brian regards

So I have a 2001 Silverado 2500hd gas 4l80e that I recently swapped a lq9 into. The truck is stock aside from an intake and some long tube headers(no egr hooked up)
the first 20-30 miles were fine, a1 at that but now I’m having some issues
so on cold start it runs fine and shifts fine, when the truck warms up this is what occurs: while driving at 45-50 miles an hour under light throttle (about 20-25%) the engine will bog down and almost shut off unless I let off the gas and then it will catch its self back. When I get back in the throttle it’ll do this a few more times and then stop. When it stops bogging down while I’m driving the transmission will start acting weird, it will shift HARD. And it will upshift,again, HARD early based on my speed and throttle input. Also the transmission temp gets a little higher than normal driving temp and this happens when the hard shifting occurs. I believe that’s due to the higher line pressure but that’s also occurring
just to note some things I did while swapping was change the fuel filter, spark plugs, wires, timing chain and oil pump. I don’t have the egr hooked up and I don’t have the rear 02 sensors hooked up
now I am running the lq9 on the trucks stock lq4 tune so I don’t know if that’s the issue
also I swapped the maf sensor with two other ones that I had in the garage and it does the same thing. I reverted back to the stock intake set up and it did the same thing. When the motor was in the Escalade I drove the vehicle home and it did not have that issue.

i have a few codes most of them pertain to the egr and the rear 02 sensors not being tuned out yet but the concerning ones are as follows
p0101
p0102
p0106
p0131
p0132
p0134
p0151
p0152
p0154
p1810

the fuel trims are negative about 2% to positive 2% before the bogging down occurs then after it happens and it doesn’t bog down and the trans starts shifting weird they’re positive 7-19%
I do have a scanner capable of live data
any insight would be greatly appreciated
also this is my first post so if you believe I’m posting in the wrong section please direct me in the right direction

mrvedit

Your codes indicate problems with the MAF, the MAP and both upstream O2 sensors which control the engine. Amazing it isn't running worse than it is.
I would check the integrity of your harness and connectors into your PCM.
Transmission shifting and fuel trims are just symptoms of the codes related to important engine sensors.

Full Power

Sounds like LIMP mode engaged.
You get all the ground straps back in the right places ?
Possible ya bumped, or broke a MAF connector wire ? Miss-connected front and rear O2 sensor harnesses ?

The LQ9 WILL RUN on LQ4 tune: The Cadillac LQ9 has about 5 degrees more cam duration, and half point compression over the LQ4.... You will need a little more base running airflow, and a touch more on most of your VE table, but on the order of 4 or 5%. well within range of the trims to catch up with.
The stock LQ4 PE and spark tables are REALLY LAZY, so: Notably massive, YUUGE driveability gains are easily made in spark map and Power Enrichment tuning.
Example: PE on stock LQ4 doesnt even begin until 90% throttle, and One sample I saw threshold was 5500 rpm... so basicaly no PE.
Also VERY lazy off idle spark advance on LQ4..
..

For reference, I stuffed an LQ9 with a 212/218 duration, .550" lift cam directly into a flex-fuel L59 Tahoe, added 6% to base running airflow and LEFT the VE table alone, the simple addition of the 6.0 liter displacement was sufficient to allow ECM to compensate, and the VE table worked good enough for immediate start-up, decent enough idle, and initial driving/commuting. we did eventual fine tuning, and of course shift points, spark timing optimization, etc.

brian regards

@mrvedit ok that’s what I was thinking. So maybe it does that when it warms up because it’s going from open loop to closed loop and relying on the maf map and o2 sensors from that point on and there’s an issue with one of those three, if not all three systems?I do have a standalone harness sitting in my garage that’s supposed to be going on the lq4 I took out of my truck to use in a 94 Camaro that I’m working on so I think I’ll swap that in there and see if that resolves the issue and determine if it’s a harness issue. I’ve been trying to find something that the map,maf and 02sensors share in common such as a ground because I thought it was kind of weird for all three to throw codes but the harness in the truck isn’t in the best shape as it is so I think the fresh standalone installed should determine if it’s a harness issue. I was just as surprised as to how good it runs after pulling all those codes . Like I said it’s so nice and smooth until it warms up and starts bogging down and shifting hard. I’m not driving it until it’s resolved because those shifts are scary in the old work truck lol

​​​​@Full Power from what I’m understanding from what you’re saying it the lq9 tune, in theory, should correct the fuel trims about 4-5%. but with my situation correcting 17ish percent the lq9 tune would still be correcting 12ish percent so the tune it’s self should be done but that’s not my issue? I’ll double check but I believe the connectors on my o2 sensors are different from front to back so I don’t think I plugged the fronts in the rear or cisa versa. The maf sensor plug looked good but that’s only at the plug I haven’t traced it back to the ecu or checked continuity yet.
the truck still runs with the maf unplugged but if I plug the maf back in and slip the intake off the throttle body with the maf plugged in the engine stalls. I have a bunch of oem maf sensors that I swapped in and it still does the same so I think @mrvedit may be on point with the wire harness integrity being an issue. I’m getting the lq9 tune flashed onto the ecu this weekend and will be installing the standalone harness tomorrow and will report back with an update for anyone else reading this thread. Thank you for the input

brian regards

So it was a O2 sensor issue for anyone reading this. I used the sensors from the 04 Escalade on the long tubes when I installed them and even though the plug is very similar, they are two completely different sensors. The trapezoid shaped sensors have two kinds the bottom notch either on the left or right. I remember when I installed them they wouldn’t plug in so I stupidly just put a notch on the correct side so make it fit. Swapped out with the correct sensors and all the engine lights and drivability issues subsided. I’ll attach some pics of the madness I caused on myself

🤦🏽