RosaP-37S-G

From all the reading, i thought heat soak + bad maf sensors was definitely it. Jan 2019 i swapped my intakes, and more importantly the throttle bodies to eps tbs (tuned as well). I haven't had the specific issue since. It's been a year now. I will say it's definitely had sluggish moments, and it didn't matter the weather. But no where near what was happening early on.

audiRS4ever

I just re-read this thread in hopes of finally solving this issue on my car; sorry to hear you're now having these problems now as well. I'm sure you can now understand why people were frustrated with your responses in posts #40, #42, and #49

Jokes aside, were you ever able to figure anything out on this with your tuner?

I've spent the past few days reading through this thread as well as several others on myG37 and on my370z. This one was a doozy, but I read all of it and there was never any clear resolution on the problem. Unfortunately, the most pragmatic contributor ultimately couldn't take it anymore and got rid of the car. I hate to say I'm not too far off from doing the same, but wanted to revive this thread to see if anyone else has found any traction on this issue (stretch of a pun half-intended).

For future reference, I've collated the common syndrome below as described by members of myG37 and my370z, supplemented with my own personal experience. I have wasted countless hours reading about and researching this issue but took notes while doing so. Hopefully, this helps people who continue to have this experience identify and solve - or at least articulate - the problem without having to burn time like I and so many others have.

Another key note to preface: this syndrome is NOT the static state of affairs for affected vehicles; It is a problem that comes and goes very noticeably. Cars with this issue experience it intermittently, and as such it is entirely unhelpful to suggest "that's normal - our cars just have no power under 3k RPMs bruh". While that may be true, this is something else entirely - the car feels normal one day/minute/hour, and then something prompts a very clear modal change in the way the car behaves.


Symptoms:

• A disconnected feeling in throttle response, characterized by a perceived lack in power below 2.5-3k RPMs
  • Particularly noticeable from a stop but ultimately occurs in any gear even at speed
  • Often described as the engine falling on its face / almost dying, followed by a surge in power
• Slow revs under load followed by regained power at around 3k RPMs
  • From a stop, throttle modulation is inaccurate and makes clutch engagement feel inexact
    • Once moving w/ clutch engaged, car bogs with noticeable loss in power despite no change in input, often prompting the driver to increase throttle
    • At around 3k RPMs, power is regained and may ramp up quickly, particularly if the driver compensated with increased throttle input
  • In high gears at speed, the loss in power can be so extreme as to feel like the car is decelerating or struggling to maintain speed, even with the throttle pinned
    • Throttle may feel touchier when applied very lightly, but more noticeable bog is felt with increased input or quicker full-throttle application
    • Surge is not as prominent due to longer gearing, but the top end of the powerband seemingly presents correctly when downshifting to lower gears, throttle-off lag notwithstanding (see below)
    • Problem seems less dramatic when slowly rolling onto the throttle, but still noticeable
• Slow unloaded revs even with full throttle applied
  • Happens both in neutral as well as when clutch is disengaged (even at speed)
  • Flooring the throttle results in slow climb in RPMs to 3k followed by an increase in rate of real/applied throttle from ~3k to redline
    • After flooring the throttle --- nothing...nothing...nothing...SURGE
• Retained perception of throttle input even after stopping application of throttle
  • In motion, car feels like it continues to apply power toward acceleration after letting off throttle in same gear
  • In between upshifts, the revs may not fall as low as expected, impacting gear engagements / smoothness of shifts
  • When downshifting, rev-matching becomes difficult as the applied throttle is not responsive to a quick stab of the gas pedal as it normally would be
  • At a standstill, revs will either remain constant or climb for a moment after throttle input is stopped, depending on level of throttle application
• Slow fall in RPMs after let off the throttle / Rev hang
  • Revs appear to fall more slowly than expected even from high RPMs and may hang or slightly increase around the 1.5-2.5k mark before slowly settling back down to idle at normally or slightly higher than normal
• Change in sound of the engine
  • Engine tone may become more "textured"
  • More popping and crackling under deceleration, possibly due to retained throttle action (even with no input)

Proposed Causes (w/ anecdotal solutions where applicable):

The most commonly observed correlates of the problem occurring include:

• Higher ambient temperatures during the summertime or in warmer climates
• Higher humidity, independent of temperature
• Heat soak due to a number of conditions including:
  • Sustained periods of low / no movement in traffic
  • Sustained high-performance driving
  • Forced induction setups

Generally, more specific theories can be categorized into two groups:

1. Theorized failure in a specific part/sub-system that causes the ECU to behave unexpectedly (in order of easiest/cheapest to toughest/most expensive)
   • Brake light switch / cruise control disengagement switch
     • Theory: sticking or failed brake/cc switch causes the vehicle to think the brakes are applied when they are not, cutting power through either a feature to prevent unintended acceleration or a feature to implement torque limiting as part of TC/VSC systems
     • Part can be had for $30-70 and is easy to swap out
   • MAP sensor
   • Throttle position sensor
     • Theory: Throttle is sending incorrect voltage value to ECU (should be b/w 1 and 5 volts)
     • Integrated TPS sensor requires replacement of the whole accelerator pedal assembly and requires throttle pedal sensor relearn procedure
   • MAF sensors
     • Dirty: clean with MAF cleaner
     • Failed: replace
   • Throttle plate position sensor / throttle bodies
     • These are integrated and sold as a complete sub assembly
     • Dirty: clean with MAF cleaner
     • Failed: replace
   • BCM
   • ECU
2. Failure of the broader vehicle systems to keep the car within normal operating parameters, prompting the ECU to pull timing or otherwise act to limit performance as a preservational measure
   • Most of the proposed solutions in this category are less compelling without knowing specifically what is causing the issue; they attempt to improve conditions to solve a problem that should not be there in the first place, but they generally focus on minimizing:
     • High IATs (eg upgrading / heat-wrapping intakes, bypassing TB coolant lines, etc)
     • High oil temps (aftermarket air-to-water heat exchangers, try using different oil - ester, synthetic, or otherwise)
     • High water temps (upgrade radiator, add water wetter, switch coolant types, etc.)
     • Carbon buildup (Catch cans / air-oil separators)
   • In addition to the above, some people report success working with tuners to reprogram the car's response to the above conditions
     • As far as I know, a tuner has yet to identify and solve this issue, but some have had luck in changing throttle mapping or other parameters to make it less noticeable
   • There are band-aid fixes that reset vehicle state / mapping by re-setting ECU or performing relearn procedures, but these are only temporary (ECU reset, throttle position relearn, etc.)

Based on my experience and those of others in the multitude of threads I reviewed, the following upgrades or actions improve overall throttle response across the board but don't have efficacy in preventing this problem (though they may make it less noticeable or annoying when it happens because of their generalized improvement to response):

• Upgraded intake
• DIY or purchased grounding kit (in particular, one that grounds the TBs)
• Catless or higher-flow catted test pipes
• Heightened maintenance to prevent and rectify carbon buildup (clean MAFs, MAP, intake tubes, TBs / throttle plate)

Outside the above categories, there are some other common suggestions for "fixing throttle response" that I generally consider unhelpful and not welcome because again, this problem is not a generalized throttle response issue but a painfully noticeable temporary state triggered by as-yet unknown factors. If you read through all this and still suggest a sprint booster to solve this problem, take a good hard look in the mirror.

This problem is nothing short of dangerous even when it happens to someone who understands vehicle dynamics and driving - I can't imagine how someone like my Mom would respond to this scenario if it happened on her car while pulling normally into a busy highway after sitting in a minor jam for a couple minutes on a summer day, and don't want to try. It is simply unbelievable to me that Nissan would allow the implementation of such a dangerous preservational ECU mode in response to what amount to normal driving conditions.

For this reason, I believe that there is an acute problem to solve here and welcome any feedback from those with a potential solution!

RosaP-37S-G

I ended up with new throttle bodies during my process and didn't experience it in that dead manor again. Seems to carry amongst the other guys that have changed out. In other words, i don't revall anyone having the issue after a change of those. Might check a junk yard or something to see if you can scoop some up cheap.

To go further, i don't think it's a matter of just cleaning them eigher. It's likely something mechanical in nature. I still have my old ones, but i wouldn't venture to try my luck in an effort to test. I'm rid of it, and happy to never look back.

AARONHL

Nice effort is summarizing the problem. (shortened your quote)..There was a guy on 370 or maybe g35 driver that was doing some testing of the brake pedal switch but he couldn't 100% say that was the problem. I noticed if I step on the brake pedal while also stepping on the gas it was not rev up, once I get off the brake pedal the engine will rip pretty good from there. To me, it's the same exact problem so I will be doing some testing by not using the brake pedal at all when coming to a stop (on flat land of course) to see if pushing the brake pedal changes something while stopped.

The worst part about this problem is it so finicky that when it happens people can see the car bucking bad like I haven't been driving a 6speed for 12 years

MickiFree

You have described my issue to the tee. I've done my fair share of googling, but you seemed to have written a thesis on this issue! There's not much I can add to describe the issue, so I'll just share an incident where this issue almost bit me in the ***.

I was driving up a street with a minor incline and had to stop. When going from neutral to 1st, I literally had to floor the gas for over a second to raise the revs above 1500rpm. As I release the clutch, there is not enough power so the revs drop. I start rolling backwards so I have to continue flooring it. Luckily, it sputters enough to get moving.

I've had this problem since getting the car. Most times, it is a minor issue that prevents you from having a little fun with the car. Other times, it is downright dangerous.

AARONHL

Good description....That happens pretty much everytime I go up my steep driveway, gotta crawl in first gear over my sidewalk and then basically floor it to get up the driveway

audiRS4ever

Thank you very much for confirming this - your testimony here (after having seen enough others like it) was the straw that broke the camel's back. Just pulled the trigger on new throttle bodies.

For those interested, the OEM parts are for sale on Advance Auto Parts and are cheaper than even Amazon - they are sold as Hitachi parts, but Hitachi is the OE supplier and the only difference between these and what you'd buy at the dealer is these won't say Infiniti on them.

They are running a promo currently that will get you $50 off, plus if you hit the Advance site through the link in either British Airways or AA affiliate portals, you'll get two Avios or miles per dollar. $279 for a pair of brand new, warrantied TBs with some free miles thrown in ain't half bad.

Hitachi ETB0008
Hitachi ETB0005

Excited to receive them. Perhaps there's a slim chance I'll fall in love with this car again. I'll report back with results once I receive / install!

Glad you appreciate it!

Unfortunately, I replaced the brake pedal switch yesterday and still had my issues today

Agreed on the bucking, though - it's painfully embarrassing and even more frustrating.

Hope it helps other people! It's such a pain to search through threads with similar issues only to find people who explain the issue so vaguely as to make it ambiguous whether or not they're even having the same problem. And then you have the Sprint Booster idiots.

I've experienced the scenario you're describing many times. I've gotten good enough at picking up on when the car is starting to go into that mode, though, that I've been able to learn how to effectively compensate for it. Of course.... that's because I've been having this issue for 5 years

Hoping the throttle bodies do the trick!

AARONHL

There are two brake switches, did you replace both?

audiRS4ever

Nope - I only did the one on the left; that is the one that people on my370z seemed to have luck with. I believe the other is the cc cut switch but hadn't tried that one.

MickiFree

Man, you just keep pumping out useful information. I'm tempted to just order a set and try it myself. But since you've already ordered it... please let us know if it fixes it.

PNW_IPL

iTrader: (5)

I'll add some information and its probably no the norm, so I was fbo and tuned with the ark grip exhaust. The stutter was still there just less pronounced than with test pipes and stock y back. 1 month after tune i bought a motordyne catback and the hesitation was gone. 4 months later, yesterday I put the stock Y back, back on to take a break and sure enough the hesitation is back like it never left.. im not sure what to make of this. Could this really be because a restrictive exhaust?
cliffs long tube headers and ark grip 2.5 in diameter slight hesitation
longtube headers Motordyne catback 3.0 diameter no hesitation
long tube headers 3.0 Y pipe oem catback 2.0-1.5 diamter. Hesitation bucking stutter badly at 2800-3k

audiRS4ever

I probably won't receive the parts and get them in the car before Monday; Advance is doing their 4th of July sale just through the weekend though (up to $50), so you may want to check the return policy and order them anyway to save $50. Then again, I feel like there are always ways to get similar discounts at autoparts stores so I'm sure the opportunity will pop up again.

But I'll let ya know either way. The one thing I'll caveat is that I have tried other things to fix this in the past, and often the problem will go away (or appear to go away) for a bit, and then reappear, so I'm mindful that even if this seems to work initially it may be a false positive. I'll be taking the car on a 6-hour each way roundtrip drive in 2.5 weeks or so; I hope to have these installed by then. I'd certainly be more confident with any success if I am able to go through that journey issue-free. Stay tuned!

I doubt the restriction in exhaust by itself would be a direct factor to inconsistent power loss / throttle issues, but perhaps this could implicate a bad sensor.

My reasoning is that plenty of cars have come off the factory line with stock exhaust, and many/most cars do not experience this issue. Variance in tolerances with a factory exhaust system on can only have so much of an impact in terms of fluid dynamics, and there is no way Nissan would expose themselves to the liability of X% of cars having a proclivity to throw themselves into such a dangerous "limp mode" scenario because the exhaust is so restrictive as to impair the car's ability to operate normally on the stock tune.

That said, maybe if an O2 sensor was acting up, the varying flow characteristics of different exhausts could have an impact on when and how the problem manifests.

You've run a cat with all the aforementioned setups, correct? I've only done y-back on my car so not familiar with where other monitors are in the system but I assume there might be a sensor in the header as well? Have you ever changed or touched the cat and/or O2 sensors?

audiRS4ever

UPDATE: Received a package today! Haven't been this excited about a Hitachi product since my magic wand!

Jokes aside, I'm really pumped to get these in the car but am trying to temper my enthusiasm with cautious optimism. For anyone who needs new throttle bodies, this issue notwithstanding, this was an insane deal - now let's just hope they work to solve the issue at hand.

I'd be down in the garage tackling this right now, but decided to order new throttle body gaskets to replace while I'm in there. Not looking to introduce any other new variables in the equation, so figure I'd best be on the safe side and do it right. The part number is 16175-JK21A for those interested, and it's the same PN for both sides. They're sold individually, so you'll need two - I ordered today from a local Nissan dealer for like $25 and they should be in the shop Wednesday morning for me to pick up.

For those who are more mindful about planning ahead, they can be had here on Z1 Motorsports.





I'll keep you all posted on progress!

PNW_IPL

iTrader: (5)

Well I put the motordyne catback exhaust back on yesterday and the hesitation is completely gone.

audiRS4ever

I wish I had a Motordyne exhaust to throw on .

So just to clarify, when you had the issue prior to doing that, was it consistently happening or only occasionally?