• Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.

1979 AMC 304 Rough idle.

Good :notworthy:
Bit low but pretty even. I would ck the compression gauge for correct readings.

What's the status on the carb base plate gasket replacement? :confused:
After it's replaced-Do the comp test again.
LG
 
Right after the compression check, I had a new distributor on the bench and it went in. Yes it.made a difference on the low end. It takes off perfect now through second gear up hill until 3rd gear. When you hit third gear it still coughs and sputters. But 1st and second are perfect. I also reset the idle screws after setting the timing. I set the timing at 12* BTDC.

I need to get to the parts store and see if I can come up with a spacer base gasket. Sorry LG, not ignoring you, just wanted to get the distributor in and see if it helped. I'll get a gasket probably tomorrow and get back here. Oh still pulling a max 18" Hg vacuum.
 
NP-Let us know when the new carb base gasket is in place. Not hard to make one BTW.
LG
 
This thing is like thick. Not quite 1/4 inch but close. I could cut a couple and use them out of the thinner gasket material, but I would lose some spacing height. I need all I can get. But I may have to cut my own.
 
Can you post a picture? :confused:
LG
 
Jafo, I am not sure if you have replaced the ignition coil or not. F.Y.I., there should be from 1.13 to 1.23 ohms between the positive and negative terminals on it. The distributor pick up coil should be getting between 600 and 800 ohms between the violet and orange wires coming from the distributor. Checking these items is a lot cheaper than replacing them.
 
Torxhead said:
Jafo, I am not sure if you have replaced the ignition coil or not. F.Y.I., there should be from 1.13 to 1.23 ohms between the positive and negative terminals on it. The distributor pick up coil should be getting between 600 and 800 ohms between the violet and orange wires coming from the distributor. Checking these items is a lot cheaper than replacing them.
Click to expand...

I already have replaced the distributor. It helped. I've done nothing with the coil. I could check that.
 
Ok another development. While test driving, I've had this slight exhaust leak on the passenger side near the back. Can't tell if it's the flange or a gasket from the exh. manifold. So I climbed under to look. There is a spring operated door gizmo between the manifold and flange of the y-pipe. It moves freely, but is closed at least at idle. It's actually causing some back pressure into the manifold. When it spits and coughs, it does it from that side. Could there be getting either cold air or just a.surge of air sucked back into one of the cylinders from the leak or is the door on the exhaust causing an issue because of back pressure? When it's running, I can operate the door open and the leak seems to quiet down.
 
If I remember correctly that flapper is supposed to help in warm up.
 
Hedgehog said:
If I remember correctly that flapper is supposed to help in warm up.
Click to expand...

Heatriser. I always called the metal on the manufold itself the heatriser, but yeh you're correct and I suspected that. I know on fuel injection, exhaust leaks are not a good thing especially near sensors. I've also heard that manifold leaks might cause running problems as well as excessive back pressure.

I mean, the riser door moves very freely and the spring is intact and doesn't appear bad. But two things are definite. It coughs from that side, it has an exhaust leak, and it doesn't appear the riser is working because it was closed on a warmed up vehicle. As soon as you open the door, you can't hear the exhaust leak anymore. It's possible that maybe the exhaust leak is causing the riser to not open? Dunno.
 
I'd get rid of it. B-T-W the "spring" isn't really a spring. It's a coil that opens the door when it gets hot. I'd get rid of it is I were you.
 
Ok. New gaskets are on. I had to reuse the old spacer base gasket between the spacer and intake. I had no choice. The spacer has a large vacuum port designed into the back. That port feeds off of the underneath side of the spacer. A thin gasket will not support that area because the intake does not provide a mounting surface for that area of the spacer leaving a thin gasket with no rigidity prone to a large leak as I found out using the gasket provided in the carb kit. So, I cut two gaskets forbthe top and bottom for the old gasket. I used a new gasket between the carb and spacer. It seems to run smoother.

I also repositioned the coil. It's no longer tucked under the air cleaner. I moved it out and up from the inake breather area. Itcs basically out in the open now which should be better.

I also unhooked the coil from the riser and zip tied it open. Sounds much better. It will be value engineered out of the new exhaust when I get to it.

I also found one more broken part. It's the backpressure selenoid guzmothingyMcbob that ties into the EGR valve. It's a vacuum controlled sensor. Well, it was a sensor now itcs trash. So I bypassed it and went directly to the EGR from the CTO vacuum control.

Going for a test drive after I throw the vacuum guage on and see where I'm at.
 
Engine runs much smoother but no more vacuum. Still 17.5 to 18 inch Hg. Now for a drive. Is it just me or is everything pointing at valve job or intake gaskets or both?
 
jafo said:
Ok engine warmed up, idle about 800 rpm and from the main T vacuum port on the front of the intake measured 18 inch Hg of vacuum, steady.
Click to expand...

Having a steady reading tells me your valve guides and springs are not bad. Your valves are not burnt, sticking, or leaking as well.

Take your vac reading directly from a full intake port not from a T. Inspect the intake for leaks.
 
:agree: with Posi here. :notworthy:
The fact that the vacuum gauge needle is so steady, seyz much. ;)

LG
 
Posi said:
Having a steady reading tells me your valve guides and springs are not bad. Your valves are not burnt, sticking, or leaking as well.

Take your vac reading directly from a full intake port not from a T. Inspect the intake for leaks.
Click to expand...

I've been taking vacuum readings directly from the intake port. Not the carb. Also, the needle is steady but not frozen. It does fluctuate with rpm.

Ok. I would agree. I just got back from driving maybe 10 to 15 miles int town driving. Did exellent from light to light. Now, here is where things went down hill, I had a few pretty good hills to climb while driving. Before it wouldn't have made it in 3rd gear, but this time it tractored right up the hills. All but one. This hill I habd to turn onto and go through all the gears from a dead stop. 1st was good, 2nd it didn't have the power and coughed then went, 3rd it was fine. Since this hill is right by the housen I went around for another go. This time 1st and 2nd was fine but 3rd just cut out, no cough or misfire, it cut out.

But intake gaskets makes sense. That has a higher probability. I've had it at hwy speeds before all the suspension mods. It never cut out then. So I'll probably do the intake gaskets.
 
Best CK the new carb gaskets for leaks.
LG
 
Lumpy Grits said:
Best CK the new carb gaskets for leaks.
LG
Click to expand...

If that's the case, I give up. If they are still leaking, then there is no sealing that sucker. But, I will check to make sure the nuts are tight as new gaskets will shrink with heat sometimes. I'll double check it.

I also checked the intake mounting surface for the carb and straight edged. I checked the top and bottom of the spacer also. I blocked them both with a small piece of wet stone to assure they were flat and free of debri or old gasket. I almost went and checked the intake bolts for looseness but after it ran so smooth, I decided not to. I'll secure some intake gaskets tomorrow. Shouldn't be too bad a job. I'd like to open it up to look at the oil galley anyways. It'll be fun!
 
You must log in or register to reply here.

Jeep-CJ Donation Drive

Help support Jeep-CJ.com by making a contribution.

Help support Jeep-CJ.com by making a contribution.
Goal
$200.00
Earned
$0.00
This donation drive ends in
0 hours, 0 minutes, 0 seconds
  0.0%
Contribute
Back
Top Bottom