Need help bad, guys...misfires, surging, lean
04-05-2010, 08:05 PM
#1
Need help bad, guys...misfires, surging, lean Some of you may have seen my thread in the forced induction section (https://ls1tech.com/forums/forced-in...r-install.html), but I wanted to post over here since I've ruled out the possibility of any part of the Procharger setup being the culprit for my issues (I disconnected all the piping connecting the Procharger intercoolers to the plenum just in front of the MAF, thereby taking the system out of the equation).
Here's the status in a nutshell. Parked the car last winter, running like a top. Installed a twin intercooled Procharger setup, along with a Warlboro 255, hotwire kit, Siemens Deka 60lb injectors, catch can, and NGK TR6s gapped at .030. I also removed the AIR system. Those are the only mods that are different than the setup I parked last fall. I also installed a boost gauge, electric fuel pressure gauge, and an AEM UEGO wideband, but I don't think they have any bearing on the issues. Otherwise stock internal LS1 with 80,000 miles.
I sent my PCM to Frost to get a base tune for the 60lb injectors as well as to have the rear O2s tuned out, !AIR, gear calibration, etc. Got the PCM back, and Steve told me I was safe to drive the car and make 2-4psi, but not to go wide open throttle. No problem.
The issues from that point until now are the same...it idles OK at 900rpm cold and then settles in to 800 at operating temp, but its lean...like 15.5 on the gauge. If I give it any throttle at all, it stumbles, picks up and struggles to find a part throttle position...surging badly. If I try to hold it at 1500rpm, it might stay there for a few seconds, but then it will swing down 200-300 rpms and then surge back up. During the hesitation, the wideband goes WAY lean...like, off the scale lean. It comes back around after a few seconds, but its still only in the 15ish range...still lean. Fuel pressure shows 62psi on the gauge. I initially threw a p0300 code, but have not tripped the light since. A friend of mine did some logging on HPT which indicates the misfires are still there, though.
I emailed Steve (who's been really helpful, BTW) and his first thoughts were vacuum leak. I have checked every hose, joint, seam and connection around the manifold with no luck. I plugged every port on the PCV system to eliminate my new catch can setup, and no luck there. Double checked my connections at the brake booster where I teed in for the boost gauge/bypass valve...no dice. I even pulled the manifold to check the MAP sensor and vacuum lines in the back, and also inspected for cracks...no luck there either. Pulled the injectors, examined them, and reseated them in the intake...nothing there either. Checked the vacuum reading, and at operating temp I'm pulling 20in at idle, and it's a steady reading...very solid, and not bouncy or erratic at all. Either way, according to Steve (who I sent the datalog to), the PCM is making major adjustments for too much air at idle. That could be due to a vacuum leak, or due to the misfires passing uncombusted air through the system. Or maybe something else? Not sure there...Anyways, I've gone through an entire can of carb cleaner in my engine bay, and have found nothing to indicate a vacuum leak.
I have changed plugs, changed wires, changed O2 sensors (new), all with no luck. I have cleaned the MAF, tried a different MAF, checked the IAC (functioning properly), TPS, and even swapped the stock throttle body back on...no change. If I unplug the connections on both O2s, the idle mixture richens up to 12.6, but the car still bucks and surges, especially under load.
I am at my wits end here guys. I have no idea what else to look at. Steve has looked at my tune four times, and can't find a problem that would cause these symptoms. Anyone have any suggestions?
Here's the status in a nutshell. Parked the car last winter, running like a top. Installed a twin intercooled Procharger setup, along with a Warlboro 255, hotwire kit, Siemens Deka 60lb injectors, catch can, and NGK TR6s gapped at .030. I also removed the AIR system. Those are the only mods that are different than the setup I parked last fall. I also installed a boost gauge, electric fuel pressure gauge, and an AEM UEGO wideband, but I don't think they have any bearing on the issues. Otherwise stock internal LS1 with 80,000 miles.
I sent my PCM to Frost to get a base tune for the 60lb injectors as well as to have the rear O2s tuned out, !AIR, gear calibration, etc. Got the PCM back, and Steve told me I was safe to drive the car and make 2-4psi, but not to go wide open throttle. No problem.
The issues from that point until now are the same...it idles OK at 900rpm cold and then settles in to 800 at operating temp, but its lean...like 15.5 on the gauge. If I give it any throttle at all, it stumbles, picks up and struggles to find a part throttle position...surging badly. If I try to hold it at 1500rpm, it might stay there for a few seconds, but then it will swing down 200-300 rpms and then surge back up. During the hesitation, the wideband goes WAY lean...like, off the scale lean. It comes back around after a few seconds, but its still only in the 15ish range...still lean. Fuel pressure shows 62psi on the gauge. I initially threw a p0300 code, but have not tripped the light since. A friend of mine did some logging on HPT which indicates the misfires are still there, though.
I emailed Steve (who's been really helpful, BTW) and his first thoughts were vacuum leak. I have checked every hose, joint, seam and connection around the manifold with no luck. I plugged every port on the PCV system to eliminate my new catch can setup, and no luck there. Double checked my connections at the brake booster where I teed in for the boost gauge/bypass valve...no dice. I even pulled the manifold to check the MAP sensor and vacuum lines in the back, and also inspected for cracks...no luck there either. Pulled the injectors, examined them, and reseated them in the intake...nothing there either. Checked the vacuum reading, and at operating temp I'm pulling 20in at idle, and it's a steady reading...very solid, and not bouncy or erratic at all. Either way, according to Steve (who I sent the datalog to), the PCM is making major adjustments for too much air at idle. That could be due to a vacuum leak, or due to the misfires passing uncombusted air through the system. Or maybe something else? Not sure there...Anyways, I've gone through an entire can of carb cleaner in my engine bay, and have found nothing to indicate a vacuum leak.
I have changed plugs, changed wires, changed O2 sensors (new), all with no luck. I have cleaned the MAF, tried a different MAF, checked the IAC (functioning properly), TPS, and even swapped the stock throttle body back on...no change. If I unplug the connections on both O2s, the idle mixture richens up to 12.6, but the car still bucks and surges, especially under load.
I am at my wits end here guys. I have no idea what else to look at. Steve has looked at my tune four times, and can't find a problem that would cause these symptoms. Anyone have any suggestions?
