Well, its been months, and it feels like my car is just getting worse. As some of you know, I have been experiencing weird jumpy idle (bouncy/jerky), horrible gas mileage (210 to a tank if im lucky), and extreme loss of power. I cant even peel out when stopped at WOT! I seriously have no idea what is going on. When I pull the codes all I get is 03 04, which is the Knock Sensor. I know for a fact that the KS is not bad because I bought it new from the factory a few months ago, so I'm wondering whats tripping the KS. Whatever it is, its ruining my timing completely. I changed my spark plugs to NGK, and replaced a coil pack. I have a new fuel filter, and changed the oil around 1500 miles ago. I have a strong feeling that it could still be one of my ignition coils causing these problems because of the way the car jerks. When I had my 86 mustang, I accidently confused two spark plug wires on the distributor cap, so when I drove, I got the same exact jerking feeling, which gave me some deja vu. Ive been thinking of many causes to this, such as EGR valve clogging, IACV problems, or even clogged fuel injectors. Today I was at a light, and my car just shut off, this is the first time it had done that. All I know is that this is getting worse.
Its real hot and humid here in florida, but even in rain or somewhat cold whether I have the same problem. I am awaiting a air/fuel ratio gauge to see how rich im running. I also realized today that my exhaust (stock) was making this real low humming sound, never really hear it before. I'm even wondering if this is an ecu problem, becaus ethe only other codes I have gotten is a rear heated O2 sensor, which hasnt come back for a while. I have not gotten ANY cylinder misfire code, and have been putting Amoco 93 octane for quite some time now.
I know this is long, but im desperate. I want to take it to a dealer or some1 professional, but I knwo that will cost lots of money right there. ANy ideas you guys would have, please post, i'm open to anything. Save my max

 

Try another gas station, I heard of gas stations using watered down gas around here

 

what gas u use btw? i heard regular gas kills the knock sensor cause it has to work extra hard to do something which i forgot. And watered down low octane can even be worst...

 

I have been using Amoco 93 octane all the time, there was a time where I would use 89 octane, but I learned my lesson. Ive been using the amoco 93 octane for a good half year now. I think I'll experiment with Chevron a little.

 

I get worse gas milage with amoco than others.... just a heads up...

 

interesting... i use it cause I have the gas card...

 

i don't think it has anything to do with gas.....how many miles you got on it??? which shouldn't matter 'cause i had a 96 with over 230,000...your exhaust isn't clogged or anything right??? i'm not an expert but it's going to be something small...and do not go to the dealer

 

Plugged up Catalytic Converter - Listen to your exhaust, you should be able to hear the individual cylinders fireing. If you just hear a hushhhhhh nice smooth sound, chances are your cat. is plugged.

You may also have a MAF sensor thats on it's way out. See if you can find another 4th gen Max and swap MAF sensors and see if that cures your problem.

 

I was talking to someone who had a similar problem to you, and nobody could diagnose it, until one mechanic finally figured it out. Crap gas milage, stalling at lights, a lot of what you are seeing.

Turns out his catalytic converter was clogged. Also since you have seen the rear heated O2 sensor before, that would be pointing directly at the cat having a problem. Also, what caused this condition was too much unburned gas from bad ignition coils down his exhaust pipe.

Cheapest solution to try this out might be to buy a test pipe, or just pull the cat out (it'll be loud) and try it out.

 

its it possible for him to unplug the cat? or does it have to be replaced?

 

http://forums.maxima.org/showthread....ght=unplug+cat

 

I'd just say go with a whole new exhaust line and run it w/o the cat... if that's the problem, then a) you've scored new exhaust, and b) you can address the issue of gettin a new cat later

 

Thanks for the help guys. Well I would say for the past couple of months, I have gotten the Rear Heated o2 sensor code only twice. But when I reset the ecu it doesnt come back. My max has about 98k on it.
I want to know that if the cat is clogged, how does it cause all the symptoms I am having? You cant hear that low humming noise from my exhaust unless you get like right next to it.
Ive only stalled twice in teh past 6 months. I will try the MAF swap with anyone who is willing to help me out And maybe teh cat thing to. But i still have no idea how a clogged cat could affect me this bad, some let me know, thanks alot guys!

 

1) Your catalytic convertor is dead. My bet. Must be replaced. No way to fix.

2) Water in fuel tank. Add 3-4 little bottles of "dry gas" or equiv. when tank is almost empty and then fill it up to fix it(100% isopropyl alcohol)

3)Poor compression. Rings/valve seals shot. Get a compression test done.

-RMB

 

When was your last time your oxygen sensors been changed? Any other codes on your ECU (lean right bank or lean left bank codes)?

 

No front o2 sensors, only rear heated o2 sensor, and that was twice.