i recently purchased a 1999 qx4. i had the rear main seal, trans seal, crankshaft seal replaced due to oil leaks. i also changed all the belts and did a full tune up, including ngk spark plugs, wires, cap and rotor, pcv valve and a maf sensor. also had a cat convertor replaced and the truck still!!! idles rough and smooths out intrmittently., the other day it stalled at the light. i even tried fuel injector cleaner on 2 seperate fill ups. the truck still idels rough!!! cant figure it out, any help will be most valued.

p.s replace the timing belt and water pump.

well i took it to the dealer and they say it needs 1 new fuel injector and 2 oxygen sensors. so i decided to fix it myself since they want 3700 dollars! i will be changing all 6 injectors and all 4 oxygen sensors. that should solve the problems.........i hope total cost to do it myself approx 1000 dollars.

....get those O2 sensors off eBay... I did all 4 on my '01 for around $100... I say try that 1st, then injector... Is the Service light on?

i changed all 4 oxygen sensors, all 6 injectors, idle is smoother but has a p0505 code which is a idle air control valve. truck does not accelerate as fast as it should(something is wrong) had a new timing belt installed and rechecked the timing!..... it is good!!

yes service light is on, p0505. i will be taking the truck to the dealer now, tired of guessing what is the problem. pretty sure it is the iac valve but will need a volume relearn done with that as well. already put close to 4000 in repairs, so i got no choice to go ahead and replace the iac valve and let the dealer diagnose it correctly.

well i took it to a infinity dealer and they say they dont want to touch it because i have aftermarket fuel injectors and they cant diagnose it correctly because of that. wtf? i told them just replace the valve and do the idle relearn. they also cant explain or diagnose the misfire. is it possible maby a bad distributor causing multiple random misfire?

oh by the way, is anyone or has anyone had these symptoms. rough idle and hesitation when accelerating, anyone? hello out there, i cant possibly be the only one!:mad:

Hi Linus! I have an 01 QX4 with the same problem. It really scares me when I am sitting at a red light and my vehicle almost dies! After checking around on other forums it sounds like it might be the MAF sensor? I really don't know! I am taking my QX4 to my mechanic (not a dealer!) on Friday. Hopefully it works, I will let you know! Also let me know how yours turns out!

well i changed alot of parts, 4000 worth! same problems!:mad:
although i did need most parts, i am convinced the rough idle and p0300(multiple random misfire is due to carbon build up and sludge in the engine. i am currently running a cleaner through the engine and will run it through the intake as well. awaiting some auto-rx cleaner in the mail!. ill keep yoou posted. and by the way it is most likely that your maf sensor is good! if you cann accelerate good then dont change it, taht part is 140 dollars and can be cleaned with maf sensor cleaner!!!!!!

do you know where the crank position sensor is located on a 2000 qx4

Do a wiggle test on your hardness. If you misfire comes and goes? Possible corrosion on hardness. Check hardness connectors to the injectors. Possible bad ground.

I wouldn't change the IAC. It's possible you installed the wrong injectors on the vehicle. Nissan has this thing about having different resistant for there injectors. So with you changing the injector with aftermarkets ones, it's possible they might be the wrong ohm resistance causing the IAC motor to compensate and making the light go on. I know it sucks. I would go back to the store where you got the injectors from and see if there is more than one type of injector and if there is, if they can exchange them for you since they got them wrong to begin with.

My Infiniti QX4 is having similar issues. I hope this thread isn't dead. I am getting random misfires. When it occurs the vehicle jerks or lurches for awhile and then will run fine. Before buying a tester to see what codes were thrown I tried replacing fuel filter, fuel pump, fuel relay, spark plugs & wires, distributor cap, and rotor. None of that helped.

The tester revealed codes P0300 Random Misfires, P1336 Cksht Sensor, P0180 Fuel Pump Temp, P0325 Knock Sensor. I cleard the codes and tried to recapture and despite the engine obviously missing, no code was thrown for a long time even though you could feel the misfires repeatedly. Anyway what was finally captured was P0300 and P1336.

Would appreciate guidance or hear what others did to resolve same issue of misfire, runs rough.

Things I plan to try if I don't get some good tips real soon:
1) Install distributor assembly
2) Replace the EGR valve
3) Start evaluating the injector circuitry (I don't know how though)
4) Injectors???
5) Manual says Drive Plate/Flywheel which I presume is Cksht Sensor
6) Front heated oxygen sensor

Please help if you can

I have been experiencing the same problems, and found the EVAP Carbon Canister had disintegrated blowing carbon granules throughout the intake system. Went through an elaborate granule removal by disconnecting all the lines between the EVAP Canister Control Valve and the intake manifold. Also changed the Knock Sensor, as it had been identified, by code, as failed, months before this current carbon problem.

All codes are now clear, except a new code indicting that my Cam Position Sensor has failed. Engine now runs erratically at all speeds, instead of between 850 and 2000 rpm. Will order a new distributor this week to see if that will solve the problem.

Incidentally, a few months ago, I began getting a lot of ignition noise on my AM radio, and attempted to change the distributor condenser to see if that would solve the problem, only to find out, from the dealer, that the condenser wasn't replaceable. A new distributor would be needed at $480+ dollars. I used to love this vehicle!

You can purchase a third party distributor assembly for $150. I recently replaced mine from one purchased from carpartswarehouse.com but they can be obtained from many sources.

Thanks for sharing the carbon canister thing. I need to check mine to make sure it's in good shape.

I finally took mine to a dealer because it would run fine one trip and not the next. The tech indicated he could hear a leak in the exhaust area on the driver side which was causing the computer to constantly attempt to balance and the consequence is eratic performance. I'll fix the leak and see if his theory hods water.