Cars interesting problems- need ideas
 

So my car has been having some interesting issues. I have searched the forum extensively and been trying to get ideas as to the issue. Ill go through everything in a time line to help. To start I have a 2010 370z sport manual. Just hit 90k miles and had plugs changed 25k miles ago. I keep it up to date with servicing. Here is my story.

starting out: I had an Injen exhaust, G3 intakes, stillen pulleys and did an uprev tune. The car ran perfectly.

then: I added test pipes and a Stillen 25 row oil cooler and the car felt even better but waited for a new tune until I got the new ported plenum. No issues with just adding TP. Got the CNT Resonated btw.

then: Installed Stillen grounding kit and drove to tuner to have upper ported plenum installed and get a new tune. - car drove ok for the ride home but I never got on it to see what it felt like as it was raining and traffic would not allow for it.

Home: After a few days I noticed that my car would run perfectly when first started and the throttle response is amazing. I can really tell the car has power in 6th gear ( for reference ill be using 6th gear as my guage) The car would then intermittently start acting up. I would be at a stop light and floor the gas and it would take a few seconds floored for it to come up. After 2k rpm it would rev quickly. I also noticed in 6th gear where I normally would pull on the freeway that my power had dropped considerably.

Back to Dyno: I took my car back to the tuner and had it retuned thinking that the timing was too far advanced. We saw on the dyno (the problem luckily recreated itself) that I had no power until 2k rpm then it would jump up. Got the retune and the car felt ok.

Home again: after a few weeks the car started to act up again. The weather had changed from scorching hot to warm and that seems to help the issue. Also when the oil goes over 180 degrees it brings the problem on. This maybe just perceived and not fact for all instances though. It seems when its warm out and the oil hits over 180 in oil temp is when it happens??


Now: I have now received a tune via email going to stock timing on the car and it still does the issue.


I need help figuring out what is going on. I have taken off the throttle bodies and cleaned them as they were filthy. I have been informed that it sounds like a:

1.Vacuum Leak in plenum or hoses going to it
2.Tune issue
3. Sensor issue.
4:?????

I have data logged the car and all of the sensors seem to be fine. I am going to pull the upper plenum off and see if I can find any leaks as wel as take it to be pressure/smoke tested. Im thinking of putting the stock tune on the car to see if the problem goes away. If it does its the tune.

I am just trying to see if ive missed anything and pick your brains a little. Im so frustrated with this. Its been 2 months of issues now. The tuner has been more than helpful but they are 6 hours away and I cant go there every week.

can you record a video of the issue? like of the gauges and your commentary regarding gas pedal application, current gear, ambient temp etc.

it sounds like my issue, but mine sounds like heaps of other issues. give me another week and i might have a lead for u. i just need to run the car more to test it more

Most likely a vacuum leak. I recently fixed a similar problem. For mine, the plastic right angle piece near the driver side post MAF tube broke in two. God knows how long I was driving around like that. Fixing it with a solid rubber hose got rid of my issue.

did you use all new gaskets on intake mani (between head and between the plastic upper), and the throttle bodies?

heaps of people will tell you sensors usually chuck a DTC when they're faulty. but if they are slightly out of spec then they wont set a DTC and you'll have to compare known good specs against yours to isolate the fault.

tuning adds another huge variable. my car has a throttle remap using the popular 'smooth throttle' map on the forum here. i have not reflashed or reverted my ecu to stock in an attempt to resolve my issue. i have my reasons but in a nutshell, the car ran fine with the software tweaks for a while before it started happening

I will make a video of when it happens. Im not sure if new gaskets were used as the shop installed the plenum. I was told last night that the problem could be a dying fuel pump that when it gets warm it runs lean and throws the car out of whack. I have just ordered the CJM fuel tap and the fuel pressure gauge to see what im running. Should be around 53. We will see if that is good. The car is running great today and its a little warmer 63 degrees with the oil at 180 so I am not sure what causes the issue.

do you have Uprev to datalog? if you do, datalog every time you drive the car. it's annoying but i finally captured the lead up to one of my lag events all the way thru to where it was actually happening until i reached my destination. Downside is that nothing stood out like a sore thumb but in depth analysis showed some leads which im still exploring.

a failing pump will show a lean AFR so datalog that, accelerator pedal sensor, throttle position sensor (these 2 you use together to ascertain your command vs the 'response' in terms of what the ecu gives you), both IVT solenoid duty, both cam sensors, rpm, vehicle speed, coolant and oil temp, both VVEL angles plus voltages, maf voltages. you can add MAP, load and a few others

failing pump would cause stuttering too.

Just read through this.

With a wideband and datalogging through UpRev, the problem should be pretty easy to find.

This does not read like a fuel pressure issue if you ask me. If you have a stock tune to put back in, that is a possible start. Perhaps its even just something they messed with in the throttle table? I dont know who tuned the car. But I would log the throttle positions and accelerator positions for sure.

Basically everything the post above me says to watch.

i'm experiencing the same problem. frustrating!

I have a lot of data logging already done. Im not sure how to decipher it all though. Is there anyone I could send it to to look at it? I have it logged where the car is running fine and then the problem occurs. I didn't notice too much that was off except I took a pic of this graph. It looks like the throttle is not being matched with the pedal position. This was a 0-60 run that I did. the dip at the mid end was due to trac control being on and me forgetting to turn it off. the front was due to the issue and no trac interference. I know that this is for accel ped 2 and throttle pos 1 but they are the same on the other ones as well.

what was the ambient temp? did you log intake air temp at the time?

Update: I have just updated the rom and it has put the car back to stock. Other than running lean it would appear that the hesitation is no longer an issue. The tuner is going to send me a new tune to get it back in good numbers and hopefully this will have resolved the issue.

Celebration has been cut short. The problem has come back. This means that the tune is out as the cause of the issue. Well at least I have narrowed it down to everything else. Nothing is easy!

Could it be the grounding kit? Wasn't there someone else that had issues with their grounding kit installation? I can't remember the specifics. Maybe someone else does.

I have the same issue, too, even when I was N/A. Everyone tells me it's a tuning issue. But this hesitation and lack of power you see is the throttle not opening up as much even when you're flooring it. I can tell because car barely hits boost in 1st or 2nd with my foot planted at 4k RPM. Like you said, power surges at 2k RPM. Try blipping the throttle past 2k RPM, and then get in 1st like usual. Or get the car going above 2k RPM, and the engine will scream. Someone mentioned throttle restrictor.

Whatever it is especially for a stock car, this lag has been discussed since 2009. At first we thought it was throttle by wire lag, but now it seems like the throttles are not opening up.

The lack of power can be referred to:
1) throttle table is negative too far in, till 35%? Turn off ur throttle table and that will let it act 0-100%. If ur loosing power still as it was but maybe its a lil better then it could be #2

2) ur air fuel ratio table is adjusted 14.7:1 ill too high rpm, adjusting this will be best if u use a dynamometer cuz u need to get timing right for right fuel burning( also if u adjust it slightly the ECU can compensate for that without a problem) beyond this gl. If this wont work then it could be faulty/dirty sensors and all.

Im going to be taking the grounding kit off this weekend. I already unbolted it from the negative.

Im seeing that other people are having this issue but it looks like no one has ever really been able to resolve it.

I would log the throttle position and accel position. That right there will tell you if its a throttle related issue. It sort of sounds like it is to me.

My car has zero drive-by-wire related lag/delay... so it is definitely fixable and not just an attribute of the car.

This a pic I have. Let me know what you think. the blip at the mid/end was due to trac control.

oops you already posted that didnt you, sorry wasnt paying enough attention.

well it looks like we can see a problem in the throttle system there. you floor it, and it slowly climbs to 50% throttle before going 100%.

i know that the stock throttle maps probably dont go instantly full when you floor it at low RPM, but I would expect it to be better than that.

perhaps it would be helpful to see RPM in the same log as those 2 you have there to get a better idea.

does anyone here have the coolant bypass mod on their throttle bodies?

and what are the ambient temps in the US at the moment?

At least a couple of people have done it. Search is your friend.

It's about 35F here, at the moment, but the US is a pretty big chunk of land. National and Local Weather Forecast, Hurricane, Radar and Report

I did the coolant bypass when I cleaned my TBs at ~10K miles ago.

Its not unusual for us to see 100F in October in Texas, but it has been cooler than usual of late. We have highs in the 70s right now.

I removed theottle body coolant lines when I did my turbo install a few years ago and have driven in zero degrees and 100 degrees and no issues.

the only reason i asked is to try and find some trends. the last thing i did before all this happened was completely remove the coolant lines to the throttle bodies. this coincided with the Aussie winter where we saw temps averaging 70F/22c in Sydney.

the issue seems to mainly occur after having the throtte open for a while, such as cruising on the motorway. The problem seems to subside after stopping the motor then restarting after a few mins. The conclusion i am at now is that these throttle bodies must be getting chilled for lack of a better explanation, chilled and then it acts funny. Maybe it compares oil, coolant and intake air temps and goes into some sort of 'ice' mode.

but Phunk says he has driven thru all temp extremes without issue, but the turbos could be keeping sufficient warmth under the hood?

I am certain that removing your throttle body coolant lines is not the cause of the problem.

The accelerator has 2 sensors in it. I would try logging them both side by side and make sure they are comparing correctly. I would do the same with the throttle position sensors since there are 2 of them.

I feel like your ECU is doing it intentionally... otherwise I would expect to see some sort of DTC if the throttles were not achieving the TPS the ECU is expecting. I dont know that for sure... but I want to feel like manufacturers are probably pretty serious about their fly-by-wire systems being dependable.. and would include it in the vehicles on-board diagnostics.

The gas pedal sensors output different signals afaik. I thought gas pedal too, because i got pissed off one day and stomped on the pedal many times in a rage at the car while the motor was off. The car behaved differently after, a bad sort of different. Another thing that made me think gas pedal was when i read a snippet where it said the gas pedal can tell the ecu how you are pressing the pedal. as in stomping it sharply vs easing it on gently and gradually. With that, it tells the throttle bodies how aggressively to open/close.
This wasnt outlined in the 370z FSM though, i think it was one of those generic DTC explanation sites.

anyway, replaced gas pedal and some $200 later it broke my heart when it happened again.

I've always had that thought mate. The ecu must be commanding it to behave like this, or else it would chuck a DTC tanty but it has never set any DTC except when i accidentally disconnected something. But why is it commanding the engine to behave like this? A wonky sensor? I've replaced both cam sensors, MAP sensor. No stock for crank sensor.

thank you for your kind help though. i might end up phoning someone in the US for a chat. nobody here in Sydney seems to know anything

I'm not suggesting this is your problem, but did you do the pedal position relearn procedure (if you disconnected the sensors on the TBs). Ignition OFF 10+ sec then Ignition ON for 2+ sec then repeat once.

absolutely! after replacing the gas pedal and also after cleaning the throttle bodies which were removed from the engine for cleaning.

i also observed the coolant temp requirements for the resets (gas pedal rest, throttle rest position and idle relearn).

bizarre thing is, behaviour of the variable valve timing system changes during the lag events. can someone provide me with some logs from their car which has IVT solenoid and angle data? I really want to get some closure on this issue because i'm yet to see any definitive proof that our variable valve timing systems dont operate in the same way as VVT systems on other makes.

Thanks!

They do read different but you can still make sure they are both comparing properly. There will be a relationship between the 2 that will be visually apparent in the log if it is correct or incorrect.

It could be a problem with the pedal or in the wiring. my 350z had the same symptoms intermittently but it disappeared forever when we changed the engine harness for a new one that had to be constructed for the new engine setup.

Anyone tried turning off the throttle map?? I actually did that on my Z and love it. No cruise control, but i dont use it anyways.

I found that the car responds better, sharper. Try.

All the 370s seem to limit the throttle below 2k rpm. Running the engine at high load and low rpm is probably not good for your engine anyways, that might be why Nissan put that limiter in there.

i have changed the gas pedal already so it cant be two dud pedals in a row. harness issue is interesting though.

how about issues relating to the VVEL system? is there any common faults since you guys have more VQ37 motors there compared to here?

I have never heard of any. But if the logs are showing that the throttles are not open when they are supposed to be, I would focus my investigation on the throttle system. I would log everything and see whats happening.

If you are having problems accelerating in 6th gear, might I suggest downshifting?

^ that is why I would like to see a better log... without RPM and speed showing, I cant tell if they are flooring it at 1500rpm in 6th, or if this is something that is happening in low speeds low gears

if you dont mind, can i direct you to my thread regarding this problem? i uploaded some logs there: http://www.the370z.com/engine-drivet...ml#post2856148

you can tell what i was trying to do in the logs by the vehicle speed, accelerator position etc. Please feel free to ask questions for more info as i want to sort out this issue not just for myself but for the community here as a reference point.

Just as a brief preface to viewing the logs, i limped the car home and tried extremely hard to not stall the motor because stalling and restarting would mean the fault vanishes. I dont stall often but when this lag hits, it's very easy to stall if you aren't aware of it. After limping home to get my laptop and cable, i went around the block to some slightly hilly sections where i attempted to accelerate from a standstill. I then tried to see if i could still access the upper rev ranges because folks stated they experienced a 3500rpm fuel cut. It did reach redline but it took forever compared to how it would normally behave. I literally ran out of road before i reached redline.

either way, poking the pedal while cruising at 60mph/100kmh in 6th gear usually gives a small kick. So it's not completely gutless on my car.

When the lag is happening, poking the pedal at the same speed/gear results in no perceptible gain in speed or shove. I have to downshift an extra gear to get satisfactory acceleration. While this is happening, the TPS on my scangauge shows a limit of 20ish degrees. I just dont get what is commanding this choking.

Thanks again for your inputs

^^^A/F ratio table thats sits @14.7:1 till 3200rpm, i think that this is ur problem.