Nissan Truck High Idle Problem

idling adjustments
Engine idle can sneak up in common or strange places. Getty

 

 

An engine that is idling too high can be very annoying. It makes your car or truck feel like things just aren't right, and it always draws a little unwanted attention at the stop lights. If you're tired of sideways glances in the grocery store parking lot, it's time to fix that high idle issue. Luckily, there aren't too many things that can cause what's commonly referred to as a fast idle problem. Some of the causes can be super cheap to repair. Others are serious bank breakers. The good news is you can usually figure out what's causing a high idle problem and estimate the cost before you jump in and open up your wallet. Often it's as simple as tracing down a vacuum leak, which is far cheaper than replacing your car's ECU (ouch$!$!).

This question came in from a reader who owns a 1997 Nissan pickup truck. The small engine in this truck is similar to many other engines in Nissans and other makes. Most of them operate in a similar manner and regulate the engine's idle speed using the same systems, so this info is useful for many car owners. 

Question

I have a 1997 Nissan Hardbody with a 2.4 liter, manual transmission, A/C, and 89,000 miles. It idles at 1,500 rpm and does not go down after it is warm. I checked all the plugs and everything seems to be plugged correctly. Any help would be appreciated.

Thanks,
John

 

Answer

The first thing you want to check for is vacuum leaks. Then make sure the throttle linkage is free and moving smoothly. Also check the fast idle cam. Make sure it is not frozen and adjusted properly. Here is the adjustment procedure.

  1. Remove air cleaner assembly.

  2. Make sure the fast idle cam alignment mark is centered on the lever roller as shown in the figure.

     

    • An alignment mark is stamped on the fast idle cam so that the top of the cam will face in the correct direction.

    • If necessary, adjust the fast idle cam screw (A) until the alignment mark is centered on the lever roller.

  3. Start the engine and warm it up to operating temperature. Or you can make it easy on yourself (and save some gas in the process) by doing this repair after a few errands you needed to run anyway. 

  4. Measure the clearance between the lever roller and the top of the fast idle cam using a feeler gauge. Clearance (G): manual transmission model: 2.0 - 2.6 mm (0.079 - 0.102 in) automatic transmission model: 1.8 - 2.4 mm (0.071 - 0.094 in)

    When engine idle is the symptom, there can be any number of possible causes. The important thing is to always check the inexpensive, common problems first. Actually, forget common, check the cheap stuff first no matter what! More often than not an idling problem is dues to a cheap part failing or something that has fallen out of spec or adjustment. Older cars will try to compensate for worn spark plugs or a failing ignition coil by increasing the engine idle. An engine with a problem that is idling at 1500 RPM is far more likely to stay running than the same engine trying to idle at 800 revs per minute. 

    • If clearance is out of spec, adjust clearance using adjusting screw to 2.3 mm (0.091 in) (for cars with manual transmission) or 2.1 mm (0.083 in) (for vehicles with automatic transmission).

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    Your Citation
    Wright, Matthew. "Nissan Truck High Idle Problem." ThoughtCo, Feb. 26, 2016, thoughtco.com/nissan-truck-high-idle-problem-3897236. Wright, Matthew. (2016, February 26). Nissan Truck High Idle Problem. Retrieved from https://www.thoughtco.com/nissan-truck-high-idle-problem-3897236 Wright, Matthew. "Nissan Truck High Idle Problem." ThoughtCo. https://www.thoughtco.com/nissan-truck-high-idle-problem-3897236 (accessed November 22, 2017).