No reving past 3500 RPM (Y34)

[candymanfb]

My M seems like it doesn't care for flooring it - which I think my wife would like!

My mechanic replaced my left motor mount on my 2004 M45 today.
While driving home at a stop light the car started to vibrate in a way it has never done. I put it in neutral and back to drive, and continued on my way. I later realised the car will not rev past 3500 and jerks when I get near that RPM. The jerk is similar to a governor kicking in.

I hope he just forgot to plug in a sensor and not something more serious. I've taken the car to him for the past 3 years but he's not an Infiniti specialist. He works on Nissans (Datsuns) though. Any advise or insight given would be provided to him.

I had this problem after his shop closed for the day. There are 998xx miles on the car.

[Ilya]

Check your MAF.

When I had a Maxima, this was a known symptom of bad MAF. What it's doing is putting the car into 'crawl home' mode (safety mode) because the MAF is malfunctioning.

[jjcuff1]

Yes I had a Z31 and this was the case. bad MAF or bad signal, pull plug off, even clean with MAF cleaner reinstall, maybe disconnect battery or clear codes if any

Open loop Safety limp mode. MAF is not reading AF ratio correctly and therefore limits RPM to avoid detonation lean conditions since it is open loop and not getting or relying on feedback from o2, TPS sensors to change fuel ,map

[jjcuff1]

correction MAF not reading air volume properly therefore AF readings are deemed invalid so it defaults to stock fuel map and rev limit

[bbs350z]

id check your crankshaft positioning sensor as well. friend of mine had a damaged one on his 350z and it would rev fine to 4k. its essentially in a failsafe mode

[Ilya]

I forgot the CPS.

I'd say most likely is MAF, but CPS could definitely do it as well.

[candymanfb]

It was a camshaft position sensor issue.
There was a code of P0340 pulled. My mechanic cleaned the connections and it's been fine since.
For all I know it could have been disconnected by accident.... all is good now though.
I was told the sensors are fairly cheap at 25-30 per and would be about half an hour of labor to install.


Thank you all for informing me of possible causes!

[Ilya]

Yeah, the Camshaft are cheaper. I think the Crankshaft ones are a bit more expensive (around $90).

What happens is they get little metal shavings on them from the crank/cam shaft and thus get dirty and stop sending a good signal. Cleaning them (usually held by 2 or 3 10mm bolts) cleans that issue right up.

[szh]

It was a camshaft position sensor issue.
There was a code of P0340 pulled. My mechanic cleaned the connections and it's been fine since.
For all I know it could have been disconnected by accident.... all is good now though.
I was told the sensors are fairly cheap at 25-30 per and would be about half an hour of labor to install.

Thank you all for informing me of possible causes!

Thanks for reporting back what it was!

Always good to get that knowledge so that others can benefit.

Z

[MaxBolus]

It was a camshaft position sensor issue.
There was a code of P0340 pulled. My mechanic cleaned the connections and it's been fine since.
For all I know it could have been disconnected by accident.... all is good now though.
I was told the sensors are fairly cheap at 25-30 per and would be about half an hour of labor to install.

sorry, late to the thread..

I had a crankshaft sensor go bad and the symptoms were identical. Dealer cleaned the contacts (must be the first step in the diag/t-shooting procedure) and it was OK for about a week, then went bad again.
got the part for 29 bucks, installed in 20 mins, easy job.
Mine seemed to be heat-related, this happened in late summer.
Just in case yours fails again..

good luck!
-m

[candymanfb]

I think you were right!!!

Short story: I replaced the crank sensor.

Long story: The car died on me while driving after the contacts were cleaned. So I had the "CAM" sensors x2 replaced. The car had the same symptoms after replacing the cam sensors (except for shutting off). I got the crank sensor done today and drove from Santa Monica to Hollywood on the freeway with no problems. Hopefully no issues with this for a while - all sensors have been changed.

The camshaft and crankshaft sensors are essentially the same part, but the angle of connection is where they differ. This 45 degree difference is what causes a 60 dollar increase in price. My mechanic said the cheaper ones could be used, but they would require moving connections.

The diagnostic (P0340) always said the camshafts were of issue ..even after replacing them. Only after reading on another topic on this forum did I realize the codes emphasize the wrong part. My mechanic called a few people and had a conversation with "corporate" when he was trying to figure things out and noted this confusion.
It was a learning experience for everyone. I replaced the 90 dollar sensors (cam) then the 30 dollar one (crank).

Thanks again for all the leads -

It was a camshaft position sensor issue.
There was a code of P0340 pulled. My mechanic cleaned the connections and it's been fine since.
For all I know it could have been disconnected by accident.... all is good now though.
I was told the sensors are fairly cheap at 25-30 per and would be about half an hour of labor to install.

sorry, late to the thread..

I had a crankshaft sensor go bad and the symptoms were identical. Dealer cleaned the contacts (must be the first step in the diag/t-shooting procedure) and it was OK for about a week, then went bad again.
got the part for 29 bucks, installed in 20 mins, easy job.
Mine seemed to be heat-related, this happened in late summer.
Just in case yours fails again..

good luck!
-m

[MaxBolus]

cool!