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rpms hanging up

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Old Jun 23, 2011 | 04:44 PM
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Default rpms hanging up

When I'm driving around and I push in clutch to come to stop. My rpms hang up at the rpms at at when the clutch gets pushed in. If I tap the throttle the rpms will come down normal.

Would any one know what would cause this issue. Thanks for any help.
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Old Jun 23, 2011 | 05:36 PM
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most usual cause would be maf, iac, tps, or vac leak. i would start by pulling the iac and see if it's carboned up. also check the port for the iac in the throttle body for carbon build up, it could be getting stuck to far open or even going bad.
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Old Jun 23, 2011 | 06:07 PM
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It has a brand new 90mm fast tb. And its speed density tuned. So it would have to be one of the sensors in the tb.

Could it be the throttle cable getting worn out.
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Old Jun 23, 2011 | 06:10 PM
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Problem started when you swapped the tb? Then that's where you look. It could be a misaligned throttle blade that's hanging up. Very common.
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Old Jun 23, 2011 | 06:45 PM
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I have the same problem. Cleaned my MAF and IAC and got nothing..
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Old Jun 23, 2011 | 07:46 PM
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The tb snaps closed with out a hick up. When off intake.
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Old Jun 23, 2011 | 11:02 PM
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if you just changed the throttle body, you should do a tps relearn.
1) with key off unplug tps.
2) turn key on while unplugged but do not start.
3) turn key off and plug tps back in.
4) start your car.
what this does is it will reset your throttle position back to 0%. you will need a scan tool/scanner to confirm that you are at 0% throttle position and while you are looking make sure your tps voltage is around .57 when your at 0% tp.
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Old Jun 24, 2011 | 08:39 AM
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i have the same problem!
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Old Jun 24, 2011 | 12:05 PM
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I changed more then just the tb. I installed a lq4 motor with the l76, l92 set up and dyno tuned.

Do u think I should do the tsp reset?
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Old Jun 24, 2011 | 05:42 PM
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damn, i would think that it would have been done when they tuned it. i would check the tps voltage and % just to be sure it's set right.
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Old Jun 24, 2011 | 09:48 PM
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It's weird is that doesn't do it every time. And when driving around with it in gear it will keep driving like the cruise control is stuck on. I don't have to hit the gas. And I took off the cruise control cable
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Old Jun 24, 2011 | 10:00 PM
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to me it realy sounds like your throttle body needs to be adjusted. this could also be tune related though. after you check it out with a scanner you may want to post in the tuning section and see what kind of results you get. did you just get it tuned? have you talked with the shop that tuned your car?
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Old Jun 25, 2011 | 01:05 AM
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No got it tuned at last year. Then now to seem to be getting worse with each day. Tomorrow I'm going to pull the sensors and tb off and play with it. I'll let u know what I find
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Old Jun 25, 2011 | 09:43 AM
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My car does the same exact ****. It kinda bucks at low rpms as well. Last time it did this the drivers side o2 sensor was going out. Replaced it and everything went back to norm. Now its doing it again, so I am gonna go ahead and replace the passenger side and see what happens.
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Old Jun 25, 2011 | 03:43 PM
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Vacuum leak is likely.
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Old Jun 25, 2011 | 03:57 PM
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I bet it is the 90mm fast tb, mine did the same thing until it didn't want to stop revving. The spring system is to weak on those 90mm. Bought a 92 mm and haven't had a problem since. 92 mm have a two springs to move the blade back and forth.
HOPE THIS HELP, before you hurt yourself trying to stop and it don't want to.
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Old Jun 27, 2011 | 03:10 PM
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Originally Posted by LS1WS6dreamer
My car does the same exact ****. It kinda bucks at low rpms as well. Last time it did this the drivers side o2 sensor was going out. Replaced it and everything went back to norm. Now its doing it again, so I am gonna go ahead and replace the passenger side and see what happens.
how did you know it was going out?
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Old Jun 28, 2011 | 08:52 PM
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When the drivers side went out it was throwing a code and I went to O'reillys and checked it. I was getting the flashing SES light, and bad surging at low rpm cruising speeds.
As far as a vacuum leak being the issue. I am not sure because the car sometimes idles fine and then bad. Usually doesn't do it till it gets good and warmed up and that is when the 02 sensors would screw up the worst the first time one went out. Either way with high mileage it ain't gonna hurt to replace the other 02 sensor. Will be doing LT's and OR-Y around September.
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