Since I did my 3.5L conversion last fall, I have installed a PLX R-300 wideband in anticipation of re-installing my dual-NX spray in the car. I did find that the engine ran pig-rich at WOT, dropping into the mid-10s at time. Dyno results were also suspect with such a low A/F.

Since I did try dropping the fuel pressure into the basement with no A/F changes, and not wanting to install any piggyback to try and correct bad A/F, I decided to try and find the real reason so many 4th-gen-3.5L conversions run pig-rich.

I built a 3" MAF with PVC and a stock sensor bar. That MAF would hardly start and run, and A/F was 19:1 or worse.. Unusable. I added a "scoop" to the sensor bar, and that got the A/F down a couple of points, but still undriveable.


Then I mounted a stock MAF in my other airbox, and experimented with blocking part of the air going through the sensor tunnel. This was the answer - a slight blockage was enough to get the A/F back to normal ranges.
For these photos, I laid a strip of real aluminum duct tape over the Gorilla tape I used, so the lower edge shows better.




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Now that my car is protected by Halo3's Master Chief, I went out on the highway for some WOT runs. The LandShark runs better now....

Oil Cap:


The first attempt was going WOT halfway into 1st gear and running through 2nd gear. All runs were with the tranny in Drive with automatic shifts. The fuel pressure was set to 43 psi.



This run was going WOT partway into 1st gear and running up to 100MPH in 3rd gear. Notice the stable A/F.


The final run was another last-half-of-1st gear and through 2nd gear.



The A/Fs seemed quite stable and repeatable. I'm pleased to find an easy solution to my pig-rich 3.5L conversion using the stock 4th-gen MAF - with a little tape.

You sure you dont have some of your background from Miami? because that it something we'd do down here.... zipties duct tape and sticks, thats how our cars run, LOL

This is a super cool find you have here I'm loving the simplicity factor the most.... TAPE... tuning with TAPE, LOL, thats just bliss lol

Well - I do live about 60 miles from Pawnee City NE, alleged home of Larry The Cable Guy, and we both do "Get 'Er Dun"......

am I reading that wrong or were you running really lean for a few hundred rpms around 6k?

Sweet oil cap

As someone who hopes to have a 3.5L in the next few months, it's good to know you got this problem under control. Pioneering for us yet again

Fuel cut at rev limit, or what really happens when you let up on the pedal... Cleans off the plugs, too. I just "let 'er eat" on the road. You gotta love the PLX log files. Thanks, NmexMAX ...

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Thanks on the Halo3 oil cap. Ebay has them - I don't have the seller's store anymore, but its there.

Glad I can contribute here and there.... walking in the steps of the *.ORG giants, you know. You gonna admit, tuning the A/F with tape is - weird -, but it works..