Guys I need some help. On Friday, I was teaching my girl to drive manual transmission, on my max.

After the "Lesson" my car started to hesistate in upper RPMS.

At first I thought i was paranoid when I said "My car feels slower". Then i looked at my air/fuel guage, and at about 4.5k RPM the car TOTALLY leans out (In all gears).

It's not getting the fuel it needs to keep going at high RPMS.

I hope this is a known issue and someone out there knows how to fix this.

I reset the ECU, and checked all my sensors and guages in the engine bay, no cigar.

P.S. I just changed my knock sensor 3 weeks ago, and I am getting NO codes from my ecu.

 

fuel filter? Do you have a fuel pressure gauge, what does it say?

 

Check the connections on your MAF sensor.
Also, check all of the intake plastic boots for good tight fit.

It could be just about anything from cam sensor to dirty injectors to fuel filter to funky connections on any of the emissions wiring.

Do the basic stuff first (filters, injector cleaner, check hoses and connectrs) and report back If it still does it.

 

Go to AutoZone and buy the fuel system treatment (Not injector cleaner, but it will actually say SYSTEM). The stuff is more expensive, but I had a clogged injector and about 2 hours of running time with this stuff, and it was back to normal.

 

I just bought the fuel filter, I will install that when I get a chance.

I have checked all vacuum hoses, and sensor connections already. I have already purchased some of that injector cleaning chemical( And used it, but it made no difference).

 

Turbomax what symptoms did you experience with your clogged injector?

 

O2 sensors..............

 

BIG D care to inform me why you think it is the O2 Sensors?

 

It's NOT the O2 sensors! If it was and you were getting that noticeable a performance failure you would get some ECU code for O2 sensors. If the Sensor can't correct the mixture within the spec range it will stay fixed in a lean or rich condition or seem sluggish to the ECU and you WILL get a code.

If you want to make sure it's not the O2 sensors just disconnect them and drive it for a while. You will get a CEL but the ECU will go into backup mode and run the mixture with fixed values that are preprogrammed to ensure the car will still run even when a massive O2 failure happens. It's not the O2 sensors but.... I could be wrong.

 

Make sure the fuel pump is getting ample voltage.

Vr4maxima

 

I just got a new O2 put in and the performance is the same so that goes out the window. Only difference is better gas mileage. It won't give a CEL til it completetly craoks on you.

 

Vr4 maxima, how can I check the fuel pump voltage?

 

unless you're running a separate O2 sensor for the gauge, then don't worry about it. The ECU goes into closed loop mode after 3k and no longer uses the O2 sensors, and in effect cut's them off.

 

Not true. The O2 sensors are no longer used when you go WOT( actually 80% throttle or more I believe) not after 3k rpm. I think it goes into open loop at WOT not closed loop.

 

So what does that leave me with then (Causes of problem)? At full throttle or any decent throttle position the car leans out, and becomes excessively sluggish above 4.5k.

 

Check:
TPS voltages
MAF voltages if you can.
Fuel pump might be dying. ie.. able to pump while at idle but not with a high load conditions