Does your scan tool allow you to reset the fuel trims? Be interesting with the new maf how a reset would do.
CK5
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Not that I’m aware of however the shorts looked better after the MAF replacement. I think I need to get through a few more heat cycles to know for sure. I also noticed the rpm went from 700sh to 800sh.
Looks good to me, run it. Do a tail pipe sniff test with a load and call it a day.
It’s still rich out the tailpipe.
This is why I think every hot rod should have a wide band o2
They are handy when you start adding performance parts and tuning.
I picked up another passenger fender yesterday to replace the one I smashed last fall and peeled back last month. I think this is my 3rd or 4th fender on the passenger side, I blame my shitty spotter for that 
The drivers fender is original btw 
Old
New one trimmed and getting fitted
Painted and installed with a new marker light.
The drivers fender is original btw Old
New one trimmed and getting fitted
Painted and installed with a new marker light.
Use your scan tool to clear the codes, that should also, reset all the fuel trims memory back to zero.
Then, start the engine, run it like normal, get it good and hot, 200° +.
Then use the scan tool to see what the fuel trims are doing, they all should be within a couple of percentage points of each other.
I don't care what exhaust smells like. As long as the ECM says it's OK, it's OK.
If everything is functioning as advertised, no check engine lights, no codes set.
The 7 readiness go/nogo lights will turn from red to green. You should be all set.
Then, start the engine, run it like normal, get it good and hot, 200° +.
Then use the scan tool to see what the fuel trims are doing, they all should be within a couple of percentage points of each other.
I don't care what exhaust smells like. As long as the ECM says it's OK, it's OK.
If everything is functioning as advertised, no check engine lights, no codes set.
The 7 readiness go/nogo lights will turn from red to green. You should be all set.
If your scan tool doesn't have a reset function for the fuel trims, turn off the ignition, pull the positive battery cable off for atleast 15 minutes. This will run down the "Keep Alive" capacitors. Then, put the battery cable back on, clear the codes with your scan tool, start it, let it run until 200°+, this will reset the fuel trims to 0.
I'll give a bit of practical experience with my setup with the Howell harness and tune. I'd check for a vacuum leak or exhaust leak upstream from the o2 sensor on that side. Either of which will cause the ecm to "assume" the mixture is lean and start dumping fuel to that side. It sure did it when my exhaust donut failed at the manifold. It started running so rich on that bank the guy driving behind me had to get around me as the exhaust was burning their eyes. The further I went the worse it got. Sealed up the donut and cleared the code it came back to running like normal.
The thing that screws you up is it totally should have set a lean code initially, but the ECM takes over and tries to correct for the added oxygen in the exhaust. It's a never ending feed back loop that will foul plugs pretty quickly. Same could be had with a vacuum leak at the intake gasket to that bank. There's two different part number intake bolts/studs that is different between early and later 8.1's. If you happen to have the bolts that are too long, the intake won't be pulled in tight enough to seal the gasket properly. That would give a vacuum leak that the ecm would see in higher than expected oxygen in the exhaust and start dumping fuel. Look at the 8.1 thread for the specific details of the intake bolt issue. But a quick shot of carb cleaner while it's running should force a quick change in idle speed and a spike in the o2 value to that side.
Keep this in mind, the 8.1 control system is no different than any early LS. They work the exact same way and use the same PN controller that the early LS engines did (0411). Plugs differ at certain connections, but everything about how it operates is identical to an LS.
The thing that screws you up is it totally should have set a lean code initially, but the ECM takes over and tries to correct for the added oxygen in the exhaust. It's a never ending feed back loop that will foul plugs pretty quickly. Same could be had with a vacuum leak at the intake gasket to that bank. There's two different part number intake bolts/studs that is different between early and later 8.1's. If you happen to have the bolts that are too long, the intake won't be pulled in tight enough to seal the gasket properly. That would give a vacuum leak that the ecm would see in higher than expected oxygen in the exhaust and start dumping fuel. Look at the 8.1 thread for the specific details of the intake bolt issue. But a quick shot of carb cleaner while it's running should force a quick change in idle speed and a spike in the o2 value to that side.
Keep this in mind, the 8.1 control system is no different than any early LS. They work the exact same way and use the same PN controller that the early LS engines did (0411). Plugs differ at certain connections, but everything about how it operates is identical to an LS.
I know it doesn’t have an exhaust leak however the intake manifold is potentially a source for a vacuum leak. The simple fact that that only bank 2 was fouled still leads me to believe that something specific on that bank is causing the issue and a manifold leak makes sense. I’ll check out the resource thread for more information about the gasket and bolts, that’s new info that I was unaware of.
The old carb cleaner trick is worth a shot to confirm.
The old carb cleaner trick is worth a shot to confirm.
Often times with these tuned and swaps the ecm cel doesn’t set. The factory setup is a lot “less stable” than a swap. A lot of times most of the warnings are turned off. Do you happen to have a way to plug it into hp tuners? My old 0411 ecm I was amazed what the tuner did.
Even though it’s efi, thinking carburetor style diag is the way to go. It just brings it into simple terms and isn’t thaaaat much different.
Enough big block talk for me, I’m going to hug a ls engine now.
Even though it’s efi, thinking carburetor style diag is the way to go. It just brings it into simple terms and isn’t thaaaat much different.
Enough big block talk for me, I’m going to hug a ls engine now.
Ideally, the LTFTs will be similar, but a difference of 5% is fine. When it's done learning, the STFTs will be at zero, no matter where the LTs settled in. Kind of the definition of STFT.
Keep in mind that fuel trim isn't "a number", it's a matrix of numbers, a 2-D table based on speed and load. That's why you see a different number when the RPM changes. An intake leak will show up as lean at idle (lowest speed + highest vacuum), and may have little effect at higher speed and load. This engine is rich at idle. Likewise, an exhaust leak would add fuel and show + LTFT. Now if your vacuum leak was drawing *metered* air, that would push one bank lean and one rich.
If both banks were reading the same, it could be a tuning issue. Sometimes a MAF is very picky about the intake duct and the factory tune is done based on the factory air box, filter and ductwork.
Ferds shit won't allow any more than a 2.5% difference between any two. That's how try to remember this stuff. If you get gm stuff to run somewhere in that circle, than it's all good
Last night I was trying to remember what the plugs looked like when I got the engine. Found a picture.
Over the past couple days I’ve continued to troubleshoot the engine issues and here’s a summary of where I stand as of now.
Sprayed carb cleaner around the intake manifold to see if a leak was detected. No luck.
I hooked up the fuel pressure gauge and found the pressure to be 53 with vacuum and 63 without. While driving it will hit 60+ when under load. I swapped the regulator for a brand new Delco and it dropped lower so I put the original one back in that’s adjustable. Turning the screw for more PSI didn’t make a difference.
While driving under load, once it hits 2k rpms or over 30% throttle it falls over on its face. Let off the throttle a little, it starts to come back to life. I have a grade behind my house and it’s hard to keep it above 45mph up it. I hooked up my scan tool and went back out and found the short fuel trims were hitting as high as -32 on both banks.
I’m waiting for it to cool down so I can check the plugs.
I have a gasket set for the intake manifold sitting on the bench. I’m planning on swapping out the fuel filter today, it’s been a couple years since that was replaced.
Sprayed carb cleaner around the intake manifold to see if a leak was detected. No luck.
I hooked up the fuel pressure gauge and found the pressure to be 53 with vacuum and 63 without. While driving it will hit 60+ when under load. I swapped the regulator for a brand new Delco and it dropped lower so I put the original one back in that’s adjustable. Turning the screw for more PSI didn’t make a difference.
While driving under load, once it hits 2k rpms or over 30% throttle it falls over on its face. Let off the throttle a little, it starts to come back to life. I have a grade behind my house and it’s hard to keep it above 45mph up it. I hooked up my scan tool and went back out and found the short fuel trims were hitting as high as -32 on both banks.
I’m waiting for it to cool down so I can check the plugs.
I have a gasket set for the intake manifold sitting on the bench. I’m planning on swapping out the fuel filter today, it’s been a couple years since that was replaced.
I had the same thing happen on my c10, no scan tool or any parts changing would make it happen. The gas tank had water in it. Might be worth it to pull a fuel sample, or a peak inside the tank.
#4
