Extreme Rough Running

[boxes]

OK 88 Cab 3.2 NA

On two occasions when rained on heavy it exhibited very very rough running... First time it eventually smoothed out. Second time died and couldn't be restarted was wet inside also. Next day all was fine and drove it another month before putting it away. Put it away last year (after trouble shooting my throttle cable linkage falling off) and when I tried to start it runs like it did when "wet" but its not wet (in my garage)... Lots of oil smoke (pretty sure) and will idle rough and when it gets warm less smoke but starts to hunt a bit and still a bit rough.

If I give it gas it will almost die and stumble but eventually rev up (again not smoothly) and if I let it fall back to idle it will hold there though rough. This was just all of a sudden. Worked.. now doesn't. all sitting in my garage. I cleaned the idle sensor with carb cleaner (no change)

Possibilites based on reading here (but hoping for some input)
Cylinder Head Temp sensor
Flywheel sensors
Plugs and wires (Some are in not great shape so that's probably going to get done anyway but I don't think thats the cases)

[steely]

Could be a bevy of contributing factors, the ones you mentioned plus some vac line leaks and/or even the O2 sensor, but the O2 and CHT don't influence things too much until it is warm.
Remove the distributor cap and inspect inside it and the rotor.
Look at the plug wires in the dark with engine running for evidence of corona from bad wires.
If you have a Bentley manual, start with the troubleshooting guide there or wait and see the help start coming in here.
You can try the oil-cap removal test too to see if your idle is negatively affected. It should drop some, but if idle is already lumpy, the test may not be that definitive.

I bought my 87 ~8 years ago, and I went after vac leaks, cap, rotor, plugs and wires, speed & ref sensors, attached a disconnected O2 sensor, replaced an ICV driver - just as a start. It responded extremely well from the TLC since the previous owners neglected some normal maintenance items over some 25 years.

[cabmandone]

I don't think it's your speed and reference sensors since if it was you probably wouldn't run at all. I'd verify all connections in the car making sure all the plug connections are tight. I'd clean grounds at the intake runner, under the car from trans to chassis, and up front in the trunk. Another member had a strange problem where his car wasn't running right and it ended up being someone had installed a performance chip and it wasn't fully seated. I'd start with the basics and go forward from there. You can check resistance of the CHT and make sure you have the newer 2 wire and you can use the paperclip method to bypass the CHT to verify if it's the problem or not.

O2 sensor makes no difference in the way the car runs with regard to your issue.

[brianlay]

Problem is likely the high voltage side of the ignition system. As someone said earlier look for sparking on the ignition cap and wires. You can simulate dampness by misting with a spray bottle of water

[pors1968]

Start with cap and wire.

[Bob Kontak]

Originally Posted by steely

Look at the plug wires in the dark with engine running for evidence of corona from bad wires.

Is corona the blue plasma stuff? How is that indicative of bad wires? I have seen it on cars that run fine.

(I agree it's the secondary side, though.)

[RSTarga]

Sounds like moisture inside your distributor cap. At least the not starting after rain.

[Nick Triesch]

Old 911's are similar to old VW bugs, when it rains
hard the cap and rotor, distributor and other electrical parts can get wet. Dry/change them out and you will be good to go. Many times, heavy rain finds a way in.

[Fixer]

good advice above.

I chased a hunting idle and poor running for weeks and finally thought to remove the Autothority chip i had installed right after buying my '86 [circa 2000]

Removed the bad Autothority performance chip and reinstalled the factor part for perfect running once again.

[Bob Kontak]

Originally Posted by Fixer

Removed the bad Autothority performance chip and reinstalled the factor part for perfect running once again.

I wonder what makes them go bad? Ever figure it out?

[Fixer]

Originally Posted by Bob Kontak

I wonder what makes them go bad? Ever figure it out?

I don't know, it took about 8 or 9 years though.

[brianlay]

It's unlikely the chip failed.
More likely something in the fuel system or ignition changed so that the engine wouldn't run correctly with the ignition timing changes imposed by the chip.

[Bob Kontak]

Originally Posted by Nick Triesch

Old 911's are similar to old VW bugs, when it rains
hard the cap and rotor, distributor and other electrical parts can get wet. Dry/change them out and you will be good to go. Many times, heavy rain finds a way in.

+1

Pull your cap off. Point a fan at the engine bay. Let it run all night.

The lazy man's way to the same outcome if moisture.

[Franks89-911]

Originally Posted by RSTarga

Sounds like moisture inside your distributor cap. At least the not starting after rain.

+1. My dad used to make me move my car out of the garage when he would drive over to our house during a rain. He said it would always fail to start otherwise. When he died and I inherited the car, I read up on the issue and changed dizzy cap and rotor. Never had that problem again.

[steely]

Originally Posted by Bob Kontak

Is corona the blue plasma stuff? How is that indicative of bad wires? I have seen it on cars that run fine.

You may have seen it, but too much is energy lost - especially if the insulation has lots of cracks.

On the wet distributor innards, John Walker did an experiment not long ago - posted about the mystery of the Porsche dizzy getting water inside - not sure if it was ever solved.

[Bob Kontak]

Originally Posted by steely

You may have seen it, but too much is energy lost - especially if the insulation has lots of cracks.

On the wet distributor innards, John Walker did an experiment not long ago - posted about the mystery of the Porsche dizzy getting water inside - not sure if it was ever solved.

I have never seen it on my 911. Saw it on a 77 XJ with newer wires. I could run my fingers over the wires and it would connect to the tips of my fingers. No zap.

I wished I had been steeped in something stronger than cheap beer.

Regardless, the late night viewing of a potential fireworks show is well advised.

Where is OP?

[steely]

Hi Boxes - I re-read your post and saw a few different symptoms there spread out over a year.
If you could, let us know how your car starts, and how it idles when cold and when warm.
And then maybe give us some feedback - you'll get better help.
I looked at some of your earlier posts too to get a better sense of what's up, and I see you had a history with some potential CHT trouble in the past - how did that go? Everything helps.

[steely]

Bob - I'm just seeing your last post after I wrote the OP.
I worked with high tension stuff for a couple of years (10K Vdc), no expert, but the blue stuff wasn't tolerated and could mask degradation down the line (in terms of time). Maybe it is normal. If you're a kid like me you may recall the buzz behind old CRT tv's when there'd be arcing (too much dust + dried out insulation). Tv still worked, but it was a sign of age - much like this memory.

Maybe that is why beru has metal braid sheathing?

[boxes]

Hey all thanks for the replies... so I have been in a holding pattern waiting on parts (new plugs, wires, cap rotor etc from Pelican...) I am going to start there only because well it cant hurt at this point. The biggest point of clarification from all the replies is in the past this issue popped up when it got super wet but I drove it into the garage running fine and dry (though the last wet issue one of only two times had happened about a few weeks before that) I was hand throttling because of throttle cable having come disconnected. I may have pressed a little hard on the accel which has a missing floor board.... I later re connected the cable when I finally figured out what happened and when I went to start it up it ran rough. I am sure it is not drivable if I give it gas it almost stalls and coughs and sputters on itself then will rev up but not hold. If I let go it will fall back into rough idle and stay there. When it gets warm it will hunt a little bit at idle. That most of what I got at this point. I have to do more searching on how exactly to test the CHT. Currently life is getting in the way a bit. You guys are truly truly awesome. I am going to attempt to rebuild the engine possibly this summer.

[boxes]

Just to give an update because it may help someone else (though not likely) I finally found the issue... there are three plug modules just to the left of the air shroud on the left hand side of the engine near the back. The very top one is actually cracked and was loose. I taped it up and started it and it runs fine... I have a photo as I am curious what that wire is for but I am guessing I had a grounding issue. Thanks for all the help... now I just have to figure out how to fix the ball cup socket on the throttle linkage. I think I am going to have to make a retaining clip as I don't see where I can buy one and I don't see a replacement piece for my year car here.