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RPM keeps climbing with no throttle?

ForYourOwnGood

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Ok I have this question in with my tuner as well but I'm just curious what you guys might know.

My car is basically stock with an Edelbrock 2300 kit on it. I have a DW400 pump and JMS bap with DW95s. Note that this was happening with the EB kit out of the box and well.

What I'm seeing is this: let's say I go WOT in 3rd and want to shift at 6000rpm. Sometimes it will work normally and others as soon as I clutch in it will Spike until it hits the Rev limiter. It's really odd behavior, I can let off the gas completely for 1-2 seconds and then clutch in and it will still sometimes just fly up the RPMs until 7000+ with no input from me.

Anyone seen this before? I'm scratching my head over it the tuner says the logs look normal and it drives fantastic otherwise.
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Ok I have this question in with my tuner as well but I'm just curious what you guys might know.

My car is basically stock with an Edelbrock 2300 kit on it. I have a DW400 pump and JMS bap with DW95s. Note that this was happening with the EB kit out of the box and well.

What I'm seeing is this: let's say I go WOT in 3rd and want to shift at 6000rpm. Sometimes it will work normally and others as soon as I clutch in it will Spike until it hits the Rev limiter. It's really odd behavior, I can let off the gas completely for 1-2 seconds and then clutch in and it will still sometimes just fly up the RPMs until 7000+ with no input from me.

Anyone seen this before? I'm scratching my head over it the tuner says the logs look normal and it drives fantastic otherwise.
Not the same situation, but my Stage two S4 (supercharger) had a similar issue...very scary. Never fixed it, just had to live with it.

But the S4 has no way close to the power you car puts down, don't you shread the tires with WOT in third? Maybe the computer cannot keep up with the wheel spin at that speed?
 
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ForYourOwnGood

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Not the same situation, but my Stage two S4 (supercharger) had a similar issue...very scary. Never fixed it, just had to live with it.

But the S4 has no way close to the power you car puts down, don't you shread the tires with WOT in third? Maybe the computer cannot keep up with the wheel spin at that speed?
That's the thing is it only happens between gears. I know the car has a shift assist built in but the rpm should not Spike over 1000+ just because you clutch in while shifting. This is with 0 throttle input at all. It isn't constant on doing it, sometimes it will and others it won't.
 

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I wouldn't like this happening at all. I was considering this kit within a few weeks.
 
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ForYourOwnGood

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I wouldn't like this happening at all. I was considering this kit within a few weeks.
I don't think it's the kit. Something else is going on and it's just hard to track down. I just got a tune revision with the shift assist shut off so I can rule that out but my gut says either the throttle body itself is bad (oem) or the bypass valve is sticking.
 

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Ok, so it’s ONLY ever happening with the clutch pushed in and no pedal input?
Am I reading that right?
Eg. The car doesn’t go into cruise control mode at any time or show signs that it doesn’t want to decelerate at the rate you might expect if left in gear?
Just trying to clarify.
 
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ForYourOwnGood

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Ok, so it’s ONLY ever happening with the clutch pushed in and no pedal input?
Am I reading that right?
Eg. The car doesn’t go into cruise control mode at any time or show signs that it doesn’t want to decelerate at the rate you might expect if left in gear?
Just trying to clarify.
Exactly. But only after WOT. The first time I noticed it I was using 4th to pass some slow traffic and when I let off I was going to shift into 6th but in the small gap that I had the clutch in with no throttle the car managed to go from 5500 to bouncing off the limiter.
 

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Exactly. But only after WOT. The first time I noticed it I was using 4th to pass some slow traffic and when I let off I was going to shift into 6th but in the small gap that I had the clutch in with no throttle the car managed to go from 5500 to bouncing off the limiter.
The logs you showed your tuner, do they capture any of these events?
Also, are you running a pill in the bypass tube?
 
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ForYourOwnGood

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The logs you showed your tuner, do they capture any of these events?
I finally managed to catch it doing a really good one yesterday and sent it in, waiting to hear back. Doesn't seem tune related since it isn't consistent. I can repeat the same WOT pull back to back multiple times and it only happens now and again. This is leading me to a mechanical problem like something sticking.
 

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It's gotta be something either with the throttle body or tune. The bypass valve getting stuck, if anything, should slow the car down once the throttle is closed because it would still be trying to compress air without the engine driving it. If it's not flashing a CEL for throttle position my money is on the tune. Also, maybe check/clean the contacts with your throttle extension harness? When mine went out it through a CEL, but maybe a intermittent or high resistance connection is giving incorrect feedback. I'm trying to remember...you went with Lund didn't you?
 

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ForYourOwnGood

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It's gotta be something either with the throttle body or tune. The bypass valve getting stuck, if anything, should slow the car down once the throttle is closed because it would still be trying to compress air without the engine driving it. If it's not flashing a CEL for throttle position my money is on the tune. Also, maybe check/clean the contacts with your throttle extension harness? When mine went out it through a CEL, but maybe a intermittent or high resistance connection is giving incorrect feedback. I'm trying to remember...you went with Lund didn't you?
Yeah its a Lund tune and it feels on point. If it was something in the tune I could replicate it every time I would expect but I can't. I did send the logs to the tuner so they could give an opinion but he said everything looks good. I'm inclined to believe him on this. I'm suspecting the TB more because it had issues in the past with the clicking/popping and the dealer said there was no codes so they didn't want to do anything with it. I'd rather not buy a new one without upgrading so I may look into getting a bigger one.

EDIT: here is the log where it does it, I minimized it to throttle pedal, throttle actual, and RPM. You can see when throttle actual (red) starts to close which should be the ECM commanded throttle position it runs up almost 1000rpm instantly (6100-7050).
t1.jpg
 

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Yah, almost has to be the TB or connection. It sees the command to close, thinks it's closing, but actually revs up. It's also very telling that the point where it thinks it's closing EXACTLY corresponds to where it starts to rev.
 

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I agree with the “something is sticking” theory. My guess would be the throttle body...
 

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Actually, I’d maybe shoot @EBtech a message and ask if it could possibly be the bypass valve. The revs increase because the load to push the car is gone (clutch in) but the throttle body is still open or the bypass valve is stuck and allowing boost still. I’d look at those 2 things mechanically.

Did you move or play with the bypass valve during install? Warning sticker on it not to move it...
 

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Three questions, is this an OE throttle body, do you have a catch can setup of some sort, and do you have long tube headers?

Something isn't playing nice with the OE rev hang programming which of course is an emissions strategy. It might be reliant on the MAP sensor seeing manifold vacuum before closing the throttle, which it won't see under boost until the throttle is actually closed or some other parameters are met.

I'd start by smoke testing for a vacuum or intake leak and go from there.
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