2004 maxima won’t rev past 1800 when in gear. Just gets up to 18 then cuts out and jerks. Limp mode maybe? Car will rev no problem when in park or neutral. Replaced maf. Old alt was putting out 15-16v so I replaced that. Only code is b1083 (right front pretensioner short circuit to ground) becasue of this air bag light is flashing. Cleared code comes right back. Car was in a small fender bender. Maybe the tensioner somehow broke? Would this put the car into limp mode?

 

Plugged cat(s)?

 

No it’s not just a loss of power. It’s like a rev limiter at 1800-2000k

 

what Brand Maf did you use..? Did you Relearn the throttle Body. ?

Have you recently done any tune up maint to the Car. Plugs or boots?

 

forget what brand but it was but was $140 at orileiys. No haven’t relearned throttle body. And haven’t done plugs but they all looked good and where gaped right.

 

I just re-read your Original Post.

The Pre-tensioner is just that. Its the seat belt you need to replace to fix the air bag light. That small fender bender may have been just enough to trip a pre stage on the seat belt. Look at the seat belts pull them all the way out and see if one is shorter or stops. Typically there is No way around this other than Replacing the Belt. They bolt in, Clear codes and roll on. This Is separate issue, and would not effect the engine.

I would tell you to start back at the original issue, Over Voltage. Start the Car and at the battery check the Voltage at idle and then when In gear with a Helper. Have you had the Battery tested after the 16 volt issue..? If you drove the car for any period of time over voltage, No telling how high it might have actually been at highway speeds. Have it tested also, You must verify the Charging system is working properly first. over or under and the car will trip out.

 

So when the car is cold and first starts up it runs fine for about 2 min. Then does same thing. I checked battery voltage after it was warm and it was up to 16.5 again. Why the hell is it this high? What could possible cause this? Alt is brand new

 

That alternator is a problem - https://partsavatar.ca/signs-of-car-...y-overcharging

 

Here is a vid of what it’s doing

 

shoot guess it won’t upload for some reason

 

You got a 2004 Maxima and a alternator that is overcharging. Electrically speaking, our cars are finicky to begin with.

Now, you have (1) an alternator that is over charging with (2) an electrical system that is old/worn out due to the car's age. That extra power could be wreaking all kinds of havoc...grounding out in place it is not supposed to, overloading circuits, literally cooking circuits.

I suggest you replace that alternator with one that works - charges at the appropriate voltage for the car.

 

if you read my upper posts I put a brand new alt in it yesterday. Just now to test I Disconnected the alt completely (2 pin positive plug and positive lead) and same thing happened. I don’t understand why it runs fine when cold but not warm

 

I think the new alternator is defective. It gets heat-soaked and gets wonky. Out of range heat values with electrical components tends to result from resistance. You would have to tear that alternator apart that figure out where the resistance is.

 

if you read my upper posts I put a brand new alt in it yesterday. Just now to test I Disconnected the alt completely (2 pin positive plug and positive lead) and same thing happened. I don’t understand why it runs fine when cold but not warm

 

what are the chances of the new alt having the exact same problem as the old? And why would it also do the same thing when it is completely disconnected

 

Ah, if both do the exact same thing, then sounds like you have a wiring issue somewhere. I agree, it is odd that both alternators are doing the same thing.

I suspect there is resistance, i.e., electrical components are not grounding properly. No easy quick fix with electrical issues. Ya gotta get into it.

 

Ended up being the rear cat. No o2 sensors after it so that’s why no codes. Runs great now

 

after replacing the cat

 

So, the Cat was plugged? If it was, then you gotta figure out why or it will do the same thing again.

 

Glad you got it sorted out so you can drive it again.