Question about 1991 Nissan Pickup

5 Answers

Adj. the tps and got the idle smoothed out, however above about 1500 to 2k rpm it falls flat on it's face,and just surges, checked the egr, working fine any other ideas

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  • 11 more comments 
  • okflyer1 Apr 30, 2010

    it doesn't seem to make any difference on where the throttle is after it starts to surge, from about 1/5 throttle to the floor it either surges or just acts like it's running out of gas

  • okflyer1 Apr 30, 2010

    did the voltage check between 1 and 2 with the locking tab up, started out with 5 volts and ended around 3 volts, however there seems to be a point where the dmm hits reads ol, but no matter how slow I try to advance the throttle position, it's never in the same place, that doesn't seem to make any sence to me...

  • okflyer1 Apr 30, 2010

    and the exaust is major black smoke, it's dumping gas out like a diesel....

  • okflyer1 May 01, 2010

    fuel pressure at idle is 35 psi, it hits 40 when it starts to bog out. all plugs are black with raw gas..

  • okflyer1 May 01, 2010

    the injectors are new



  • okflyer1 May 01, 2010

    and all 4 plugs are loaded with carbon from unburned fuel



  • okflyer1 May 01, 2010

    I find it hard to believe that all 4 injectors are leaking so bad that the vehicle will no run above 1500 rpm with out loading up so bad it looks like a diesel with bad or # i fuel...

  • okflyer1 May 01, 2010

    I have no tried it out with the agr disconnected on the road, it won't even get out of it's own way, all the tests have been done in the garage, I can feel the diaphram on the egr valve when I try to rev it up and it isn't opening. I know you guys are the experts, however I'm wondering if the mafs could be causing this problem.

  • okflyer1 May 02, 2010

    fuel pressure is 15 psi at idle and hits 40 as it starts to cut out.

  • okflyer1 May 02, 2010

    oh, and it has no cat. conv.

  • okflyer1 May 02, 2010

    ooops fp is 35 at idle and 40 at cut out.

  • okflyer1 May 02, 2010

    I found a little 4" vacuum line under the intake that was cracked, now the idle is perfect but it still is cutting out like it's running out of gas at about 1/5 throttle, and it doesn't matter if the MAF sensor is hooked up or not,

  • okflyer1 May 04, 2010

    thank you, that was the conformation I was looking for, 4 others never mentioned the MAF sensor. between that and the cracked vacuum line(under the intake manifold ( only the Japs would put something that important in a place you can't see and almost can't get to.) replaced the MAF and it's a new truck, again thatnk you..Bill

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5 Answers

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Hi! Have you tried checking the MAF (mass air flow) sensor? This may be causing you this trouble. You may need to replace it and see how it goes. HOpe this helps and have a good one!

Posted on May 02, 2010

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Actually the TPS on this vehicle is not to be adjusted...
lets test this to see if it is the source of your problem
voltage at pin 20
key on and engine off
.5 volts with the throttle closed
4.0 volts with the throttle wide open
and you should see a nice smooth increase in voltage and you open the throttle

however, the most common problem I see with this vehicle at this age is with the air flow meter
voltage engine running should be 1.0 to 3.0 volts depending on rpms

Posted on May 02, 2010

  • Sean Reisdorf
    Sean Reisdorf May 21, 2010

    if your DVOM shows OL during the sweep then either your DVOM is too slow or you have a bad spot(s) in the TP

    replace and retest

    by the way...was the TP disconnected?
    your readings may be skewed if the sensor is connected



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First off i would get a pressure test on your fuel. That will tell you if you fuel pump is pushing the correct pressure its supposed to this may be the problem, also pull out the fuel filter and replace that!!! i dont know how many times ive answered these and its been fuel filters. Also i would go through and check all of your vacuum lines they maybe clogged so do a thourough job on those lines, then if still no luck i would check that cat converter it maybe bad. good luck

Posted on May 01, 2010

  • dave taylor May 07, 2010

    wow thanks for the negative feedback i said check vacuum and wow suprise i was off on sensor but i was 1/2 right and u gave me negative thanks bud that what people on here get for trying to help out.

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  • Nissan Master
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Try disconnecting the erg valve then try it again ,yes the valve appears to be working but under load whilst driving is different,old vehicles never had this fitted and they run ok.So try it please before you dismiss it

Posted on May 01, 2010

  • Colin Stickland
    Colin Stickland May 02, 2010

    pull the vacumn pipe off the ERG valve ,then see if its ok

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  • Nissan Master
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HAVE U HAD A VOLT METER HOOKED UP TO SEE IF THE TPS HAS AN OPEN, THIS WILL CAUSE A HUGE STUMBLE, ALSO IF U HAVE A MAF THAT CAN CAISE THE PROBLEM.

Posted on Apr 30, 2010

  • 1 more comment 
  • yadayada
    yadayada Apr 30, 2010

    PLEASE DO THE CHECK I OUTLINED, SEE IF THE VOLTAGE INCREASE SMOOTHLY AS U OPEN THE THROTTLE, NO JUMPS OR THE TPS IS DEFECTIVE, I WOULD HAVE REPLACED IT, ESP IF THE TRUCK IS HIGH MILES

  • yadayada
    yadayada Apr 30, 2010

    U need to have the fuel injectors flow tested u may have one that is dumping fuel, pull the spark plugs and check carbon on the plugs, you will also need to verify that the fuel pressure regulator is not stuck and your fuel pressure is to high, unless u have allot of electronics training u are going to need a good shop to run these tests.

  • yadayada
    yadayada May 01, 2010

    well I guess my advice is falling on deaf ears herem you need to have the injectors flow tested.

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