1997 lean condition

[Surfnski]

I just went through this on a 5.4. Same symptoms anyway... Did a smoke test and found a minor vacuum leak at the intake manifold. Replaced the manifold and gaskets and all is good now.

 

[Killer Ride]

The clogged cats can cause the fouled plugs,extreme exhaust pressure and heat from having nowhere to go can cause predetonation and other issues including blown heads and bent springs

Sent from my SM-G950U using Tapatalk

 

[Killer Ride]

An exhaust guy does not screw a gauge in he drills a tiny hole then affixes a pressure gauge to that tiny hole. Has you start the car and gas it a few times and voila. Once he's done he just zaps the tiny holes with the welder. Takes about 5min they usually don't charge for the test

Sent from my SM-G950U using Tapatalk

 

[1955moose]

I've heard of that way too. Most guys here in the Bay area unscrew the 02 and take a reading that way. Yeah those exaust benders do love their torch.

Sent from my N9131 using Tapatalk

 

[TobyU]

I've heard of that way too. Most guys here in the Bay area unscrew the 02 and take a reading that way. Yeah those exaust benders do love their torch.

Sent from my N9131 using Tapatalk

Yes, and he spot where he welds will be the first to rust out on the pipe.

 

[1955moose]

Most muffler guys I've run into are hacks. Their are some good ones don't get me wrong. But an acetylene torch, and a half inch drive air impact is pretty much their tools. It's a win win though for the shop. They get paid for 95 percent of their work. They rarely get away from their comfort zone, mufflers and pipes. But beyond having them diagnose and replace a bad catalytic converter, you don't want them chasing anything real techy. And that's ok. You wouldn't ask your shoe cobbler to make you a custom pair of Italian Boots, in most cases it's not in his wheelhouse.

Sent from my N9131 using Tapatalk

 

[crowncrazy87]

Ok. So before I break loose the exhaust from the manifolds (rusty as all get out) I took my IR thermometer and did temp tests per what I found online so I let the engine run till it reached operating temp (roughly 10 to 15 minutes)... I didn't write down the numbers but here is what I observed.

On bank 2:
front cat had a temp on the back(outlet) weld seam of about 100° hotter than the front (inlet) weld seam.

Rear cat back weld seam was roughly 100° cooler than front weld seam.

On bank 1:
Front cat had almost the same temp on both weld seams.

Rear cat was about 100° cooler on the rear weld seam.

Looks like my next step in diagnosis is to get that's rusted up bolts loose and drop the exhaust from the manifolds!

I do appreciate you guys helping me out with this!

 

[Killer Ride]

You bet. Just paying it forward! Had a couple of Ol' guys help me out in the past with these trucks and motors. Now it's your turn when somebody has this type of problem.

Sent from my SM-G950U using Tapatalk

 

[VoxVeritatis]

Lean condition most frequently points to vacuum leak. In addition to vacuum hoses, the entire edge of the plastic intake manifold is suspect. My '02 developed a manifold leak at front of engine above crossover, but underneath where it could not be visually inspected. Couldn't locate it until it became bad enough to manifest itself. Replaced manifold and completely resolved the issue.

 

[crowncrazy87]

The 1997 4.6L has the aluminum 2 piece intake. I have tried everything to check the gaskets short of tearing it apart. If it was leaking bad enough to cause the severe drivability issues I'm having. The water test and spraying of carb cleaner would have found it!

That being said not saying that a leak somewhere is not contributing to the issue. I'll know more once I get the exhaust dropped and see what happens!