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Old 10-12-2009, 12:43 PM   #1
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Default Boost Stutter/Hesitation Problem

Saturday at the track I started getting this stutter/hesitation when I was under lets say 75%+ load or so when in boost. Wideband reads the same from what I can tell, boost reads the same from what I can tell, but rpms just drop down to idle almost instantly and then rebound back and then hesitate, etc. Feels like slamming on the brakes for a second. It seems to be getting worse. Was only maybe 1 in 4 times getting into boost. Now its practically 4 out of 4 times. Stutter, then pops/gurgles after, then boost, then stutter then pops. Runs fine out of boost and at low psi/low load.

I am running MSPnP. Ignition problem? I haven't touched anything yet - I got home late last night and everything was super hot.

Is this descriptive enough?
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Old 10-12-2009, 01:00 PM   #2
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Could you post a data log of this problem happening, along with your MSQ? This'll give me a better idea of what is going on inside the ECU.
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Old 10-12-2009, 01:18 PM   #3
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going to just guess overboost protection...
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Old 10-12-2009, 04:47 PM   #4
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Overboost is what I thought too, but my protection is set at like ~16psi and I will get this set in at 5psi+.

My money is on ignition.

Matt, I can try to soon. Maybe over the weekend. Thanks for the extension of help.
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Old 10-12-2009, 04:49 PM   #5
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then yeah, it's a miss or CAS dropout or something.
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Old 10-12-2009, 05:29 PM   #6
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Quote:
Originally Posted by Braineack View Post
then yeah, it's a miss or CAS dropout or something.
Brain, any way to tell in MS or a datalog if it's either of these? Will a CAS dropout create a weird anomaly in the spark angle?
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Old 10-12-2009, 05:32 PM   #7
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Also, make sure anti-rev is off?
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Old 10-13-2009, 11:01 AM   #8
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Quote:
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Brain, any way to tell in MS or a datalog if it's either of these? Will a CAS dropout create a weird anomaly in the spark angle?
Look for downward spikes in the RPM graph; this is a tip off the CAS is misbehaving.
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Old 10-13-2009, 11:40 AM   #9
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thanks for the help so far guys. CAS and plugs are cheap and easy enough. I'd say I'm going to order both and see what happens. At the least I can eliminate them. The RPM graph will for sure show downward spikes. Its almost like someone shuts the car off for a second and starts it back up with the foot on the gas in boost.

Thanks Matt. I will still try and get you a data log.
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Old 01-05-2010, 11:17 PM   #10
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Any luck? I think I'm starting to have the same problem. Just replaced the plugs and still the same issue. Just stutters a bit when jumping on the throttle at about 3.5-4k rpm when I just start to hit boost.
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Old 01-05-2010, 11:37 PM   #11
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I had a similar issue; mine cropped up seemingly out of the blue. It drove fine out of boost and with light load but over 3-5 psi it would cut out it felt like the someone was slamming on the brakes.
I logged it and was getting occasional resets on the MS when it was misfiring(around ~60% of the time.)
My problem turned out to be the power wire to the starter. I had lost the cap for it about a month before and ended up wrapping it up with tape to keep it from potentially shorting out. I managed to get a little corner of the tape in between the contact and the wire and it managed to corrode enough or wiggle itself a little loose that it didn't get a great connection.
I pulled it off cleaned the connection bolted it down and haven't had a problem since.
I only checked it because I eliminated everything else and that was the last thing I had done the the car before it had issues.

It's worth a shot I suppose.
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Old 01-06-2010, 12:06 AM   #12
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Quote:
Originally Posted by Fidgitk View Post
I had a similar issue; mine cropped up seemingly out of the blue. It drove fine out of boost and with light load but over 3-5 psi it would cut out it felt like the someone was slamming on the brakes.
I logged it and was getting occasional resets on the MS when it was misfiring(around ~60% of the time.)
My problem turned out to be the power wire to the starter. I had lost the cap for it about a month before and ended up wrapping it up with tape to keep it from potentially shorting out. I managed to get a little corner of the tape in between the contact and the wire and it managed to corrode enough or wiggle itself a little loose that it didn't get a great connection.
I pulled it off cleaned the connection bolted it down and haven't had a problem since.
I only checked it because I eliminated everything else and that was the last thing I had done the the car before it had issues.

It's worth a shot I suppose.
There may be merit to this. I have had the same problem. Occasionally on the street, and it happened a few times when I took it to the track. Long story short I found my positive terminal on starter is missing the nut. I've never messed with it because it always starts and never thought it would affect anything. Interesting
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Old 01-06-2010, 12:47 AM   #13
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hrmm i think i'll be checking that out manana
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Old 08-21-2010, 06:19 AM   #14
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so did you find out the problem?
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Old 10-16-2012, 04:38 PM   #15
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So better really late then never - the issue was that one of the rivots that holds the coil pack to the frame came out. Replaced it with a nut and bolt. Problem gone.
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