SORRY FOR THE LONG POST!!!!!

Here's my problem:
I have been getting poor gas mileage so I decide to start gathering parts to do a "tune up" on my Maxima(2002 GLE). So saturday I did the plugs, rear valve cover and gasket, NWP Spacers, PCV valve. I had some other things to install but I was running out of time, so I buttoned up what was done and thats when the problems started. I started the car and there was a loud rattle and misfiring, along with a bad exhaust smell. I checked all the vacuum lines, electrical connections and found no problems. The next day, switched around plugs, coils, and injectors, resealed the spacers. Rattle is still present, as well as the misfire. Im puzzled as to what could have happened, the car was perfect before I took it apart. I have an idea that its either an intake leak, or the rear cat converter has broken and clogged, causing the misfire. Also, I noticed when I drove the car home after the last time I checked everything, the cat was glowing red when i parked it. What could this possibly be? Any help and input is much appreciated.

 

you usually get the red glowing cat from the coils being switched up. recheck everything again one coil at a time.

 

What SES code are you throwing?

 

I'm getting 2 p0300 codes.

 

Obviously, you blew a coil or two or you are using "internet plugs"!

Are the plugs OEM NGK laser platinum or iridium? They better be.

Now disconnect one coil at a time and start the car. If the engine does NOT get even worse, this is your bad coil/plug/cylinder.

When you have massive misfire with blinking CEL, it should be trivial to isolate which cylinder(s) is giving you the trouble. Given that you have the mechanical skills to do valve covers etc, this should be easy for you.

I have no idea how retarded one has to be to switch the wires (because wiring is of exact length) but it never hurts to recheck.

If you do not come back and update this topic, we will assume that you had switched the wires :-)

- Vikas

 

OK, so I finally got a chance to check out the max and found out the coils were indeed switched. Drove the car afterwards and still have poor acceleration, but car is driving much better. I still think the cat is clogged as when I floor it, as it reaches 4k rpm and higher, it sounds as if its breaking up and becomes very sluggish. Looks like I have my excuse to buy some headers.

 

How in the world did you manage to switch the wires? You have to try very hard to mix them up as their length is different for each cylinder.

If you have been running with misfire for a while, you could cause problems with the converter but it is not difficult to check. Hook up a vacuum gauge to the intake and verify if your convertor is clogged.

There could be other factors such as low fuel pressure, fuel pump dying, non OEM spark plugs, clogged injector. Any of these could give you problem at high engine rpm and under load. You have not clarified if you put NGK laser or went with Bosch plugs :-(

- Vikas

 

They are OEM plugs directly from the dealer and I have switched injectors before. I do have a fuel filter I need to install and I guess it wouldn't hurt to change the pump, I have appoximately 130k. I still believe its the cat because it was rattling like crazy at one point.

 

Take a look at this http://www.aa1car.com/library/converter.htm
You would know if it is your converter or not.

You could also hook up a fuel pressure gauge to the fuel rail and monitor it as you drive the car. That will tell you if you have fuel delivery problem or not.

Vacuum gauge and fuel pressure gauge are cheap investment in tools before you start replacing the parts without making sure if they are bad. A visit to Harbor Freight would get you both these items under $50.

- Vikas