01 QX4 misfire

[computerdna]

Dear all,

My 01 QX4 with 75000 miles has a misfire problem. I drive to and from work everyday ¨C 30 miles round trip.

(75000 is the correct mileage, I posted the mileage of the old Quest in my earlier post)

1. Going to work in the morning (cold 20-30F), everything works fine ¨C no misfire 2. At work, parked in an indoor garage (65F) for about 8 hrs.3. Going home, started the car, feeling a little unusual - a little vibration from the engine, vibration gets stronger as the idle drops, then engine light started blinking. The engine light is either blinking or steady.4. Driving the car, the engine light is blinking and sometimes steady. Blinking most of the time when accelerating. I can feel a bit of lost of power. 5. This same routine happens almost everyday now for the last 3 days. My mechanic says most likely to be the coil #1.

A code scan shows 1. Cylinder #1 misfire 2. Catalyst efficiency low bank #2

On top of all these, I have reported a trouble code earlier - Catalyst efficiency low bank #1. I changed the fuel filler cap and it seems to fixed the problem. At least it didn't show up since the last tank of gas.

Any ideas would be greatly appreciated. With my limited knowledge, the only things that I can think of are the coils, spark plugs and the injectors.

Oh, one more, I am only getting 12 - 13 MPG with combined city and highway miles. I don't think this is normal since it is supposed to get to the 15-19 area, I am nowhere near that.

Thanks

[NISTECH]

stop driving the car till you get this fixed. the blinking engine light indicates catostrophic failure of your cat is going to happen if your keep diving it with the misfire.[thats if it hasent happened yet. You are correct about it either being the plug or the injector. fortunitly on your vehicle if it is the #1 injector it is accessable with out pulling the plentuim. start by replacing the plug if that doesnt stop the misfire then you are looking at the injector. it could be a wire to but usually you see a spark jump to ground somewhere along the wire when you accel. the only other cause would be valve problems or other internal engine catastrophy which is very unlikely.

[NISTECH]

the wire doesnt come into play if it is the 3.5l engine though since its coil overs. if you have the 3.5l engine the coil could be your problem as well. easy test for a shop is to swap the coil with another cyl and see if the miss follows the coil. if so it needs a coil.

[computerdna]

Thanks NISTECH!

As usual, everything was fine this morning - even the engine light is off after a few miles of driving. This is a miracle with all these problems I reported. The change of the fuel filler cap definitely fixed the "Catalyst efficiency low bank #1" problem.

Yes. the engine is the 3.5L. I am going to change the spark plugs first. Do u have good plugs to recommend?

Many thanks.

[computerdna]

Thanks NISTECH!

Yes. the engine is the 3.5L. I am going to change the spark plugs first. Do u have a good one to recommend?

[NISTECH]

NGK factory plugs are the best to use on nissan/ infiniti products. For the record the fuel filler cap has absolulty nothing to do with cat efficiency. I think it was pure coincidence the light went out after. the only codes that would be thrown for fuel cap would be P0440 evap small leak or P0455 evap gross leak. Cat efficiency is determined by a comparison between the O2 in front of the cat and the O2 in the rear of the cat and how closely they cycle from rich to lean. if they get close to sweeping in unison it throws the efficiency code P0420 or P0430

[computerdna]

NISTECH - your are right about the fuel cap, the engine light came back on today. I'll go pull out the code later.

Can anyone post back with information on what kind of mileage (MPG) you are getting from your 01 QX4? I just want a confirmation of the mileage (12-13 MPG) I am getting is not normal.

Thanks

[NISTECH]

your decreased fuel milage is most likely due to your cyl one misfire. if that cyl misses the o2 will detect an high oxygen content . The ecm will determine this as running lean and add aditional fuel to the cyl to try to richen it up. and it will continue to add till it sees the desired oxygen content from the O2. Figure out the missfire and correct it and you will most likely see a increase in your fuel milage.

[jarhead1]

Hello, I am new to site-but I will tell you that the same conditions just occurred last week to my 93 Pontiac Grand am, my mechanicdid something with a box that has spark plug wires going to it and said " no spark from the #1" so he shut car down took off 2 star type screws and replaced one of the 3(coil relays?) -it was fast and easy took all of 3 minutes.And off I went.. this little chunky piece took on 2 of the spark plug wires...no problems since.

Good luck Steve

[NISTECH]

GM cars are totally different then NMC cars. What he has is a single coil mounted over each spark plug there are no plug wires.

You have a 3 pack of coils with plug wires. the coil you mention is a waste spark system [2 wires per coil] it fires both plugs at the same time only one of the 2 cyl is at TDC for the power stroke.

[computerdna]

Just replaced the Coil of cylinder #1 and all the plugs. Misfire seems to be fixed.

Coil was ordered from Everything Nissan online from a banner on the left side. Good price and service, recommended.

I have also started a new thread regarding to the values of oxygen sensors. NISTECH , please share your knowledge database

Thanks.