Rough Idle
10-08-2008, 08:34 PM
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Rough Idle
Hey folks, my idle is rough. Seemed like it started right after installing a full turbo back and swapping out the ECU for a GIAC M-Box. Any ideas?
I was throwing codes for both banks running rich, 2 EGT sensors, and 1 O2. The ECU would basically cut boost at around 4k RPM, the car would buck a little bit and then act pretty gutless.
Replaced 2 EGTs + O2, and pressure tested, this seems to have fixed the problem when getting into boost, and no codes are being thrown now, but my idle still fluctuates between 500 and 1200 RPM. Usually happens for a few seconds after coming to a stop light or something like that. I didn't find any boost leaks after pressure testing. I also haven't swapped out the TBB and DVs for anything better yet, hoping to do that in a few weeks. Thanks in advance
I was throwing codes for both banks running rich, 2 EGT sensors, and 1 O2. The ECU would basically cut boost at around 4k RPM, the car would buck a little bit and then act pretty gutless.
Replaced 2 EGTs + O2, and pressure tested, this seems to have fixed the problem when getting into boost, and no codes are being thrown now, but my idle still fluctuates between 500 and 1200 RPM. Usually happens for a few seconds after coming to a stop light or something like that. I didn't find any boost leaks after pressure testing. I also haven't swapped out the TBB and DVs for anything better yet, hoping to do that in a few weeks. Thanks in advance
10-08-2008, 10:56 PM
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Sounds like possible overboost throttle cut.. Run block 115 and 03 on 3rd gear WOT to redline from
3K RPM and post your results.
When I had this with GIAC-X looked like link pic. SW update cleared it up.
Bruce<ul><li><a href="http://pictureposter.audiworld.com/44443/giac-x_boost_log_041705.jpg">GIAC-X overboost TC.</a></li></ul>
When I had this with GIAC-X looked like link pic. SW update cleared it up.
Bruce<ul><li><a href="http://pictureposter.audiworld.com/44443/giac-x_boost_log_041705.jpg">GIAC-X overboost TC.</a></li></ul>
10-09-2008, 06:16 AM
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Sorry, I have lumped two problems together here...
One problem was boost cutting around 4k RPM. That problem has been fixed with the EGTs. The car pulls perfectly smooth and runs great under boost now.
The second problem is that of the rough idle. If it's the MAF, won't it usually throw a code?
Thanks in advance
The second problem is that of the rough idle. If it's the MAF, won't it usually throw a code?
Thanks in advance
10-09-2008, 07:47 AM
#5
Bad ECT sensor and/or vacuum leak will produce rough idle w/o error code.
Also could be dirty trhottle body plate. Bad MAF or ICM's will typically throw a code. If you have a tip, also the suction pump/PCV system could be clogged and might contribute. Check other items 1st.
10-09-2008, 10:04 AM
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Post your MAF g/s at idle, your idle load percent, and tell us what blocks 015/016 show...
does your problem change if you have your clutch pedal depressed and/or your A/C compressor on?
Check for vac leaks too.
Check for vac leaks too.
10-09-2008, 08:50 PM
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I'll check out the ECT/vacuum lines this weekend...
However, if it were the ECT, wouldn't I be throwing a code for running rich? I had a code for running rich before, but since replacing them, the codes haven't come back.
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10-13-2008, 09:19 PM
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ECT Seems to be working...
Here are a couple of logs. Log 1 is from idle to operating temp. Log 2 is a quick drive to try and replicate the problem when returning to idle from driving. Before anyone asks why I didn't run it above 3.5k or so -- it's never mattered in the past. When coming to a stoplight (regardless of speed/RPM) the idle will sometimes stutter.
I put a "Mark" when the idle started to sound like crap and fluctuate. As you can see, the idle is fairly consistent but definitely has the occasional issue. There are a couple of misfires, I think 6 was the max I counted. Usually 0-2.
Check out the O2 readings at each mark. Any ideas???
Log 1:
http://spreadsheets.google.com/ccc?key=pPcDIgLbBAK6F8UFhn90KcA
Log 2:
http://spreadsheets.google.com/ccc?key=pPcDIgLbBAK5qsVF4UEoEKQ
I put a "Mark" when the idle started to sound like crap and fluctuate. As you can see, the idle is fairly consistent but definitely has the occasional issue. There are a couple of misfires, I think 6 was the max I counted. Usually 0-2.
Check out the O2 readings at each mark. Any ideas???
Log 1:
http://spreadsheets.google.com/ccc?key=pPcDIgLbBAK6F8UFhn90KcA
Log 2:
http://spreadsheets.google.com/ccc?key=pPcDIgLbBAK5qsVF4UEoEKQ
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