Hi

The facts..

-2008 350z w/ 32,000 miles. Everything bone stock.
-Sythetic oil
-Only use shell 91 gas.
-bought used from Nissan dealer w/ 4200 miles.
-6 MT

So I brought the Z to the dealership a couple weeks ago to get a few things fixed. One of them was my rough idle which I have had since about 10,000 miles. Drops pretty low then shoots up again when in neutral, AZ off. Will do this from time to time. They said the Z did not reproduce the event while the checked it out.

After the Z was checked out they said idle was a little low and they raised it. Service person said a dirty MAF might cause this? Is this easy to check? Well seems like the idle raise did not solve the issue as its still doing the rough idle thing. What else can I have them check to fix it? Its really starting to annoy me. Bought this sports car because they were known as being reliable. So far looks like I might have problems in the Z's later life

I have read somewhere on this forum of something else in the engine that might cause this rough idle. After I post I will search again. I remember it being a $130 part.

Also, the passenger window is acting up. Tomorrow 11/23 is the last day on my basic warranty. Hope it acts up in front of them and they replace. Will be the second time its been replaced.

Mason

 

Besides a dirty MAF, a dirty/sticky throttle body could be the cause. Could also be a vacuum leak anywhere in the intake system, glitchy electronics in the ignition circuitry and probably a dozen other things. The big problem is without a lot of trial and error, it's going to be hard to find much less demonstrate to them so they will actually search for something.

Basically, if it doesn't show up in a diagnostic check, there's not a whole lot the dealer can or will do to find a problem like this. Nissan isn't going to pay them the hourly rate to try and track down a non-specific problem.

BTW - a new throttle body runs around $130 IIRC.

I am curious as to how they raised the idle though. It's not adjustable on any but the 2003/early-2004 models. I wonder if they did the re-learn process (https://my350z.com/forum/6008226-post2.html) and called that the "idle adjustment".

 

Hi,

Was not a throttle body. If I remember correctly it was almost like a timing belt for the engine. I'm no expert on the Z but is there something in the engine that is like a timing belt? Still can't find the post. Member had similar issue. RPM would all of a sudden drop to 250 rpm then shoot up to 1000. Then re-steady at 600-700. After this $120-150 part was replaced problem solved. He had to pay the cost as engine was still under 60,000 warranty but part was wear item.

Mason

 

Agree.

These problems are a unusual for a stock 350Z with 32,000 miles but anything can happen. Self-diagnostics may seem inexpensive, but will prove costly in the long run. You can replace the probable culprits: intake filter, MAF sensor, exhaust oxygen sensors, reset ECU. Problem is that you may be replacing components that are function properly.

2008 is know for fuel problems. I got $20 says one or more of the fuel injectors are bad. Any takers?

 

So what you are saying is I should dump some injector cleaner in the tank and call it a day? Many seem to frown at that. I wish Nissan put a fuel filter on the Z. I mean, I'm sure Shell is the best I can buy but all fuel is dirty to some respect. The car started having this idle issue around 10,000 miles so either the original owner used gas from Mexico or shell fuel is not what its built up to be.

Looks like I might be living with this idle issue. I just hope that in the long run it does not make this a 80,000 mile Z. Would like to drive it till 200,000+. This was one of the major reasons I purchased it in the first place. Long term reliability.


Mason

 

That sounds more like a cam or crank position sensor. The Z doesn't have a timing belt - only a chain which wouldn't require replacement like a belt. A bad cam/crank sensor usually causes more serious problem than just a rough idle. If it's flaky or going bad, i guess it could be a cause.

 

You would have been a lot better off if you posted this thread a month ago. There are a bunch of things you can do to test your different systems (fuel, vacuum, spark, etc.), but not in one day and it does require a little investment and preparation. I hope your car doesn't run into any major problems, but if your warranty's expired, you might want to start shopping around for a non-dealership garage and start forming a relationship with your new mechanic - you'll save a bundle.

 

Good point, Well the basic 32,000 warranty is over but still have two years under the power-train warranty so I think I'm OK?

 

Just want to re-bump this post (know you guys love this). Still have the jumpy idle with Summer coming up. Idle sits at 550-700 rpm then drops to 250 and sound like engine is sputtering. Then jumps back up to normal all within a second. I should get a video of it for you guys.

So question is how do I check for a vacuum leak on my 08 Z? Also I have two MAF's? How do I clean these. Any other tips? Would like to diagnose easiest to hardest/ Most likely to unlikely if possible.

BTW, Z has 36,000 miles now. Everything else going strong.

Thanks,

Mason

 

Vacuum Leak - smoke machine
Clean MAF - grab a can of MAF cleaner from autozone and spray it in the little holes