1978 NYB engine running rough and noise (Videos)

[Chinoz71]

Hello all,

I'm slowly but surely closing in on the issues with the NYB rough idle and hesitation. So far I have replaced plugs, wires and vacuum hoses. The engine runs a little better but still runs rough and stalls when launching from a stop. My next step is the TQ carb rebuild.

Ever since I bought the car i noticed a knocking noise but i didnt kkow where it came from. I finally figured it out. It is coming the air cleaner housing. Has anyone ever seen this on their cars? See videos below....thanks!

Cold start:




After driving for 20 minutes:




Exhaust sounds almost like a sucking sound.

 

[traintech55]

This is an emission control device to help filtered air into the exhaust. There is a one way valve on the end of the pipe. The valve is shot, you can plug it off if the noise bothers you.

 

[73 T&C]

Yep. Mine does the same. I also have a minor hesitation. As soon as I finish the first round of refurbishing and repair I’ll get to it.

Like you I’ve changed the plugs, cap, rotor and wires all to open spec. Rebuilt the carb too (several times, long story). Still it persists. Raised the idle a bit but I know I’m only maskin the situation.

Thinking it may be a timing issue. The lean burn cars appear to need a magnetic pick up for timing set.

Still reading and looking into it. It behaves for all the world like it is too advanced.

Will post when I figure it out.

 

[Chinoz71]

Yep. Mine does the same. I also have a minor hesitation. As soon as I finish the first round of refurbishing and repair I’ll get to it.

Like you I’ve changed the plugs, cap, rotor and wires all to open spec. Rebuilt the carb too (several times, long story). Still it persists. Raised the idle a bit but I know I’m only maskin the situation.

Thinking it may be a timing issue. The lean burn cars appear to need a magnetic pick up for timing set.

Still reading and looking into it. It behaves for all the world like it is too advanced.

Will post when I figure it out.

Yes sounds like we are in almost the same situation. Mine pings like timing is off when I go up a hill and it almost has no power until that 2nd gear kicks in then it takes off. Come back to a full stop...rough idle again. Im tempted to just bypass the whole lean burn system with a new electronic ignition kit and edelbrock 1406 carb but i want to give the lean burn a chance because my car only has 34,000 miles so I figure maybe its not the lean burn...id like to keep it stock if possible.

 

[Chinoz71]

This is an emission control device to help filtered air into the exhaust. There is a one way valve on the end of the pipe. The valve is shot, you can plug it off if the noise bothers you.

Thank you for the info! I thought it was something more serious. Maybe there is a way to clean the valve? Im going to do some research on it. You mean the valve is on the air cleaner end or the exhaust manifold side?

 

[traintech55]

You guys have to forgive me as it has been over 35 years since I worked heavy on the Lean Burn systems, but I do remember there is a plug you have to disconnect and ground to be able to set the base timing. If the plug is not grounded, then the timing will move while you are trying to set it. Any other members remember where the plug is located?

 

[traintech55]

Thank you for the info! I thought it was something more serious. Maybe there is a way to clean the valve? Im going to do some research on it. You mean the valve is on the air cleaner end or the exhaust manifold side?

There is a pipe coming off the right manifold, and the valve is right behind the hose that connects it to the air cleaner assembly. Thrust me, it is shot.

 

[Chinoz71]

There is a pipe coming off the right manifold, and the valve is right behind the hose that connects it to the air cleaner assembly. Thrust me, it is shot.

Thank you! I'll probably just plug up the hole in the air cleaner with a rubber stopper or something like that.

 

[traintech55]

Thank you! I'll probably just plug up the hole in the air cleaner with a rubber stopper or something like that.

I always plugged the end of the valve. I do believe the valve and pipe have been discontinued for over 20 years.

 

[Chinoz71]

I always plugged the end of the valve. I do believe the valve and pipe have been discontinued for over 20 years.

Would that faulty valve affect drivability and performance?

 

[traintech55]

Would that faulty valve affect drivability and performance?

NO. Just noisy.

 

[Davea Lux]

You guys have to forgive me as it has been over 35 years since I worked heavy on the Lean Burn systems, but I do remember there is a plug you have to disconnect and ground to be able to set the base timing. If the plug is not grounded, then the timing will move while you are trying to set it. Any other members remember where the plug is located?

Doing this from memory, so I could be wrong. The early lean burn systems had two pickup modules, one for start and one for run. The run module varies the electronic advance relative to throttle position and it provides some advance even at idle. You would need to disconnect the lead to the throttle position sensor to get rid of the electronic advance for timing purposes.


Dave

 

[Davea Lux]

Doing this from memory, so I could be wrong. The early lean burn systems had two pickup modules, one for start and one for run. The run module varies the electronic advance relative to throttle position and it provides some advance even at idle. You would need to disconnect the lead to the throttle position sensor to get rid of the electronic advance for timing purposes.


Dave

Also see: Chrysler Master Tech-1976, Volume 76-5 Inside the electronic lean burn system.

If you google the previous header, it is still up on U-Tube.

Dave

 

[Chinoz71]

Also see: Chrysler Master Tech-1976, Volume 76-5 Inside the electronic lean burn system.

If you google the previous header, it is still up on U-Tube.

Dave

Thank you Dave!

 

[73 T&C]

Thank you Dave!

Watched them all. Very helpful. Nothing on the 78 version though.

 

[Davea Lux]

Watched them all. Very helpful. Nothing on the 78 version though.

The operating methodology was pretty much the same. The '78 version has a different distributor and some updates to make the electronics more reliable, but it still worked pretty much the same way. There were Tech videos for the 78 and later versions, but I have yet to find them on the internet.

Dave

 

[Davea Lux]

Watched them all. Very helpful. Nothing on the 78 version though.

If you happen to be working on a '78, the main thing you will notice is that the newer distributor only has one pickup module as opposed the two in the '76 to early '77 models. The advance curve was also changed for '78. The double module was troublesome as there were problems in the electronics with the transfer from the start module to the run module.

Dave

 

[Davea Lux]

The operating methodology was pretty much the same. The '78 version has a different distributor and some updates to make the electronics more reliable, but it still worked pretty much the same way. There were Tech videos for the 78 and later versions, but I have yet to find them on the internet.

Dave

The 77-78 lean burn system uses more that one method of advancing spark settings.

The first is the throttle position sensor. This sensor has a variable resistor installed that sends an electrical signal to the lean burn unit relative to the throttle position. My previous post stated that this device needed to be disconnected prior to timing the engine. If the throttle position sensor is properly adjusted and the carb is off fast idle, the sensor goes to ground and no advance signal is present. We used to unhook them to eliminate this as a signal source because of improper adjustment. The wire to the lean burn needs to be grounded if the sensor is unhooked.

The second method of spark advance is the temp switch. On a cold engine, the switch goes to ground and no advance signal is given to the lean burn unit. On a warm engine the connection to the temp switch should be disconnected and grounded. The vacuum line to the lean burn vacuum transducer should be disconnected and plugged. The unit can now be timed without any lean burn interference.

There was a magnetic pickup device used with the lean burn analyzer and this could be used to time the engine. The engine can also be timed with a timing light provided the above factors are in place.

Dave

 

[Davea Lux]

For those of you into tech video, www.mymopar.com/index.php?pid=434
has the use of the lean burn analyzer. There are many others listed in the technical reference section.

Dave