Is your car breaking up/bucking at high rpm?
04-09-2011, 02:34 AM
#1
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Is your car breaking up/bucking at high rpm?
i see threads on here all the time about people having issues on different engine management setups with their car braking up under wot at high rpm. well, i found this today on the aem forums and figured it might be worthwhile to mention it on here.
just wondered if anyone has tried this on the tc's wiring harness?
While tuning a friend's car, a cutout appeared at heavy throttle. It wasn't just any old misfire, it would cut out and buck violently briefly, then come back. I checked the overboost cut, and that wasn't it. I checked injector times, dwell, and timing, no probs. I noticed that RPMs dropped very very sharply right when the cutout happened. Not physically possible.
Suspicious, I logged timing errors from the advanced cam/crank screen. There was a sudden jump in timing errors right when the cutout happened. I then looked at the crank sensor gap (to the teeth). It was fine. I figured it must be some electrical noise. Now what electrical noise would increase with load? Ans: ignition coil generated noise, due to the increased spark voltage requirements at increased load.
Looking at the cam sensor wiring, it passed near the ignition *primary* wires. I separated them, problem solved.
Suspicious, I logged timing errors from the advanced cam/crank screen. There was a sudden jump in timing errors right when the cutout happened. I then looked at the crank sensor gap (to the teeth). It was fine. I figured it must be some electrical noise. Now what electrical noise would increase with load? Ans: ignition coil generated noise, due to the increased spark voltage requirements at increased load.
Looking at the cam sensor wiring, it passed near the ignition *primary* wires. I separated them, problem solved.
just wondered if anyone has tried this on the tc's wiring harness?
04-10-2011, 04:17 AM
#10
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Scikotics
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wow, I have been experiencing this problem for a while now. I swapped coils with my wife's tC, changed sparks, performed two boost leak checks, swapped injectors, etc. After all of that I just blamed it on the FIC, but couldn't find the problem. I'll try shielding the wires to see what happens.
For me it's mostly felt at part throttle at low psi between 3k and 3.6k rpm's, at wot it's not as bad (although it varies, sometimes it falls on it's face) but def visible on a log.
For me it's mostly felt at part throttle at low psi between 3k and 3.6k rpm's, at wot it's not as bad (although it varies, sometimes it falls on it's face) but def visible on a log.
04-10-2011, 12:29 PM
#11
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04-11-2011, 05:31 AM
#14
not sure if its a fuel cut though, just the way you had described it before sounds like what i delt with at anything above 16psi. afrs were dialed in but im guessing it was either spark or knock issues. car didnt buck but felt alot like what happens when you dont have the resistors in on the fic.
04-14-2011, 02:21 AM
#19
I had some similar symptoms, but for me it was from using a ribbed Spectre intake extension tube that I plumbed into the fender wall to try to lower IATs on a pull through set up. When I smashed the gas pedal down the car would seriously bog because there was too much turbulence at the MAF. I've since switched over to a blow through set up and have been doing well ever since. *Running the APR X1
