North American Turbocoupe Organization

4.6L catalytic converter problems
Liquid_force Offline
Senior Member
Updated: not engine problem -- catalytic converter noise.

Hey all. Hope there's some 4.6l knowledge lurking around here.
My wife drives a high mileage '03 Aviator - DOHC 4.6l.
It has run great since we've owned it (137-162k), but there's an engine knock in the bottom end that has become painfully obvious over the last week or so.
I'm assuming the worst and planning for an eventual engine replacement.
I'm a "decent" self-taught home mechanic, but I've never done an engine swap in anything, and I feel like this one might be out of my league.

Is it even worth considering?
What, if anything, would be the major road blocks for a job like this?
Rough time required?
88 TC -- Dark Blue 283k
RIP - 9/22/07
She was a great TC and went down swinging Smile
Now -- Me: A minivan, I'll spare you the details.
Her: '09 VW Tiguan AWD 2.0T 101k

Not B Anymore Offline
I don't know anything about the 4.6 or the Aviator, but the way I feel is, as long as you can take a lot of photos and notes, and have or can make the right tools, and have patience, nothing is out of your league.
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels

natmac3 Offline
I have an '05 Aviator and although it would be a significant investment of time and probably a couple thousand dollars in parts/fluids/etc, I agree with B completely.

Take your time and do your due diligence & it shouldn't be too overwhelming.


Liquid_force Offline
Senior Member
Took a few minutes today to look into it.

It does not sound like it's coming from the engine. I got under it and had a helper rev it to produce the noise. It's a loud "rattle" that seems to be coming from the top of the transmission.

I'll have it looked at this week, but any guesses?...

btw - the transmission was rebuilt/replaced about 30k ago by Lincoln

Sophosis Offline
May be worth pulling the inspection cover or the torque converter nut access plug, if it has it, and make sure the torque converter nuts aren't loose. I think I've also heard of a broken/cracked flexplate fooling some people into thinking they had rod knock.
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims

Liquid_force Offline
Senior Member
Took it by a general mechanic today. Surprisingly, they traced it to the DS catalytic converter.

That's good news vs new trans or motor, but still not cheap.

I contacted a 2nd shop specializing in exhaust and they were somewhat cheaper -- still pretty pricey.

The cat system is generally sold in one large 3 piece assy. (Walker 16381 about $460 at RA). But I found one company (DAVICO) that sells it as individual pieces and the DS is right at $200. Warranty is the same as Walker.

Does anyone have any experience with Davico?


Not B Anymore Offline
Will a universal converter not work?
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels

Jeff K Offline
Many "cheap" no name converters are cheap because they dont have anywhere near as much Platinum / Palladium / Rhodium precious metals as the more expensive ones. The cheapos will work for a year or so, and then you will get the dreaded CEL coming on with P0420 / P0430 cat efficiency codes. Only solution is to replace the cats again.

Check out Bear River Converters. They are very high quality. Not the cheapest out there, but they will last. No clue if they have any for your application.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized

Dan S Offline
The converter for your Aviator should be the same as the '03 Explorer with a 4.6. Just like the name Cadillac, Lincoln drives the price.
Dan S
Custom 88 TC, Mandarin Copper Pearl Metallic
1972 Ford F-100 SWB Styleside
2015 Lincoln MKC 2.3 EcoBoost AWD

Liquid_force Offline
Senior Member
yeah, dan, you'd think, but even walker provides different part numbers.
Lincoln has the 4v heads (Marauder/Cobra) vs 2v (I think) of the Ford. There's at least a difference in the y-pipe section.
In replacing the entire assy. either one might work, but trying to replace just a piece I'm guessing it will have to be lincoln part.

Also, the Lincoln part is actually a few dollars cheaper through Rockauto vs the Ford part.


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