distributor cap and replaced that, replaced - plugs, wires, coil. On damp mornings, it misses badly, stumbles badly on acceleration, (sounds like it's running on three cylinders), sometimes dies. Problems don't go away when it warms up - I'll drive it 15 miles to work and it's still missing when i get there. After several hours of heat-soaking (all day in the sun until I leave at 5), it starts up just fine and runs great. None of this occurs on days of low humidity - it starts up and runs great right away.

As far as I can tell spark is intermittent when this problem occurs, but it always seems to be the same two or three cylinders - it's difficult to tell but at idle the miss is regular, and on takeoff when it is really having trouble it feels just like someone pulled three plug wires and the car barely moves. Then another cylinder will kick in suddenly and things are better. Could condensation somewhere be causing my problems? I've never heard of such a thing but I can't imagine what could be going on here. I still have not replaced the magnetic pickup wire but it looks like it's in good condition and I can't find a replacement anyway. Everything else looks like it's in good shape too - the only other thing I can think of is that my new set of plug wires are bad and I don't really want to believe that, they were pricey

What could this possibly be?

[kalpol]

OK it wouldn't start at all for a while this morning suddenly, and when it did finally start it barely runs. I ran around to the front while it was sputtering and saw that two or three plug wires are arcing to each other and to the distributor cap from under the boots. What would cause that???? Do I indeed have a bad set of plug wires?

[ozawa]

sounds like you have a bad set of wires. couple of things you can still try:

make sure that your wires are routed so that adjacent wires (as far as the firing order goes,) are not routed next to each other. double check that they're firmly seated in the cap and perhaps add a little dielectric grease to the rubber boot.

an easy way to see if your wires are bad is to use a spray bottle and squirt them with a fine mist of water, (try to do this out of direct sunlight.) if the wires are bad you'll see the spark arc into the air or at the very least the car will start to miss.

what brand wires are you running; (hopefully not Bosch.)

[kalpol]

Originally Posted by ozawa

what brand wires are you running; (hopefully not Bosch.)

Yeah I think they're Bosch. They were damn expensive, something like $150 for the set. Is Bosch having quality problems? Where can I get a set of good plug wires? local parts stores?

As for the misting idea, I may already have my answer, seeing as how things act up on damp days only. I'll try it for real when I get home.

[ozawa]

i'm not a big fan of bosch wires. i'm an auto mechanic and over the years their wires look more and more like the el cheapo autolite or borg warner ones you see at kragen, autozone, etc. at work i've seen Bosch wires fail prematurely to the point where we won't use them anymore.

i'd recommend Beru, (my personal favorite,) PVL, or Karlyn.

be sure you have the correct wires...for your make, model, and year, there's an engine serial number split; two different kinds of wire setup. if your distributor has little threaded screw on terminals, then you need a different wire set than if you have a distributor cap with the female holes, (push in type.)

[kalpol]

I did the mist test last night in the dark - the car was idling nicely after heat-soaking for several hours. I misted the wires and voila, nice little web of sparks from leaking voltage. So the wires are indeed bad, at least three or four of them. I looked and they're not Bosch wires, they're Beru, and they seem physically fine - no outside cracking etc. (not that I would expect any, they're only about six months old and I haven't driven the car much).

I'm obviously getting another set of wires, but this is really puzzling me and I am hoping there's not an underlying cause. The wires are clipped into their holders, I don't see any weird chafing, I haven't been yanking on the wires or anything like that. The voltage leaks are all up and down the wires, many by the distributor cap boots, not quite as many arcing to the air cleaner or valve cover. There were also a few down in the plug wells. I have the correct wires (I've got the threaded terminals). I inspected a plug from an arcing wire and it was fine, light tan, good gap, no apparent wear. The only thing I can think of is that maybe they were abused in shipping, or stepped on at the factory causing the cores to break.

anyway, enough ranting, i'll get new wires and clean and regap the plugs and check everything else, and hopefully this stupid problem won't recur. Thanks for the help!

[kalpol]

Called the vendor I got them from originally, they're still under warranty so free replacement set is shipping. Even if I do end up paying for them eventually, at least maybe I'll get to find out what's wrong with the original ones.

[ozawa]

glad you got that sorted out. you've just learned one of the most important mantras amongst the auto mechanic world; just because something is new doesn't mean it's good.

i've chased my tail a few times trying to figure something out, (never checking the "new" part,) only to find out that the new part was the culprit.

just curious but what vendor did you use...good to hear they're going to honor the warranty...

[kalpol]

Originally Posted by ozawa

just curious but what vendor did you use...good to hear they're going to honor the warranty...

It was from ***************. I generally just call up and order stuff, it seems to get into the database more accurately that way rather than using the web.