[Gerk]

OK all. So I had to step away for a bit and regroup.
I actually called every mechanic within a 100 mile range and nobody works on older vehicles anymore.
Its only an 86 sheesh.,
Anyway, I have decided to try to fix it again myself.
At idle she seems to be running very well.
Put into gear and immediately dies unless I tap on the accelerator.
I tried a trans stall test. Foot on brake and try to rev it up in F and R and immediately dies. Not even remotely a chance of revving up.
I also then climbed under the truck. Pulled off the vacuum line on the vacuum modulator and out came some transmission fluid.
Not a lot, but is there supposed to be any?
Any thoughts on this matter?
What else should I test/check?
I did read that some have had issues with the filter coming loose and getting air is system.
Also loose or bare wires causing a short, but I didn't see any.

BTW, 1986 351W with auto trans. Brand new rebuilt carb. New Cats, all new ignition parts except distributor.

 

[NoMoJoe]

I would assume is a C6- it’s a 3 speed, right? if so, trans fluid is not supposed to come out of that. It doesn’t sound like your whole problem though. You should be able to disconnect at the tranny and plug the line and the engine should still run, even in gear. It’s been quite a few years since I’ve dealt with a C6 though. Someone may jump in and correct me.

 

[sackman9975]

C6 - vacuum modulator is bad, it shouldn't leak fluid.

Your research seams like you've been reading about the E4OD. Locking converter, filter drop..... etc. These are not the case with a C6.

For it to immediately die, there's something else going on. Clogged cat, bad timing, bad fuel filter., or fouled plugs from transmission fluid being sucked into the intake from the bad modulator.

I do not suspect the trans being bad except the vacuum modulator. And that shouldn't cause it to stall out.

 

[Gerk]

Yeah, I really didn't want to pull the pan.

Now it doesn't even stay running.
The only fuel filter I see is in the carb inlet.
Has new fuel
Has new cats
I will look into the plugs.
I now need a 2nd person to use my timing light as it will not stay running. When I timed before, I think I am around 12btdc
She fires up very easily. Just need to keep foot in it a little to keep running. Let off of gas and dead.
Keep foot on pedal enough to keep rpms in proper range, put in gear and dead

 

[Gerk]

What about torque converter locking up?
I have read about that.
She actually seems to shift really well in general

 

[sackman9975]

My bet, fouled plugs. Fix the modulator before installing or cleaning the plugs you have.

 

[sackman9975]

What about torque converter locking up?
I have read about that.
She actually seems to shift really well in general

That's not a locking convertor..

 

[Gerk]

That's a really good thought.
I will check plugs and fix the modulator.
They are new plugs but if they are coated with trans fluid, they could have fouled.
However, she sounds really good and healthy and strong before dropping in gear.

 

[Gerk]

I am waiting for the new modulator to come in later today.
I checked the plugs and they look great.
Guessing maybe a vac leak? I cannot seem to find one.
Not sure what else to look for.

 

[slimpartywagon]

I am waiting for the new modulator to come in later today.
I checked the plugs and they look great.
Guessing maybe a vac leak? I cannot seem to find one.
Not sure what else to look for.

Install the vacuum modulator… your modulator has a leaking diaphragm which could be the root of all your other symptoms.

 

[miesk5]

Yo Gerk,
As well advised!

 

[Gerk]

BRILLIANT
Shifts in and out of neutral perfectly.
Now I gotta go through and test everything else again as I think everything is working.
Timing may be off now due to vacuum changing.
Has an off idle

 

[sackman9975]

I am waiting for the new modulator to come in later today.
I checked the plugs and they look great.
Guessing maybe a vac leak? I cannot seem to find one.
Not sure what else to look for.

The vacuum leak was the modulator

 

[Gerk]

OK, so I was wrong.
At least partially.
When I replaced the modulator she shifted in and out of gear with ease. She really didn't shift all that well between gears when driving.
I then remembered that I forgot the pin that goes in the end the goes into the transmission.
Once I put the pin back in the new one, it went back to how it ran before. Dies when put in gear.
This new one is adjustable and I don't think the old one was adjustable (I dont think)
I can't find the old one, but I am going to keep looking for it.
Anyone know how to properly adjust these things?

 

[Gerk]

I found the old one. It was a purple striped modulator and not adjustable.

 

[sackman9975]

They're all adjustable. You need a little screwdriver and you pull the vacuum line from the modulator. Inside the nipple is the adjustment screw. You slowly turn it in or out and then drive it. It's been so long I can't tell you which way does what but a couple of test drives will tell you.

 

[Gerk]

Thank you.
I did a bunch of research on them.
I think I must have a vac leak somewhere else.
I just for the life of me cannot find it.

I hooked my vacuum gauge up to the back of my intake manifold, and I am getting a pretty steady 10