HELP! Severe acceleration lag
 

Hey guys, i have this peculiar problem that has occured twice in the past 2 weeks now.

Background: Car is a 2011 6MT and has Berk HFC, exoticspeed midpipe, y-pipe, G3 intakes. It is currently winter here in Sydney so temps are usually below 20*c when i am driving. I have the fan control mod and the 2300 throttle map curve via Uprev. No other tuning has been done. All maintenance is up to date and correct fluids used except for 5w40 oil instead of 5w30. i always use 98 octane fuel from the same supplier.

The throttle response suddenly becomes really sluggish and the engine feels like it's struggling big time when taking off - especially on anything more than a slight incline. It feels like driving a crapbox 1.5L on a hot day - i have to drive it like a crapbox. Normally i can get it up to speed with minimal effort with less than 2000rpm in each gear. Now i actually have to rev it all the way to 3000+ rpm to even get it to 60kmh. It's so bad it feels like it's going to stall. It usually happens after i have been driving for about half an hour, so the engine and all fluids are warmed up to normal operating temps when it occurs. Oil and coolant temps are below 95*c. Intake air temp is usually within a few degrees celsius of the ambient temp.

Even when i sink my foot to the floor, the car hardly accelerates and takes an eternity to reach 100kmh in even in 3rd. Going downhill, the problem is less noticeable.

I described the problem in another thread which i forgot now, but it feels like the brake switch problem that Digitonium had where the car lags then screams to life after a while. It is not VDC as conditions were dry both times it happened. I also disabled VDC via the button (i know it's not a complete disable) on the 2nd time it happened but that did not cure the lag. I don't think it's my brake switch because cruise works fine and i dont see my brake lights blinking madly or staying on when they shouldnt. For good measure, i also held up the brake pedal with my foot but this didnt fix the problem.
It could also be described as the lag u get on a hot day with heatsoak and a/c blasting - but to a much more severe extent.

It feels like the CVTC system isnt working as it should. Down low (<3000rpm) there is hardly any response. Once it passes 3500rpm the motor screams but it still doesnt go as hard as it should. Travelling at 100kmh in 6th then downshifting to 3rd results in ok-ish acceleration but it still isnt as enthusiastic as it usually is. Revs will climb ok though.

I cured it last time by restarting the motor and the same solution seems to have cured it this time. Last time i didnt have my laptop and uprev cable with me to datalog but this time i drove all the way home to pick up the gear and do some logging - believe me, it was a challenge to not stall the motor because it was bogging badly on each take off. I couldn't stall the motor before logging because the problem wouldnt be there anymore.

From a glance, it does seem that my intake cams are locked at 0 degrees until about 1500ish rpm. Comparing it to some logs i made when things were running well, i should be getting 35+ degrees off the bat.

Can anyone shed some light?

also, with foot to the floor i get a throttle position angle of no more than 25 degrees when this problem is present. i also dont have coolant flowing thru the throttles so they are nice and chilly. definitely not frozen as it's not sub zero here

I have a very similar issue but running the stock throttle map. Feels like 25% throttle when asking for 100%, until I hit 4k. I've resorted to running with ETC off in uprev as I have no idea how to fix it.

yep! it feels like it awakens around 3-4000rpm but logs indicate the CVTC solenoids doing something from about 1500rpm.

Did the problem occur prior to Uprev? I'm leaning towards an uprev related cause because i've never had this issue until i tinkered with Uprev.

Switching maps didnt resolve the problem for me either (all 5 map slots are identical).

I might try disable ETC next time - but doesnt it require an ignition off then on cycle to disable/reenable ETC? Ie it cant be toggled while live

Sounds like the aftermarket tune 2 me...That's why I refuse to drop over $200 on a "closed tune". :twocents:

Check the brake switch.

It a hard to pinpoint when it started but I know it didn't occur immediately after uprev, I had an NA tune without issue and was boosted for awhile with no issues as well.


Now that you mention it, I wonder if my problem is related to the brake switch after installing the RJM pedal....

my brake switches are fine - brake light switch has been adjusted for maximum sensitivity about a year ago and i can confirm that the brake lights dont spontaneously come on or blink when i drive over bumps in the road etc - confirmed by gf following behind me.

And the one for the cruise control cancel works fine too - kills the cruise when brakes are tapped. Again, cruise does not randomly disengage.

Tank was 3/4 full when it happened too. I cant remember how much fuel i had the first time it happened but it was at least half.

after scouring the forum for similar threads (a few circulating), it seems cool weather is a common factor.

I assume not many folks have bypassed the coolant lines from their throttle bodies so ice or moisture build up/condensation in the throttle bodies shouldn't be the issue.

Here are my logs:
During the lag: https://www.dropbox.com/s/ztsairihtm...0up%20hill.csv
and
https://www.dropbox.com/s/s7s4usm6li...rse%20park.csv

A few days before, normal engine response:
https://www.dropbox.com/s/j1yl8mhgfr...6-27-24_PM.csv

most folks with a similar issue reported inability to rev past 2500 or 3500rpm.
My car on both occasions did feel like it hit a ceiling around 3500rpm (when it did eventually reach those revs) but on both occasions i was near some road where i could do some tests. I could reach redline both times but it would take forever.

Another test i did with syncrorev match ON was drive up to 100kmh in 5th or 6th then downshift to 3rd. It happily matched the revs as it should and i was again able to wring it to redline. BUT the engine didnt seem as keen as it usually is. It felt laboured and choked.

I also noticed in the logs that the gas pedal voltage was almost 5v while the throttle body voltage was less than 1v.... wtf

have you tried reverting to the stock throttle maps? are you running the latest ROM available for your ECU?

ROM should be the latest as i only started tinkering in the last month or so.

Reverting to stock as in unmarrying the cable? That's an option but with the unpredictable nature of this problem, it might be a while before i can report back so i'll add reverting to the list of last resort options - like if it begins happening too often or causing too many hairy moments where the car becomes a sitting duck for example.

From the threads i've read and the majority of posters running stock tunes i'd say Uprev is unlikely to be an issue. Although it seems most likely to be tuning related in my case because i've adjusted the throttle mapping and that could explain the almost 5v gas pedal signal and <1v throttle body signal. I guess small throttle plate angle results in less commnd for the VVT solenoids and it just snowballs from there

you mentioned you're using the 2300 throttle maps from the forums, I'm asking if you tried putting the throttle maps specifically back to the stock values.

This is going to sound like basic sh*t but...

I had similar symptoms as far as felt power loss, without any indication, my engine was bone dry of oil and now is being replaced with only 6,800 miles on it. It sounds dumb, but it could be an oil consumption issue.

i'll load the stock map into one of the slots and see how it goea.

as for oil level - it's as full as it was when i changed oil 3000km/2 months ago

hey guys, what are your thoughts on the possibility of VDC interfering due to a slight difference in tyre wear (rears naturally being slightly more worn than the fronts)?

I switched VDC off via the button when i last experienced this lag but it didn't make any difference.

The thing that stands out most to me is the huge difference in accelerator pedal voltage vs throttle body voltage.

During lag: 4.66v pedal vs 1.03v throttle.
Normal: 2.01v pedal vs 1.13v throttle.
These figures are taken from logs where vehicle speed and acceleration requirement was similar - ie. taking off from a stand still in 1st gear, 10mph, similar rpm, afr and mass air flow. I assume 4.66v is pretty much foot to the floor so it clearly shows a huge lack of correlation between the pedal and throttle.

Intake cam solenoid duty % were similar for both logs.
However, "INT/V TIM(B1) (Deg CA)" shows another huge difference.
During lag: 7 deg CA
Normal: 49 deg CA.
(nb: just specifying Bank 1 readings for simplicity, bank 2 readings were different but similar)

Dud cam angle sensor? Dud throttle position sensor?? Or a false failsafe trigger. Whatever it is, there is no CEL or error codes :mad:

You can still hit redline, right?

Can you blip the throttle past 2k RPM and then get the car rolling in 1st like normal? I hate how the throttle fully won't open up under 2k RPM causing the surge in power after 2k RPM after nearly stalling.

yep, but it just takes forever to get to redline. getting up to 60kmh takes a lot of effort and gearbox rowing.

Yep, i can take off at any revs (i actually have to ride the clutch for a while with the revs above 2000 to avoid stalling when this happens) but i cant feather to clutch without touching the gas pedal - let's say like backing out lf a carpark spot. It literally feels like i am driving an old hatchback.

Surge is a good way to describe it when the revs reach about 2000. It's not a smooth drive.

I thought you fixed your problem?

Glad to know this is "normal"

I always attributed that to the fact I always leave VDC on

it's not normal mate. what you are experiencing is probably heat related. Something along the lines of heatsoak or warm intake air temperatures. That will easily cause a lag on take off that feels more like nothing is happening for a second or 2, then the engine roars to life.

i drive with VDC on 98% of the time too.

another way i can describe my issue is to imagine your gas pedal has been remapped to only open the throttle plate up to 1/4 of its full range. so foot to the floor = 25% throttle. halfway = 12.5%... painful. Scary when merging into traffic - esp if you expect normal acceleration but get nothing.

Page EC-481 of the fsm describes this as being the cause for P1805 (brake switch fault) : "A brake switch signal is not sent to ECM for ex- tremely long time while the vehicle is being driv- en."
This supports the highway driving situations where some people have experienced this problem. but i've had it happen to me while driving in urban areas where there are a lot of turns, traffic, speed bumps etc - basically lots of brake use

Mine's not a temperature problem, but more of a the tune that came with the kit. I've decided to leave it alone for now since it's driving fine.

but when you had a faulty brake switch, you had the same problem as i have ay? except yours seemed constant but mine comes on randomly and stays on when it does.

have you tried the 2300 curve? or do you only have the basic Uprev license?

IMO, this sounds like the tune. Throw the stock tune on and see if the issue persists. This is beyond problems caused by temperature. I would have also indicated the brake switch as a possible condition but that seems to be ruled out.

I don't have the tuner license, and I can't quite justify $700 for a tuning session at the moment (60k on the motor). That doesn't include the mini road trip to a shop in TX either.

The brake switch issue definitely resolved the power cut issues I had when the car was bone stock. The car literally stalled under 2k for a couple of seconds while making a left turn! I've even floored it in 1st and 2nd while making the turn. There were issues where I could feel power cutting at each 1k intervals to redline, and the tech thought it was fuel cut. The engine is fine, but the throttle wouldn't open up. Once I had the issue remedied, the car sounded different. The motor sounded different, and it hauled angrily to redline and even spun the tires.

Right now it's just the tune under 3k RPM that's a bit sluggish, but I guess it's keeping my rods from snapping. Basically the throttle response is not 1:1 or is limited under 2k or so. The 350Z never had this problem, and it felt great. It might require more skill on the foot, but I rather deal with that than a lazy response.

How many miles do you have now? Have you taken a look at the throttle bodies? That's what I plan to do sometime in August whenever I have time to work on the car.

I had a very similar issue, it was in my tune, though I'm not sure what about the tune caused it. It would happen after the car warmed up, I checked to see if it was my brake switch but messing with that did nothing. After getting my car re tuned the issue was gone.

Mine right now is happening as the car is warming up or starting up after the engine is already warm. It takes about 5-10 minutes for the throttle start opening up. I can see this by monitoring the boost with my foot planted in 2nd or 3rd. At 4k RPM it barely makes 2-4 PSI, and it ramps up slowly. Once it starts opening up, though it easily hits and exceeds 5 PSI at half throttle.

i have 52000km so about 33k miles. Throttle bodies appear fine but i have never removed them from the manifold collector tk inspect the dirty side. I have bypassed the coolant lines completely so they do feel stone cold after a good run - would that cause an issue? Definitely no subzero temps here though so i doubt ice formation.

i have a Scanguage II in my car so i can watch some parameters live. When i am experiencing the issue, throttle position (TPS) gets pegged at 25 degrees max. Even with my foot to the floor.

What do you guys think about the MAP sensor theory? if the throttle plate opens no more than 25deg under full load then there would be a lot of vacuum right? I'm not sure how vacuum for brake booster is managed on our engine but my guess is that under certain conditions, the throttle flap closes slightly to generate vacuum - thus avoiding the need for a separate vac pump

Sounds like the issues that have been discussed on here for years. The lag off the line when engine temps hit 180+ Mine did it before my UPREV and it's still an issue after, even with Fan Control Mod. I am thinking heatsoak is the issue. It never happens when Engine oil temps are under 180.

I was able to get Intake temp readings with a OBD2 reader and saw Intake temps go from 90 to 180! That's why it bogs off the line sitting at a red light for a few minutes!

http://www.the370z.com/intake-exhaus...erience-3.html

this is definitely not the heat related timing pull lag.

i'll get a video recording next time it happens but if you flick thru my logs posted on the first page of this thread, you'll get all the data and a good baseline to comparw against

Mine wasn't just a lag either, it felt like I had no power or just wasn't WOT all the way to redline, in any gear. It also took more effort to take off in 1st compared to normal, had to feather the clutch for longer.

Even if my car wasn't hot, as long as it was running for about more than 15 mins and well warmed up, this no power state would happen on my previous ecutek tune. Wish I could tell you exactly what it is but I'm fairly sure it's something in your tune, based off your description.

ok, so the brake switch theory might hold some merit. Not sure if it's the brake light switch or the one which kills the cruise - more experimentation to follow.

Basically what i did was at various speeds and gradients i pressed the brake pedal enough to switch the brake lights on, then floored the gas pedal. The result is the throttle remains as it was just before the brake pedal was pressed. So acceleration is still available but at a much lower rate. It still didnt feel the same as the last few times i experienced the issue. Acceleration was still reasonably strong
Another thing i observed was that once i released the brake pedal, within a second the throttle would behave as per my gas pedal input. So if my foot was to the floor, release brake and it roars to life.

Back to the issue, i still could not replicate the dangerous lack of throttle response. I am guessing this could be because i cannot press brake and take off from a standstill at the same time (dont have 3 feet to operate all pedals) so the best i could do was feather it into 1st and get the car rolling, then brake and gas.
Once i find a safe place to test, i will disconnect brake switch and test again.

If there is an issue with brake switches on my car, i'm betting it's the cruise control one because i dont see my brake lights staying on longer than they should or spontaneously blinking. No one following me seems pissed off either, so i doubt the brake lights are blinking.
Cruise still works ok too..........

I've been following these throttle response / lag threads for some time, and I keep seeing people mention the brake switch as a possible root cause. Though I can't seem to find a thread that covers the symptoms and fixes for it. Is it a new part replacement fix? An adjustment?

Look here:
http://www.the370z.com/engine-drivet...tml#post664697

@juld0zer, the switch might be intermittent. I added a shimmy and it stopped working after awhile, so that's when the switch was replaced. The engine definitely sounds different when it actually opens up. It screams! Haha. At 60k miles it's definitely time to clean the intake system... just lazy.

cheers for your guidance - if the switches are cheap enough i'll just replace both. let me test more first

[QUOTE=DIGItonium;2865205]Look here:
http://www.the370z.com/engine-drivet...tml#post664697

Thanks a ton for this. I recently purchased my Z and it has over 60k miles on it, and throttle response/lag is very random but becoming bothersome. Most likely needs to be inspected anyway.

On a side note, while reading all these hesitation/loss of power posts, I have been keeping track of everyones reported oil temps - most seem to be 200 or lower during normal driving. Seriously? It's been upper 80s and humid here in PA lately and I'm at 220 while driving very cautiously. If I get on it even briefly I'm up between 230-240 almost instantly. From what I understand limp mode isnt until the 260-270 range, but does it seem normal for my oil temps to be consistently that high?

09 model doesnt come with the factory oil cooler so that can be a factor. until you start getting live data from your engine's sensors it's hard to pinpoint the cause

Ok, so i finally had some time to do some experiments - because driving around with no brake lights or brake lights constantly on is not cool. In short, i was eventually able to replicate the problem/induce it.

The system is more complex than one would expect, so i don't understand why Nissan chooses to do it this way on all their cars. My gf's Mazda2 makes do with just one switch assembly which activates the brake lights, cuts the cruise control and frees the gear selector.

If you press the brake pedal while accelerating, you will NOT be able to open the throttle any further than the position it was in the moment you pressed the brake pedal. When you let go of the brake pedal, the motor will roar back to life and accelerate as it should. Sort of feels like brake boosting in a way. This is supposed to be a safety feature, preventing you from accelerating while braking.

The brake lamp switch is a normally CLOSED switch. Ie. continuity only exists when the pedal is pressed.
The ASCD (cruise control) switch is a normally OPEN switch. ie. no continuity when the pedal is pressed.
These two switches act like an interlock, as described on page EC-505 of the FSM.
Therefore, disconnecting both switches or one at a time will not induce the problem.

To induce the super-lag, i had to simulate a depressed pedal. I did not want the brakes to interfere with my experiment as we all know the brakes can easily slow down the car. I already knew that pressing the brake pedal even lightly while accelerating will not allow me to go any faster, even with my foot to the floor.

To simulate a depressed pedal, i disconnected the ASCD switch and used a jumper wire across the terminals of the brake light switch connector (loom side). This is the point where i blew 2 fuses because the jumper wire shorted to ground. OOPS! Be careful :)

With this set up, i was able to induce the lag and learn a little more.
I could not get the throttle to open up more than 18 degrees. Test conditions were similar to the night i created the logs.

It seems that once the ECU realises you've been trying to accelerate while braking for a certain period of time (or distance?), it will switch to this limp mode where the throttle plates open extremely slowly and only to a narrow angle/range. I realised this when i removed the jumper wire and reconnected the brake light switch. Brake lights worked as they should (when jumpered, the brake lights were constantly on), but i could not escape this limp mode. The ECU at this point must be thinking the car is in a runaway situation. This explains why the problem vanishes after the engine is shut down and restarted.

Now, as i've outlined above, having one faulty switch shouldn't cause the problem. Bizarre? I think so.
Being electronic, i wouldn't rule out both switches failing at the same time as they are used equally as often as each other. My theory is that the rubber blobs on the pedal assembly could be worn out or causing the switches to stick in their respective pedal down positions or some gunk has accumulated inside the switches.

The other day I accelerated at WOT in 2nd from 1.5k RPM because the car wouldn't scoot at the light. It took forever for it to reach redline. Even if it did, the engine wasn't screaming even at redline. It felt like a 3rd to 6th shift at low speed. I am starting to feel a bit of "roughness" as if he car isn't sure if it wants to accelerate or let go while the foot is planted, so it's pretty rough getting in gear. Plus, it feels like the motor briefly shuts off in between shifts as it bogs. The entire weekend I couldn't get anything close to 7-9 PSI. In fact, the car barely hit 5 PSI at full throttle in 2nd gear and it's obvious the throttle wasn't fully open. You're right. Back then when I had this issue I had to shut the car down, wait a bit before starting, and the "problem" went away.

Too we can't apply throttle with skill without the nanny ware kicking in. Looks like it's time to get it checked again.

disconnect the brake light switch and give it a go. do it in a quiet area though. it's the right side one with a chunky connector (white)

I plan on cutting the brake light signal to the ECU and disabling the DTC via uprev, I'll report back if it actually fixes things for me, if not at least I can do some fun burnouts