Jump to content

Stumped on lean


Recommended Posts

Okay fellas. Roman here and I’m almost two weeks in having my ‘84 King Cab 720 4x4 with the z24s and stock hitachi. She’s a beaut. Amazing body, looks like she just rolled off the floor. I really need help figuring this one out.. she really drives great but is running lean, can’t get her to idle lower than 1k and diesels a little. So here’s the scoop...


Driving her home the only bolt holding the exhaust flange on popped off and she started screaming at me. First date is going well. Took a look and yep, big ole crack in the manifold and o2 sensor melted.  Motor mounts had her throwing fits. Got one of the last exhaust manifolds left on earth and rewired the sensor. The motor mounts were flubber, changed those and that made her happy. Found some vacuum leaks and replaced all carb vacuum lines and the base plate gaskets, pulled the carb and tightened the throttle body to it and the carb back on, motor mounts had it almost finger tight! I should mention the base spacer insulator plate there on the intake under the carb has some hairline cracks. Someone rtv’d it but I scraped and cleaned it and left it in the hairlines and sandwhiched new gaskets and no more air leak there. I also found on of the last ones in the world and have it coming just in case. Fuel pump was leaking, changed it and filter. New OE spark plugs, the right ones for the intake and exhaust. They had them all the same. Timing is fine, 3 degrees BTDC. Maybe a slight misfire though? She drives beautifully although runs lean says Karl the smog guy in town and isn’t passing (although I didn’t know and had the EGR vacuum line unplugged last time he was testing it😡)

 I welded a new cat on too and cleaned out the muff. High idle, lean and dieseling? Halp.


Link to post
  • Replies 3
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

Possible high idle causes....


1/ Choke not fully off when warmed up causing the fast idle cam to be engaged. OR fast idle cam sticking on.


2/ Throttle cable too tight not letting the carburetor close fully.


3/ Secondary not fully closed. Stuck or debris stuck in throttle plate. Use a flashlight and look.


4/ BCDD not resetting or turning off when returning to idle.


5/ Idle speed screw not adjusted properly



The fast idle is the reason the engine diesels on shut off.




  • Like 1
Link to post

Manifolds are rare? Better check my supply, have several. Also better keep the ones off the parts 84 I am scrapping.

  • Like 1
Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.