P1606 VVEL issue/code

mendoza_ms

December 11, 2017
The fires here in SoCal made it tough for me to work on the Z, but the car is finally FIXED!

Ok so I feel REALLY STUPID, but basically it came down to one or both of the Camshaft Position Sensor connectors coming loose.

I basically found this out while the car was running - I was frustrated and started tugging on wires and plugs when suddenly I felt a tiny "cough" in the idle throttle response. Turned out it was the driver-side CPS plug. So, I cleaned it up and connected it and throttle response came back the next time I started the engine. Ahhhh... 5000+ RPM revs, how've I've missed you.

Hindsight
Looking back, I do recall having replaced the spark plugs recently (~6,000 miles ago maybe). Part of that process involved disconnecting/unplugging various connectors in order to remove the intake manifold and parts. My guess is when I put everything back I didn't double-check my connectors, which that one then later unplugged itself under some harsh driving conditions.

What I don't understand is why I didn't get other codes, like for the Camshaft Position or Idle Air Volume or something else. I just got a vague P0300...Anyways...

Lesson learned - Always make sure you push connectors until you feel/hear a 'click', otherwise they will unplug themselves and cause you a bunch of headaches.

Anyway, I hope my experience helps someone in the future!

mendoza_ms

February 4, 2018
It f**king happened again...

This time I had just recently did an engine flush and oil change. Along with a fresh change of 5W-30, I added some Lucas Heavy Duty Oil Stabilizer and Slick50 Engine Restorer (my z just hit 100k).

I took it out for a spin after the oil change and went to get gas at the Costco nearby. Everything was smooth until the first stoplight on the way back home. I suddenly lost throttle response and get the CEL. Its a good thing I was on surface streets this time!

Code reader gave me a P1606, P0300 and a U1024 (wtf?). Rough Idle.

After some troubleshooting I stopped getting the other codes and stayed with the P1606. I recalled that tugging on the driver's-side Camshaft Position Sensor plug had some beneficial effect so i tried that. Nothing...

So I unplugged the sensor while the car was idling...nothing...

Finally, I unplugged the passenger's side Cam sensor as well and the car DIED, so I guess it was a bad sensor? To verify this I pulled out both Cam sensors - which were really hot - and saw that they were caked in oil (not burned though). I sprayed both down with degreaser and popped them back in. Still idling rough, still getting P1606. I had to think about it hard.

February 5, 2018
Today I went home to try and swap the Cam sensors to see if I could learn anything new, but I didn't need to - the Z started right up and sounded STRONG. "I know what this is!" I said. It's a faulty Cam sensor that has accumulated some heat damage over several years of harsh driving conditions. I let it run for a few minutes and throttled it like I usually do and didn't have any problems. That one sensor must get hot over some time and start to fail intermittently.

I ordered replacement sensors online and will replace both of those before I actually try to commute with it again - call me paranoid. I'll keep you guys posted!

mendoza_ms

February 20, 2018

Replaced the Cam sensors but she didn't idle right this morning. Starting to get really tired of borrowing the wife's car - she is too as she can't leave the house nowadays. I need to fix this ASAP. Starting to consider taking it to the stealership or trading it in for a new ride altogether...

February 21, 2018

Tried troubleshooting after work. I noticed that the voltage dropped quickly after idling and shutting off the engine, so I decided to do a full stress test of the electrical system.

What I did was I let the car idle for 3-4 mins, then I started turning on the accessories - High beams, A/C, Defroster, Hazards, Heated seats, blasting stereo on full bass, etc. Normal voltage while driving is usually 14.5v. With everything else running it dropped to 14.1v over 1-2 minutes. Then I turned off accessories and let the car idle so the battery could recover before shutting it off again.

After shutting it off, I switched the ignition to the "ON" position without starting the engine so I could run my code reader and I noticed it dropped from 12.7v all the way to 12.2v within about a minute. That didn't look right so I switched it off and used a DMM (voltmeter) to read the voltage off the battery directly and it was reading 12.13v, which is below spec.

After this discovery I ran the code reader and started/idled some more and got the same P1606 and P1606 pending with an additional P0300 and a random U1024 and P1421.

I checked my yellow top Optima battery's date of manufacture and reads 05/2013. The Optima website says battery life can range anywhere from 18 months all the way up to 4 years - depending on operating temperatures and whether or not the battery is properly maintained by the Alternator, etc:

https://www.optimabatteries.com/en-u...r-battery-last

I'm hoping the battery is the root cause - it seems like it would be time to replace it, but the symptoms don't add up. I really don't know anymore... I'm a former Computer Science/Electrical Engineering student, a full time web developer and consider myself proficient with tools and technology but I'm just out of ideas now and really tired of this. I don't want to get rid of my Z...

Any help would be appreciated at this point...

aireoh

i have a friend that’s having the exact same problem and symptoms. i’m gonna keep researching the forums, but hopefully you find a solution brother.

__________________
FBO, Cammed, E85, 12.6 1/4 mile

Vorex

Did either of you have any luck finding root cause? I'm having the same intermittent issue. Typically if I leave it alone overnight it just works. I fidgeted with the MAF and camshaft sensor connectors one time thinking that actually did something (the next morning) but I think it's just time (or ambient temperature) that solves it.

mendoza_ms

Vorex, yeah that was my experience as well. Typically the symptoms would go away overnight or after a day or so.

My understanding is that the capacitors and inductors inside the relays discharge and reset over time. Relays are basically made of light metals, plastic and ceramic so it makes sense that extreme temperatures would negatively affect them (mainly heat), but that's probably not the root cause.

My 370z is a 2009 and since it's a first generation model some parts are more likely to fail since the engineers don't have all the bugs worked out yet. If your car is newer, I would buy a brand new relay and replace the VVEL relay with that one, disconnect your car battery for a few minutes, plug it back in and drive modestly for a bit before pushing it harder.

Here's a video that you may find useful:
https://www.youtube.com/watch?v=DWmt6gorzUg