replaced IAC, still revving to 2k?
07-23-2012, 03:25 PM
#1
Staging Lane
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replaced IAC, still revving to 2k? I made a thread a while back asking for help with an issue i was having when pulling the car out of gear while coming to a stop. It always revs to 2k rpm when i go into neutral and then comes back down to idle (950rpm) after i have been stopped for about 5-10 seconds. I replaced my IAC sensor (old one was gunked up bad) and cleaned out the housing with TB cleaner and a toothbrush. I also replaced a few vacuum lines that I noticed were pretty worn. I have noticed a difference since then but the car is still revving to 2k like before. Could an exhaust leak or vacuum leak cause this? Any suggestions would be great.
My ses light did come on today for a random misfire so I pulled the info and am not sure what all of it means to be honest. If anyone can enlighten me some on this info that would be great cause the -13.3 has me wondering
STFT B1- 3.1
LTFT B1- -13.3
STFT B2- 0
LTFT B2- 3.1
MAP- 12.2
RPM- 1310
MAF lb/min- 2
TPS- 2
My ses light did come on today for a random misfire so I pulled the info and am not sure what all of it means to be honest. If anyone can enlighten me some on this info that would be great cause the -13.3 has me wondering
STFT B1- 3.1
LTFT B1- -13.3
STFT B2- 0
LTFT B2- 3.1
MAP- 12.2
RPM- 1310
MAF lb/min- 2
TPS- 2
07-25-2012, 07:23 PM
#4
I would guess it is your TB not closing all the way. I have a Holley that had a similar problem. Look at them and see if that is the problem. I actually had to carefully file the throttle blades so they closed fully. Oil the shaft good too.
07-25-2012, 07:34 PM
#5
I tend to disable the LTFT Long term fuel trims and go off of STFT's only.
What the -13 is saying is the engine is running rich on that bank and the 02 sensor is pulling 13% fuel out of that bank.
Vac leak doesn't seem likely considering its running "rich" opposed to lean.
Was it showing 2% TPS at idle?? If so do a TPS reset, unplug TPS/IAC then key on, key off plug back in, should say 0% at idle then.
Was the car recently tuned??
Seems like an airflow issue, with too much airflow between the Park and drive Base running airflow tables.
What the -13 is saying is the engine is running rich on that bank and the 02 sensor is pulling 13% fuel out of that bank.
Vac leak doesn't seem likely considering its running "rich" opposed to lean.
Was it showing 2% TPS at idle?? If so do a TPS reset, unplug TPS/IAC then key on, key off plug back in, should say 0% at idle then.
Was the car recently tuned??
Seems like an airflow issue, with too much airflow between the Park and drive Base running airflow tables.
07-26-2012, 08:17 AM
#7
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I'm dealing with this same issue on my lt1 with 24x conversion. Idles high at start then eventually settles down. Idles high whole rolling then goes down when I stop. I'm hopefully finishing the tuning on mine this weekene
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08-03-2012, 03:42 PM
#9
Same damn deal. Been chasing my tail for months. My tuner even worked on the tune for a while with no luck (very reputable tuner also). I swear to god, every forum I have read regarding this problem, from 10 different forums, it is NEVER resolved. Supposidly some people believe it is an issue with particular GM ECU's. Its god damn embarrising, especially when your car is as loud as mine.
08-03-2012, 03:48 PM
#10
Same damn deal. Been chasing my tail for months. My tuner even worked on the tune for a while with no luck (very reputable tuner also). I swear to god, every forum I have read regarding this problem, from 10 different forums, it is NEVER resolved. Supposidly some people believe it is an issue with particular GM ECU's. Its god damn embarrising, especially when your car is as loud as mine.
08-04-2012, 02:29 PM
#12
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I also have this issue. It started after I got it tuned. However while my PCM was out of the car I removed AIR pump, EGR, and replaced header gaskets, and put chrome valve covers on. So I am unsure of what could be the issue. TPS is set right at .70 and have new IAC. If it is the tune, what part the tune is wrong, and is it safe to drive it?
I definately don't have a vacuum leak as I have replaced all hoses.
Plus the exhaust smells like **** (always has though, maybe the fact I have no cats?)
I definately don't have a vacuum leak as I have replaced all hoses.
Plus the exhaust smells like **** (always has though, maybe the fact I have no cats?)
08-05-2012, 06:15 PM
#14
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Okay, I'll change the TPS angle and reset the TPS.
Is it safe to drive it like this or is there a chance this is also robbing me of any horsepower?
Thanks for your help.
Is it safe to drive it like this or is there a chance this is also robbing me of any horsepower?
Thanks for your help.
08-06-2012, 06:21 AM
#15
Staging Lane
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ok sorry guys I didn't realize that anyone finally replied. It very well could be the tune. I was told by a guy who knew previous owner that I should get a tune but car never had any problems until this. I didn't reset IAC, didnt know you could, but will do so after work today. I did have the TB off recently and the blades do close all the way. The car has 3.73 gears. The car does idle high at start up. One question I have is, if it is in the tune why did this just become a problem a year after I bought the car? I do DD this so it gets driven everyday. Thanks for the replies, good to know I'm not the only one with this problem
08-09-2012, 08:04 PM
#16
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I have had a similar issue with my Edelbrock 52mm TB. It starts and revs slowly from 1000 to 1350-1400 then settles down around 1000-1100 cold in gear. It also begins to "whistle" which I've heard Edelbrocks and BBKs do this. I've heard several theories including that the TB needs a hole drilled in the butterflys to help get more air in at idle versus setting the blades to open more at idle(which seems like it would rev up on start and stay high at idle). Is everyone that is having this problem running an aftermarket TB? Maybe this has to do with not enough air coming through the IAC passages at idle? Or maybe the TPS just is not set right?
08-09-2012, 11:51 PM
#17
Same damn deal. Been chasing my tail for months. My tuner even worked on the tune for a while with no luck (very reputable tuner also). I swear to god, every forum I have read regarding this problem, from 10 different forums, it is NEVER resolved. Supposidly some people believe it is an issue with particular GM ECU's. Its god damn embarrising, especially when your car is as loud as mine.
08-10-2012, 04:57 PM
#18
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had the same issue with mine had it tuned and 6 months later mine was jumping up to 3,000 rpms when i pushed in clutch or before i came to idle super super annoying, I stopped driving it cause it pissed me off lol.. its def your tune though
08-10-2012, 05:36 PM
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You mentioned you had the TB off recently, could have a leak where the TB meets the intake manifold or your pulling in some air after your MAF on the elbow. But then again your running rich so I could be way off.
08-16-2012, 01:00 PM
#20
Staging Lane
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ok guys I reset the IAC & TPS and no change. This all started when the stock TB was on the car (did have air foil) and hasn't changed between a new TB and IAC sensor. My rubber intake hose from the filter to TB does have a bad rip in it right where it meets the TB, wonder if this is a factor. I will be getting the car re-tuned once I get longtubes put on. The car does run really rich right now but always has and it recently started to have trouble under load mainly in the low rpm range. once i get past 2krpm in 1st and 2nd it clears up but any time I get over 2krpm in any gear except 6th it backfires pretty bad. Im hoping that new plugs and wires this weekend will help out with some of that. thanks for all the replies guys.