CT05Legacy Posted July 19, 2016 Share Posted July 19, 2016 I've recently completed a rebuild of my 2005 LGT engine due to a burnt exhaust valve on cylinder 2. The car feels like it's driving fine. Idle is pretty good. No surging or stuttering. But about 40 miles on the rebuild and it threw the P0171 code. I've focused on trying to find vacuum leaks, but I haven't found it yet. I reseated the intercooler on the turbo compressor outlet after a smoke test revealed something in that area (didn't see smoke but could smell the cigar I used to generate the smoke). But after reseating and a reduced/gone cigar odor in that area, AF Learning #1 A, B, and C are still all over 14. (AF Learning #1 D is at 0.0.) I still can't pinpoint the leak, even using the sticky as a guide (http://legacygt.com/forums/showthrea...de-235626.html). I'm also trying to stay out of boost to go easy on the engine at first. I'm hoping to get some help with solving this. Any tips, maybe some in-person help, or a good referral to a shop. (The local dealer said they'd charge about 270 for a smoke test). I'm also open to the idea of it being an exhaust leak (but I imagine it would be large and audible), a bad front O2 sensor or a bad MAF sensor (but not sure how to find out if they are known bad from logs). I can post some logs if that would help as well. What would be the best parameters to capture and what driving conditions? I'm at about 90 miles on the rebuilt engine. I want to get this solved before I accumulate any lasting damage. I'm in the New Haven, CT area. Thanks for the help in advance! Link to comment Share on other sites More sharing options...
SBT Posted July 21, 2016 Share Posted July 21, 2016 Bump. - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
jeannie Posted July 22, 2016 Share Posted July 22, 2016 I'm having the same problem with my car. I took it in to a shop they told me it was the fuel pressure regulator so I got that fixed. Still have the code put a new MAF sensor in new air filter. I fixed a exhaust leak. It's still there! It's making me crazy lol. So if you find something out please let us know Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
apexi Posted July 22, 2016 Share Posted July 22, 2016 There's EFI in Bethel, but I'm not sure if that's too far from New Haven. http://www.efilogics.com/ Link to comment Share on other sites More sharing options...
CT05Legacy Posted July 23, 2016 Author Share Posted July 23, 2016 There's EFI in Bethel, but I'm not sure if that's too far from New Haven. http://www.efilogics.com/ I've tried calling them. No answer. Left a VM and no callback yet. I'll keep trying. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Max Capacity Posted July 24, 2016 Share Posted July 24, 2016 I've tried calling them. No answer. Left a VM and no callback yet. I'll keep trying. Sent from my iPhone using Tapatalk You do realize its the weekend.... Have you ever replaced the front O2 sensor ? Seems mine go every few years. Read JmP's sticky up top to find out which ones we use. It simple to replace. In fact, the last time mine through the CEL I knew what the problem was before I read the code. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
JF1GG29 Posted July 24, 2016 Share Posted July 24, 2016 Also chasing P0171 - my issue isn't the front O2 sensor, changed it but didn't do anything. I don't have anything to log fuel trim, but in pretty sure I have a post MAF intake leak. At low rpm on light throttle, fueling seems wonky and the car bucks until I'm over 2k rpm or heavier on the gas. Fwiw, my CEL only comes on after 45 minutes on the highway, never around town, no matter how much time or how many miles. Link to comment Share on other sites More sharing options...
Max Capacity Posted July 24, 2016 Share Posted July 24, 2016 What brand O2 sensor ? 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
JF1GG29 Posted July 25, 2016 Share Posted July 25, 2016 Not OP, but I replaced the front O2 sensor with a Denso unit. Link to comment Share on other sites More sharing options...
CT05Legacy Posted July 25, 2016 Author Share Posted July 25, 2016 You do realize its the weekend.... Have you ever replaced the front O2 sensor ? Seems mine go every few years. Read JmP's sticky up top to find out which ones we use. It simple to replace. In fact, the last time mine through the CEL I knew what the problem was before I read the code. I had called EFI a few times during the week, not over the weekend. At any rate, I'll try them again this week. I struggle to believe it's the front O2 / A/F sensor. There's no A/F sensor codes that came along with the P0171. Over the weekend, I've also looked at the A/F sensor signal and it seems to be responding as expected. I'll post some logs of snap throttle at idle when I get the chance. This weekend I've tried flowing low psi air into the air intake boot (post MAF) and sprayed soapy water around the intake and vacuum hose areas. Nothing obvious although I'm sure I missed some spots that are hard to reach. I plan to investigate the fuel pressure this week. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
ehsnils Posted July 26, 2016 Share Posted July 26, 2016 Also chasing P0171 - my issue isn't the front O2 sensor, changed it but didn't do anything. I don't have anything to log fuel trim, but in pretty sure I have a post MAF intake leak. At low rpm on light throttle, fueling seems wonky and the car bucks until I'm over 2k rpm or heavier on the gas. Fwiw, my CEL only comes on after 45 minutes on the highway, never around town, no matter how much time or how many miles. Check fuel pressure - you may have a failing fuel pump or the fuel filter may be clogged. If that's OK, then it's going to be more complicated. And be careful since the engine running lean may result in burnt valves. Link to comment Share on other sites More sharing options...
CT05Legacy Posted July 26, 2016 Author Share Posted July 26, 2016 I logged some data last night. I logged at idle and then snap throttle at idle both with my previous ROM and then with a break in ROM. Fuel trims at idle are high for both. And the snap throttle tends to show a properly working front O2 / A/F sensor I think. Is there anything else to take away from this data? Next steps?OldTune_Idle_romraiderlog_20160725_222415.csvOldTune_Idle_Snaps_romraiderlog_20160725_222526.csvBreakInTune_Idle_romraiderlog_20160725_224131.csvBreakInTune_Idle_Snaps_romraiderlog_20160725_224608.csv Link to comment Share on other sites More sharing options...
JF1GG29 Posted July 27, 2016 Share Posted July 27, 2016 Check fuel pressure - you may have a failing fuel pump or the fuel filter may be clogged. If that's OK, then it's going to be more complicated. And be careful since the engine running lean may result in burnt valves. Thanks for the tip; will add to the list! Link to comment Share on other sites More sharing options...
CT05Legacy Posted July 27, 2016 Author Share Posted July 27, 2016 I think I made some progress tonight, but not sure if I'm out of the P0171 woods yet. Tonight I switched the K&N panel filter out for a new paper filter. I took some logs and didn't see much difference compared to what I had last night. But then I cleaned the MAF sensor. THere was certainly a difference. AF Correction #1 started to go negative and take away fuel and ended up bringing down the AF Learning #1 a little bit. AF Correction #1 settled out around 0.78 and the AF Learning #1 started at around 14.8 and settled out around 6.25. So it still wants some fuel at idle but things are headed in the right direction. Should I expect to see both AF Correction #1 and AF Learning #1 at almost 0 at idle? I attached the logs if anyone is interested, one at idle and one of throttle snaps at idle. I'm planning to drive the car in the morning gently and see what the other AF Learning values come out to be. Hopefully I'll get some logs at cruise too. The original P0171 CEL came on in closed loop, 36mph, 2248 rpm, and 30.93 g/s MAF.BreakInTune_paperairfilt_cleanMAF_Idle_romraiderlog_20160726_233629.csvBreakInTune_paperairfilt_cleanMAF_Idle_Snaps_romraiderlog_20160726_234101.csv Link to comment Share on other sites More sharing options...
ehsnils Posted July 27, 2016 Share Posted July 27, 2016 I think I made some progress tonight, but not sure if I'm out of the P0171 woods yet. Have you checked the injectors so they are good and not mismatched? A mismatched set of injectors can cause headache. Link to comment Share on other sites More sharing options...
CT05Legacy Posted July 27, 2016 Author Share Posted July 27, 2016 Have you checked the injectors so they are good and not mismatched? A mismatched set of injectors can cause headache. What do you mean by mismatched? Some flowing well and others not? With a screwdriver, I can here them all ticking away. I'm not sure what I would do otherwise to ensure they are not mismatched. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
ehsnils Posted July 27, 2016 Share Posted July 27, 2016 What do you mean by mismatched? Some flowing well and others not? With a screwdriver, I can here them all ticking away. I'm not sure what I would do otherwise to ensure they are not mismatched. Yes, exactly - some flowing well, others not. And you need a test bench to check them. Or you have an injector that don't close well and instead drips additional fuel. Another factor is the pattern of the spray. It shall atomize (well not really since the molecules aren't cracked) well and give a good fine even mist resulting in a good mix of air and fuel. Just like you can create a mist with your garden hose or just let it pour. http://1.bp.blogspot.com/_DPYNwBLhZb4/TKmzgt2eqMI/AAAAAAAAAFA/jiXzDqnQ9bw/s1600/injector+spray+pattern.jpg Injectors ages due to deposits and mechanical wear, so checking them, cleaning if possible and if not possible replacing them with a matched set will keep the engine healthy, give more power, put less strain on the cat and give you a better fuel economy. Just because you hear them tick doesn't mean they are good, just that they are electromagnetically operating. But it can be like a relay with burnt contacts - it still ticks but yields no result. I have myself suffered a car with a burnt valve due to mismatched injectors. A head job and clean-up of the injectors made that engine tick fine again! Link to comment Share on other sites More sharing options...
SBT Posted July 27, 2016 Share Posted July 27, 2016 Flow-balanced is what ehsnils is referring to. Some injectors flow more than others, but some injectors don't flow enough or it's not consistent across the RPM range - which will cause mis-fires. The only way to know/fix this, is to send them someone like Deatsch or Witchhunter for cleaning and flow-balancing. - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
GTEASER Posted July 27, 2016 Share Posted July 27, 2016 I threw a P0171 (bank 1 lean condition) code last weekend in my 2009 FXT. Turns out the BPV signal hose had blown off the manifold. GTEASER's 2012 Legacy GT - Sold GTEASER's 2009 XTeaser - Sold GTEASER's 1992 Legacy SS - Sold Link to comment Share on other sites More sharing options...
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