Truck surges when idling

1991 NISSAN HARDBODY
40,000 MILES • 2.4L • 6 CYL • 2WD • MANUAL
Avatar
JASONCOWAN
  • MEMBER
  • 1 POST
My truck surges at idle and I am not sure why. I have checked for vacuum leaks and changed plugs and no change in idle. I have changed out the MAF (mass airflow sensor) still no change. Any suggestions? Thanks in advance!
Nov 3, 2016 at 8:48 AM
Advertisement
Avatar
HMAC300
  • ASE Certified Mechanic
  • 48,601 POSTS
  • ASE Certified Mechanic
try cleaning throttle plate on both sides and IAC hole with choke cleaner.
Nov 3, 2016 at 9:30 AM
Avatar
AL514
  • ASE Certified Mechanic
  • 5,587 POSTS
  • ASE Certified Mechanic
so you mean by surging, rpm's up and down, like its hunting for the correct idle? If that is the case it does sound like a vacuum leak. This would be suspect also because you have such low mileage and the vehicle is older. Gaskets harden up after sitting for so long. Have you tried using starter fluid and spraying it lightly around the intake manifold gasket, throttle body, valve cover gaskets? any place that air could be getting in. Just be very careful spraying fluid around any hot parts of the engine. This is a very good way to locate a vacuum leak. If there is any change in rpm's that is where your vacuum leak is. Usually a hunting rpm's is the result of a leak like that. Also is the check light on and has it been scanned for codes recently? Even if the light is not on there may be a code stored in the ECM. You may want to have a fuel pressure test done to make sure everything is within specs.
Nov 3, 2016 at 9:49 AM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.