Any Mechanics Out There

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The Black exhaust means Carbon, unburned fuel, like chopsaw chopsaw said. O2 sensor does seem to be a common item that causes it. Does it happen more when you have the Boat hooked up to it? Has your overall gas mileage gotten noticeably worse?
 
Another thing...what do you use for gas? Ethanol blend or not? What type of driving...many highway miles or just slow speeds in town driving?

Ryan
 
I had a '96 grand that I put over 250k on. My cat crapped out right after warranty and the one I put on didn't have a place for an O2 sensor (back then circa '99 Chrysler was the only place you could buy that cat and they were about 400$, and a generic one was about 80$) - so downstream is def no big deal. that 4.0 was manufactured for about 60 years, they never should have retired it. My money is on the O2 sensor that matters. I hate throwing parts at something but you gotta start somewhere
 
IMO if you changed the MAP and flow sensor and it fixed the problem I would test them components to make sure they are working properly before trying to fix the issue by guess swappping parts (AKA Swapatronics). Stay away from aftermarket parts if possible. I use NAPA if I cant get OEM and even NAPA can be bad out of the box. With after market parts you never know what your going to get. Its possible one of the parts you replaced already went bad.
You should be able to check voltage or ohm out the components to verify they are working correctly before moving on.

My 2 cents
 
For a cheap way to look at and reset data. It's hard to beat the Torque app and a elm 327 dongle from amazon. Less than 25.00
NICE. Amazing price for live data. Diagnosing cat would be simple, look what voltage... With current shop rates I think live data is a must for the owner that tinkers.

Ni mechanic but like tinkering. 96 Grand 5.2. Try this first/dead simple. Try unhooking ground for 10m to reset CPU. Make sure engine is cool. Helped me a ton of times and not just the Jeep.
 
IMO if you changed the MAP and flow sensor and it fixed the problem I would test them components to make sure they are working properly before trying to fix the issue by guess swappping parts (AKA Swapatronics). Stay away from aftermarket parts if possible. I use NAPA if I cant get OEM and even NAPA can be bad out of the box. With after market parts you never know what your going to get. Its possible one of the parts you replaced already went bad.
You should be able to check voltage or ohm out the components to verify they are working correctly before moving on.

My 2 cents
Correct these 4.0 do not like aftermarket 02 sensors use NTK
 
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Always something. Trying to replace windshield reservoir 2003 Park Ave and master cylinder in the way. Guess oil change places don't use the right fluid. Mine cracked all the way down last freeze.
 
Guess going to see how long before messes up again. May be months again. I gotta pull master cylinder out of my 2003 buick park to replace windshield fluid reservoir tomorrow. Brake lines in the way. Had to order a 15mm since mine disappeared. Nothing like driving old cars.
 
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There's a date range there that had the super charged V6 engine . Those are the ones to have . Not sure of the cutoff date , but '03 is right around the end of them . Great vehicles .
My son's 02 Buick Regal has it...it's got some snap! :emoji_blush:

Ryan
 
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Guess going to see how long before messes up again. May be months again. I gotta pull master cylinder out of my 2003 buick park to replace windshield fluid reservoir tomorrow. Brake lines in the way. Had to order a 15mm since mine disappeared. Nothing like driving old cars.
Beats the alternative Brian...paying for a new one! I have several vehicles...some the same age as yours...know what it's like!

Ryan
 
You guys don't deal with salt-brine do you. You can almost see the rust holes forming on your car during our winter months. Nasty stuff that gets in every nook and cranny

Chris
 
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