HELP! Severe acceleration lag

juld0zer

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?

juld0zer

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

esfourteen

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.

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juld0zer

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

L33T Z34

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

DIGItonium

Check the brake switch.

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esfourteen

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....

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juld0zer

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.

juld0zer

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.

juld0zer

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

esfourteen

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

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juld0zer

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

esfourteen

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.

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DangJones

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.

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juld0zer

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