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Old 09-18-2012, 12:40 AM   #1
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Default Car wont rev over 5k rpm after a few sessions at the track.. Ideas?

Hey guys,

Not sure where to put this but im hoping someone can help me out here. I did a track day today. 5 sessions in the car was driving fine. 6th Session when i pulled out it wouldnt rev over 5-6k rpm.. Felt really hesitant as soon as it got to that point. It sorta cleared up after a few laps but still wasnt revving anywhere like it use to..

When i packed up an drove home it was doing the exact same thing but worse.. just stopped revving past 5k as u can see in the video below.

Few specs about the car.
motor is an nb6 motor so it has crank and cam angle sensors.
its turboed with a 2871r making 330rwhp.
full 3 inch exhaust.
ls2 coils
1000cc injectors

um im not sure what else i can include but it anyone needs more info i can provide it. Unfortunately i havent had the chance to setup a good datalogging system yet.

Any help would be great.


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Old 09-18-2012, 03:55 AM   #2
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Which ECU?
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Old 09-18-2012, 04:17 AM   #3
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Haltech Sprint 500
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Old 09-18-2012, 04:48 AM   #4
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Check with your tuner/installer then. Can you pass 5000rpm free-revving?
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Old 09-18-2012, 04:59 AM   #5
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Originally Posted by Reverant View Post
Check with your tuner/installer then. Can you pass 5000rpm free-revving?
Nope at the time it just wouldn't budge. I could rev out in 1st but that's it. All the other gears were capped at 5k rpm. It now drives perfectly fine today with no issues whatsoever.
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Old 09-18-2012, 05:43 AM   #6
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Have you changed the CAS with a trigger wheel?
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Old 09-18-2012, 05:47 AM   #7
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When I said cam angle sensor I meant position. The one at the front of the valve cover.. And no I haven't. Could this be why it acts like this after its been thrashed for 4 or so sessions?
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Old 09-18-2012, 06:34 AM   #8
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They are easily heat affected.

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Old 09-18-2012, 08:07 AM   #9
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What are? The crank and cam sensors? From heat soak?
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Old 09-18-2012, 08:36 AM   #10
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Yes both.

NB crank sensors are notorious for failing.

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Old 09-18-2012, 09:46 AM   #11
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I am using different ECU, but I consider crank angle sensors to be maintenance items now. I have the same problems, but new crank angle sensor clears it up every time.
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Old 09-18-2012, 11:22 AM   #12
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I have had those sensors fail on a NB and it caused me no end of pain trying to diagnose it. The problem comes and goes with heat, so it can mimic a tuning issue. Replacing the sensors fixed the problem.
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Old 09-18-2012, 12:29 PM   #13
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This is actually shocking easy to diagnose with the proper ECU.

I had one case where a car would misfire above 2500rpm or so, but randomly. Using TunerStudio, I was able to see that there was a problem with a specific tooth on the trigger wheel. I described to the shop exactly which tooth was missing at certain moments, and they found out that the trigger wheel was bent a few (1.5) millimeters (something your eye wouldn't normally catch). They flattened the crank wheel and all was good again.
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Old 09-27-2012, 04:28 AM   #14
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Update with this:

So went down and swapped over the sensors in anticipation for a bit of highway racing tonight. So i could test and see if it still did the same thing. Swapped them in and set the correct air gap on the crank sensor and went for a drive. Did not rev over 6k rpm. A bit surprised i went back and fiddled around to see if i could get it better and nothing.

Started driving back home only to have the car **** itself and had not throttle at all. Pulled over and tried to start the car and nothing. Went and swapped over the old sensors hoping it would fix it and it didnt. Still didnt work.

So question is what went wrong. We managed to get it starting but as soon as u press the accelerator it dies. Only thing i changed was the sensors.. Thoughts ?
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Old 09-27-2012, 08:58 AM   #15
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Did something done blown up? If you have the ability, try re-flashing the haltech. I've had the sport 2000 just get stupid and forget parts of the tune before. Literally, car runs like crap, connect to computer, "what the **** is this garbage, this isnt my tune" then re-flash and it was all good.
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Old 09-27-2012, 09:05 AM   #16
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You really, really need to connect the ECU to a laptop and check all the sensor readings are ok. RPM, MAP, TPS, coolant, air, etc.
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