P0300, high idle,

[Sidz]

This nismo is killing me.

Cel came on over 2 weeks ago. I replaced the spark plugs as a first step in finding my multiple misfire issue.

Cel came back on next day, fine. I order coil packs but in the meantime my fiance convinces me to just take it to Nissan. I do.

I drop it off to perform a diagnostic on the ecu. They tell me an hour later it's idling high and they performed a learn on the ecu and cleared the code.( the service tech is convincing me someone either plugged in my ecu and messed with the stock tune or I've had my motor swapped) I tell them no, none of that.. I bought the car at 7 miles.

5 days later, same issues, cel on, p0300 being thrown, high rpm at idle 1100-1300, horrible gas consumption.

I take it back and the service tech takes it over the weekend to only call me today and let me know that i need to replace the left and right throttle body.

I figure it wouldn't hurt to just clean the TB, replace the intake filters, and carefully clean the maf sensor.

I've never had any issues other than the steering lock mechanism failing. I am currently at 51k miles.

My question is.. anyone having TB issues? Has anyone replaced the TB?

[Mandingo]

I've heard of this with 350s. It was always after someone moved the plate in the throttle bodies while cleaning them though. The idle position would never reset no matter what relearning procedure was performed and eventually they had to be replaced.

Is there anything that might have upset the butterfly valve in the throttle bodies? Or did you unplug them for any reason then start the car?

[MyKindaGuise]

Bad AFR sensor. Ive seen this before personally.

[Osiris]

I've had to have one of my TB's replaced....it was putting the car into limp mode but without the cel. All good after replacement.

EDIT: correction, yes it did throw the cel's....i was thinking of a separate occaision where it went into limp mode without cel.

[Sidz]

My fiance and I were really careful about the sensors and the throttle bodies when doing the spark plugs.. he did the passenger side and I did the driver. We didn't clean.

The only strange thing is that it was idling high, eating up gas, and cel was on before the spark plug change. Prior to that I had never touched the TBs.

I guess we'll see the verdict when I pick her up today.

[MyKindaGuise]

Originally Posted by Sidz

My fiance and I were really careful about the sensors and the throttle bodies when doing the spark plugs.. he did the passenger side and I did the driver. We didn't clean.

The only strange thing is that it was idling high, eating up gas, and cel was on before the spark plug change. Prior to that I had never touched the TBs.

I guess we'll see the verdict when I pick her up today.

I have a good idea youll find it to be the AFR sensors on the headers.

I had the same thing. I was averaging like 16mpgs and idling at 1100rpms and had a reoccurring CEL.

[Sh0velMan]

Originally Posted by Sidz

My fiance and I were really careful ... he did the passenger ... and I did the driver. We didn't clean.

[Sidz]

Originally Posted by Osiris

I've had to have one of my TB's replaced....it was putting the car into limp mode but without the cel. All good after replacement.

EDIT: correction, yes it did throw the cel's....i was thinking of a separate occaision where it went into limp mode without cel.

no limp mode here.. at least not yet.

[Sh0velMan]

Originally Posted by Sidz

no limp mode here.. at least not yet.

... nah, too easy.

[Sidz]

Originally Posted by MyKindaGuise

I have a good idea youll find it to be the AFR sensors on the headers.

I had the same thing. I was averaging like 16mpgs and idling at 1100rpms and had a reoccurring CEL.

yup.. 15mpg, around 1100, cel wont go away. lol


I guess I'll post up the fix as we find it.

[MyKindaGuise]

Originally Posted by Sidz

yup.. 15mpg, around 1100, cel wont go away. lol


I guess I'll post up the fix as we find it.

DAT Ferrari gas mileage. haha yeah. I mean its hard to say over the interwebs but I think that's the issue.


If that's the case get the AFRs from FB Nissan here on the forum. Cheapest genuine parts Ive found.

[chrischhorn]

Did you check around for vacuum leaks? When I installed my intake manifold, it didnt torque down corrrectly and I had a leak on the intake manifold seal so I had to readjust it. I dunno if you took off the intake manifold to do the plugs or not but if you didn't use a new seal, thats one spot to check.

[Sidz]

Originally Posted by chrischhorn

Did you check around for vacuum leaks? When I installed my intake manifold, it didnt torque down corrrectly and I had a leak on the intake manifold seal so I had to readjust it. I dunno if you took off the intake manifold to do the plugs or not but if you didn't use a new seal, thats one spot to check.

I didn't take off the intake manifold.
I want to go over everything myself when I get it back.

[cheshirecat]

OP, any mods? intake/exhaust, etc? This code is generally thrown with an aftermarket intake.

[Sh0velMan]

Originally Posted by Sidz

I didn't take off the intake manifold.
I want to go over everything myself when I get it back.

There's multiple places you can get a vacuum leak without removing the manifold.

The symptoms you're getting are strongly indicative of either

A: A sensor failure somewhere in the closed-loop system.
- MAF sensor
- Primary O2 Sensor
- MAP sensor (unlikely)

B: Vacuum Leak

C: Horrific exhaust leak at the header/head interface...very unlikely. You'd hear/smell/see it immediately. And you'd probably catch something on fire eventually hahaha.