bigmike83

About one year ago I discovered that my fiance's 2004 Maxima had the symptoms of common timing chain tensioner problem. I have never attempted this level of repair before but I figured this was the perfect chance for me to learn something new on someone else's car. During this time I also took the opportunity to replace some common wear items such as the water pump and spark plugs. After about 2 weekends and lots of choice words I was able to get the car back together and running. I was thrilled when driving the car that the original symptoms of the loose timing chain were gone. However the car seems to have developed a slightly rough idle. It also once in a while sets a random multiple misfire code (P300). Outside of idle the car runs and drives just fine. Knowing this I figure I will get to the idle problem when I have time.

Fast forward to a year later and of course the rough idle condition still exists. At this point my now wife does not have faith her car is reliable. I would like to fix the issue so she once again feels comfortable driving it. I have done a few small things but before taking anything apart again I would like to go down the right path. Here are some of my possible theories (in no particular order).

-One of the spark plugs I replaced does not have the proper gap. I bought spark plugs that were pre-gapped but I did not think to check them before installing them.

-I damaged one of the spark coils somehow. Would a damaged coil cause a random misfire code? I would think the ECU would recognize which cylinder had a bad coil.

-I misplaced one of the timing chains and the timing is slightly off. I triple checked this before putting everything back together but it is always possible.

-I missed replacing one of the vacuum lines properly or damaged one of the hoses and there is a vacuum leak. However I tried spraying some carb cleaner in different areas under the hood and did not notice any change in engine speed.

-I did not seal the valve covers or upper intake manifold properly. I did replace all seals and gaskets. Also see spray test above.

-I damaged one of the motor/transmission mounts. To remove the front timing cover I had to remove the front engine mount. I supported the engine on a hydraulic jack, and after one night I noticed the jack lost pressure and the engine sat unsupported by the front mount for a night. Could a bad mount set a misfire code?

Any thoughts on if the rough idle could be any of the above. Any good ideas on how to diagnose besides what I have already done?

L36

iTrader: (4)

When i did my timing chain job, i had a p0300 code but its turned out the spark plug in cylinder 1 had no gap at all. Somehow the new spark plug lost its gap so that caused my code. A bad coil can cause a misfire, in your case id check all of the spark plugs to make sure they all have the right gap.

If you happen to mess up the timing on the chain, you should get a P0011, 12, 21 or 22 code. I over advanced the timing in bank 1 so i got a P0011 code and my car did idle slightly rough after i fixed the misfire code.

A good way to check if you have messed up timing is first fix your misfire issue and rev the engine into 4-5K territory and let it get back to idle. If it stalls, timing is messed up in one bank or other. Also check your IVT solenoids with a multimeter, the resistance between two terminals should be 7-7.5 ohms @20C.

Kryogen

honestly I would bring the car to nissan for a diagnostic, and then, if you want, fix it yourself. You will save yourself alot of pain.

RandyZ

When I had my 05 done I also had a slightly rough idle and would throw a code when I would merge into traffic or get on it a little. Turned out the Nissan tech had the chain one tooth off. He fixed it and was back to normal. This was a couple years ago and I dont remember the code.

calmnrelaxed

I have a similar issue in my 2004 Maxima. I took to Nissan and they tell me that my rough low idle issue is my ECM