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Discussion Starter #1
So, my brother and I have had some problems with his 95 240sx for a while now. My question isn't so much about how we are fixing it, but more with the check engine light. We had checked the codes, 4 came up, one being the mass air flow sensor. We then decided to reset the codes. While the car was running, he unplugged the MAFS and no engine light came on whatsoever. With the car still running, he plugged it back in....still no light. We shut it off, then back on, took it for a drive came back, and yet now light had shown up. Does anyone know if the car has to go through cycles before it will throw up a code...like a reoccurring problem? Is that why the light isn't poppin up, or what?
 

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Discussion Starter #2
engine chug problem

So, we have been working on my bro's 95 240sx for a while now. He has replaced so many things, from the cams to the plugs and wires, to the pistons and rings, and a new starter.

Now, whenever it is idling, it is a little rough like it sounds like its missing or something, maybe the timing is off by a notch or so. When he punches the gas, you can hear it chug real bad, but once he holds the gas down at higher rpm's, and then punches the pedal...it doesn't chug at all. And, we took it for a test drive and it's like, by the third lap, he had the pedal to the floor and we were barely moving. Then, all of a sudden the car would lunge forward, and he would have to let off the pedal.

We have checked the mass air flow sensor, coolant temperature sensor, egr, fuel pressure, and the injectors. They all test fine. The only thing we know is wrong with it is the o2 sensor, but I'm thinking that is not what is causing his problem.

We are really wanting an outside opinion on this because we are running out of options. We don't want to start replacing things that may not need replaced and it still not work. Any feedback on this would be greatly appreciated...some fresh ideas and outlooks. Thanks
 

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Yes, you could have a major vacuum leak. Attach a vacuum gauge to a full vacuum source. With the motor fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be 21 InHg.

Run a compression test on all cylinders to determine engine condition. Do an ECU code readout to determine if a fault code is set. Also the cam and ignition timing can be off if you serviced those items.
 

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Discussion Starter #7
everything we have checked has checked fine. I am out of options really. I think we are just going to take it out...and apart......again for the third time and just start completely over. But thanks for the suggestions!
 
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