Rough/ Low Idle

[720mintal]

I’ve read as many old posts as possible about the low or rough idle but still can’t seem to get my 85 Nissan 720 (Stock Carb) running right. I’ve checked all the vacuum lines (I think). I adjusted the idle speed to be a tad higher. But it still seems to want to die after it gets warmed up and tries to idle. Just looking for more things to check. I am particularly wondering if exhaust could play a role as my exhaust tail pipe has completely fallen off. 

my other issue if anyone has suggestions is that there is probably 2”+ play in the steering wheel. 

other things to note: truck smells very rich when running. 
truck has 240k miles. 

as mentioned above exhaust is in terrible condition. 
I bought the truck this way. 
I am kind of a noob to all of this. 

[]2eDeYe]

Welcome.

With 240k I am sure some things are a bit loose. 🙂
 

The idle issue could be the idle solenoid or junk in the carb. 

For the steering have someone turn the wheel back and forth just past the end of play while you watch each component of the steering. 
Also jack it up and check the wheel bearings and ball joints by pushing and pulling on the top and bottom of the wheel. 

[720mintal]

3 minutes ago, ]2eDeYe said:

Welcome
With 240k I am sure some things are a bit loose. 🙂
 

The idle issue could be the idle solenoid or junk in the carb. 

Where would I find the idle solenoid ? How do I check it ? Would it need cleaned or replaced if it’s bad ?  Like I said I’m kind of a noob, but I’m willing to learn. 

[datzenmike]

Check one plug from the intake and the exhaust side to confirm that they are both firing. It will never run right if one side isn't firing.

Check the valve lash is 0.012" on hot engine. Too tight must be avoided

Check the timing is 5⁰.

 

The electrical plug at the rear right of carburetor... Is it small two wire connector? or large round connector and 6 wires? There are two totally different carburetors used and how the run and are fixed.

 

The idle solenoid is a shut off for gas to the idle circuit. Off with the ignition off to help stall engine and prevent 'run on' or 'dieseling'. It has little effect when the choke is on but needs to work when choke off and warmed up. Listen near carburetor while ignition switch is turned on off on off. (not starting) You should hear soft clicking sound.

[bottomwatcher]

If you are keeping the truck first thing is a tune up, probably needs it anyways.  Plugs, wires, cap and rotor, adjust valves, new fuel filter and your problem might go away. If it doesn't you have eliminated a bunch of possibilities and can narrow things down. Low budget? Rough idle most of the time is a vacuum leak. Hoses my look ok but if they are old can crack in wierd places. Also carb bases, intake manifolds and even the diaphragm in the vacuum advance can leak. You tube finding vacuum leaks. There are various methods using different levels of flammable liquid or gas so pick what method you are comfortable with. Still rough move to the idle circuit. Come back when you get to that point.

[720mintal]

22 minutes ago, bottomwatcher said:

If you are keeping the truck first thing is a tune up, probably needs it anyways.  Plugs, wires, cap and rotor, adjust valves, new fuel filter and your problem might go away. If it doesn't you have eliminated a bunch of possibilities and can narrow things down. Low budget? Rough idle most of the time is a vacuum leak. Hoses my look ok but if they are old can crack in wierd places. Also carb bases, intake manifolds and even the diaphragm in the vacuum advance can leak. You tube finding vacuum leaks. There are various methods using different levels of flammable liquid or gas so pick what method you are comfortable with. Still rough move to the idle circuit. Come back when you get to that point.

That’s not a bad idea. Oil definitely hadn’t been changed in a lonnng time when I got it. I’ll go ahead and do all this. Thanks for the common sense advice. 

[Thomas Perkins]

Time to get a Weber....

[datzenmike]

While cap is off distributor, pull the hose off and suck on the end. What you should see is the rotor rotate clockwise about an inch and hold till you release it. If no movement check the hose for cracks. Distributor vacuum advance has no effect on intake vacuum so a cracked or hose that is off has no effect on it. There is no vacuum advance at idle. A working vacuum advance is good for economy.

 

The only two actual intake vacuum leaks from hoses are the brake booster supply and the smaller hose to the air cleaner ATC servo. The EGR valve can get crusty and not close properly at idle and THAT will really cause problems for idling. All you need do is remove the valve and wire brush it clean. Vacuum advance and EGR hoses are ported from the carburetor not the intake.

[720mintal]

16 minutes ago, Thomas Perkins said:

Time to get a Weber....

My budget is pretty low and I’m hoping to swap the engine, eventually when budget allows or this one dies. 
 

6 minutes ago, datzenmike said:

While cap is off distributor, pull the hose off and suck on the end. What you should see is the rotor rotate clockwise about an inch and hold till you release it. If no movement check the hose for cracks. Distributor vacuum advance has no effect on intake vacuum so a cracked or hose that is off has no effect on it. There is no vacuum advance at idle. A working vacuum advance is good for economy.

The only two actual intake vacuum leaks from hoses are the brake booster supply and the smaller hose to the air cleaner ATC servo. The EGR valve can get crusty and not close properly at idle and THAT will really cause problems for idling. All you need do is remove the valve and wire brush it clean. Vacuum advance and EGR hoses are ported from the carburetor not the intake.

To check the distributor vacuum advance I do that with the vehicle off, correct ?

any pics of the EGR Valve or any other lines I should check ? 

[datzenmike]

It won't run with the cap off.

 

The EGR valve is mounted on the right rear arm of the intake manifold with two bolts. There is a small hose to it and a finger size metal pipe from it that goes around the back of the head to the exhaust manifold. It's the round thing on the lower left

 

 

 

[720mintal]

6 minutes ago, datzenmike said:

It won't run with the cap off.

 

The EGR valve is mounted on the right rear arm of the intake manifold with two bolts. There is a small hose to it and a finger size metal pipe from it that goes around the back of the head to the exhaust manifold. It's the round thing on the lower left

 

 

 

Awesome thank you for the pic. 
 

[dat_sun720]

About the steering wheel play, I'm having the same issues and I'm trying to see if there is a bolt I can tighten to reduce the play, but no luck

[bottomwatcher]

Do you have a helper? Kids age 4 and up qualify. You need to get under the front of the truck while someone moves the wheel back and forth. You will probably see plenty of movement in tie rod ends, centerlink and idler arm. It only takes a tiny bit of play in each component to equal a lot of play at the wheel. Warning disconnect battery if using 4 year old you don't want anyone turning the starter if you are under the truck.

 

[datzenmike]

Wear or slack in the steering can be in...

 

Worn steering box

Any or all of the 6 steering ball joints

Worn wheel bearings.

 

If all the play adds to just 1/8" or 0.125" the steering box ratio is 19 to 1 so the steering wheel play is 2.375 inches!!!!

[720mintal]

On 1/7/2023 at 10:17 AM, bottomwatcher said:

If you are keeping the truck first thing is a tune up, probably needs it anyways.  Plugs, wires, cap and rotor, adjust valves, new fuel filter and your problem might go away. If it doesn't you have eliminated a bunch of possibilities and can narrow things down. 

Got all the parts to do this in the mail yesterday. Only had time to do the fuel filter yesterday. The filter I took off was a plastic housing with a tiny filter in it. Is that normal ? I put on a new “factory replacement” and it was like a normal metal style one. Anyways. Should be doing the rest of this today. 

On 1/7/2023 at 8:31 AM, datzenmike said:

Check one plug from the intake and the exhaust side to confirm that they are both firing. It will never run right if one side isn't firing.

Check the valve lash is 0.012" on hot engine. Too tight must be avoided

Check the timing is 5⁰.

Got the lash feelers so I’ll be checking the valve lash soon. How do I adjust them if they are out of spec ? Waiting on a timing gun to come in the mail and then I’ll be checking that too. 

[bottomwatcher]

Your on your way. Good to see someone taking maintenance seriously. Most just want a quick fix to get back on the road they rail on what a POS thier truck is. Keep us posted.

[datzenmike]

Metal filters are ok factory Nissan ones are plastic and fit the holder on the passenger side fender. They should be replaced every 3-5 years.

 

 

 

[720mintal]

On 1/14/2023 at 8:02 AM, bottomwatcher said:

Your on your way. Good to see someone taking maintenance seriously. Most just want a quick fix to get back on the road they rail on what a POS thier truck is. Keep us posted.

Well finally had time today! New distributor rotor and cap, plugs, and plug wires, plus I ended up doing a complete vacuum line and egr delete. Far as I know the only vacuum line left is the one for the vacuum advance. Truck is running super smooth now. No more dying. 

On 1/14/2023 at 8:14 AM, datzenmike said:

Metal filters are ok factory Nissan ones are plastic and fit the holder on the passenger side fender. They should be replaced every 3-5 years.

 

 

 

Tomorrow I’ll be doing that! Wish me luck! I am very nervous to take the top of the engine off haha! Loving this truck and this forum. 

[datzenmike]

Wait, you have an '85??? OK forget that post on valve adjustment.... that's for the L series engine.

 

The Z series clearance is 0.012" on both. It's also much easier to do. At the valve spring end of the rocker arm is an adjustment screw held by a lock nut, loosen adjust and tighten. The feeler gauge goes between the cam and the other end of the rocker am. Cam lobes must be pointing down to set the lash.

[720mintal]

15 minutes ago, datzenmike said:

Wait, you have an '85??? OK forget that post on valve adjustment.... that's for the L series engine.

 

The Z series clearance is 0.012" on both. It's also much easier to do. At the valve spring end of the rocker arm is an adjustment screw held by a lock nut, loosen adjust and tighten. The feeler gauge goes between the cam and the other end of the rocker am. Cam lobes must be pointing down to set the lash.

This is my first time really working on an engine. So I’m gonna ask some stupid questions because I basically didn’t understand any of that hahaha. 
 

What is a valve spring ?or a rocker arm ?

 

or is there a video for my truck ?

 

also my clutch recently has an issue where I basically have to force it into the floor to get it into gear? Any advice for that ? I thought it would be like other cars I have worked on and could be adjusted back up by adjusting a nut somewhere ? Fluid in the little tank looks a little low… maybe just top it off ?

[NC85ST]

Your clutch issue sounds like your slave cylinder may be going bad. It’s on the passenger side of the transmission. Follow the hard line coming out of the “little tank” where the fluid is, down to the slave cylinder. Most likely it will be wet with fluid.

[datzenmike]

I would leave the valve adjustment till you are more learned about what to do.

 

 

Yes to the top up of the brake fluid. See if it gets better.

[720mintal]

9 hours ago, datzenmike said:

I would leave the valve adjustment till you are more learned about what to do.

 

 

Yes to the top up of the brake fluid. See if it gets better.

Can’t learn if you don’t try, I’ll do some of my own research and see what I can learn. Hopefully I can figure it out. But I bought this truck to learn this kind of stuff. 
 

hopefully that works and is a simple fix. 

[datzenmike]

"You have to learn to crawl before you can walk"

 

"In over your head"

 

"Bite off more than you can chew"

 

"Look before you leap"

 

... are all good sayings. Absolutely learn all you can but take your time. It's easy to innocently take something apart that is better off left alone and it's now a huge undertaking to set it back to right. Research, research, research..... and then ask questions.

[720mintal]

3 hours ago, datzenmike said:

"You have to learn to crawl before you can walk"

 

"In over your head"

 

"Bite off more than you can chew"

 

"Look before you leap"

 

... are all good sayings. Absolutely learn all you can but take your time. It's easy to innocently take something apart that is better off left alone and it's now a huge undertaking to set it back to right. Research, research, research..... and then ask questions.

Just finished setting the valve lash by following this video

it was actually pretty easy to be honest. And now it’s running way smoother!

16 hours ago, NC85ST said:

Your clutch issue sounds like your slave cylinder may be going bad. It’s on the passenger side of the transmission. Follow the hard line coming out of the “little tank” where the fluid is, down to the slave cylinder. Most likely it will be wet with fluid.

It is completely covered in fluid. Guess I know my next project 😞