Frustrated but going in the right direction.

[Q_SHIP]

Ok guys keep in mind that I have a 99 Q45 now.

The car is starting to run even worse now. I am not throwing a SES light just yet but I can't believe Im not. When the car is cold it runs fine. When it warms up, it stumbles and barely make it up to speed. It coughs and has a real problem untill I hit 3500-4000 RPM's. I read the codes lastnight and came up with this.

P0325 Knock Sensor 1 Circuit Malfunction (Bank I or Single Sensor)

P0330 Knock Sensor 2 Circuit Malfunction (Bank 2)

Anybody have any ideas?

[elwesso]

Im wondering if the MAF is bad.....

the KS wont cause that problem but its a bummer that they are bad!

[Q_SHIP]

Thats what I was thinking but I read this

http://www.obd-codes.com/troub...n.php

[Q_SHIP]

Does anybody have any ideas where the knock sensors are on the 4.1?

[elwesso]

Theyre going to be under the plenum.....

The KS failure wont be much different that it is on the G50 since theyre the same sensor...

[Q_SHIP]

You think the plenum has to be removed? Or is it reachable without it? Your input is always good Elwesso. Thank you.

[elwesso]

The plenum will definitely have to come off.. Someone with the user name of duck(something) wrote a little blurb on him doing it on his 98

PLenum does come off but apparently its not as complicated as the G50..

[Q_SHIP]

Is there anything else that can be causing this code to be? Like you said, first thing that came to mind was MAF but no I don't know what to think.

[elwesso]

Sometimes the harnesses go bad and that COULD be whats throwing the code and the KS really arent bad..... Still its best to replace the KS and harness together, especially if you have higher miles. I dont know what kind of miles your 99 has on it, but i would suppose its over 100k, in which case the KS dont owe you anything.....

Anyway the only way to truely find out is to get another Y33 MAF and try it out..

[90Q45blue]

Your probably need to replace your KS anyway as they're over 100k old most likely. Depending on if you get new or used parts, new KS are cheaper than a new MAF.

Nick

[metaverse3]

Ok guys keep in mind that I have a 99 Q45 now.

The car is starting to run even worse now. I am not throwing a SES light just yet but I can't believe Im not. When the car is cold it runs fine. When it warms up, it stumbles and barely make it up to speed. It coughs and has a real problem untill I hit 3500-4000 RPM's. I read the codes lastnight and came up with this.

P0325 Knock Sensor 1 Circuit Malfunction (Bank I or Single Sensor)

P0330 Knock Sensor 2 Circuit Malfunction (Bank 2)

Anybody have any ideas?

Here is a cartoon that might aid a bit..

[maxnix]

FSM and TSB still available at http://www.nissan-techinfo.com/infiniti/

[Q_SHIP]

Thank god for Nico again. thanks for the diagram.

[FarFetched]

I have similar problem, just not as bad as in your case. I have an occasional stumble in D or R at a stop, or when there is a slight change in throttle with slight increase in load. I think it is MAF is going south!MAF alone won't throw a MIL.

[DAEDALUS]

It will if the resistance is too high, probably if it's too low as well.

[FarFetched]

Indeed, only on the ECM end it will set a DTC.

[MarcoMan]

I am new to working on my 99 Q45t. I have the P0325 error and I want to check the harness before pulling the plenum. I have a service manual that shows an exploded view of the sensors but not where they are located on the engine nor does it show a good picture of where the harness is located. Can anyone recommend a god repair manual which gives this level of detail?