Cars interesting problems- need ideas

mike12002us

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.

juld0zer

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

dP3NGU1N

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.

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juld0zer

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

mike12002us

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.

juld0zer

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.

phunk

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.

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TKomodo

i'm experiencing the same problem. frustrating!

mike12002us

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.

Attached Images

Throttle position.jpg (56.6 KB, 21 views)

juld0zer

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

mike12002us

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.

mike12002us

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!

JARblue

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.

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DIGItonium

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.

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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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