Rough idle, now check engine light, no codes, where to start? - Nissan Forums : Nissan Forum
 
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Old 10-19-2011, 11:51 PM
wolfman wolfman is offline
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Rough idle, now check engine light, no codes, where to start?

I had my distributer replaced a while back and then had a very rough idle at stops, to the point where it would almost stall. They couldn't find anything until they noticed some oil getting past a seal in the distributer. So they replaced it for free. It ran much better but still had almost too low of an idle. I wasn't sure how to adjust this, so I was going to clean the MAF. Well now the check engine light is on. It's a 95, so I can't get any codes read anywhere for free. Where should I start? The plugs and wires are fairly new. Just clean the MAF and reset the light?
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Old 10-20-2011, 02:59 AM
Klayton Kress Klayton Kress is offline
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Funny I'm having the same issue. How many miles are on your car? I've looked into it on mine and cleaning the MAF helps but it has an extremely rough idle when the engine is cold and will stall out if put into gear before it gets sufficiently warm. I'm going to be checking for some common problems, vacuum leaks, MAF voltage, various sensors etc etc to try to diagnose. I'd start there for you as well.
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Old 10-20-2011, 03:36 PM
jserrano jserrano is offline
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Search around this forum on how to do an ECU self-diagnostic test and then post the codes. Very rough idle implies to me that the engine must be misfiring.



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Old 10-21-2011, 09:28 PM
wolfman wolfman is offline
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I tried the method where you turn on 3 seconds, press accel in/out 5 times in less than 5 seconds, wait 7 seconds, press accel for 10 seconds wait for flash and depress. But it didn't work? I also wanted to clear the check engine light this way. Is there another way? I'll search. I cleaned the MAF today, checked the plugs, they all look OK. Wires fairly new, and I replaced the fuel filter. Engine light is still on. Not sure how it drives, going out later to put some injector cleaner in. I'll try to figure out codes.
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Old 10-22-2011, 06:09 PM
wolfman wolfman is offline
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I was able to get codes off the ecu. They were 11, 12, 34, which I believe are camshaft position sensor, MAF, and knock sensor. I cannot get to the library to get a manual until Monday. Which of these should I start with, and wher are they. I know wher the MAF sensor is, have replaced it with a used one in the past. Should prob. buy new?
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Old 10-23-2011, 02:10 AM
Klayton Kress Klayton Kress is offline
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You said it's a 95 right?

I have that haynes manual I can get you all the codes you need and if need be scan pages for you if you need to replace or check something. I'm trying to figure out why my mpg dropped by about 10. The idle adjustment screw is below and just to the right of the left most intake manifold pipe. It's almost directly behind the oil filler cap. I'll get a pic up as soon as I can but here is a website explaining the adjustment and a drawing of it's placement.

As for the sensor positions I'll post back in a couple of mins when I run out and get my manual as to where they are and to how to replace them. The knock sensor is near the oil filter but I'll describe it in more detail in a sec

Also, you know that if you take the back bottom-left plastic siding of the center console, under your radio on the floor near accelerator pedal, there is a computer unit. To check codes simply turn ignition to ON and turn the screw on that computer unit all the way to the right then back to the left. The Check engine light will flash the codes. a long pulse is a 10 a short is a 1. So a long flash followed by a short is an 11. There will be a long pause in between codes. It will continue to flash til you turn the screw all the way to the right and back left again and restart the engine.

Edit:

The codes you pulled are correct. It's the cam maf and knock

The Camshaft Position Sensor:

The CPS is part of the distributor so to replace that you have to replace the distributor.
To check it you have to remove the distributor. If you need to know how to do this let me know and i'll post what the book says. These steps assume the distributor is already off.

1. Remove the rotor retaining screw
2. Remove the rotor from the shaft
3. Remove the sensor dust cover retaining screws and remove the cover
4. Inspect the CPS plate for dirt or dmg and blow out any dirt if no dmg
5. Reinstall cover and rotor.
6. Inspect your electrical connections for dmg and corrosion and correct any defects
7. w/ distributor still removed reconnect the electrical connector to SPS and turn ignition to ON
8. Back probe the electrical connector, orange wire +, for battery voltage
9. If no battery voltage check teh circuit from CPS to ECM main relay for open circuit or blown relay
10. Check for 180 degree CS position signal. will be indicated by a fluctuation on volt meter from 0-5V two times for every complete rotation of distributor shaft. Back probe the blue wire (+) and rotate the shaft to do this.
11. Next check one degree timing signal. Do this by back probing the yellow wire (+) and observe 360 fluctuations of 0-5V for 1 complete rotation of the distributor. you need to rotate the shaft very slowly to observe this. It's 360 times because it measures every 1 degree of shaft turn.
12. If the CS sensor signal test results are incorrect replace the distributor. This will run between $150-200 new.
13. If they are correct reinstall the distributor.

The Knock Sensor:

The knock sensor is located below the intake manifold near the oil filter. I believe it's to the left of the oil filter if you were sitting in the drivers seat. It'll be to the right if your looking in from above or on the left from below.

to check:
1. disconnect the electrical connector at the knock sensor
2. using ohm meter set on high scale check for a resistance between the terminals of 500-620 K-ohms
3. Also check for a loose sensor and tighten with a wrench if necessary. (This is probably a 10mm wrench from the size of it. start there and go up accordingly)
4. If the ohms aren't right replace it. It'll run about $23 online. Advance has a $123 dollar one...... so just google oem 95 altima knock sensor and get that.

The Maf you said you know but I can tell you this from when i replaced it.

take all 3 connectors off and remove from air intake
remove the 4 bolts for the power transistor housing
attach PT housing on new maf.
install back on car

Last edited by Klayton Kress; 10-23-2011 at 03:18 AM. Reason: got the book for info
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Old 10-23-2011, 02:13 PM
Klayton Kress Klayton Kress is offline
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The post tells you where they are and how to remove them. What are the symptoms of your car? You neglected to say what was wrong with your car. Are you having a similar issue as the OP?
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  Nissan Forums : Nissan Forum > Nissanclub.com Nissan - Infiniti Enthusiast Forums > NISSAN ALTIMA FORUMS > 1993-2001 Nissan Altima Forums > General Nissan Altima Discussion (1993-2001)

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