Need help with exhaust. Loss of mpg&hp - TCCoA Forums
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post #1 of 15 (permalink) Old 06-25-2018, 02:45 AM Thread Starter
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Need help with exhaust. Loss of mpg&hp

Hey guys..thanks for the forum.
I hope I'm not asking the same questions that others have asked.
I have a 97 Mercury cougar XR7 4.6l.
I had a smell from the exhaust so I took car to exhaust shop and had the cat removed and had a y pipe install.
I thought it would have helped the car but I was wrong.. I've lost hp and I've lots mpg. The car had good power and good mpg until I had the cat removed.
Should I put another cat back on car.
I don't understand unless I loss back pressure to engine and that hurt it all together.
Has anyone else had this prob?
What is my best options for getting my car back to the way it was or maybe better.
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post #2 of 15 (permalink) Old 06-25-2018, 03:32 AM
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Isnt there 3 cats? What one did you had removed? I think it would be best to take out the 3rd cat and the resinator and replace both with a X-pipe. Thats what I have on my 92 SC and it seems to do well with that setup. Can you post up some pics for us to see?
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post #3 of 15 (permalink) Old 06-25-2018, 08:37 AM
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It sounds like he already removed the 3rd cat and replaced with a y-pipe.

Nothing about removing the 3rd cat would hurt your gas mileage. Maybe the front cats are clogged?

Replacing all 4 o2 sensors is a good idea - they may have contributed to the cats going bad from running too rich.

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #4 of 15 (permalink) Old 06-25-2018, 11:02 AM Thread Starter
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I did remove the third cat. I just don't get. The only two things I did was remove the air filter box and replaced with cone filter and had the third cat removed and then it all with down hill. I think putting the cone filter didn't really help it considering that the filter is under hood and it's breathing engine heat too, but I didn't notice much of a drop in mpg until I took cat out.
I was going about 190+ miles to a half a tank now I'm lucky to see 150.
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post #5 of 15 (permalink) Old 06-25-2018, 11:38 AM
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Did they fix the exhaust leak when you took it in or did you take it in purely to have the cat removed? Did they say it was the rear that was clogged? Did you have any engine codes prior to or after taking it in?

First: Stacie, 1996 Tbird LX, mild build NPI engine, PI cams and intake, Long tube headers, Jmod.

Second: Ellie, 1989 Tbird SC, r̶e̶s̶t̶o̶r̶i̶n̶g̶ ̶t̶o̶ ̶b̶e̶ ̶n̶e̶w̶ ̶d̶a̶i̶l̶y̶. off the deep end

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Fourth: 1990 Tbird SC, GT40 5.0 mated to m5r2, BBK long tubes, motor out the hood, drift car.
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post #6 of 15 (permalink) Old 06-25-2018, 12:17 PM
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Exhaust shop should have verified your catalytic converter was no good with a temp gun - they should have checked all three.

Was the 3rd cat removed at your request, or is that what the shop determined ?? Yes this can cause a loss of back pressure that will lose torque on the low end.
If your 3rd cat was clogged, you would have noticed a lack of power before removing it. Even if your 3rd cat was completely empty and hollow, it shouldn't have made any difference.

The rotton egg smell doesn't necessarily indicate a bad catalytic converter - but its heading that direction.

Changing your o2 sensors probably wont do anything either. The computer uses the first two for air/fuel feed back and the second two to verify catalyst efficiency on the primary two cats. If you had any kind of problem with anything in this area, you would most likely have a Check engine light. Ford had a pretty high threshold for failed cats .. they will still run then down to 40% efficiency or so before throwing a code.

Your air filter probably isn't doing much ( hot engine air and all ) .. youre not really going to feel any noticeable change in power / MPG in this area.


I would make sure you didn't dirty the MAF sensor with the filter install .. and reset your PCM by unplugging the battery if that hasn't been done so already. blah blah blah … I was just trying to do a quick reply, fuck. Do you have access to a scan tool, fuel trims, catalyst efficiency ??
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post #7 of 15 (permalink) Old 06-25-2018, 12:19 PM
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My car had a cone filter when I got it. The PO gave me the original air box and suggested I might want to reinstall it. I wasn't sure why he would say that because after all it was a genuine K&N air filter and it looked so cool. After a while, I realized that something just wasn't quite right with the way the engine ran and the K&N was poorly installed. The air intake temp sensor regularly fell off too.

Before installing the original airbox I cut off the snorkel. The difference was amazing. I don't know if the K&N was incorrect for the 4.6 or what. But I'm sure glad it's gone! There seemed to be a huge restriction. Now, this same air filter is on my friend's Nissan Sentra. The original air box with the bottom cut out sounds better too and can be heard outside the car more than inside.

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post #8 of 15 (permalink) Old 06-25-2018, 01:43 PM
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Now that you mentioned the cone air filter, I would yank that out of there like you're pull starting a lawnmower. Get a new paper filter and put the stock air box back in. That should fix you back up.

Al
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97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #9 of 15 (permalink) Old 06-25-2018, 05:15 PM
No, Mr. Lemmywinks, No!!!

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There are actually cone mods that work with our cars really well; the 2002 maf and Cone airbox swap is great, but you have to have it tuned to use it.

I have that mod in 2 cars, and it's really nice, but it pulls air from the same spot the factory air filter box pulls from, the hole in the fenderwell.

I use a paper cone in my cars, because oiled filters do not go well with MAF sensors; they require frequent cleaning, and cleaning MAF sensors is inherently risky, so needs to be minimized; break that tiny wire, and you're out some bux.

The stock air filter is good to 350HP easy; the MAF, not so much. There is much discussion.

The 02 GT maf is supposed to do up to close to 500hp, but is also a better sensor than our stock one. Again, tune is required for that upgrade.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
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post #10 of 15 (permalink) Old 06-25-2018, 05:45 PM
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Quote:
Originally Posted by Grog6 View Post
break that tiny wire, and you're out some bux.
Its just a platinum wire .. cant be all that expensive ..
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post #11 of 15 (permalink) Old 06-25-2018, 06:47 PM
No, Mr. Lemmywinks, No!!!

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Quote:
Originally Posted by dDUBb View Post
Its just a platinum wire .. cant be all that expensive ..
The expensive part is the machine that trims the maf electronics to work with that piece of wire, and the $100 an-hour plus guy who pushes the button to run the program on the machine, lol.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


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Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #12 of 15 (permalink) Old 06-26-2018, 02:22 PM Thread Starter
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I had no check engine lights. I did have a bad smell under full trottle. I requested pulling cat off. I'm not good with this types of cars I've got older like 88and 90.
I quess I might need to put car back to stock even put cat back on it
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post #13 of 15 (permalink) Old 06-26-2018, 04:00 PM
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I think if you just put the air intake & air box back to stock, you'll be fine. A lot of sensitive electronics in that air box.

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #14 of 15 (permalink) Old 06-26-2018, 05:51 PM Thread Starter
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Ok..thanks for all yalls help
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post #15 of 15 (permalink) Old 06-29-2018, 12:57 AM Thread Starter
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Ok guys. I know what u told me and I do understand know, but I had order a cold air intake tube that relocates the filter under the car B4 I talked to y'all and got y'all's imfo.
I wanted to return it and I explained to the guy that it's probably a bad decision because of it being a oiled cone filter.
His reply was that the filter is a dry filter that needs no oil and that he has sold many of them and had no feedback of issues.
He also said that there would be any problems with sensor especially MAF.
I could return it but it's a restocking fee and I got to pay to ship.
Has anyone used this system?
I want to install it so I don't waste my money, but from what y'all have told me it might just be a waste.
I've got the factory airbox and I'm planning on cleaning the MAF and reinstalling it tomorrow.
What do y'all think, I'm quessing I just wasted my money
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