Hi Towncivilian,
Thanks for reply!!! Infiniti qx4 2001 with 183000 kms on it.
I cleaned today MAF sensor again and throttle body both with special spays still have backfires after engine is hot.
Maybe you're familiar with another issue - vibrating on high speed 100 km per hour and between 2300 rpm and 2500 rpm. when accelerator is on 3000 rpm it's gone.and if i remove foot from accelerator everything is ok as well.

Try to measure the resistance of the engine coolant temperature sensor to see whether it's within specified limits - see page EC-173 of the factory service manual for reference values and see the prior page for the harness location.

Were spark plugs replaced with OEM specified NGK plugs at 168,000 km?

Your vibration could be a loose exhaust heat shield. Crawl under the vehicle when it's cold and try to wiggle the heat shields around the catalytic converters. If any are loose, you can just remove them without worry.

Hi Towncivilian!
Thanks for answers, I got this car month ago and have no records of maintaining of vehicle.
I'm in Canada and every fall i did tune up for my previous cars some times temperature falls here to -16.6F so i was going to do the same for infiniti. Old spark plugs were ok but they were not NGK they were cheap stuff - "champion".
I put new ones - NGK.
I'll try to check coolant sensor and do something with heat shields cause vibration is really bad for me cause back window is knocking.

oleh57 wrote:Hi guys! after got everything done as on pictures got problem with a car. While it's cold idling pretty ok but when engine is hot it has backfires especially high frequency when transmission is on driving. Any codes has appeared. What might be a problem is it MAF sensor or coli or idle air control. Any suggestions?. Thanks!!!

I agree with Towncivilian. First try to clean the MAF sensor and the throttle body. When I was changing the spark plugs, I cleaned both the MAF and the throttle body and saw a significant improvement. I ran into a little difficulty because the MAF sensor screws were completely rusted and bit head turned into a circle, however what I did was I sprayed the cleaner from the front opening and that seemed to have done the job. If your screws look rusted, do not force the bit on it, first use a blaster liquid to remove all the rust. That is what I should have done but did not so now I cant take the MAF sensor off if I need to. I am glad I have no issues with the MAF.

vibrating on high speed 100 km per hour and between 2300 rpm and 2500 rpm. when accelerator is on 3000 rpm it's gone.and if i remove foot from accelerator everything is ok as well.

Followed great link Thank you so much kkamakasi for write up and Towncivilian forPathfinder / QX4 General Information and FAQ!
I just replaced all sparkplugs with NGK PLFR5A-11(old ones had 1/4 inch gap ), cleaned throttle body,replaced air filter, and cleaned MAF as per Sticky and I still have same problem as you. fault codes are:
P1140 Intake Valve Timing Control Position Sensor (Bank 1)
P1320 Ignition Control Signal Circuit Malfunction
P1490 EVAP Vacuum Cut Valve Bypass Valve Circuit Malfunction
and finally P0300
I don't think problem is gone when accelerating I'm guessing when I kick out of Overdrive, RPM goes up and roughness smooths out.
Paid $1000 for it last Feb, week later Son hits fire hydrant passenger door and fence(only snow we had last year and he found it). took out small dent in Aframe, replaced passenger floor and door, bottom half door hinge frame, both rocker panels, rusted wheel wells, both front fenders. What a tank. Cost me another $1000-1200 for replacement parts, welding and paint supplies. 6 months later it works but runs rough.
I'm going to try the trick of disconnecting one coil at a time and notice when it runs worse, if I get a warm day.

^^^ might be those vacuum hoses need clearing....sometimes those symptoms seem to stem from clogged vacuum hoses....maybe an air compressor can blow it out clear...

just a tip since I saw a couple of threads with rough idling problems

Hi,

Why are you adding anti-seize to the spark plugs ? I am about to do this job and NGK stated spark plugs are installed at the factory dry and adding anti-seize can lead to over-tightening. There's no mention of adding anti-seize in the Nissan service manual either when changing the spark plugs. But everywhere else I research people are applying anti-seize to their spark plugs . I am new to auto repair can somebody explain this to me?

Thanks
-Rich

I have read that you should decrease the torque setting by ~15% if using anti-seize, so I opted to go with 18 lb-ft. Unfortunately, I misread my wrench and accidentally set it for 28, not 18. I did two plugs before I noticed. I could have pulled them out, but then they wouldn't have a fresh washer. Since the QX4 has 200k miles on it, I don't expect to ever have to replace them anyway.

Gary

Just did this today so thanks to kkamakasi for making this.

Torqued all plugs to 18 ft lb with anti seize and in addition I put a little dielectric grease on the tips of the plugs.

Made the mistake of putting back everything on passenger side to find out I HD 2 extra bolts sitting in my tray. These two bolts were for the bracket on the passenger side, had to take everything back off. Sheesh what a waste of time. Make sure you double check before putting everythin back!

Also the MAF sensor might be sorta stuck on the intake piping so take your time and twist and pull slowly.
I found it a bit harder to unplug the harness from the boots on the passenger side due to a bit less room.

"Service Engine Soon" light as well - P1320 ODB2 code per scanner - (no secondary codes) and car seemed to be running fine. Just completed the job (coil packs and plugs) on a 2001 Qx4 (108k miles) and have a few comments. Purchased OEM coils from local Infiniti dealer @ $105 each (Hanshin brand - same brand that the originals were) and OEM plugs - NGK platinums (PLFR5A-11) @ $14 !!! each locally. Not sure if it is necessary to remove the air filter box but since I've done it twice prior to replace headlamp and ballast it was no big deal (4 bolts and unclipping MAF sensor connector). Speaking of that connector... you have to push down REALLY HARD on the spring/clip thing with downward facing arrow - and while it is pushed down - pull up on the connector and it comes off with ease. It initially stymied me and ate up at least 45 minutes of frustration and almost wanting to use the "get a screwdriver and start prying technique" - not a good thing... Regarding the "black sensor thing" in the pictures - be very careful as previously alluded to - the philips screws will strip easily. As far as I can tell it needs to be removed otherwise you won't be able to access the coil pack on #4 cylinder. If you strip the screws you'll have to remove the throttle body for access which will eat up more of your time. Regarding the pictures of the throttle body... mine had another cable dealie mounted on the top two screw holes in the picture (above the upper left allen bolt - anyone know what that is?) and removal would have been even harder than just the 4 allen bolts and two connectors -just a fyi. Removing the two screws on the 'black sensor' thing for me was difficult as no matter what length of screw driver I tried I simply could not get enough torque or push to break them free due to logistics / arm strength and awkward position they did start to strip - you may have better luck. (use a good fitting philips and not a standard (as it slotted in such a way that it looks like you could use a standard screwdriver as well but you won't get much "bite" and the screws will strip). What I ended up using to remove the screws was a small ratchet with short extension and socket with hex head which allowed me to insert a philips screw bit I normally use in my drill. Using the ratchet allowed me to tackle these screws from a 90 degree angle and they broke free with ease - yay. The next obstacle was pulling the boot off the throttle body - took a lot of swear woods, wiggling, twisting, walking away from it, coming back, more swear words and finally after a prayer or two - it came off (another 45 minutes ate up) - your mileage may vary but it was a bugger for me. btw - getting it back on was just about as much of a challenge - perseverance and some blood, sweat and tears I was finally able to slide it back in. So that summarizes why an hour and 1/2 job took me two partial afternoons. Additional comments: you will need a 10" socket extension to remove the plugs - my 6" left little or no room to remove them. Used a 5/8" plug socket with rubber boot insert to slip over and hold the plug tips when you pull them out. Also, since these were the original factory plugs never before changed - most of them seemed damned hard to loosen (after 108k miles) - (didn't want to break something) -but used an extension bar on my ratchet and they slowly broke free. After all six were out they were definately worn - the electrode tip was almost non existant and the threads were clean to barely/slightly rusted in spots which probably attributed to some of them being difficult (or more strength than I thought) to remove. The electrode and tips were a nice cream / golden color which showed that they were burning well and in a good heat range - but they were well worn as I said. One of the plugs (one of the easiest to remove) did have some oil around the threads so I suspect it might have been a bit looser than the others - it was the #5 plug). I didn't use any anti-seize compound on the new NGK plugs but did use some dielectric boot grease inside the rubber coil pack boot before inserting. I did use a torque wrench set at 20 ft/lbs. when screwing in the plugs. In the old days I used to do it by hand and feel but what may 'feel' tight might just be the crush washer giving a false 'tightness' impression. Since these plugs are rated at a 100k mile life span I wanted the piece of mind that they were torqued properly. In summary - the wire harnesses DO get in the way for both passenger and driver sides so removing the mounting brackets is almost a necessity for the extra room/space you need. Getting your fingers at the bolts to remove the passenger side coils was more difficult and tighter of a fit than the drivers side. You do not want to risk dropping one into the bowels of your cars under carriage. Finally - my motto - "a project you think will take you two hours - multiply that by two or three". On an end note - fired up the car after the coil pack/plug change was complete... guess what? SES light remains on... was expecting it to be cleared after all the work. Took it to the local auto store and P1320 again. (perhaps it takes some driving cycles for the ECM to 'learn' the new parts???) Talked the guy into clearing the code. Time will tell if it returns - I got 4 miles on it to date and no SES light :-)

It's a shame the hosting of the photos has timed out or similar ... no pictures anymore ... either on this main thread .. or the link at the beginning of this post ..