rough idle/irratic Check engine light

[ptc1625]

i got a check engine light the other night on my 95 maxima, i did the diagnostic on the pcm, and got the o2 sensor code, 2 days later the car started to drive and idle very funny, in the mornings when its cold i have to give it the gas slightly to start the car, other wise it will turn over and just die. after it stays running the idle has been around the 400 range which is very odd, and the car vibrates when its idling, you can feel it if you hold the steering wheel.. i just replaced the o2 sensor from the CEL code. i also cleaned all the carbon build up (alot) from the idle air control valve. idle is still semi erratic.....any ideas?!?!?!

i also noticed that in the top of the idle air control valve there is a black plastic screw, i think it changes the idle of the car, when i turned it one way the idle got worse, turned it the opposite way it got a little better, anyone know where this should be set at?

im thinking maybe fuel filter, maybe new spark plugs would help, any help would be greatly appreciated, thanks in adavnce

[Nahkapohjola]

Is this only when cold? TPS Throttle Position Sensor is used only until engine is warmed. Then O2 supersedes TPS.

MAF Mass AirFlow sensor is also suspect...

[ptc1625]

Originally Posted by Nahkapohjola

Is this only when cold? TPS Throttle Position Sensor is used only until engine is warmed. Then O2 supersedes TPS.

MAF Mass AirFlow sensor is also suspect...

it only does the wierd start thing during the really cold mornings, i crank it the first time thinking it will start right away, it just turns over then dies, then crank again give it a little gas and it starts but the idle is low.

but the idle is funny no matter what,whether the engine is warm or cold

what exactly is the tps. can it be cleaned????

why do you think it could be the MAF sensor?

thanks for the reply

[Nahkapohjola]

what exactly is the tps. can it be cleaned????
- Your TPS similar like this, at throttle axle end. Its input to ECU changes always u touch gas pedal.
http://www.cardomain.com/ride/748507/6

why do you think it could be the MAF sensor?
- u said u already cleaned IACV, gas pedal push hlps, O2 swapped, also problems after warmup...
- Find tst part from junkyard, 100$. First test it with multimeter http://www.cardomain.com/ride/748507/9
- Tst also the two coolant sensors.

- Run self diags http://www.cardomain.com/ride/748507/21 , to locate ecu see http://www.cardomain.com/ride/748507/15

- lots of oxidized places which may cause this, to be cleaned... http://www.cardomain.com/ride/748507/14

I do hope this hlps some. The -94 manual (see my CDomain 'Favorite Links') should cover models 89-to-98... it has extensive pages for each sensor diag. See FSM Diags Index EF&EC VG30E p.34 & VE30DE p.190. Even if u have VQ engine, these procedures are valid as sensor tecnology hasnt changed much. (edit: there seems to be -98 available, that would fit better for u)

[ptc1625]

i replaced the rear o2 sensor,i thought on my 95 maxima there were 3 o2 sensors i replaced the one thats installed on the back end of the cat, yet for some reason im still getting the codes 0707 0304 which is for the rear o2 sensor and the other code was for a knock sensor, my sisters boyfriend is a master mechanic for nissan and he said in tthe 5 years hes worked at nissan taht hes never seen a bad knock sensor. he said al the do is adjust the sensitivty of the knock snesor and then they charge people for putting a new one in. hopefully my sisters boyfriend can talk to him again and see if he can do anything , any thoughts or ideas?

i dont have a lot of money and would rather not just start replacing all sosrts of stuff trying to find the problem

[Nahkapohjola]

Originally Posted by ptc1625

...trying to find the problem

- My -93 knock s was dead. Link shows how to bypass, 5c (your conn location differs)... I'd say dead KS is just question when. Power loss is the symptom, not what u say. Ask the mech for Nissan consult tester for loan for weekend. Ask him: How do u 'adjust' KS sensitivity? huh.
- the transient codes may come from oxidized bad connections, voltage & gnd problems... cleanup time, Read the p.10,14. This is cheap but laborous, no self respecting mech will not d it, its owners problem... Buy cleaner + contact grease
- use the sensor which was ok, and replace second O2 with that.
- coilpacks & injectors are known to fail starting 100k (multiple problem causes?)