Jump to content

1990 Ls400 Erratic Idle


akls400

Recommended Posts

I have a 1990 LS400 with 125k miles. Starts fine. Runs well cold but idle seems a bit high. 800 - 900 rpm. Once it warms up the idle becomes erratic in gear or in neutral/park. It will range from 1000 rpm to 0. Eventually it dies, but will start right back up. If i hold the pedal down a bit it will stay running and the rpms stay even. Hwy mileage is 23mpg. I have replaced plugs, fuel and air filters.

Any suggestions?

Link to comment
Share on other sites


When the engine is at temperature, the idle should be 800 RPM's. When cold it should be around 1600 RPM's. Sound to me a lot like carbon buildup in the throttle body. The easiest and cheapest way to try to fix the problem is to add 2 bottles of Complete Fuel System Cleaner to a new tank of top tier (major brand) fuel. I have used both Valvoline and Slick 50 CFSC with excellent results for similar problems. You need to make sure you spend around $10 for each or you are getting junk.

If it fixes it, you will be happy, if not you spent $20 and only a few minutes. I always start with the easist and cheapest first then go from there.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
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...

Forums


News


Membership


  • Unread Content
  • Members Gallery