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Irregular idle on Deceleration

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Old 01-29-2010, 11:46 PM   #1
simplexdesign
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Default Irregular idle on Deceleration

I recently starting having a problem with my RPM Idle and was wondering if anyone else has shared the same problem and has any info. It usually happens when I am slowing down and I put the car in neutral the rpms will go down and then start jumping around under and over 1k without applying the gas pedal at all. At high speeds slowing down quickly with make the Rpms drop so low the car will shut off. The only real motor mod is a tune and intake by brenspeed running a 91 octane tune with exhaust work.
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Old 01-30-2010, 12:05 PM   #2
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If you recently reinstalled the tune or disconnected the battery, then drive around for 20 miles or so, and see if that clears things up.
If it still happens, then there's a procedure in the battery maintenance section of the owner's manual that addresses an erratic idle.

If you did not reinstall the tune or disconnect the battery, then make sure all of the air intake connections are secure.
If they're ok, then clean the MAF sensor and TB.
If no luck, then either the TPS or TB may be bad.
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Old 01-30-2010, 04:16 PM   #3
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Quote:
Originally Posted by ski View Post
If you recently reinstalled the tune or disconnected the battery, then drive around for 20 miles or so, and see if that clears things up.
If it still happens, then there's a procedure in the battery maintenance section of the owner's manual that addresses an erratic idle.

If you did not reinstall the tune or disconnect the battery, then make sure all of the air intake connections are secure.
If they're ok, then clean the MAF sensor and TB.
If no luck, then either the TPS or TB may be bad.



The Battery was discounted when it was back in the bodyshop a few weeks ago but it has been driven well over 20 miles and is still doing it
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Old 01-30-2010, 04:55 PM   #4
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You should be asking Brenspeed. It's a tuning issue.
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Old 01-30-2010, 11:37 PM   #5
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This happens to me also. When i am slowing down for a red light and i put it in nutural the RPMs will jump around with out me applying any gas.
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Old 01-31-2010, 01:19 AM   #6
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This happens to me also. When i am slowing down for a red light and i put it in nutural the RPMs will jump around with out me applying any gas.



Glad its not just mine but now makes me more curious as to what it is. You do have the same brenspeed tune
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Old 01-31-2010, 01:16 PM   #7
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I believe some people have fixed this by cleaning their throttle body and/or the MAF sensor. Could be worth a shot...
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Old 01-31-2010, 07:16 PM   #8
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A friend of mine has a 06 gt with about 60,000 miles on it and it is bone stock and he was also telling me his car is doing the same thing when slowing down. My car is a 08 gt and only has 17000 miles on it hope it is nothing bad.

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I believe some people have fixed this by cleaning their throttle body and/or the MAF sensor. Could be worth a shot...
How should i go about cleaning it? I thought you were not really exsposted to touch the MAF sensor,
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Old 01-31-2010, 09:54 PM   #9
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How should i go about cleaning it? I thought you were not really exsposted to touch the MAF sensor,
Oh, boy. I had a feeling that questions was coming I personally have NOT done this before, so please take my advice at your own risk. I believe there is such a thing as "MAF Cleaner" that you can use (obviously) on the MAF. Likewise, I believe that there is a throttle body cleaner for cleaning the throttle boy. You're best bet is to wait for someone else to chime in here and/or search around the forums; I know it's been mentioned several times before.
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Old 01-31-2010, 10:24 PM   #10
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The same thing happened to me 3 months ago....my buddy told me to check my spark plugs and there was the problem. 4 of the 8 were completely out. I changed them and its been running like normal now.
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Old 02-01-2010, 07:24 AM   #11
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Quote:
Originally Posted by HypromanGT View Post
Oh, boy. I had a feeling that questions was coming I personally have NOT done this before, so please take my advice at your own risk. I believe there is such a thing as "MAF Cleaner" that you can use (obviously) on the MAF. Likewise, I believe that is a throttle body cleaner. You're best bet is to wait for someone else to chime in here and/or search around the forums; I know it's been mentioned several times before.


I cured this same problem by cleaning my MAF really good. i now do it every time I change the oil.

Just go to your local Autozone and buy a can of MAF cleaner. DO NOT USE THROTTLE BODY CLEANER OR ANY OTHER CLEANER. MAF specific cleaner doesnt leave any residue. Just remove the sensor and make sure you disconnect the wiring harness before spraying it. Spray it down really good and give it a few minutes to dry thoroughly. Replace and you're good to go!


To the OP, you may also try bumping up your idle speed by 50-100 rpms using your programmer. My SCT2 allows me to adjust the driving idle and neutral idle. i had to do this for my BAMA tune a while back.

Good luck!
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Old 02-01-2010, 09:23 AM   #12
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DO NOT USE THROTTLE BODY CLEANER OR ANY OTHER CLEANER.
Good luck!
Yeah, you're absolutely right. Looking back on my post, I wasn't nearly clear enough (and there was a typo that made it even worse). My intention was to say:

1. Use MAF cleaner for the MAF.
2. Use TB cleaner for the TB.

I'll edit my previous post to make it clearer.
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Old 02-01-2010, 10:40 AM   #13
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Oh, gotcha. I'm notorious when it comes to typos so I understand.
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Old 02-05-2010, 08:11 PM   #14
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Cleaned my MAF sensor(Wasnt very dirty), took out battery, re-installed tune and I am still having the problem. I am thinking about doing the sparks soon even though there is only 24k on the car I figure its good to get the motorcraft ones out now anyway. Anymore ideas if the sparks dont work?
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Old 03-23-2010, 03:38 PM   #15
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Still having the Problem and any help would be greatly appreciated. At this point I have Cleaned the MAF Sensor, Cleaned the Throttle Body, Changed the Spark Plugs, Changed the Fuel Filter, Took out Battery and Re-Installed my Brenspeed 93 tune
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Old 03-23-2010, 04:57 PM   #16
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CRC MAF cleaner, dont brush or wipe it just spray it according to diections on the can....CRC Throttle body cleaner again read label to be sure it is safe for the coated TB's like ours. Both can be found at NAPA and are what I use on mine. Disconnect the battery before doing any maintenance, I would invest in haynes or chiltons manual as well. If I remember correctly the MAF uses 2 #20 torx screws and the TB is 2 8mm bolts and 2 10mm nuts(deep socket).
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Old 03-23-2010, 07:32 PM   #17
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CRC MAF cleaner, dont brush or wipe it just spray it according to diections on the can....CRC Throttle body cleaner again read label to be sure it is safe for the coated TB's like ours. Both can be found at NAPA and are what I use on mine. Disconnect the battery before doing any maintenance, I would invest in haynes or chiltons manual as well. If I remember correctly the MAF uses 2 #20 torx screws and the TB is 2 8mm bolts and 2 10mm nuts(deep socket).


I hate when people do not read thru threads thoroughly or at all for that matter. This has all been done like I stated ^^^
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Old 03-23-2010, 07:57 PM   #18
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Still having the Problem and any help would be greatly appreciated. At this point I have Cleaned the MAF Sensor, Cleaned the Throttle Body, Changed the Spark Plugs, Changed the Fuel Filter, Took out Battery and Re-Installed my Brenspeed 93 tune
Long shot, but can also check for any vacuum leaks, and/or clean the air filter. Check the bolts attaching the intake if you've added the delete plates. Also, check the mounting screws for your MAF.
Usually the idle issue ends up being a dirty throttle body, have you also cleaned the side behind the butterflies?
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Old 03-24-2010, 03:27 AM   #19
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Long shot, but can also check for any vacuum leaks, and/or clean the air filter. Check the bolts attaching the intake if you've added the delete plates. Also, check the mounting screws for your MAF.
Usually the idle issue ends up being a dirty throttle body, have you also cleaned the side behind the butterflies?



Haven't really checked any vacuum lines. Cleaned Air Filter, All bolts are tight, The Throttle body got completely taken off and cleaned.

If my MAF sensor was just bad for whatever reason I am sure it would be throwing a code?
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Old 03-24-2010, 12:46 PM   #20
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how about changing the throttle position sensor on the throttle body? I fixed an idle issue on another car by doing this. It was a pretty easy/cheap swap.
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Old 03-24-2010, 12:46 PM
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