Hello,

I have a 2003 350z MT with 141k miles. I'm having 2 sets of problems. Firstly, warm start stalls. Car will start perfectly fine when it's cold, but when trying to start it after the engine has been fully warmed up, it stalls if i don't apply extra gas. 1 out of 5 attempts, it will catch itself, choke a little then return to normal idle, but mainly it just stalls.

Backstory, brake pedal switch broke and as result my brake lights didn't shut off / drained battery dead. The car sat dead all weekend, upon getting things back up and rolling, warm start stalls were the outcome.

-I've read MANY posts about doing the TB relearn procedure (Pedal Dance) which i've done successfully, but it didn't resolve the warm start stalls. Checked for vacuum leaks, but didn't find any. TB not relearning? MAF?

Secondly, At the same time as the brake light issue described above (great luck i know) the starter burned out on the car, which i had replaced. This leads me to the 2nd issue and more important issue VOLTAGE DROPS.

When the RPMs bottom out, either from blipping the throttle at a complete stop in neutral or coming to a stop in traffic / upon pressing in the clutch, the volts will drop off from the standard 14.4v down as low as 12.9v. When the volts fall, it will slowly tick back up to the 14.4 range.

What i've done to remedy,

-Replaced Battery
-Replaced Alternator (ACDelco)

But the same problem persists as it did with the OEM alternator / old battery. This is where it gets interesting, if i nurse the idle down when stopping and wait to push in the clutch until the RPMs have already reached the 600-800rpm range, the voltage drop doesn't occur. This leads me to believe that is idle related. I was leaning towards fuel related, but the car doesn't really want to die, no hard starts, just the voltage drops way off when the RPMs bottom out and resettle to the normal idle.

I've had the car hooked up to Consult II while driving and confirmed the voltage showing on the dash was the same reading that i was seeing with Consult, so it's not a gauge issue.

Myself and my mechanic are currently stumped. My instincts are telling me that the TB is out of whack and not relearning, causing the warm start stalls and the RPMs not catching themselves / causing voltage fluctuation, but i'm inside the box and can't think clearly.

Mods
Fully Bolted
Injen Intake, Motordyne Plenum Spacer (Upper and Lower), Borla headers, Berks high flow cats, Borla full exhaust

^Mods have been on the car for 10+ years without issue.


I've ready many posts within the forum that start off relating to my problem but spin off in one direction or the other from the posts being revived after many years in hibernation, which brings me to this point. I'm fairly mechanically inclined, but not a pro in any shape or form. I am humbly thankful for your time and input.

Kind Regards,

OldManZFL

 

I know it's a nightmare scenario and i'm not confident that the two problems are related, but no one wants to take a stab at it? I'm thick skinned and willing to answer additional questions quickly.. HELP!! )

 

Mine had similar symptoms for a couple months this summer before the ECU spit out a bad camshaft position sensor code. It's been fine since I replaced them. If you have not already replaced them, it's time. It's a very common failure for the Z. Had to do the crankshaft position sensor a couple years ago as well.

Also, what weight oil are you running?

 

Hey Mike,

I haven't had to replace the camshaft nor the crankshaft sensors yet, it's crossed my mind because i've read about that as well, but without a code i chalked it up as not an issue. They are fairly cheap, camshaft is easy to replace, so i will start with that one. Do you know if the generic brands work ok or if i should just go with Hitachi?

10w30 full synthetic. I've had her for 15 years, so i've done other weights here and there, but been on 10w30 for quite some time now.

Thanks for your reply!

OldManZFL

 

For this, go OEM if you can. With that said, my crankshaft position sensor was purchased from AutoZone out of desperation and has been working 100% fine for years now. Also has a lifetime warranty and I don't need a receipt since it's stored in their computers.