Mechanics

ENGINE IDOLS ROUGH WITH MAF PLUGGED IN

1995 Nissan Altima

Engine Performance problem
1995 Nissan Altima 4 cyl Front Wheel Drive Manual 140000 miles

I am having a problem with my 1995 Nissan Altima. It started out wanting to stall when I was out driving and would push in the clutch when coming up on a stop sign. Then it wouldn't start back up without pushing down the accelerator a little bit. It seemed like it was having a hard time going from the normal mode back to the idol mode and it was letting the idol drop to low which was making it stall every time you came up to a stop sign. I replaced the fuel filter thinking it was starving for fuel but that didn't seem to help. I bumped the idol up 100rpms and it kept it from dropping so low when pushing in the clutch when coming to a stop that it seemed to be ok for about a week although I knew this was not the root problem. Now it has gotten much worse. It runs very rich and idols very roughly at only about 500rpms. When I unplugged the MAF it idled much better so I bought a new MAF sensor and it still does the same thing. The error codes that were pulled from it were for O2 sensor and a misfire on #3 cylinder. I replaced the rotor button and distributor cap (not that I thought that was the problem, but when I pulled the cap off there was some corrosion so I just replaced them, no change in performance) Also, if I take the break booster line off it actually idols better with the vacuum leak (i guess it would since it is idling so rich but I was just doing that to see if it was a vacuum leak) which makes me wonder if there could be a line somewhere plugged that is not allowing it to get enough air? What is telling it to dump so much extra fuel? Could it be an O2 sensor or a stuck injector? I don't think it is a fuel injector since it idols so much better with the MAF unplugged. Is there another place to plug into the computer at other than under the dash right next to the fuse block (looks like obd2 hookup there)? My friend has a " snap-on" computer and it calls for a Nissan 2 adapter which does not fit the plug under the dash so I was wondering if there was another plug someplace that we can't find?

All replies will be appreciated. Thanks
Swami
Avatar
Swamibob
January 11, 2010.



The o2 sensor can do exactly what ur saying. Its purpose it to maintain a constant oxygen and exhaust ratio, if its misreading it will tell the computer it has to much air and adjusting fuel supply accordingly. Or. It will tell the computer it has to much fuel and leans out causing power loss. If you change it make sure you change both up stream and down stream. After changing them disconnect your battery for 20 mins to clear the computer memory and reset the check engine light so that if it comes back on you know you have more problems. Ps 95 is a nissan 1 plug. Its a first gen. Altima. And for future reference your motor is a ka24de. If you need more help just post.

Tiny
Raceme0911
Jan 15, 2010.
I replaced both o2 sensors and it did not fix the problem. We finally figured out where the Nissan 2 plug was (it was a little dongle plug in the same area as the fuse box but not part of the fuse box). The Nissan 1 plug adapter would not plug in. This is very confusing since there is an obd2 plug that is on the dash under the steering wheel exposed. Anyway, once we got the snap-on computer to interface with the car, we could get all the sensor readings. The injectors were idoling at 8-10ms and the snap-on said it should be 2.5-3 ms pulses at idol so this is why it was running so rich. We checked out the MAF and it was at a constant 5.12v. I knew this was not right as I have seen them in operation before and they were always bouncing around. Then we went to the troupleshooting area in the snapon computer and it said for rough idol and running rich to check the ground going to the MAF. This made sense because it looked like the MAF was not reading proplerly too. I stipped off a smal section of the ground wire (the white wire) going to the MAF plug and took another piece of wire and grouded it to the intake plentum where the snap-on computer suggested and it started running perfectly! I guess this is a common problem since this was the only suggestion to try for my problems and it was it. I hope this helps out someone else who is having a similar problem.

Tiny
Swamibob
Jan 23, 2010.