Idles strong, but P0172/P0175 are lit up...help!!
06-18-2019, 05:49 PM
#1
Idles strong, but P0172/P0175 are lit up...help!! Hey all, been doing a lot of research and went through a write up this evening that explained some tests I could run due to having the DTCs P0172/P0175.
Some background info before we get to the test results.
I swapped a LS1/T56 from a 2004 Pontiac GTO into a Mazda RX8 (I have a build thread on here as well
).
The car starts right up, and idles fine, but when I go to drive it, it is ok at VERY low throttle, but if I try to get on it AT ALL it bogs down and shutters. As noted I got the DTCs P0172/P0175 so I know it’s running rich.
I verified the MAF was clean, and hooked up in the correct orientation, both front O2 sensors are brand new, injectors I don’t know since it was from the swap. Visibly they look fine, but that doesn’t mean much, so that’s my guess as of now to the problem? I ran some tests I found on here and got the freeze frame data from the latest DTCs that got thrown. Can anyone help explain this:
STFT B1: -7.8%
LTFT B1: -18.8%
STFT B2: 3.1%
LTFT B2: -18.8%
ECT: 199 F
MAP: 9 inHg
RPM: 1107
MAF 1.21 Lb/min
So bank 1 is completely rich, but bank 2 is lean short term, rich long term? Am I understanding that right? Anyone have any ideas what to test/check next, could it be the injector/injectors? Any help is much appreciated, cheers!
Some background info before we get to the test results.
I swapped a LS1/T56 from a 2004 Pontiac GTO into a Mazda RX8 (I have a build thread on here as well
). The car starts right up, and idles fine, but when I go to drive it, it is ok at VERY low throttle, but if I try to get on it AT ALL it bogs down and shutters. As noted I got the DTCs P0172/P0175 so I know it’s running rich.
I verified the MAF was clean, and hooked up in the correct orientation, both front O2 sensors are brand new, injectors I don’t know since it was from the swap. Visibly they look fine, but that doesn’t mean much, so that’s my guess as of now to the problem? I ran some tests I found on here and got the freeze frame data from the latest DTCs that got thrown. Can anyone help explain this:
STFT B1: -7.8%
LTFT B1: -18.8%
STFT B2: 3.1%
LTFT B2: -18.8%
ECT: 199 F
MAP: 9 inHg
RPM: 1107
MAF 1.21 Lb/min
So bank 1 is completely rich, but bank 2 is lean short term, rich long term? Am I understanding that right? Anyone have any ideas what to test/check next, could it be the injector/injectors? Any help is much appreciated, cheers!
06-18-2019, 07:33 PM
#3
I’m about to go grab a fuel pressure gauge that I can put on the rail and see what psi I’m getting. It should be around 55-58psi for stock LS1 right? What about under load?
I didn’t tune the PCM I sent it off to Speartech to have VATS removed, and have a base tune put on it. I’m going to contact them tomorrow and have them look it up, and tell me what tune they put on there. I know the stock injectors (like I have) run at ~25.5 I want to make sure it’s not tuned for 42 or something insane..good call.
I didn’t tune the PCM I sent it off to Speartech to have VATS removed, and have a base tune put on it. I’m going to contact them tomorrow and have them look it up, and tell me what tune they put on there. I know the stock injectors (like I have) run at ~25.5 I want to make sure it’s not tuned for 42 or something insane..good call.
06-18-2019, 09:20 PM
#6
It’s because one bank is lean and one is rich and eventually they will swap symptoms because the PCM is trying to correct the issue. It because of the firing order. The PCM expects certain conditions when certain cylinders are firing and what bank they belong to.
I could be wrong but it’s the most common cause for the symptoms you have.
I could be wrong but it’s the most common cause for the symptoms you have.
Trending Topics
06-18-2019, 10:05 PM
#8
Is it safe to say it hasn't been tuned at all? Just killing the Vats or something, but not playing with the fuel?
Original MAF?
Is the MAF located next to a bend or something that would change the velocity of air past the sensor?
If you unplug the MAF where do the trims go?
When you turn the key off does the fuel pressure stay in the rail or leak off?
Do the Intake Air Temp Sensor and Coolant Temp Sensor read the same after a long cold soak?
Joe
Original MAF?
Is the MAF located next to a bend or something that would change the velocity of air past the sensor?
If you unplug the MAF where do the trims go?
When you turn the key off does the fuel pressure stay in the rail or leak off?
Do the Intake Air Temp Sensor and Coolant Temp Sensor read the same after a long cold soak?
Joe
06-18-2019, 10:35 PM
#9
Is it safe to say it hasn't been tuned at all? Just killing the Vats or something, but not playing with the fuel?
Original MAF?
Is the MAF located next to a bend or something that would change the velocity of air past the sensor?
If you unplug the MAF where do the trims go?
When you turn the key off does the fuel pressure stay in the rail or leak off?
Do the Intake Air Temp Sensor and Coolant Temp Sensor read the same after a long cold soak?
Joe
Original MAF?
Is the MAF located next to a bend or something that would change the velocity of air past the sensor?
If you unplug the MAF where do the trims go?
When you turn the key off does the fuel pressure stay in the rail or leak off?
Do the Intake Air Temp Sensor and Coolant Temp Sensor read the same after a long cold soak?
Joe
Your guess is as good as mine. Like I said I sent it off to get "tuned", and it has an invoice note saying it was, along with the VATS removal ect...but who knows if it was or not. I have the "5 wire maf" where the iat/maf sensor is in 1 plug. stock size though.
Haven't tried un-plugging yet, but here is picks of the setup...you can see there is bends, but there is a decent ~6in space where the MAF is that I would say is straight. Also I ordered a fuel pressure tester gauge it gets here Thursday so I can know then what really is happening to my fuel pressure.
06-19-2019, 12:22 PM
#11
I have heard a lot of stories similar to this, so it very well might be the case. Problem is, in my opinion the shuttering/bogging down is so bad, that I don’t consider it “drivable” to get to a tuner. Around town maybe, but highway or anything over 40-50 MPH, as soon as I try to step on it, it bogs down. I’m looking into getting HPtuners now, that might help being able to look at everything myself.
06-19-2019, 01:01 PM
#12
Just got off the phone with speartech and we 100% found A problem. Don't know for sure if it is the problem, but it is a problem none the less! When I sent the PCM off to get tuned (way back in the day at the start of the project) I had them tune it for a stock 2004 Pontiac GTO since that is what my pullout was from. However, along the way during the build I changed to the 5 wire MAF (pictured above) so that I didn't have to drill/plumb into my intake for the IAT sensor. Well the tune/PCM still thinks I have the original 3 wire MAF and seperate IAT sensor that came stock on the 2004 GTO.
Going to pull the PCM and send it off to speartech to have the correct MAF configuration input, then we will see what problems (if any) pop up! Ill keep this forum up-to-date...since from the research I did this problem is fairly common (meaning the P0172/P0175) so I assume it will be beneficial to knowing what the actual fix ends up being.
Going to pull the PCM and send it off to speartech to have the correct MAF configuration input, then we will see what problems (if any) pop up! Ill keep this forum up-to-date...since from the research I did this problem is fairly common (meaning the P0172/P0175) so I assume it will be beneficial to knowing what the actual fix ends up being.
06-19-2019, 04:10 PM
#13
Glad you're moving forward on it. Having the IAT circuit open could certainly cause negative fuel trims, but it wouldn't be enough to cause performance problems.
Plan on getting more work done once you get the PCM back.
Joe
Plan on getting more work done once you get the PCM back.
Joe
06-19-2019, 09:30 PM
#14
The tune thinks it’s the LS1 MAF which has a completely different tune table then the LS2 style MAF currently installed. So the tune is definitely wrong, but wether that’s driving the current problem or not who knows. I think it makes sense though since the PCM is essentially trying to tune off the MAF and O2 sensors, but the MAF isn’t working like the PCM thinks since it’s the LS2 style. We will see though! Plan on popping it out tomorrow and shipping it off to Speartech to re-tune it. In the meantime I can still test fuel pressure, leaking injectors, ect!
06-20-2019, 09:43 AM
#15
Launching!
The MAF is going to be the primary input for fueling and the O2 sensors are just there to help the ECU make corrections. If the MAF transfer function is incorrect, then that is going to make a big difference.
Just for laughs, I downloaded a stock 2004 GTO tune and compared it to the "stock" tune for my 2005 truck engine, which appears to use the same MAF you are using. Looking at the two MAF functions, they are very different, so replacing one MAF with the other, without making appropriate alterations to the tune, absolutely would make the car drive very poorly.
Depending on how much your time and frustration is worth, and whether or not you intend to make other alterations to your setup, I would strongly suggest either buying the HP Tuners package or finding someone local to you who can help you mess with the tune. If you didn't have to ship the ECU back to Speartech, this would take all of about five minutes to fix.
Just for laughs, I downloaded a stock 2004 GTO tune and compared it to the "stock" tune for my 2005 truck engine, which appears to use the same MAF you are using. Looking at the two MAF functions, they are very different, so replacing one MAF with the other, without making appropriate alterations to the tune, absolutely would make the car drive very poorly.
Depending on how much your time and frustration is worth, and whether or not you intend to make other alterations to your setup, I would strongly suggest either buying the HP Tuners package or finding someone local to you who can help you mess with the tune. If you didn't have to ship the ECU back to Speartech, this would take all of about five minutes to fix.
06-28-2019, 05:10 PM
#16
Just for laughs, I downloaded a stock 2004 GTO tune and compared it to the "stock" tune for my 2005 truck engine, which appears to use the same MAF you are using. Looking at the two MAF functions, they are very different, so replacing one MAF with the other, without making appropriate alterations to the tune, absolutely would make the car drive very poorly.
I wish this was it, but I just got the PCM with the tune that has the correct MAF, and it has the same feel/problem when driving. Starts right up, idles strong, but when you step on it AT ALL is shutters/bogs down.
Whats weird is this time now though with the “correct” tune I get different codes. Now it’s throwing P0174 only (lean bank 2). I just ohmed all the injectors out and they all were consistent at ~13.0-13.3 ohms.
It’s odd how the problem changed though. Went from having the wrong MAF tune throwing both banks are rich, to correct MAF tune, only bank 2 is lean. Is it worth just throwing a filter on the opposite side of the MAF is the turn I have too close to the MAF causing an issue, maybe?
06-29-2019, 08:26 PM
#18
Going to hook up a fuel pressure gauge and check it at idle and driving around to see where that lands me. Starting to wonder if the injectors are just clogged from sitting for 5+ years.
06-30-2019, 07:14 AM
#19
"Found the wiring schematic on lt1swap.com for 2004 GTO and it matched the wiring for my O2 sensors so I didnt end up swapping the O2s since I verified they were correct (i.e. bank 1 was hooked up to bank 1, and bank 2 to 2. "
Did this check include confirming the wire locations at the PCM?
Did this check include confirming the wire locations at the PCM?
06-30-2019, 06:54 PM
#20
"Found the wiring schematic on lt1swap.com for 2004 GTO and it matched the wiring for my O2 sensors so I didnt end up swapping the O2s since I verified they were correct (i.e. bank 1 was hooked up to bank 1, and bank 2 to 2. "
Did this check include confirming the wire locations at the PCM?
Did this check include confirming the wire locations at the PCM?
On another note, I found what seems to be the problem today. First I tested fuel pressure at the rail, and everything looked good, as well as while cranking and under load. So then that led me down the path to check the MAF. I checked it, and everything looked fine, but just for "fun" I unplugged it, and BOOM everything was running/driving better. Now there is ZERO hesitation or sputtering when I step on it. I'm glad it is driving normal now, but still confused just because the MAF is brand new out of the box. Only other thing I can think of is I messed it up making a custom CAI. Maybe there was too many bends or something that was throwing it off. I just got done converting it over to a short ram style intake...going to go for a test drive and see if it goes back to being messed up, or drives fine like if the MAF was unplugged.
My thought process is, if it drives fine now with the short ram style intake then I did mess it up with my CAI setup. If its bad/poor driveability again then it must just be a DOA MAF sensor.