Aftermarket Intake trouble shooting MPG

[Matthew Jeschke]

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.

 

[Matthew Jeschke]

Made another post on troubleshooting fuel system HERE

 

[Matthew Jeschke]

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?

 

[Matthew Jeschke]

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!

 

[Mudsport96]

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.

 

[Matthew Jeschke]

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.

 

[rockola1971]

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.

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

 

[Mudsport96]

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.

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.

 

[Matthew Jeschke]

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

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.

 

[rockola1971]

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.

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.

 

[Matthew Jeschke]

Awesome thanks! @rockola1971

 

[Matthew Jeschke]

I was able to unplug the converter. It was source of at least part of my efficiency / MPG problem. I used lye / powder drain cleaner. Filled exhaust with a water solution of that. Let it sit for an hour. Drained it out. Started truck. Carbon shot out EVERYWHERE. I then drove the truck for about an hour... Also making sure to beat the heck out of it so I could heat up the cats. At first the temps were not in line / cat was still plugged. Afterwards cats have been right at 20% hotter on outlet... The EGT have held in spec ever since.

Now I have a new question. I'm trying to fine tune efficiency of the truck. There's still some gremlins in the closet. I have logged every single tank of gas since I bought the truck. However, there's variance in pumps. I typically fill at the same station every time. However, I want to figure out how to fill the tank more consistently so I get a more accurate gallons measure of what was consumed in tank. Any tips?

 

[SnowDrifter]

I was able to unplug the converter. It was source of at least part of my efficiency / MPG problem. I used lye / powder drain cleaner. Filled exhaust with a water solution of that. Let it sit for an hour. Drained it out. Started truck. Carbon shot out EVERYWHERE. I then drove the truck for about an hour... Also making sure to beat the heck out of it so I could heat up the cats. At first the temps were not in line / cat was still plugged. Afterwards cats have been right at 20% hotter on outlet... The EGT have held in spec ever since.

Now I have a new question. I'm trying to fine tune efficiency of the truck. There's still some gremlins in the closet. I have logged every single tank of gas since I bought the truck. However, there's variance in pumps. I typically fill at the same station every time. However, I want to figure out how to fill the tank more consistently so I get a more accurate gallons measure of what was consumed in tank. Any tips?

Not sure if your rig has the 'gallons used' counter on the DIC. Mine has it, it's been accurate for me within 5%

As far as filling consistently, see if you can find a spot that has you aimed slightly nose-down. The fill neck is on the rear of the tank. Will reduce any air lock in the tank. Parked nose-up vs nose-down is about 2 gallons

 

[Tonyrodz]

I was able to unplug the converter. It was source of at least part of my efficiency / MPG problem. I used lye / powder drain cleaner. Filled exhaust with a water solution of that. Let it sit for an hour. Drained it out. Started truck. Carbon shot out EVERYWHERE. I then drove the truck for about an hour... Also making sure to beat the heck out of it so I could heat up the cats. At first the temps were not in line / cat was still plugged. Afterwards cats have been right at 20% hotter on outlet... The EGT have held in spec ever since.

Now I have a new question. I'm trying to fine tune efficiency of the truck. There's still some gremlins in the closet. I have logged every single tank of gas since I bought the truck. However, there's variance in pumps. I typically fill at the same station every time. However, I want to figure out how to fill the tank more consistently so I get a more accurate gallons measure of what was consumed in tank. Any tips?

So did that solution clean the cats ok?

 

[Matthew Jeschke]

Yeah it actually worked AWESOME. I think so long as your cats aren't broken up.... that is if the media is intact, this would work. For more severe blockage you may have to pull them off to do this, but it seemed to work perfectly leaving them on for me. I almost feel like it'd be prudent to do if ever pulling old cats off to do other work. Heck I think it cost me all of $5 for the powder drain cleaner, Sodium Hydroxide. To test it I dipped my O2 sensor in there. Carbon just shed off it everywhere. Pretty amazing.

I have other issues now with MPG. It seems my 4th gear TCC lockup is decimating my gas mileage. Oddly I go from 16MPG highway & city. To around 14 to 15 mpg highway locked up in 4th. It maybe something I did to the tune though. Trying to figure that out. Right now my theory is I more or less disabled TCC partial apply. Whenever the TCC applies merging on interstate I get some pretty serious knock with otherwise factory settings. It's a long shot but will see what happens. In the least it'll clean up a bit of knock retard which probably won't do much of anything.

I did notice in my tuning though the engine is running at a lower pressure now due to cleaning the cats which is AWESOME!

 

[Fless]

Now I have a new question. I'm trying to fine tune efficiency of the truck. There's still some gremlins in the closet. I have logged every single tank of gas since I bought the truck. However, there's variance in pumps. I typically fill at the same station every time. However, I want to figure out how to fill the tank more consistently so I get a more accurate gallons measure of what was consumed in tank. Any tips?

Although the level can vary a bit from each fill event, the secret is to calculate the average over time. Small variances in the absolute fill level won't have much of an impact on the cumulative number of gallons used. Of course, each tank's calculation will vary but that's not something I'd bother evaluating. Your driving habits and environment will have more of an impact on the consumption.

 

[Matthew Jeschke]

Would be nice if I could get precise measurements regardless. That aside I have a bunch of data. Need to transfer it to a spreadsheet. It's in a log book in the truck right now.