Cars interesting problems- need ideas

mike12002us

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

DOOMMONKEY777

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.

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juld0zer

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

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

SouthArk370Z

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

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phunk

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.

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mike12002us

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

Attached Images

Throttle position.jpg (56.6 KB, 15 views)

phunk

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.

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JARblue

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.

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phunk

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.

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juld0zer

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?

phunk

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.

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juld0zer

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.

phunk

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.

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juld0zer

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

JARblue

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.

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