QuestionQUESTION: I have a 1986 nissan hardbody with a v6, it does not want to start when it is cold. When it does start it does not want to run smooth. There is an odor of gas coming from the exhaust which is very strong. The engine has been lacking power and is only getting worse. The last time I tried to drive the truck when pushed the throttle it did not want to go at all. The engine also wants to idle very low, sometimes below 500 rpm. If I adjust the idle screw to put the idle back up to 750 rpm, the next time I start the engine, the rpm has dropped again.
I have changed the fuel filter. Checked the fuel pressure, it holds 38 pounds at initial start and while driving. I have noticed if I leave the gauge on the truck over night the pressure goes back to zero. Not sure if the pump is bleeding off or the gauge is bleeding off. Could that be the problem?
I tried to start the truck a couple of weeks ago it would not start, even with pouring gas in the throttle body. Engine turned over but never started. Checked spark coming from coil, from distributor, both were present. The temperature was about 30 degrees outside. Today I tried starting the truck, while it was 70 degrees truck started first time I cranked it. It ran rough a few minutes and stalled. It would not crank back up.
I hope you have some helpful input. Thanks for your help in advance!
Kevin
ANSWER: Kevin,
A couple of things here. First, the fuel pressure is supposed to bleed off after that long so there are no leaky injectors. That would have been my first guess... Second, pull the vacuum hose on the fuel pressure regulator and see if the fuel pressure goes up about 8 to 10 pounds. If the fuel pressure stays the same replace the regulator. Third, replace the temperature sensor for the computer. There is one for the computer and one for the gauge or light. Anyway, make sure you replace the one for the computer as it tells the engine it is time to richen up for a cold start and it sounds like that is not happening. I would assume you have checked the air meter for proper operation as that sounds like a problem too. A Haynes manual would be great since that will give you the process to check the air meter and other sensors on the truck. All you need is a volt/ohm meter for reading values. Lastly, I would be looking at the distributor for the presence of oil on the optical shutter wheel and the pickup and receiver. It sort of works like the computer mouse where there is an LED and a receiver.
---------- FOLLOW-UP ----------
QUESTION: Thanks for the fast response! I forgot to mention that I was having problems with it running poorly when it was raining or damp outside. For some reason I decided to put an old distributor cap and rotor button back on the truck. Much to my surprise the truck started I have not driven it yet but it seems to run ok, except for the idle that fluctuates. It goes from 700 rpm up to 1100 rpm bouncing back and forth. The closer it gets to operating temperature the less frequent it does this, once it reaches operating temperature it stops and idles normal at about 700 rpm. Any suggestions as to why it does this. Oh by the way I have a Haynes manual and a Chilton's manual for the truck. So feel free to offer any tests you can think of.
Thanks again Kevin
AnswerKevin,
Yes on the cap and rotor. I always purchase Nissan caps and rotors since the aftermarket parts seem to be a hit or miss on quality and fit. That would explain the wet weather problem with running bad. The idle problem is most probably the idle air control valve. Simply disconnect the battery and then replace the valve and reconnect the battery and the strange idle problem should be corrected.
