Milosis

I've searched the Forum Posts about High Idle / surging idle but nothing seems to help my issue. Nissan wont look at the car because its twin turbocharged, got a polite no over the phone.

My Platform:
2007 Nissan 350z Base Model
*AAM Competition Twin Turbo kit
*CJM Motorsports Fuel Rail + Fuel Return System
*FIC 1000cc Fuel Injectors
*Aeromotive 340lph fuel pump
*Stock Internals

To do this install you have to pull the motor and transmission and sortof hammer the sides of the frame to allow the wastegates to clear. I disconnected the ECU from the harness and pulled it out of the grommet to keep from having to disconnect every sensor from the engine to remove it. After the reinstall I Trailered the car to Z1 motorsports where they tuned it. The idle issue has been there ever since. I took it to Prostuning down in Riviera Beach, Florida to have the tune adjusted on a mustang Dyno instead of a dynojet. Either way the car still idled high around 1500's. as a test the tuner blocked an intake with his palm and the car idles down to target. Moved his hand away and its right back up to 1500's.

Just about every post says the same things, do the idle relearn or bad throttle bodies. Well I've done the idle Relearn Pedal dance several times, tried the idle relearn using NDSlll only to have it fail. Taken it to a local shop that had a Snap-on Verus scanner only to have it fail the relearn anyway. Pedal release procedure done several times. Replaced the Throttle bodies with Hitachi OE ones only to get the same result in engine idle. The car wont idle anywhere low enough to do the relearn. I've done the battery disconnect for 24 hours to reset ECU. I've also removed the upper charge pipes and reconnected my factory air boxes with the MAF's in and returned the car to stock via uprev reflash. Car still wants to idle badly, 1400 then 1800 over and over. Cruising and accelerating the car performs great. Cruise control works(Had Jon at Z1 use a ROM that had cruise and got the sensors and switches). Pulled the intake manifold to check if the gasket was damaged in the install but no, the intake seats evenly and firmly in place.

If I unplug the throttle bodies and start the car it idles evenly at 800, sometimes 1100. If I unplug the accelerator pedal it will do the same thing. Unplug the MAF sensors and it will idle rough but still a lot lower than when they are plugged in.

I'm not getting any DTC's with any TPS - APP - MAF sensor failure. I get the usual PO507 code.

I have no clue how to proceed except to have it trailered back to Z1 Motorsports and have them take it apart to sort out an answer, over the phone they say you've gotta do an idle relearn but as I said the car wont idle stable enough to even try. Pull a coil plug and it just gets worse as far as idle goes. Same with an injector.

my Accelerator pedal reads kinda high as far as the Factory Service manual goes, 5.9 volts with pedal fully depressed. with it released it sits at .76 volts. this is with the car off key on. Can my pedal / tps be bad even though it doesn't throw codes??

Theres gotta be someone on these forums that has experienced this issue as I am now. I know its impossible to diagnose a car over the net, but if someone else is running a z with a VQ35HR that's twin turbocharged and has experienced this issue please share your insight. I've put a lot of money into this car to have some fun with at events and on the street and I'm losing my mind trying to diagnose whats causing this issue.

aarrgghh

Man you've tried almost everything.

A quick way that may find a problem before you tear it apart is to do a boost leak test. I see you've gone back to the stock intake, but you may have a hose off/cracked somewhere.

rcdash

iTrader: (18)

Manifold leak somewhere past the throttle body. Read the TPS %. If it is low (as in 5% or less) and you have a high idle then the throttle is as closed as it can get. If AFR is at stoich or lean then it has to be a manifold leak. The ecu has no way to compensate for that so will idle poorly.

EDIT: if you have a manifold spacer, then it probably is a leak there. Even without a spacer might be folded gasket. Could also be boost control hoses or brake booster hoses with a crack - replace all of them since that is easy 1st step.

Milosis

Theres not a lot of places the intake can leak vacuum. The pcv valve and breather tube are tied into the intake pipes on the turbos so theres not real positive pressure on the pcv system. I've plumbed in wastegate and boost source lines from the brake booster hose but that's about it.

I will say while waiting for my laptop to update I noticed a bit of oil on my MAF sensor passenger side. pulled the charge pipe off and oil had built up at the first silicone elbow going from the charge pipe into the intercooler. Had a recent oil change and this looked old like maybe it leaked down from the intake manifold. As far as I knew, the VQ35HR didn't have the channels the DE Plenum does that allows oil to pool in it. I had just cleaned the passenger side MAF yesterday so I know it wasn't there before. Turbochargers barely have 3k miles on them. Car gets driven maybe 5 times a month, less with this issue happening. Either came from the PCV or Intake I think.

I'm gonna pull up my earlier tune with Z1 and flash the PCM to see if the idle is normalized. I feel like if it idles with the Throttle bodies unplugged or the pedal unplugged its gotta be either a timing issue with the injectors or cam timing or a bad gas pedal. I've had my son turn the key on and off so I can see both throttle valves working.

Thanks for the response I appreciate you taking the time to help trouble shoot

Milosis

As far as I know there isn't a spacer on the market for the VQ35HR intakes. The gasket is the type that is rubber and fits into grooves on the intake manifold that mates up to the flat surface of the upper plenum. I can definitely replace that as its easy to get. I've never removed the upper plenum before, I suppose there could be an issue there that's become more noticeable after forced induction. I'll source the gaskets for it and pull it apart this week. I've gone over every boost line(I.E brake booster - Pressure source for the oem FPR - and the balance lines that go from the throttle bodies to the emission sensor. Originally id used those to plumb in the vacuum lines for the bypass valves but didn't like how they pinched the lines and replaced them and tee'd into the pressure source for the OEM . I'm using the brake booster line to plumb in pressure sources for the Greddy Profec boost controller and Defi boost gauge and Aeromotive FPR. Vacuum lines to wastegates are coming from the boost solenoid. Ive got everything run from the battery compartment area so there is a lot of vacuum lines. Some had to be connected via plastic junctions, I'm working to replace all of them eventually but I've gone over the bulk of them with soapy water in a spray bottle and eliminated leaks.

Nick at Prostuning.com is gonna hook up with me over the phone and we're gonna mess with injector timings to see if it changes the idle. Its a long shot but theres a very slim possibility that there may be an issue as the car has idled badly since the first tune. Nick and Roger added timing slightly and the car took the adjustments like a champ, gave the car greater power response and put her at about +40hp with 1lb of boost increase. But it might've caused the issue to be more aggravated. Not sure though

I cant get my head around how unplugging the throttle bodies or pedal causes the car to idle evenly, with everything plugged in it idles 1400 - 1800 surging like. With the TB's unplugged it idles at 1100, slightly increases but pretty much stays there. Same with pedal. Hell same with MAF sensors. I really hate the fly-by-wire system. I miss the good ole days when my GSX idle could be adjusted by adjusting the CAS or throttle screw.
Thank you for helping me troubleshoot this issue!!

aarrgghh

A visual check may not find it. When we do a boost leak test, we plug the air filter couplers with what look like hockey pucks with a PSI gauge and air valve in them. We then use an air compressor to bring around 5-7 PSI of air in the system and watch the gauge/listen for leaks. We've found many that can't be seen this way.

Milosis

That sounds very similar to my setup I use to boost leak test.


sourced everything from home depot, cost me about 40 bucks.

Milosis

wanted to shoot an update here, recently bought a used set of MAF sensors just to test and see if mine were worn out. No change at all in idle or drivability. Pulled the trigger on a set of used G37 throttle bodies as they are apparently interchangeable according to Go Auto Recycling Inc. Get them on Friday, I plan to warm the car up then disconnect battery, uninstall my tb's and install these used ones. Do relearn etc.. im also looking at accelerator pedals as an option.

I changed out spark plugs to see if there was a reason, turns out autolite iridium plugs don't work all that well.. Factory Denso iridium FXE22HR11 seem to work great so ive ordered some new ones. thinking about changing the air filters out as well. Some of the forums have said pulling hot air in from the engine bay may have an effect on idle performance so I might consider buying some mandrel bent elbows and source air from the front bumper.

keep everyone posted

aarrgghh

That's basically our setup too.

If you passed that, one thing to consider is that it could simply be the tune. When you plug the throttle body back in, you're also reconnecting the two feedback sensors on it's position. There will be a little noise (electrical and other) on this, and you could be just bouncing between two cells in the tune causing an overreaction to the noise. I had similar issues.

Milosis

Bought a new pedal sensor.. FSM says volts need to read .5-1.0 fully released and it reads .59 so ok then.. turn the key on do my pedal released learn then throttle valve closed learn.. start the car, idles above 2k but it's cold so I'm just waiting.. starts to come down then it starts to idle like before, surge hunts 1500-2000. So I start to tamper with the pedal sensor as it is adjustable.. now I'm getting sensor codes.. so I'm out of time today to mess with this, I've pulled the battery so ital reset and start fresh Tuesday. I plan to start by having the sensor set a bit higher like .70 then reset throttle pedal / throttle valve etc and go from there

I'll keep updating

Milosis

New pedal didn't do anything for the situation. I've pretty much replaced all there is now as far as sensors go. It's so odd how if you unplug the tb's or maf or pedal the car idles steady but with everything plugged in the idle lopes.. I'm now to the point where I'm gonna bite the bullet and trailer it to z1 motorsports. Gonna do a compression test tomorrow and then a final boost leak test once the charge pipes are back in place. I really feel like this issue is sensor driven.. flashing the car to stock doesn't clear up the symptoms at all. Maybe I've damaged my ECM to where it will take a flash but won't run right otherwise.. I called the guys at Uprev and they say if you can flash it then the ECM is fine but alot of guys on the forums say their solution was to get a new one. Smh this **** is killing me

rcdash

iTrader: (18)

Can you log pedal, throttle, AFR, timing, rpms, load, during the surging?

I forgot you had the plastic manifold. If you have never touched it then the leak is likely not there although it does sound like a leak past the MAF sensors. Logging is the best way to start narrowing down the options.

EDIT: If you have UpRev then you have access to Cipher, right?

Milosis

If your talking about the plastic intake manifold yes I did have to remove it to install the injectors and rail etc. I have logged it while it idles. I've never removed the lower plenum. I thought for a bit that my issue could be injector grommets maybe or hell maybe a faulty injector but I'm not getting any cylinder misfire. And if you unplug the TB's the car will idle pretty steady around 1k. I know the ECU goes into a failsafe mode when it doesn't get signal from pedal / MAF's / TB's but even so if it was a grommet then it would behave the same way.

I've attached the log. Pedal stays the same throughout operation, the other sensors do change but it is idling / surging badly

Milosis

Since ive removed the intake manifold I've ordered some fuel pressure dampers. Never bought new ones so ill eliminate them as an issue

Faasnu

Have you tried asking AAM Competition for advice? Maybe they ran into the same issue when testing their kit.

rcdash

iTrader: (18)

Problem is not idle, TB, or APP. It is AFR, which is all over the place. You have a faulty injector or an air leak. MAFs read constant so the leak would have to be past that.

Most likely scenario is a leak past the MAF. It could also be a leak at the exhaust manifold (install error), but that should give an error only on one side, unless both sides have a leak. This causes the air to be sucked in only during idle causing a false lean condition and then attempted correction.

This seems unlikely vs a leak at the manifold somewhere.

Or a faulty injector. It could be the injector is not idling but opens up when commanded for longer periods. You have to be sure dead times, etc are set up correctly. Again, if it was just one injector, the WB would show on that bank. Both banks affected, so I think it is upstream of the injector (again unless multiple injectors).

Milosis

I have in the past, the sales guys try to act as go between with their tuners / engine tech's. I've asked questions in the past and was told to hold while they went and asked a question or two. Id love to just bring them the car but they're based in Maryland I think which is about an 11 hr drive.

I've been going through Z1 and Jon but he doesn't have much time to respond to my questions. When I first had the car tuned hes the one that set everything up. When I had a protuning mess with it on a mustang dyno all they did was add timing here and there to get me a 40hp bump and better throttle response. After that tune I was idling a bit higher than it ever had before, around 1500 steady. So in the parking lot I tried a relearn, did a hard reset and ever since the car has been doing a surging idle deal.

Milosis

Thank you for taking a look at the log for me and the insight. I can see it possibly being a faulty injector(s) but I'm unsure how to diagnose which. I suppose I could pull em and send them off for testing/cleaning.

I did the install myself so its possible I could've messed up but I don't recall any issue with the exhaust manifolds. I've only put about 3k miles on the car since the install last april. I cant check all the manifold bolts to see if ones loose but I tightened the **** out of them because its not serviceable once its in the car, I don't think I've got a loose manifold but as a last resort I can drop the motor again and check.

Yesterday I pulled the intake manifold and the lower plenum and replaced the metal gaskets with new felpro ones that came as part of the kit with the intake manifold gasket. Intake manifold gasket was wrong for my engine so ill have to get another one. I pulled it apart to replace the fuel pressure dampers, I reused my old ones with the fuel rail install and wanted to replace to see if that was my issue. All the Injector grommets are new so I don't think they are leaking. I used to Tee into the brake booster / Fuel Pressure Regulator vacuum source to get my Boost control line / bypass valves / boost gauge but while I had the manifold off ive drilled and tapped it for Aeromotive Vacuum barbs. clears up a boat load of Tees and potential vacuum sources. Engine behavior unchanged so I don't think think the additional sources ive created are the culprit.

I've drilled out the pcv valve to create an open air source and now have 2 catchcans installed routing the lines from pcv valve on passenger side valve cover / breather on drivers side valve cover to catchcans and then intake tubes of the turbos. I'm still getting some blowby symptoms(oil cap has some soft airflow coming out) but I've read that's pretty normal.

As far as the deadtimes and etc go, as a troubleshooting measure I reflashed the ecu back to stock to see if car would behave differently. It doesn't, as soon as car switches from closed loop mode to open loop I get the engine surging which made me think the tune wasn't the culprit. It made me think the issue was mechanical / sensor driven. Unplugging any of the vital sensors(MAF - TPS - APP) causes the car to go into limp mode. If I had an injector issue wouldn't it still show in this situation? In limp mode the car will idle at 1000 -1100 pretty steady, no more surging etc...

I'm of course not an expert at Uprev so I don't know how to check deadtimes, I have experience with DSMlink and its pretty straight forward. I have the tuner addition so I can make changes to my rom but I don't know where to make changes to trouble shoot it as a potential issue. RC are you able to tell if deadtimes for a specific type of injector are correct on a rom? I can email you my tune if you wouldn't mind checking to see if the deadtimes are off. Uprev said that the surging can happen if the injector settings are off.

I could plug my EVAP system off entirely and test, the line to it is connected to the balance tube right behind both throttle bodies.

boost leak test has it holding 10 pounds for more then 15 min. If I had a leak wouldn't it show here as well?

T-dizee

iTrader: (6)

this might sound silly, what fuel are you running with your setup. i have the same setup with a AAM TT kit on my 07 nismo HR. my idle gets a little jumpy with Uprev. im running the same size injectors and the same pump as you are. if i run E85 in it, it starts to surge. as soon as i put in E54 or straight 91 it idles right out and smooths out.

Milosis

its tuned on E85, I never did a pump tune. I regretted it at first because I had very few stations nearby that had E85 but ive gotten lucky here in the last few months as a Gate has opened about 6 miles away that sells E85. I don't know how itd run if I filled it up with 93 at this point with the amount of fuel its sending. I could try to run a few gallons through it, my tank is almost on Empty now. Any ideas anyone on how it would behave? I think itd run rich but would it flood and stall?