Engine wants to stall

[Posi]

Interesting - If I plug it, the engine runs worse...

I'm guessing your new looking weber was tuned with a huge vacuum leak present. Also, vacuum leaks can raise your idle, so when you cap it your thinking it's running worse, but in fact your on your way to making it run better. Take a vacuum reading and post up your findings.

 

[R717]

Something else to check - it looks like there may be an old pcv valve in the rear port of the valve cover (hose to the air cleaner). If so that would prevent filtered air from flowing through the crankcase and into the intake manifold , thus giving the symptoms you describe.

 

[JeepCJ5]

Thanks - I thought that was some kind of breather in the back of the valve cover since the OEM PCV valve has a T on the end. Should it just be an open plastic fitting?

I couldn't get to an auto store to pick up a vacuum tester today, but I will tomorrow.

R717 - I was going to go to sleep, but I had to check first. You are correct, I had two PCV valves. I went ahead and rigged up a temp plastic L. Now it doesn't quite stall when I cover the manifold vacuum port, but it does idle down.

Another dumb question - the PO put one of those chrome oil breather type caps on the front of the valve cover: something like this:
https://www.amazon.com/Edelbrock-44...d=1486008012&sr=8-5&keywords=oil+breather+cap

Could this cause problems? Is it better to just have a sealed oil cap?

 

[JeepCJ5]

I picked up a vacuum gauge this morning.

At the intake manifold port that used to go to the air cleaner, I have 15inches of vacuum. My PCV has a Tee on it. On the other side of the T, I have between 15 and 19 inches. The needle was moving back and forth quickly.

I tightened up the nuts holding the carb down. They moved a little. I also tightened as many of the Intake/Exhaust manifold bolts that I could get to. Some didn't move at all, but a few tightened up a bit.

Here's a video after I did this:

https://youtu.be/D3WRBbkBVW0

Thanks for all the help guys.

 

[Lumpy Grits]

Time to ck ign timing.
Plug the port-Bring idle rpm up.
LG

 

[JR74CJ5]

I'm with Posi and Lumpy - Co ahead and plug all that off and recheck timing, and retune carb for the plugged off condition and see what you're looking like.

If you have a vac advance on distributor, I believe you remove and plug it for setting the timing.

Then with all vac leaks repaired and the tuning redone, see if you get better results...

 

[Lumpy Grits]

Yeah-That 15Hg reading is a give away to the vacuum issue.
You should be see'n 17-19Hg, with a steady needle(no more than 1HG of movement).
LG

 

[JeepCJ5]

Ok guys - I think I've made some progress. I put my vac gauge on the port and adjusted the idle speed until I got the max vacuum. I ended up with a max of 19 and a min of 16, with the needle going back and forth quickly. It seems like a quick push of the accelerator revs normal now.

I also checked the timing with the dist-advance port plugged. It is at 9 degrees right now (I have not adjusted the timing since I got the jeep in November).

One weird thing. When I checked the timing a month or so ago, when I plugged the dist advance, the idle speed sped up. Now, I don't notice anything when I plug it. Is this normal?

I also tried to look for vacuum leaks using a propane source, but that did not reveal anything. So right now, the only vacuum system I have is the line going to the PCV valve (other end of T is capped) and the line going to the dist advance. These are all brand new items.

Any thing else I should do? The only thing I can think of now would be to remove the carb and check that I tightened the spacer plates properly and finally removing the intake manifold and replacing the gasket.

 

[Lumpy Grits]

Make up a spray bottle of very soapy water. When you spray that. You will hear a change in engine pitch and RPMs when you find a leak, and you will see the soap bubbles pulled inside.
LG

 

[JeepCJ5]

Make up a spray bottle of very soapy water. When you spray that. You will hear a change in engine pitch and RPMs when you find a leak, and you will see the soap bubbles pulled inside.
LG

No luck with this. I went through three times and sprayed everything, but I didn't get any change in idle or bubble movement. I will say that now the motor runs better with the manifold port capped then when it isn't.

 

[R717]

Could this cause problems? Is it better to just have a sealed oil cap?

With the pcv fixed, yes you are better off with a regular sealed oil fill cap.

One of the best place to tee into with vac gauge is in line with dist vac advance. The pcv line has flow from atmospheric and wont give you a good reading on your vac gauge.

Keep following the good advice from LG et al, sounds like you're getting closer.

 

[Posi]

Ok guys - I ended up with a max of 19 and a min of 16, with the needle going back and forth quickly.

Sticking valve.

 

[Lumpy Grits]

Is the needle moving while it idles, or are you working the throttle?
LG

 

[hdgapeach]

Sticking valve.

That's what I was thinking, too. Either that or a burnt valve. Might want to add a compression test to the list of things to do, just to be sure.

 

[Posi]

Is the needle moving while it idles, or are you working the throttle?
LG

At idle, if he was working the throttle the needle would move more then 3". Good question though.

Working the throttle would drop the needle down to 2-0" then back up.

 

[Lumpy Grits]

At idle, if he was working the throttle the needle would move more then 3". Good question though.

Working the throttle would drop the needle down to 2-0" then back up.

I agree with you. Just had to ask as many folks are not familiar on the use of a vacuum gauge and what to look for. When I learned how valuable of a tool a vacuum gauge truely is. Was a huge 'eyeopener' for me when I was just learn'n to 'wrench'.
I'm also of the 'valve issue' school here. I have also seen this type of read'n with a head-gasket starting to go bad.
Wonder what the difference in Hg is, from cold engine to hot engine when everything expands a bit?
LG

 

[JeepCJ5]

Yes, that reading is at idle. I think the engine was pretty hot when I took the reading. Today, I also noticed that I am getting some carbon or something coming out of the tailpipe. It leaves a circle of black dots on the concrete. I don't know what that might indicate. I'll start doing some research on sticking valves...

Thanks for all the info

 

[Lumpy Grits]

IF the exhaust system is hot and that is not condensation. It could well be coolant.
I strongly urge you to have a compression and leak-down test done ASAP.
What color is the engine oil?
CK the coolant level.
LG

 

[Posi]

Today, I also noticed that I am getting some carbon or something coming out of the tailpipe. It leaves a circle of black dots on the concrete. I don't know what that might indicate.
Thanks for all the info

Your running rich or have been in the past
It will build up carbon in the exhaust.
When you start the engine you will have moisture
The water and carbon mix and shoot out the tailpipe
This is what gives you the black dots on the concrete.

 

[JeepCJ5]

Thanks guys - I'll pick up a compression tester on the way home and post my results.