1990 NISSAN PICKUP - ROUGH IDLE/OVERFUELING

[FZR600RIDR]

1990 Nissan Pickup 2.4L RWD. 180,000 Miles. Has Always Been Reliable. Out Of The Blue, Truck Will Not Idle Smoothly. Drives Just Fine, But, Roll Up To A Stop Light Tach Bounces Between About 200 RPM - 600 RPM. Gently Put Your Foot On The Throttle, Everything Clears Up. Since This Problem, I Have Replace The Oxygen Sensor, Coolant Temp Sensor, And Throttle Position Sensor. I Have Done The Carb Clean Spray Down Looking For Vaccuum Leaks, Still No Change, However, Now At Idle, I Notice I Am Overfueling Big Time.. If I Tap The Throttle Up To About 3000 RPM, Black Smoke and The Smell Of Raw Fuel Emmit From The Exhaust.. Please, Any Suggestions Would Help Me Out!! Thanks!!

[mrecoolgar]

I have a 90 2.4 5 spd 2wd with 192,000. I'm experiencing the same thing. I replaced the o2, plugs and wires upon purchase. It help things considerably. My next step was replacing the idle air valve. Napa $100. It helped as well but on cold starts, especially in cold weather I would have a surging idle until the engine came to operating temps. Even now in warmer weather it does it to a lesser degree. When I first had the truck it was running especially rich and it still is but not as bad. I'm getting about 19mpg now which is better than the 15mpg.

[Rev_D21]

15-19MPG, that's pretty low. I was able to sqeak 27MPG out of mine last week. Leaking injectors come to mind. Malfunctioning FPR comes to mind. Air filter comes to mind as well. See the real problem is that you threw so many parts at it already, you could have saved a lot of $$$$. Any mods?

[FZR600RIDR]

Thanks For The Info... Funny Thing About Your Reply... I Am Actually A Manager Of 20 Years Of A NAPA Auto Parts Store Where I Live... Today Is My Second Day Off For The Week And I Am Currently Waiting For An Idle Air Control Valve To Come In For Myself.. I Have Had Local People Tell Me The Same Thing...So, Now That I Have A Little More Consistency Behind My Problem, Maybe Now I Am Headed In The Right Direction... Thanks!!

[mrecoolgar]

I have another set of injectors I could try.Air filter is new.Unsure what the FPR is.Please elaborate.

[nismopu]

the FPR is what attaches to the fuel rail and has a vacuum line going to it. These are known to go out and cause similar problems. Idle air control valve really is only good for cold starts but doesn't function once warm. The idle up solenoid works anytime you have any strain on the engine like a/c or a load on the alternator. So, think about these things when your driving and trying to diagnose the symptoms. peace.

[mrecoolgar]

Thank you.

[vballcoach]

were you ever able to figure out the problem? I have the same symptoms on a 94 2.4L.

was it the FPR - fuel pressure regulator?

[mrecoolgar]

I have not gotten to it yet.The FPR must be the fuel press reg.I wasn't sure myself until you spelled it out.

[Rev_D21]

Yes Sorry, FPR= Fuel Pressure Regulator

[nismopu]

my bad, I forget not everyones a nerd like me. lol!CAS FPRECUECCSIACVEGRCHTSCTSCRASMAF.....................im done

[vballcoach]

any updates on this?

[FZR600RIDR]

After 3 weeks and lots of money and parts replaced.....I finally narrowed down and fixed my problem of having (1) faulty fuel injector.... Turns out it was it was stuck open causing my overfueling and rough idle... Driving the truck it runs/ran find...Just would not idle on its own to save its life... Anyhow, hope this helps some more people other than myself!! As a little more insight as to parts that I did replace they included - - Throttle Position Sensor, Idle Air Control Valve, Coolant Temp Sensor, Oxygen Sensor. Thank god I work for NAPA!!

[nismopu]

good to hear you figured it out!

[mrecoolgar]

Thanks for the info.I havn't gotten to mine yet.For inspection, a simple brake pad replacement turned into ...New pads, new rotors, new calipers and an inner wheel bearing.The Pside calipers was stuck, note how worn the pad is.

[searey]

Just a question, i have a 1990 2.4l 248k/mi and just blew the head gasket a few months ago. had the work done and got it back. the mechanic told me that he had to "pump the pedal like it was flooded to get it to start" (he knew it was fuel injected), and that when warm it would not start back up, and smelled very rich at the exhaust. i have just cleaned the throttle body and replaced the injectors (all of them as a set) and it does seem to have made an improvement, but after checking for leaks and general warm up time, i shut down to restart and same issue. still acts up when hot on starting like its getting too much fuel. not sure which direction to head just yet. thanks in advance for help and suggestions.