Hey all, been lurking for a few months heavily but finally needed to make a post. ***Before I start, I searched the forums/internet thoroughly. I have an inclination that it may be camshaft position sensor failure, however I just did alot of work to the car at once, I'm unsure if something unique may be in play. Hoping someone has some insight***

I recently purchased a 2003 Z (VQ35DE) bone stock with 152,000 miles, ran excellent extremely well taken care of, but when I took it to Nissan for an inspection they found "heavy seeping from valve covers". Previous owner knew it consumed about a quart every 3000-5000 miles. I know there are common issues with VC and the plug seals etc so , I purchased two used valve covers (40k on them). Checked out fine, good rubbery play to the seals, no cracks.

Today I did the following with battery disconnected not in this particular order. Followed the service manual and used YouTube as a cross reference.

- Replaced stock valve covers with the newer ones.
- Added some RTV sealant to the newer valve covers plug seals.
-replaced VC gasket with felpro. RTV'd a bit of the inside groove and outside.
-degreased upper and lower plenums with degreasers and seafoam while off the car. Wiped everything imaginable down.
-cleaned both VTC solenoids, MAF sensor and oily coil packs with MAF cleaner
-Installed the Motordyne ISO thermal plenum spacer with copper throttle body plating. Necessary gaskets as well.
-Replaced spark plugs with NGK iridium's (gap checked). The back two plugs were soaked on oil, the coil pack was drenched. Tried to pump most of the oil out with a hand pump before removing the plugs. Anti seized and installed.
- Cleaned throttle body, both sides of plate. Used my finger to open the buttery to really wipe down everything but read that's fine if battery disconnected.
​​​​​- Everything torque spec'd , wiped again, wiring harness connections double/triple checked firmly snug. All tight grounds.
- ECU reset/Throttle Body/Accelerator Pedal calibration pedal dance

So with everything together, after the pedal dances, I start the car to get it to operating temp to complete the idle air valve calibration. Idle was firm at 1.5k. Slight vapory white smoke coming from drivers side valve cover seal area but it slowly went away (lingering seafoam, idk.) Before it went away completely the car stalls. I hop back in, she cranks and now won't start. I disconnected battery, pump brakes to drain capacitors and do the pedal dances again. Still won't start. Rechecked all connections I had access to, everything seems to be where I should be. I didn't reinstall the strut brace yet.

I am fairly confident the valve cover gaskets didn't get dislodged on install. I'm slightly concerned I may have broke a connector or jostled some wires (the blue to black connection on the passenger side is clicked in but has some play). Also concerned that MAF cleaner on the coil connection might not have been a good idea.

So did I do anything wrong or out of the ordinary or can I bet that this is a camshaft position sensor failure? Anything else I should try/explore? Thanks for reading this.

 

Welcome.. Just some 'feeler' questions: Was your CEL on before you started all of this? How much oil (in inches deep) would you say was in the rear two spark plug tube wells? How many minutes, if any, would you say it was running for after you put everything back together before it stalled?..

 

CEL was not on before any of this. Also I forgot to mention about 1 week before I did the job, I seafoamed the intake through brake booster and threw Lucas Fuel Injector cleaner in the gas. Neither of those threw a code and I ran it hard (3.5k - 5k rpm for about 3/4 of a mile). Again the car seemed to be running fine but I had no baseline butt dyno to compare it to. Coming from an 03 v6 Mustang and 03 Mini S, I didn't notice crazy performance losses or gains.

Fast forward to after the job, the car was running for maybe 4-10 minutes locked in at 1.5k rpm. I was inspecting all my connections and hoses at the time it stalled. Pretty sure it reached operating temp. There was about 1 to 1.5 inches of oil in the wells, the metal tip of the plug was visibly above the oil level. Ambient temp of my garage was probably 65-75 degrees F.

 

Start by checking the fuses and relays that connect to the fuel delivery system.

 

SO I noticed a ring of gunk around the back end of a ground... cleaned it off and the car started! (*shaking my head profusely*). After the idle reset its still at 1k rpm firmly, not the 700-800 I want but with 152k on the clock perhaps that is normal? MPG seems fine, accelerates and decelerates normal HOWEVER, a new noise has come on and I'm not sure if it has to do with the plenum spacer. Its SOUNDS like a bad rotor because it sounds rotational, like a bowling ball rolling on a hardwood floor but it is not brake induced. It is idle dependent. I may make a new thread because it might be unrelated but figured I'd try with you guys. Car does have the stock clutch at 152k but not sure how that could be in because it happens in both neutral+gear. Thanks for the help!

 

Sounds like you need to do an idle air relearn to bring the idle down. No idea on the noise.

 

I did the idle reset with my phone's timer in hand. At the end of the reset, it idled at 700 but upon the next start up its back at 1.1k

I read somewhere in the forums that an overnight battery disconnect may solve the problem, which I will do tonight. I read that pumping the brakes with the battery off will drain the ecu capacitors but I'm not convinced unless I have a wiring diagram in front of me. Any other ways to drain excess voltage?

Last resort will be to take it to the stealership for the CONSULT tool b.s I keep reading about. Will report back!

 

Idle surge may be related to cleaning the throttle body.

https://my350z.com/forum/vq35hr/616039-another-throttle-body-cleaning-surging-idle-thread.html

 

My question here is, how could I have fried the ECU if everything was unplugged (battery and TB)? Or are you saying I need a new TB? Just my luck...trying to save $ in labor and end up with a new problem.

 

I don't know the answer to that question since I disconnected the battery when I cleaned my TB, as well. The shop I took it to replaced the TB and it seems to be the typical procedure for this. When that didn't fix the idle problem they suggested I replace the ECU and that fixed the problem. You can try replacing just the ECU based on that info and info from the other threads, however, you do risk frying the replacement ECU if the reason this one is wonky is because the TB. Then you'd have to replace both (ECU again).

 

May I ask where you purchased your throttle body and ECU? Also was the throttle body OEM or another brand? How much did you pay?

 

It's been awhile since I fixed that problem. IIRC, I paid the shop ~$400 for troubleshooting, the TB, and labor to replace the TB. They wanted to charge me pretty steep for a new ECU so I went on eBay instead and found a used ECU there then had the dealer do the swap and program my keys.

 

Sorry for the long update. Replaced the MAF sensor and that did not solve the issue. I then replaced throttle body with a used one with 17k miles and all codes are gone, car runs great. Something I noticed that might be of interest.....

I removed my original throttle body (153k on it) and compared it with the newer one (17k miles). When I shook the newer throttle body (laterally along the butterfly axis), I could hear some shaft play, like a sliding sleeve internally. My old, broken throttle body with 153k did not have any of that play. This may be a point to troubleshoot since I am led to believe that when I cleaned the old throttle body, it seized the internals somehow, reducing shaft play and thus causing the plate to remain open (causing high idle). Just a tip for anyone having a similar issue as me, gently shake the throttle body in question along the axis of the butterfly opening. The one with the shaft play ended up working.

Thanks my350z.

Best.

 

Or just leave the throttle body alone and consider it a non-serviceable part. The number of posts where people end up neck deep in debt trying to fix issues caused by a cleaning is ridiculous.

You might want to check all your grounds at this point. With 150K+ miles on the clock and a gunked-up ground already discovered, it couldn't hurt to check and clean the remaining connections.

 

I have to disagree with you, all throttle bodies on all cars should be cleaned with some sort of degreaser over time. The amount of carbon buildup that was on the original one was appalling , it may have been working fine simply because the layer of carbon was acting as a good seal for a partially closed plate (already broken). Opening the valve should be avoided since it isn't drive-by-wire, but spraying both sides and wiping it down is no issue. Think of it as the same sensitivity as an MAF.

 

Then we agree to disagree. The 350Z's throttles are not like your typical car's. They are a disaster waiting to happen. I've been wrenching (at times professionally) for over 30 years. You have what... 8 posts on this website?

 

And for the love of Jeebus dude, you've already used your keen knowledge about throttle cleaning on 350Zs to the tune of having to buy a new one for your screw up.

Show a little humility.

 

As long as the valve isn't touched, I could not possibly see any damage coming to cleaning bare metal in front and behind the plate. There is alot more turbulence and stress on the component at WOT than seeping degreaser. Comparing years of experience to post count is also futile; apples and oranges.

 

Welcome to the forums then. I look forward to your helpful posts.