Need help fixing LM7 running lean

[12turnda]

Hey everyone,

I'm having an issue correcting a lean condition on my LS swap (or what I think is actually a lean condition) and was hoping someone could help! I'm very new to tuning and HP tuners in particular, but I've spent the last month or so reading stickys from this form and watching videos to try and get a grasp of what I'm doing.

The car in question is a 1989 Volvo 240 with a 5.3 LM7 swap out of a 2001 Silverado mated to a 5speed AR5 from a 2wd Colorado. For wiring I'm using a thinned out version of the stock harness connected to a p01(?) PCM that had VATs removed from LT1swap and I'm guessing a segment swap for the manual transmission or possibly just a 4.8 manual Silverado tune all together? As for modifications the engine is entirely stock truck besides a SS2 Jegs cam (228/230), Pac 1218 valve springs, an eBay 4" intake connected to my stock MAF, and block hugger cast manifolds .

The first thing I did after saving my stock LT1swap tune file was adjust the idle using the Idle Tuning Guide;

https://forum.hptuners.com/showthread.php?36318-Idle-Tuning-How-To-amp-Guide-(w-pictures)

This smoothed out the idle and helped the car stop dying when coming to a stop. Next step I figured was the attempt to tune the MAF scaling, so following what I learned about OL from here and a video from youtube (https://www.youtube.com/watch?v=xO_b8T6d_nI). I disabled SD and turned off LTFT's and hooked up my new wideband to the passenger O2 bung and connected it for serial data logging. Took the car out and drove for about 30 minutes taking a couple of different logs trying to figure out how to graph AFR Error. Unfortunately I only saved 1 5min log from this (attached) but everything seemed to be a normal slightly lean reading (which I expected from the cam) of 14-15:1 AFR. Fast forward to the next day I take the car out to go to a local cars and coffee on the same MAF tune, get about half way there (2 miles maybe) and the AFR's drop drastically into the 17-19:1 range. I stopped to check out the car, couldn't find anything glaring, and then limped the car the 1/2 mile to the show. Start the car up to leave the show, same thing, 17-19:1 AFR so I limped it home

So far I've swapped wideband sensors, wired the gauge directly to the battery, swapped the sensor to the driver side bank, tightened down all my exhaust manifold and collector bolts, and tightened down the intake and intake manifold clamps and bolts with no change in the symptoms.

I've also tried multiplying my VE table until I could get the car into a rich state and I almost had to double the table before it would run rich. When it finally did it was a drastic change the car would start normally then dip down to 9-10:1 AFR before raising the RPM to prevent stalling. Also when I flash the car back to the standard non-MAF tune the car runs lean as well. I haven't driven the car since the show but I will attach my log and tune files from idling with both the MAF tune and the MAF tune with my VE table multiplied by 30% and the 5 minute drive I have the day before the show with more normal AFR's.

At this point I'm not sure if I even trust the wideband to be reading correctly or if i'm actually running this lean. Is it possible I'm getting a fake reading by having it too close to the exhaust ports? Its past AEM's 18" distance requirement. Or is this something to do with IFR? I compared my tune file to a stock 5.3 file and they seem to have the same rates unless I'm looking at something wrong.

Any help or input would be appreciated, thanks!

[5FDP]

Make sure you reset the trims with the VCM scanner so the long term trims do not carry over while you do tuning.

What is your fuel pressure like? A constant 58psi like it needs to be??

If you haven't double check for vacuum leaks or exhaust leaks pre-o2 sensor.

[55Belair]

Start with the stuff 5FDP says to check.

Other than the gauge reading does the car change it's demeanor at all or does it run the same?

Any chance you are running the AEM (30-4110) UEGO Air/Fuel Ratio Gauge ?

If so, you may want to read this thread: https://forum.hptuners.com/showthrea...-leaner-it-got!

It turned out to be a bad 3 week old sensor. Hope this helps.

[12turnda]

Make sure you reset the trims with the VCM scanner so the long term trims do not carry over while you do tuning.

What is your fuel pressure like? A constant 58psi like it needs to be??

If you haven't double check for vacuum leaks or exhaust leaks pre-o2 sensor.

Thanks for the reply! Yeah I figured that out after a couple of logs. I didn't realize you had to do it in the scanner too.

I picked up a fuel pressure gauge to check just that and at the rail its a constant 52psi while the car is running. My fuel rail is a return style with the built in fuel pressure regulator if that matters also.

I didn't find any leaks exhaust side and I was spraying some carb cleaner listening for vacuum leaks and haven't found anything yet but i'll keep looking.

[12turnda]

Start with the stuff 5FDP says to check.

Other than the gauge reading does the car change it's demeanor at all or does it run the same?

Any chance you are running the AEM (30-4110) UEGO Air/Fuel Ratio Gauge ?

If so, you may want to read this thread: https://forum.hptuners.com/showthrea...-leaner-it-got!

It turned out to be a bad 3 week old sensor. Hope this helps.

When the car is idling you can hear the rpms drop as the gauge leans out, but nothing drastic, sounds like a normal idle settle after a startup. Also when the AFRs initially dropped while I was driving it, there was no change at all in the demeanor of the car.

I think my gauge is the successor to that? AEM 30-0300 UEGO gauge. It does sound similar what was mentioned in that thread. I could be going crazy but it does seem to get leaner and leaner over time. When it happened while I was driving my AFRs were 16-17:1 now it will read as lean as 19:1. However I swapped the sensor for my friends same wideband sensor and ran into the same AFR. I think the gauge just reads voltage from the sensor itself so I don't know if that could be faulty or not? But it's only 7 days old.

I also did the rag test that was mentioned in the thread and it did go full rich to 8:1.

[55Belair]

You would think that if it was actually going as lean as 19:1 that there would be SOME change in the car, it would buck burp and backfire when you were getting back on the gas.

Log the output of the remaining O2 sensor, if it drops really low (under about 200 mv) then you really are running lean and the wideband is not the issue.

[12turnda]

You would think that if it was actually going as lean as 19:1 that there would be SOME change in the car, it would buck burp and backfire when you were getting back on the gas.

Log the output of the remaining O2 sensor, if it drops really low (under about 200 mv) then you really are running lean and the wideband is not the issue.

It stumbles a little at idle but I thought that was from my quick idle tune not being dialed in enough.

Last night I logged two more idle sessions checking O2 voltage as per your suggestion, I flashed on the "as found" original tune I pulled off the PCM when I got it back from LT1swap, and the MAF tune file again and monitored the other O2 sensor.

The passenger side O2 is the only one plugged in which I think is then B2S1, and it looks like I truly am lean and it's not the gauge, around 23-33 mv once the idle settles. I'll attach those logs.

So I compared that to the the 1st MAF log I posted where I was getting reasonable AFR's and that mV is in the 800's (B1S1 because I swapped the wideband). So between that 1st MAF log and the the MAF log I'm posting now from yesterday I made no tuning changes besides clearing my LTFTs in the VCM scanner.

[5FDP]

You can't trust anything the o2 sensors says if you are only running one sensor, the computer does not use them when the car is in open loop. So whatever they are saying at idle means nothing. If you put the other o2 sensor back in and allowed the car to enter closed loop, you'd see if the short term trims start really jumping around and then see if the long term trims work there way towards +25% meaning it really is lean.

You shouldn't have to do this but you can try just hitting the MAF/VE with 5% worth of fuel everywhere and see if the wideband responds to the change.

52psi seems a tad bit low, I'd be curious if it can maintain that under load. I also wouldn't be surprised that once you figure this part out that you won't even have enough injector to make the power you want.

[12turnda]

You can't trust anything the o2 sensors says if you are only running one sensor, the computer does not use them when the car is in open loop. So whatever they are saying at idle means nothing. If you put the other o2 sensor back in and allowed the car to enter closed loop, you'd see if the short term trims start really jumping around and then see if the long term trims work there way towards +25% meaning it really is lean.

You shouldn't have to do this but you can try just hitting the MAF/VE with 5% worth of fuel everywhere and see if the wideband responds to the change.

52psi seems a tad bit low, I'd be curious if it can maintain that under load. I also wouldn't be surprised that once you figure this part out that you won't even have enough injector to make the power you want.

Thanks for the info! So even the voltage readings are meaningless if the car is in OL? Also I've upped the main VE table 30% and seen no change in AFR's, I'll try to add to the MAF table instead after I troubleshoot everything mechanical.

I decided to check my fuel system some more. This time I noticed that on key on without cranking it will prime to about 60psi but then the pressure will drop quickly to 3-5 psi within a couple of seconds. I also pulled the fuel rail to make sure the injectors weren't leaking, I primed it a couple of times and none of them were leaking. I'm not sure if this is a fuel pressure regulator issue or maybe fuel pump check valve issue? I pulled the vacuum line from the regulator and it had no fuel in it, which from what I found is a common symptom of a failed one.

I also checked the fuel pressure with engine running with throttle, and as the revs go up my pressure goes down to about 48-50psi at 1500-2000rpm. I'm using a Walbro in-tank GSS340 255 also.

I don't have any power goals in mind right now. I'm just trying to get the car running well enough to see what the body/suspension/drivetrain needs before trying to make power.

[5FDP]

Your calibration is setup to use MAF only right now, so adding the VE only won't exactly do what you want. Someone set the dynamic airflow high rpm disable to 100rpm instead of the factory 4,000rpm.