Love the sound

 

Weird situation last night; loaded up a new tune file with some different MAF calibration data from Lingenfelter, then when I went to start it, the truck lost all power. Checked the battery with a multimeter, and it showed 12.40V, so that was good. Right after checking it I went back to the cab and the autocal was lit up so it was getting power, so I tried starting it again and all I heard was a click of a relay then nothing, all power gone again.

So after checking ECM fuses and relays, I connected a battery charger, just to see if it would do anything, and pretty much instantly the interior lights came on. Cranked it over, it kind of hesitated, but then started up. I started scanning with efiLive and just at idle the LTFTs are still way off; once the engine warms up to temp, both LTFTs stay constant at 29.7

I'll drive it around tonight maybe to get some more data, maybe the new MAF data will help some low speed driveability, but just from monitoring it at idle last night I think it's back to the drawing board...

 

Well I ******* found it! I made two changes last night:

• Removed the corrugated flex coupler that comes standard with the TVS kit and replaced it with a straight 4" silicone coupler between MAF and intake tube, and pushed it up high onto the intake tube; and
• Disconnected the MAF from the airbox, so basically an "open" intake without pulling air through the filter.

Result? LTFTs dropped to ±0-2%

So at that point I thought the problem was the corrugated flex coupler, and because I lost the flexibility of the coupler, I had to get a piece of 4" PVC, rotate the intake tube clockwise a bit to get a straighter angle to the air box, but at the same time in order to get the two ends to connect, I had to pull the straight silicone down from the intake tube to move the whole assembly closer to the airbox.

And the result with the straight silicone coupler (moved about an inch away from the intake tube) and connected to the airbox? LTFTs were 22-25%

So then to confirm the previous results I disconnected the MAF end from the airbox, and pushed the straight coupler up the air tube, scanned and LTFTs were back to negligible.

So now it's either the transition between the MAF and intake tube needs that long overlap of the silicone coupler up the intake tube to form a completely secure seal, or there's some effect of the airbox/airfilter which I can't imagine because if my understanding of positive LTFTs is correct, the PCM is adding fuel, and if the filter was a restriction, I would be running rich.

Now I'm going to take the airbox apart and connect the filter to the MAF in the exact position where I'm seeing perfect fuel trims; that way I'll know if it's the filter. If that test shows no difference in results, I'll order some long silicone tubing and recreate the positioning of the MAF with fewer connections.

In any case I'm pretty ecstatic to have at least tracked down the source of my misery!

Couple pics from late last night:

This configuration generates perfect LTFT numbers, but obviously can't be driven on the road for the lack of filtration:



This pic shows what I was describing about how far up the intake tube I pushed the straight silicone coupler:

 

Well for the good news: I put the stock air box back in (with paper filter) and LTFTs are <10%. Still not as good as the MAF disconnected from the air box and without a filter, but a lot better than what I've been running around with the past couple months. Future tests will include data logging with the stock air box and no filter, and stock air box and the flat K&N Magnuson sent with the TVS kit. Might also get an oil-free flat filter from Airaid just to test it out. In the meantime though I'm just gonna leave it as it is and enjoy driving without CEL lights.

Drove around to collect some data, and while on the highway, trans shifted into 4th, converter locked then I tried to give it a little throttle to get the converter to unlock and the engine responded with a disproportionate amount of throttle...then a CEL popped up and it turned out to be p0121, which is for TPS, and I think it's the third time I've encountered it. So it's something I'm going to have to chase down eventually, but as long as the lean codes are gone, I'm not too overly concerned about the TPS issue.

Now for the weird ****; I put the Metco Fuel pressure gauge onto the fuel rail to satisfy my curiosity, because through the scan cable I monitored a PID called rail pressure, and it showed around 45ish psi of pressure, but I couldn't see a pressure sender near the rail so it always made me wonder where that pressure was being monitored, and also what I would see if I tested the pressure right at the rail.

So after the gauge was installed I put the key to ACC mode to prime the fuel system, and pressure looked good at the rail, ~58, so all seemed good. Next test I started the truck and watched the gauge; good pressure of around 60 for a couple minutes, but then it dropped to around 48, and stayed there. Raised RPM to about 2000, having the gf watch the gauge and it stayed where it was under 50. It was also 46° today, so I'll read up about the effect of ambient temp on a fluid filled gauge, but I'm a little disappointed if fuel pressure is low at the rail.

Now for some pics:

Here's the setup as it sits now:



Metco fuel pressure gauge kit:



I also ordered a 90° fitting, because the fitting on the fuel rail on the TVS would be in an awkward spot to read and it looked like a gauge would hit the coil bracket:





Installed:

 

Any updates? Man, what a build. It took me two days to finish (while at work) but awesome write up. The details and everything were so, well, detailed that I thought I actually installed this stuff myself. Popped the hood of my truck and still stock :o( Hopefully by now you got everything worked out, but still curious.

 

Are you using a 4" MAF housing, and butting it up against the stock Maggie air inlet tube? That could be part of your problem right there. The I.D. of that Maggie tube is only around 3.3". That's going to cause turbulence, and screw with the MAF readings, and the MAF is controlling your fueling.

 

Thanks, glad you got something out of it. Plenty of little things came up that I felt would be useful to pass along.

I'm confident to say I solved the issue with the fuel trims/lean codes by changing the filter/airbox and replacing the corrugated rubber coupling with a straight silicone one. I don't think the coupler has any effect, but for whatever reason, disconnecting the K&N filter completely from the air tube gave perfect fuel trims, and connecting it back made the trims go back to the +25% range. I never recharged the K&N filter since I first put it on 2 years ago, but my mileage over that time was extremely low, and just visually inspecting the filter, it was still red and hardly had any dust on it. I didn't bother trying to recharge it to see if it made a difference, I just put the stock airbox and paper filter back in. I have the flat K&N filter that came with the magnacharger kit, so I may try that at a future date, and I also want to get a dry Airaid filter to try as well and compare fuel trims.

There's not that much of a disparity between the two diameters, maybe a 1/4" to 3/8". It's not ideal and I still have a plan of fabricating my own one or two-piece tube out of 4" aluminum someday.

 

I've had it in my mind to fab up an intake tube, and winter boredom has motivated me to put pen to paper, so here's my rough outline for it.

I want a two-piece design, connected with a Vanjen clamp, and only two silicone couplers in total (at each end) to make a clean, simple design. I'm going to weld in a MAF adapter and either 2 or 3 bungs for a nipple to connect the clean air line for the PCV system, and future possibilities of running meth or nitrous nozzles. Then once finished I'm going to have it ceramic coated possibly inside and out to create a thermal barrier for the intake charge.

So for supplies:

4" aluminum tubing
GM #19166574 MAF adapter
4" Vanjen clamp
2x 4" T-bolt stainless clamps
Either 1 or 2 1/8" NPT female bungs and plugs
and/or 3/8" NPT female bung and plug for air inlet line

Anything to consider for nozzle placement? I was planning on putting the bungs at either 9 or 3 o'clock position.

 

So was the valley cover causing the vacuum leak? Or was it fixed as a coincidence?

 

Sweet truck, like the rims... Please keep us updated!!