Questions and Answers
240 Won't Idle
Q. Hey Vince, I have a 1991 Nissan 240SX. It is a 5 speed manual transmission, P/S, 106,000 miles, A/C and a 4 cylinder engine, idle RPM 800. My problem is: Any time I push the clutch, while I am driving or coming to a stop, the RPM will not settle to the idle RPM and just continue down until the car just dies.
The RPM's needle seems to go down from whatever RPM it is at to about the 1000 mark gradually and slowly but once it hit the 1000 mark that it seems that it goes down real fast. (It seems that at the 1000 mark the motor is about to die and at the same time something is trying to tell it increase the RPM to keep the motor running but it does not.)
It seems like it can not stop the motor RPM from stabilizing at the idle speed as it is dropping the RPM. Also after doing this when you crank it back up it will do the same thing. to keep it from going dead you have to give it some gas. Also some times when it will stay cranked at idle the RPM's will go from 300 to 1000, 300 -1000, 300 - 1000, The RPM's will just keep going up and down.
I have turned the idle up to 1300 rpm and it will do the same thing. Just another note the exhaust stinks a little, (catalytic converter?) PLEASE HELP!
Kim
A. This type of problem cam be a little difficult to diagnose because there are several things that can cause it.
If you are getting a rotten egg odor from the exhaust, then I would say you have an overly rich fuel mixture. This could be from a bad O2 sensor or had fuel injectors. It is also possible the Fuel pressure regulator is bad and not keep the fuel at the proper pressure. A Nissan fuel pump will put out 90 to 100 psi of pressure if not regulated.
I would say at this point you need to do a fuel pressure test to make sure all is well. If it is, then the next thing I would suggest is the idle Speed Control valve. This engine uses a small stepper type motor to adjust the idle speed to engine conditions.
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