Aftermarket Intake trouble shooting MPG

Awesome thanks! I never saw over 50 PSI even with key in engine off. Was around 50 PSI with engine running though (maybe that's cause of my Flex Fuel injector swap...)

I don't know why it bled pressure like it did. Looking a bike pump test to check the system for leaks as well as the check ball.

Made another post on troubleshooting fuel system HERE

This is lovely... So first off fuel pressure it a good 10% too low. Working with Delphi to get it sorted out, pump is brand new warranty replacement. No electrical faults, no injector faults, brand new pressure regulator, and certain no line set issues (blew lines out with compressed air multiple times) and no leaks.

Now I'm on a road trip here and I'm getting 13MPG highway YUCK. One of my friends noticed the right rear rim is HOT to touch. I think it's a brake fault... Brake doesn't seem to rub. However, if I use brakes that rim heats up FAST. So I replaced the rotor on my trip here (inside inner radius was ripped up / bad surface). It seemed to have eliminated the heat issue except for under heavy braking (down mountains). I assume is due to me not also replacing the pads and had warn an ever so slight grove on that inside pad (not flat surface on pad now)... However, he thinks I have a rubbing condition somewhere / excess friction contributing to my decrease in fuel mileage.

Anybody had issues like that? I can spin the wheel by hand. Doesn't seem to be any rubbing and if an issue at all... it's only the right rear tire. And or, elsewhere a friction issue creating a decrease in fuel mileage?

Somebody just told me something that makes a whole lot of sense... I am a thick skulled person for not realizing sooner. I'm at 275000 miles on the original Catalytic Converters! Starting to get rear O2 codes. I think my mileage issue may actually be old converters!

It could be. Especially if you were off on the tune a bit while dialing things in. It could have started a slow death for one or both of them.

I have to drop the front exhaust to get at the transmission pan. I drilled some of the separate plate holes too big when I built the transmission... Long story short, I'm thinking about soaking the cats in a solvent. Certainly wouldn't hurt. Anybody done this? Which solvent works best... I asked a chemist and they said Alcohol would be best for carbon buildup.

Matthew Jeschke said:

I have to drop the front exhaust to get at the transmission pan. I drilled some of the separate plate holes too big when I built the transmission... Long story short, I'm thinking about soaking the cats in a solvent. Certainly wouldn't hurt. Anybody done this? Which solvent works best... I asked a chemist and they said Alcohol would be best for carbon buildup.

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They can be hollowed out and rear o2's turned off in the PCM.

Matthew Jeschke said:

I have to drop the front exhaust to get at the transmission pan. I drilled some of the separate plate holes too big when I built the transmission... Long story short, I'm thinking about soaking the cats in a solvent. Certainly wouldn't hurt. Anybody done this? Which solvent works best... I asked a chemist and they said Alcohol would be best for carbon buildup.

Click to expand...

I honestly couldn't tell you. But, you should be able to tell from the front side if they are clogged. As just going bad wouldn't hurt mileage since the downstream sensors just tell you how the cats are functioning and don't change the fuel mix. Only clogging and increasing pumping losses will hurt mpg. Apparently there is a product for dishes called carbon off that may work.... says it is safe for any metal.

rockola1971 said:

They can be hollowed out and rear o2's turned off in the PCM.

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I'm completely **** retentive. My main concern is gutting them w/o cutting up the exhaust. The cats are in the middle of the downpipe. I cannot get a chisel or anything in there around the bend. Any ideas?

If I cut the downpipe I have to weld and then it's just as easy to spend a couple hundred bucks and put new cats on.

Matthew Jeschke said:

I'm completely **** retentive. My main concern is gutting them w/o cutting up the exhaust. The cats are in the middle of the downpipe. I cannot get a chisel or anything in there around the bend. Any ideas?

If I cut the downpipe I have to weld and then it's just as easy to spend a couple hundred bucks and put new cats on.

Click to expand...

You can try to beat the living hell out of the converter chamber with a mallet to get the guts broken up. Then the exhaust will just blow most of it out the tailpipe. If you live in a state that doesnt have emission testing then im sure there are exhaust shops around that will install "test pipes" in place of the converters and then see if your problems go away (because the suspected plugged up cats are out of the picture). If you like the way it runs you can have the rear 02's programmed to not flag that there isnt any cats because the PCM will believe they are defective because of the rear 02's not seeing any reduction in the exhaust after the cats.

Youre looking at around $200+ per cat new.