hey guys...
i have had my APS ST mounted on my car for about 6k miles, everything is flawless, until i ran into a lil problem 3 days ago..
okay its hard to explain what is going on, but ill try my best...

so i was driving one day, (cruising) and my car jerked (rpm went up and down) this happen closer to 3,500rpm, i guess thats when the boost builds up. so i didnt think much of it, i thought it was me for some reason. so then i drove after that. and the car jerked again, like it was lagging , after jerking several times, it died. so i pulled over to the side.

i started the car again, i realize there is NO Vacuum leak..so i started to drive, it drove normal for about 20 seconds, then the car jerked again. and rpm flucuated from 2k-3k...now i pulled over, again, the car is still running, NOT even idiling or anything.. and i tried giving some accelerration and realize when it gets to closer to 3k rpm, it lags , like something is cutting it and it wont pass 3k - 3500k rpm

now realize no check engine light was thrown or any code was thrown

2nd night it did throw the check engine light and slip light along with another light.

so on that night i drove home with disconnected the battery terminal, connected it in the morning, and drove it. and it was fine.. but then later that day it hesitated again and lagged. so i had to drive it home going under 2k rpm, and making sure no boost is build up.

i am tuned at safely at 9lb of boost on a unichip..

to my understanding has to do something with a wiring maybe, unichip or my stock ecu??

I have talk to Sharif in atlanta, im going to bring it by him by next week, but its hard cause the car is fine and then its not working right..
i know there is nothing wrong with the MOTOR at all. something to do with a wiring, im hoping it might be a easy fix, or just something loose electrically!!!

thanks in advance for any feedback!

 

did you pull the code? RPM shudder? Tranny?

 

turn off the traction control. let me know if that'll fix the prob.
your car could be dumping too much fuel, but try that first.

 

my aps kit did the same exact thing once after i installed it. but it was so long ago, i forgat what i did to fix it or what caused it

 

sounds like to me that you are in limp mode if it won't rev past 3K. probably something to do with the throttle body or possibly your maf reading too much flow (the unichip map sensor may not be clamping the voltage properly)

My suggestion is to shut the car down, reset the ecu by pulling the battery cable and then rerun the car. the issue will most likely come back, but this would be a temp fix till you can have a shop fix it up for you

 

i had the unichip on my car and it Fried my ecu somehow and it would go into limp mode. but i didnt think that was the case from ur description. so the car drives but the rpms dont go up or go up very slowly at wot? please be more detailed

 

First what was the code for the check engine light and second is it an Auto or Manual

 

it is manual car...
the check engine light came on once only along wiht the slip sign

 

i drove the car today, in the morning, drove to work , it drove fine, then going to lunch it started hesitant again...and jerking again
but no check engine light came on

 

I agree.

OP - how are you positive it's not a leak? Sounds strangely like one to me. It's definitely more plausible than having fried something.

 

yeah im positive there is no leak!!!

 

it is very difficult to diagnose a problem over the net. How are you 'positive' you have no leak? pressure test the system? I guess you are right that there isn't a leak, but just want an idea how you are so sure of it.

Also, you need to get yourself a code reader of some sort. It will help a ton to know what code(s) are being thrown. At least give us a frame of reference to start from.

My orginal thought/diagnosis still seems correct. You are most likely in limp mode. The car will start bucking and jerking if you attempt to run beyond 3000 rpms. This can be caused by a number of things, but the 2 that come to mind are an issue with the throttle body - and being it is drive by wire, it isn't uncommon. 2nd, it could be caused by an improper maf voltage clamp by the unichip. Your maf might be seeing too much air flow and put you into limp mode - I call it "popping the maf". If this is the case, you need to take the car to your tuner and have him resolve the issue for you

 

i just dropped my car off at sharifs, at forged
so lets see what happens, or what the problem was!!
im very curious

 

Please report what you find out is the problem..I am having the exact same issues, except I have a 5AT.

 

You'll be in good hands with Sharif, thats for sure.

 

If the slip light comes on that generally indicates a TB issue, or more likely an ECU that's on its way out. The MAF may be causing it but its unlikely due to the intermitance. Definelty let us know what Sharif find's.

 

hey so i gota call back from sharif.
it is the crank sensor

all i know im not very inclined about turbo, but am learning!!

any suggestions

 

The crank sensor was about 4th on my list of things to consider. Glad you got it figured out!

 

so i guess i need to go to a new engine management system???

basicaly sh*t out of luck

 

no you dont need a new engine management system we have had some of the wires become loose in the plug. If you wiggle them or the car vibrates at the right time it will cut out have him check for loose wires in the plug at the transmission. Unichip will also warrenty the harness if it can be proved that its something wrong with the harness. The quickest and easiest way to determine this would be to unplug the aps harness at the ecu and the crank angle on the bottom side of the transmission, plug in your stock one and drive the car but keep it out of boost the car will run rough but if it revs above 3k theres your answer.