theWalkinator

First, it started with MAF sensor and knock sensor, replaced both, then bank 1 O2 sensor, replaced that as well. Then P0400 code came up, so I order gaskets and cleaned TB, IACV and EGR tube. EGR tube is almost complete blocked. But after everything is cleaned and put back, idle is little rough in gear and little high, tried to adjust idle speed followed instruction on this board, does not seems to make much difference, still rough idle in gear. Idle in park and neutral was 600rpm before the cleaning, now is around 750rmp, adjusted throttle cable, throttle response is little better. Occasionally still feel hesitation when starting from full stop, ECU is cleared after done of the cleaning. Yesterday wife found out windshield washer does not spray but wipers are still working, so it is not fuse, I can hear pump sound so this morning I went to Autozone to get the washer pump, on the way, CEL was on again and since I was at Autozone, I had guy scan the code for me, two code comes out, P0325 and P0400. So it is still knock sensor and EGR code. What could else be wrong? I suspect GER temperature sensor is bad since its tip looks like rusted after I removed gunk. I also checked vacuum leak and found none.

theWalkinator

Look at what I just found, a plastic valve behind throttle body next to the PCV valve, it looks like the PCV valve but my PCV valve is still there on the hose, and I don't remember I ever cleaned or replaced PCV valve and I don't remember my mechanic did that neither, so what is it? It got part number 45B61 on it.

nismomaxgtr18

iTrader: (5)

If you have a knock sensor code and you have never changed it, change that first!

theWalkinator

I did replaced knock sensor at the time I replaced MAF sensor, it is eBay knock sensor though.

theWalkinator

I just cleaned EGR solenoid valve this morning and will see if that clears the ECU code.

theWalkinator

Seafoamed the car on Sunday. Initially used the spray version of seafoam in the throttle body, but it didn't work well, I just seemed cannot get the can to spray, so after holding and shaking the can for like 20 minutes, I gave it up. Went to Autozone and grabbed a regular can, connected a spare hose to the vacuum line, poured liquid into a cup and slowly let the vacuum line sucked seafoam in, used like half can, then put the vacuum line back, let the car sit for 5 minutes, started the engine and stepped on gas peddle to raise the RPM to 4000 ~ 5000, a lot of white smoke came out from the exhaust. After the exhaust became clear, I poured the other half can of seafoam to the gas tank. The car now runs more smoothly and seems to have better acceleration.

The other thing I attempted to do before seafoam was trying to take off GER valve, but the big nut connect to the exhaust gas pipe just won't budge, prayed a lot of DW40 but I just cannot loosen it so I gave it up. I used my fingers to feel if the valve moves up and down when RMP changes but I didn't feel any movement, so I use my fingers to push the valve up and them it seems working so the EGR valve might stick before.

Cleared the code and will see if CEL comes back again.

Maximus92

iTrader: (4)

it may just be the egr temp sensor. i was having the same problem and cleaned everything but nothing until i changed the sensor.

caseymaxima

iTrader: (1)

How about the EGR valve itself? Have you checked that?

Zack

Justaguy

Just curious to see if you also have a coolant leak..can you show me the front of the TB please.

I want to see if you also have a green residue on the "Element Kit"....(this can cause high idle).

(BTW: this has nothing to do with your sensor issue)

Thanks

theWalkinator

I know what are you talking about, I don't see green residue anywhere but I will take some pictures tomorrow.

theWalkinator

Like I said, I couldn't loosen the big nut so I was not be able to take it out and checked that way, but I did push the diaphragm of egr valve up to make sure it is not sticky and I do feel the valve move up and down, so the valve itself works.

theWalkinator

That could be the problem, I checked the resistance, it seems to be fine but I will check again.

Trini Boom

iTrader: (5)

Remove the EGR and inspect and clean to make sure its not sticking. I have been in your shoes and did exactly everything you did. I also went and replaced the EGR and the EGR-BPT valves and the P0400 still came back after some time. Went to the dealership and bought a new gas cap after that and haven't had the code since. Just so you know in case.

theWalkinator

EGR valve is not sticking, I can feel the diaphragm move up and down. Not sure that gas cap has anything to do with egr, would you please explain?

theWalkinator

The car runs good for half tank of gas and then this noon when I took the car out for lunch, the hesitation comes back again at traffic light after full stop, and it even feels worse than before. No code yet, CEL remains off. However, in high speed, the car is running fine, acceleration is decent. So I know that egr tube is cleaned, egr valve is working, egr solenoid valve is cleaned, PCV valve has been replaced, TB and IACV all cleaned. Possible culprits: egr temperature sensor, vacuum leak somewhere, what else?

theWalkinator

After coming back home from work, I tried to adjust idle speed, tried adjust the black idle speed screw on IACV and also the idle stop screw on TB, checked EGRC solenoid valve and connector. I don't know what happens, suddenly, the car fired up and die few seconds later. Re-adjust stop screw again and managed to fire it up running, but this time, the car run really rough, kinda shaking in park or neutral, in gear, shaking more, tired to drive and the car kinda jump. I pushed the EGR valve open, it made the rough idle worse, almost stalled the engine. Again, checked vacuum leak everywhere and couldn't find any leak. At this point, I think it might be a misfire though no code, so I had wife sitting in the car stepping on brake and put in reverse, then I pulled out coil plug one at a time, when coil 2 and 4 was unplugged, the engine stalled, plug back and again, engine fired up and die in few seconds. Again, managed to fire engine up, I identified coil 6 misfired, so I swapped 4 and 6, now coil 4 misfired, so it is determined that coil is bad. Now I need to replace that bad coil.

Trini Boom

iTrader: (5)

My case may be slightly different from yours but the gas cap solved my problem. Seeing that I am a 95, the FSM for that year shows the gas cap as being part of the P0400 diagnosis. Its been one year and the code has not returned.

RushNatU

I would bet its the injectors. If you have no codes and it is misfiring at idle and not at rpm then I had the same problem and it was one of the front three injectors. Easy to change, just go grab some lower mileage ones from a salvage yard. If you're lucky, it will be one of the fronts, if not.....then you have to take off the UIM to get to the other three.

theWalkinator

Injectors are fine, I went to local junk yard, man, they have at least 7 4th gen Maxima, though I only need one but I got 2 front coil packs and 1 back coil pack as spare, also, get the knock sensor, altogether cost me $85. Went back home, first thing took knock sensor out, measured with multimeter between the two terminals, no reading, measures sub-harness, there is continuity, so the eBay knock sensor is no good. I replaced it with the junk yard one which read 530k oms between two terminals. Then I replaced coil pack #6, fired it up, rough idle is gone! Cleared code, warm it up then took the car out for quick test drive, now it is very smooth, no hesitation at stop, pick up is fast, throttle is very responsive. Came back, check the code again, now it is only flashing 0505 which is code for no error code, sweet! Adjust idle again, bring it down to 650rpm at normal operation temperature with no load, test drive again, no problem, running like it should be. Thanks for everyone's input, I will give it another tank of gas to see if the problem is gone for good.