Idle fluctuation question?
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Instructor
Joined: Mar 2007
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From: Casper WY
Idle fluctuation question?
I have an idle question. When I am coming to a stop and push in my clutch sometimes my cars idle will fall down to a few hundred rpm's and then catch itself and rev back up and then fall and rev several times till it evens out at 650rpm when at normal operating temp. It doesn't do it every time so I am stumped? Car info is: 2005 C6 M6 w/ forged 402 stroker motor. Vararam, tb spacer, cnc ported and hand finished LS3 heads and intake, lg longtubes etc. I have put about 1500 miles on the engine now and would assume if the computer was going to adapt it would have by now. So what causes this? is it not getting enough idle air to compensate for the extra fuel injected in the motor? What is most confusing is that it does it erratically. One time it idles down and almost dies or does occasionally or it just acts normal? Any help would be appreciated......Craig
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From: Casper WY
Mine has been with a/c off mostly. Already cool weather here in Wyoming. My tuner told me that the computer would adapt and learn rather quickly. I am thinking that 1500 miles should be long enough? Also the fact that it only does it about 30% of the time? So if it was in the tuning will the computer not be able to learn it and adapt correctly? It is just hard to make it back to my tuner which is 5 hours one way for a retune right now?
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From: Casper WY
Where would air be leaking in? How is the best way to test that? I will check this and if it doesn't improve I will have to make a trip. Was hoping it might be something simple that I could fix myself.
Le Mans Master
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From: N Carolina 08 Z51 Coupe
I don't know what intake you have or other mods.. but if there is an air leak that affects the MAF, the engine will not run correctly. Look at the intake parts and make sure there are no air leaks.. You can sometimes hear a leak sucking air.. make sure all the connections are air tight and the wiring connectors are on correctly. You should also check to see if there are any engine code logged. This could help you pin point the problem. Not all error codes set off the CEL.
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Melting Slicks
Joined: Aug 2006
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From: Powell TN
Cruise-In VIII Veteran
Stock cam?
What it "learns" is fuel trims. If it was tuned correctly, it should not have to even learn these. Fuel trims will only take about 100 miles to learn.
Oh, and take the throttle spacer out.
What it "learns" is fuel trims. If it was tuned correctly, it should not have to even learn these. Fuel trims will only take about 100 miles to learn.
Oh, and take the throttle spacer out.
Last edited by 'VETTE PHASE; Oct 19, 2008 at 09:25 PM.
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From: Lakewood Ranch, FL
I have an idle question. When I am coming to a stop and push in my clutch sometimes my cars idle will fall down to a few hundred rpm's and then catch itself and rev back up and then fall and rev several times till it evens out at 650rpm when at normal operating temp. It doesn't do it every time so I am stumped? Car info is: 2005 C6 M6 w/ forged 402 stroker motor. Vararam, tb spacer, cnc ported and hand finished LS3 heads and intake, lg longtubes etc. I have put about 1500 miles on the engine now and would assume if the computer was going to adapt it would have by now. So what causes this? is it not getting enough idle air to compensate for the extra fuel injected in the motor? What is most confusing is that it does it erratically. One time it idles down and almost dies or does occasionally or it just acts normal? Any help would be appreciated......Craig
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From: Casper WY
No, it is a pretty aggressive cam. Has some lope to it. Not exactly sure the specs right now? Also the tb spacer? How would taking that out help? It never did this before with it in. I thought it only increased the volume of air?
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From: Casper WY
I don't have HP tuners but thanks. I Checked all the plugs and stuff last night when I did my second break in oil change for the new motor. Everything seems to be good. Didn't hear any sucking sounds but my car is pretty loud so if it was small it could easily be missed. I guess I will have to make a road trip sometime and see if it can be retuned.
Melting Slicks
Joined: Aug 2006
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From: Powell TN
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From: Casper WY
OK, well I guess that means a trip back to my tuner. Weather in Wyoming is pretty bad this time of year anyway so maybe I should just drop it off and have the Procharger installed at the same time? Thanks for all the input everyone....Craig
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St. Jude Donor '08 thru '13
I don't know what intake you have or other mods.. but if there is an air leak that affects the MAF, the engine will not run correctly. Look at the intake parts and make sure there are no air leaks.. You can sometimes hear a leak sucking air.. make sure all the connections are air tight and the wiring connectors are on correctly. You should also check to see if there are any engine code logged. This could help you pin point the problem. Not all error codes set off the CEL.
If you're spraying, and the thing about dies, you've found something leaking.
GL
scotty
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From: Casper WY
Well the weather here in Wyoming got quite cold and I have been really busy. I hadn't started my car in several weeks and went to start it a few nights ago and it was dead. Totally dead. I figured being an 05 it was about time for a new battery anyway so I went and bought an Optima red top dry cell battery. After installing it I started it and drove it to charge the battery fully. Shazaaam. Guess what. All idle problems are gone! It has no fluctuation, doesn't die, acts exactly as it is supposed too! I can't believe that is all it took to rectify the problem. Either the battery wasn't putting out enough juice to run the idle speed controller correctly or just unhooking the battery reset the parameters in the computer? One way or the other it is fixed and I am very happy. Figured I would share just in case this happens to someone else.
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Joined: Mar 2003
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
The base minimum running airflow table is incorrect and needs an adjustment. The computer doenst learn that and needs to be tuned.
I am really surprised at the number of things people think the computer does on its own. Adjusting for bolt-ons such as air cleaners and headers comes up the most and it just isnt going to happen. Things like that are major and require tuning.
I am really surprised at the number of things people think the computer does on its own. Adjusting for bolt-ons such as air cleaners and headers comes up the most and it just isnt going to happen. Things like that are major and require tuning.