Stumbling in the rain?

Engine troubles? Try here.
kdiqq
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Stumbling in the rain?

Post by kdiqq » Fri May 27, 2016 4:53 pm

So my Pinzgauer has now had this issue twice. Far more pronounced the second time. So I'm in Houston and we are getting hammered with rain.

The first time I went out in rain, she fired RIGHT up. Idled great, ran awesome. I forded about 18", still no problem. This is all low speed. Continued driving for another 20 mins. Then I went to go to the store (still raining) and got up to 50MPH. At this point I noticed light stumbling anywhere under 2000RPM but it still Idled perfect. Going to WOT produced a tiny hiccup and then good performance. I shrugged it off. Fast forward 4 weeks and >500 problem free miles of mixed driving/wheeling.

I drive to work this morning and she performs amazing as is usual. Pours rain at work and it's pouring when I get in to leave. Fires up first crank and after a few seconds of warming up, holds a perfect idle. I drive for about 10miles and then the stuttering starts again. This time though, at anything under 2000RPM, it's bucking and behaving very poorly till I get sped up. I have to rev up (using precisely 1/4 throttle) to 2k, slip clutch and keep rolling. 2k to redline runs fine. At cruising it will begin bucking under 2k badly. At stop lights I'm noticing idle is sometimes dead on, but is rough feeling. More engine rumble in the seat. Sometimes idle will drop 200-300RPM but is otherwise steady.

When I got home, I promptly popped the engine cover and found the carbs bone dry, distributor dry, coil dry, and carb solenoids dry. I couldn't see the plug wires down by the head but those are very hot and wouldn't have issue evaporating water quickly. The conditions only happen when I can pull water through the fan for some period of time and it responds to throttle input... anyone experience this before? All feedback is welcome

Thanks!

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1977 Austrian 710M

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Jimm391730
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Re: Stumbling in the rain?

Post by Jimm391730 » Fri May 27, 2016 5:35 pm

When you said "distributor dry", did you mean the outside or inside? I've had problems with water INSIDE the dizzy, even after just playing in puddles. Richard's SSI and/or Jim's EFI and distributorless ignition have solved this for me in both my trucks.
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kdiqq
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Re: Stumbling in the rain?

Post by kdiqq » Fri May 27, 2016 6:23 pm

The cap and wires are all dry. I did not remove it to check the inside. But it idles good and runs at high RPM without issue.

Intuition tells me that if it's throttle dependent, it shouldn't be ignition related. So if I stab the gas at idle, it will stumble and nearly the exact same RPM as it was idling at.

I will for sure check the dizzy since I've been wrong many times before.

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Jimm391730
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Re: Stumbling in the rain?

Post by Jimm391730 » Sat May 28, 2016 12:33 am

Intuition tells me that if it's throttle dependent, it shouldn't be ignition related. So if I stab the gas at idle, it will stumble and nearly the exact same RPM as it was idling at.
The energy needed for the spark to jump the gap at the plug is related to how much air and fuel is in the cylinder - more air/fuel, the harder it is for the spark to jump the plug. So a weak spark will cause those exact symptoms. Water inside the dizzy will cause the spark to get directed the wrong way (to the metal of the distributor base, for example) if it becomes too hard to get the spark to travel in it's proper path. I've also had the exact same issue due to the 4500 RPM box failing. The spark was very weak, but the engine idled smoothly. But ask for a bit of power and it would stumble badly. What voltage do you see at the "+" coil terminal, when idling? 16-18V is the right range; anytthng less and the RPM box is the very likely culprit.

It may just be coincidence that it happened in the rain, then again moisture may have gotten inside the distributor cap. WD-40 inside the cap will both fix it and help to prevent it from returning.
Jim M.
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Re: Stumbling in the rain?

Post by undysworld » Sat May 28, 2016 7:22 am

I'm not sure what ignition is being used (stock or civvy), but couldn't this also be caused by bad plug wires or plugs?

I've had plug wires leak, and only cause problems when wet. (I know you stated that everything was wet when you checked, but with the air flow past the engine and the heat, perhaps things dried out before you looked?) To check, run the truck in the dark, mist the distributor and plug wires down with water, and watch for the light show where current may be leaking.

I've also experienced a couple of cracked plugs on one car. It idled okay, but ran rough, and mostly you could hear compression leaking through the cracked porcelain.

kdiqq
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Re: Stumbling in the rain?

Post by kdiqq » Sat May 28, 2016 10:57 am

Sorry, it's a civ ignition. I ohm'd all the wires and they were all very low. 2-6ohm range. So between the cap and plug everything appears good. I'm hoping the distributor cap will hold more secrets. I'm out of town for the long weekend but will be ripping it apart once I get back. I was convinced it was carb related, but everyone's similar experiences are leading me down a different road.

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edzz
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Re: Stumbling in the rain?

Post by edzz » Sat May 28, 2016 12:01 pm

also recognize that its a mechanical advance distributor and the advance mechanism my not be operating freely and be in need of cleaning and lube. this is also a good time to insure when the adjustment clamp is loosened the distributor turns freely in the block (make a reference marks first to reorient it with out loosing timing, reference the relationship of the distributor body to the block and the relationship of the rotor in relation to the distributor ) if it will not rotate easily remove the distributor and clean and lube the housing shaft that fits into the block.
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Texas710
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Re: Stumbling in the rain?

Post by Texas710 » Sat May 28, 2016 4:55 pm

RPM limiter is very easy to take out of the loop to test. I had to recently jumper mine and it was an easy fix to my intermittent, poor running issues.

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audiocontr
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Re: Stumbling in the rain?

Post by audiocontr » Sat May 28, 2016 5:32 pm

Condensation on inside of cap. The vacuum line of the distributor working properly? Too much vacuum and it pulls in moisture, especially when sprayed on from rain.
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Re: Stumbling in the rain?

Post by EmbarkChief » Thu Jun 02, 2016 8:44 pm

audiocontr wrote:Condensation on inside of cap. The vacuum line of the distributor working properly? Too much vacuum and it pulls in moisture, especially when sprayed on from rain.
This


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unipus
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Re: Stumbling in the rain?

Post by unipus » Mon Jun 06, 2016 9:29 pm

Following, as I was experiencing sorta similar performance today – although in the complete absence of rain here in SoCal (there is a marine layer that's typical to this time of year but otherwise uncommon, though).

kdiqq
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Re: Stumbling in the rain?

Post by kdiqq » Wed Jun 08, 2016 8:11 am

Sorry I didn't follow up on this.

I found the issue. So when I got my civ ignition, the black adapter plate has two machined holes in it that stretch past the sealing gasket. No big deal, small dab of gasket in each hole and wipe down with WD-40. Driving from Galveston to Houston in rain showed no issues whatsoever. Admittedly, it was not pouring, but was still coming down.

My issue now is that I cannot find the vacuum hose that yall were talking about. There is absolutely no vacuum hose on my distributor. Does anyone have a picture of what this hose looks like? If for some reason mine is missing, I'd love to replace it ASAP.

Thanks!

EDIT: Is it this port sticking 90deg out of the dist shaft? Image
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mm58
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Re: Stumbling in the rain?

Post by mm58 » Wed Jun 08, 2016 8:24 am

That's it

1976 Pinzgauer 710K
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'76 710K

kdiqq
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Re: Stumbling in the rain?

Post by kdiqq » Wed Jun 08, 2016 8:26 am

Crap! Where does the other end of the hose that'd go here terminate?
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mm58
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Re: Stumbling in the rain?

Post by mm58 » Wed Jun 08, 2016 8:41 am

Connects to same vacuum port that your brake booster connects to.

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