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Quick throttle blip results in stumble

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Old 07-13-18, 10:35 PM
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Quick throttle blip results in stumble / stumble under boost

Hey guys, just wanted to see if this was normal and some potential fixes with the datalogit. My car is all stock minus the power fc, and if I quickly blip the throttle I'll hear a suction type noise and the rpm will dip, motor will stumble, then all recovers. I can slowly rev with no stumbling issues, it's only if I do it quickly. I read up on some ideas behind this, but all of those motors were modded. Has anyone experienced this on an all stock motor? If so, what are the fixes? Thanks,


Joe

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Old 07-14-18, 12:43 AM
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What engine?
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Old 07-14-18, 12:52 AM
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93 Californian car with all original parts 67k miles. Air pump etc is all installed, it almost sounds like some sort of air pump suction noise. Vacuum is fine at 470 mmhg, don't suspect a leak.
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Old 07-14-18, 07:00 AM
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Throw a wideband oxygen sensor on there... I'd bet the car is running extremely rich during this transition. Should be around 0.85 Lambda under a quick blip (high load), then taper off to 1.00 Lambda (stoichiometric) as it settles.
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Old 07-14-18, 02:26 PM
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Download the map and load it here. Even the stock PFC map has bad values in it!
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Old 07-14-18, 02:44 PM
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Originally Posted by cewrx7r1 View Post
Download the map and load it here. Even the stock PFC map has bad values in it!

Actually just sent you an email with the Igt, Igl, Ing, and base map screen shot! I had some stumble under boost today when I was heading into Cars and Coffee, first time I've experienced that. I did the idle relearn process when the car was already warm, so the fans came on during the "no electrical load" first 10 minute portion. I'm letting the car cool all the way down today and then I'm going to do the relearn (I already reinitialized). Here are my results from the current map installed...


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Old 07-15-18, 11:40 AM
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Here is the map currently installed (.dat file) with the fan speed changes I've made under setting 3 tab. I've also thrown in 2 data runs on 3/4th gear pulls into the .RAR file here.
Attached Files
File Type: rar
Datalogit logs.rar (88.7 KB, 6 views)
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Old 07-30-18, 11:18 AM
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I'm experiencing this same issue to a T, base map PFC (brand new even) with stock engine, intake, downpipe, intercooler. So far, it's only when I go to blip the throttle to downshift at lower speeds. Besides that, it idles fine and runs much better than the stock ECU. Figure out the issue at all?
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Old 07-30-18, 11:24 AM
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I did not figure it out, but I did make it go away. When I first installed the PFC I did it from a cold engine, and didn't have any noticeable issues (although I didn't actually test the blip at that time). I then did some work and had to redo the learning process, but that time I did it from a warmer engine and the fans kicked on before the first 10 minutes were up (idle with no electrical loading phase). After that, I had the issue. I then Got home, let the car sit overnight, changed the fan temp back to 95 C from 85 C so they wouldn't come on during the first 10 minutes, and did the re-learn. No issues from that on. I should say that I have the stock dp, so I'm sure my heat up rates are quicker than yours, so you shouldn't have the problem with the car warming up to NOT within 10 minutes. I'd just suggest doing a relearn from ice cold again, doesn't hurt, and make sure you do a full 10 minutes, take out your phone and actually use a timer. 10 min idle no load, 10 min idle rear defrost, 10 min idle A/C on.
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Old 07-31-18, 07:25 PM
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You can try this:
(1) remove the ISC solenoid and clean the valve by filling it with a cleaner and then applying 6 volts to 12 volts. A cheap charger will actually buzz the solenoid due to it not having a pure flat voltage output.
Some people have found pieces of trash in their valves.
(2) also check the TPS voltages to be in compliance.
(3) if all of the above are good, time to play with the Settings 2 Accelerate Injector (ms) or Inj vs Accel TPS1.
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Old 08-08-18, 08:49 PM
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Reset the PFC, did a full 30 minutes of idle learn per instructions. Issue still persists, so I think i'll give the ISC a clean and go from there, last I checked the TPS was good to go. It's not the most inconvenient issue, just a tad annoying, especially in traffic.
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