Help-trying to troubleshoot surging/bucking
12-12-2015, 01:30 PM
#1
Melting Slicks
Thread Starter
Help-trying to troubleshoot surging/bucking
im working on a friends 2009 Z06. We pulled the heads and had the guides replaced and new exhaust valves put in, then put roller tip rockers on it. we put it all back together and went to drive it home and the thing surges/bucks like crazy when speed levels off. during acceleration the car runs perfect. Its just while cruising and maintaining speed. It does this no matter what gear im in and no matter what RPM. Im looking for somewhere to look at the tune to see if thats the issue. we checked compression and all 8 cylinders are 170-175# and reaplaced the plugs,wires, passenger O2 extension and sensor. we noticed the timing erradically jums from 18 to 47 during cruise and the passenger side O2 doesn't oscelate like the other side during cruise. it just flat lines at 80mV
he said this problem did not exist before we pulled the heads and had them re done
he said this problem did not exist before we pulled the heads and had them re done
Last edited by Mallett Z; 12-14-2015 at 01:34 PM.
12-12-2015, 02:03 PM
#2
Melting Slicks
Thread Starter
Looking at the scan some more I see that the short and long term fuel trims for bank 2 are both at 0 the whole time.
12-12-2015, 04:34 PM
#3
Safety Car
Have you triple checked that everything is plugged in well? The small plug on the engine coolant temp on the driver's side head is easy enough to miss.
Can you share the log?
Last edited by sevinn; 12-12-2015 at 05:12 PM.
12-12-2015, 09:36 PM
#4
Melting Slicks
Thread Starter
When I get in front of a computer instead of my phone I will figure out how to post the scan file on here. Or I can email it to you.
12-13-2015, 09:51 PM
#5
Race Director
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St. Jude Donor '15
PM me your email address and I'll take a look at the log.
The other obvious question is are there any codes?
The other obvious question is are there any codes?
Last edited by schpenxel; 12-13-2015 at 09:52 PM.
12-13-2015, 10:59 PM
#6
Safety Car
I thought I remember something in the OP mentioning the STFTS, and that's why I mentioned anything about closed loop...but anyhow it seems to be going into closed loop, because he is getting ltfts on both banks in the log but only getting stfts on one bank. Pretty strange.
Last edited by sevinn; 12-13-2015 at 11:00 PM.
12-13-2015, 11:06 PM
#7
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St. Jude Donor '15
Pretty sure when it goes to different fuel trim cells it would go to whatever long term fuel trim values it has in memory if it's got nothing else to go on. So that might be what's going on there
12-14-2015, 12:28 AM
#8
Melting Slicks
Thread Starter
12-14-2015, 12:48 AM
#9
Le Mans Master
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St. Jude Donor '13-'14-'15
A flatlined 02 sensor means that it has stopped working----and the fuel trims on that side are all askew---- I would replace it or both---also make sure you haven't mistakenly got the right and left pigtails mixed up very common also if you have deleted the cats make sure you didn't plug the rear pigtails onto the front locations as they will reach
Erratic P/T fueling is normally not a timing issue but a fueling issue caused by the front 02's---as the front 02's control ALL the P/T fuel and are extremely important
Erratic P/T fueling is normally not a timing issue but a fueling issue caused by the front 02's---as the front 02's control ALL the P/T fuel and are extremely important
12-14-2015, 08:28 AM
#10
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St. Jude Donor '15
His aren't flat lined in the screenshot.
I'd still replace them to be sure they aren't causing issues. Like tblu said.. they are extremely important for part throttle fueling.
I'd still replace them to be sure they aren't causing issues. Like tblu said.. they are extremely important for part throttle fueling.
12-14-2015, 11:54 AM
#11
Melting Slicks
Thread Starter
got it figured out. There must a short in the rear O2 sensor. The CEL's for both rears are disabled so it wasn't throwing codes for them. I unplugged the rears and just went on a test drive and it is completely normal. Both O2 are functioning propery now and no surging.
schpenxel, tblu92, SEVINN, Thank you very much for the help!
schpenxel, tblu92, SEVINN, Thank you very much for the help!