Rough Idle 1995 pickup truck 2.4 liter 4 cal 4WD

I have a new problem- I drove out to a favorite spot in the mountains (up a dusty road) and when I got to the end of the road my truck was suddenly idling REALLY rough. I was able to drive it home and it runs “OK” as long as you stay on the gas (I say OK but it does want to die and especially wants to die after it warms up and then harder to restart until it cools)- as soon as you let off the gas the idle is on the extreme side of rough. It did not act like a fuel filter has historically (hesitate when giving gas), but I had a filter so I replaced the fuel filter anyway. I also pulled the air duct work and cleaned it all out, put a new air filter in and used CRC MAF sensor cleaner on the MAF sensor. I did pour in a Chevron fuel system cleaner but it would likely take a tank full at least to work and it does not run good enough to run a tank full through. I put in all new plugs (gapped) and checked resistance on the plug wires and cap- all seems to be acceptable. I checked all the vacuum lines and did replace a couple that were dry and crumbly. I am now at a loss- Please help- work has cut hours and I can’t afford to take it somewhere right now

If you cleaned the MAF sensor in the throttle body and the engine still doesn’t idle right, then the next suspect is the IAC valve.

You can try removing and cleaning the IAC valve. But I’ve found on my 95 Nissan pickup replacing it fixed the problem.


I have a busy afternoon but I will let you know as soon as I have a chance to try this- Thank You :slight_smile:

I had a similar problem on my pickup and found it was the MAF sensor. Good luck and let us know what it is.

I had a similar issue with my 97 Nissan PU, same motor and it also was the MAF. It took awhile before it finally turned on the CEL and gave me the MAF code. I used a cheap (about $60) MAF from Amazon rather than an OEM $500+ MAF that is unavailable. It works fine, just disconnect the battery for at least 10 minutes when you change it.

If the MAF doesn’t fix it, I’m thinking some kind of leak in the vacuum system is making it idle too lean. Are there any “lean” diagnostic codes in the computer memory? The fact that some of the vacuum hoses were bad makes me doubly suspicious of the vacuum system. That and it is worse when the engine is hot, b/c the computer is offering up a leaner mixture anyway when the engine is hot. Stepping on the accelerator helps b/c a higher % of the air is coming through the throttle valve, so a small add’l amount from a vacuum leak isn’t noticed as much.

Checking the vacuum system is a three step process.

  1. Check the intake manifold reading at warm idle, and compare to the shop manual spec, or when the engine was operating correctly.

  2. Visually check all the vacuum hoses and connections. This is a good time to make a diagram of how it all fits together, if you don’t have one already. Most modern cars have this diagram underneath the hood. If so, check that your vacuum hose configuration matches what the under-hood diagram says.

Also check any rubber boots and/or weird banana shaped things (air capacity buffers) in the intake air path between the air filter and the throttle body for cracks or loose connections.

  1. Individually all check the vacuum operated devices (e.g. brake booster) for diaphragm leaks with a hand held vacuum pump.

I finally got it :). I pulled the idle air control valve as per Tester’s recommendation. I cleaned it out good with throttle body cleaner, let it set overnight, got a bit of gasket material the next day and made a new gasket, installed it an :smiley: . It runs excellent now- with the new plugs (that it needed about five years ago it actually runs better than before). Thanks guys!! Best to you all!!

Congrats, and thanks for the feedback. IAC problems are a pretty common thing reported here. And the new plugs can’t hurt. Happy Nissan-ing, & best of luck. Good call @Tester !