I have an 03 sedan with only about 138,000 Km`s on it now. I`ve had her for about three years now. Haven`t had many problems, just part of the exhaust replaced. I have a Stillen Z-tube and K&N stock style filter.

For the past couple months I`ve noticed a bit of hesitation when accelerating from a stop. On a couple of occasions the idle became very rough but then smoothed out after I hit the gas a bit.

Recently, in a touchless car wash, the idle became very rough again and the service engine light came on. After a few off and on`s the light reset itself and hasn`t come back on.

I have had the car for about three years now, since it was at 98 k. I haven`t replaced plugs or wires yet.

Anyone have a similar experience or any thoughts at what to look at firstÉ I did notice that the hard plastic stillen z-tube doesn`t really fit the rubber intake hose very well...I`m going to check that and make sure air isn`t getting in at that connection. Although I don`t think that would explain the car wash part.

Thanks.

 

Like you said check plugs and wires. Could be bad gas in the tank. U pump a high octane?

 

Actually, someone reminded me we dont have wires but suggested it could be a bad coil. I always use premium gas.

I had a look at the z tube and noticed it wasnt sealed tightly. This is after the MAF so it could be causing an issue. I tightened it up good and will see if that solves it.

In the meantime I'm going to bring it in because its due for an oil change and have the code checked if it's in the history.

 

There are 6 coils, and a bad one should cause a code.

Biggest hint to diagnosing is a code, so of that CEL comes back on..RUN to a code reader and get it. The code might also be stored as a "pending code" so make sure whatever reader you use can read the codes AND pending codes. It's a different function.

Is the k&n filter open to the engine bay? Do you have a picture of the setup? Is there an opening AFTER the maf that air could be sucked in through.

You could reinstall the stock parts, and see of the issue goes away.

 

The K &N is the stock replacement...so it sits the same way a stock one would...not open to the engine bay. The end of my z tube closest to the throttle body was not installed correctly. I fixed that today and will see if that solves it.

I'm not sure if that would explain why the idle got so rough during a car wash though

 

Clean the maf with maf cleaner. It could be dirty from over oiling the filter.

 

Get the code(s), and go from there. I just went through this same thing, albeit with 149k miles on my car. Showed a P0301 code. I swapped coils with another and eventually it happened again, this time threw a code indicating the cylinder I had moved the coil to. So that was pretty good circumstantial evidence the coil was starting to go bad. Replaced it and no issues since then.

Symptoms for me were random times the car would idle extremely rough but was fine once you got it up to speed. Did not happen often. The CEL would come on every time it did happen.

Could also be a fuel injector going bad. Good luck.

 

Something got wet under the hood.

 

Ok, so it's been sbout 4-5 days since I tightened up my air intake hose near my throttle body, behind the MAF. The engine light has not been back on and throttle response seems to have improved.

I brought the car in to a buddies shop today and they checked the code history for me. There was a P0171 code - system too lean bank 1. So that is inline with the air being sucked in after the MAF, not being measured and therefore creating a lean condition.

So if you ever have the same symptoms..check for air leaks first. Cheaper than coils/ plugs etc.

The garage did mention that Infiniti coils aren't usually a problem and don't fail often.