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  #1  
Old April 17th, 2014, 10:08 AM
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TJ Spencer
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Black exhaust 97 NAS

Why would my exhaust be so sooty? The picture here is of my 6 week old tail pipe. What would cause it to be so black and sooty? My right catalytic converter is hollowed out but even before that the exhaust was always pretty dark and on the rate occasion I gun it it would put out a little black cloud. Only 70,000 miles on the whole truck and less than 30,000 on this engine. 4.0 v8. Thanks for the help!!

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  #2  
Old April 17th, 2014, 05:22 PM
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obdiii likes to have catalytic covertors
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  #3  
Old April 17th, 2014, 05:43 PM
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I'm about to cut all 3 cats off. She's registered in Michigan so I'm never going to have to pass emissions. Even if I did register it here in MO I would just pay someone to pass it lol.
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  #4  
Old April 17th, 2014, 07:09 PM
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Anthony Nelson
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Your ECU/Gems is likely gonna go screwy if you cut them out. There are only 2 cats though. The other is the muffler. Weld in new ones.

I could be wrong, but the fuel systems management will cause the truck to run lean/rich depending on the sensors that should need to be in the system unless you can reprogram the computer to run without...which could be possible.

Just a heads up.
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Old April 17th, 2014, 08:20 PM
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have defenders had gotten this cheap, generally these questions on the discovery/range rover forums.
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  #6  
Old April 17th, 2014, 08:44 PM
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Quote:
Originally Posted by rover4x4 View Post
have defenders had gotten this cheap, generally these questions on the discovery/range rover forums.
Maybe defender owners don't slum on discovery/range rover forums.

For the OP- what grade fuel are you using?

I use non-ethanol fuel and my '94 seems to like that better as its not my DD
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Old April 17th, 2014, 10:22 PM
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She's only ever had premium fuel (91+). I had the right side cat hollowed around the same time I had the tail pipe installed but I remember back in the day the OEM tailpipe was always very dark. Also, whenever you would have to really get on the gas it would usually cough out a lil black puff. Again, it only has around 70k miles on it. It did have a fire years ago but was restored in 2002 and has since had the "service engine" light on for as long as I can remember. The code is p3999 which usually means a shifty ground to the ecu.

------ Follow up post added April 17th, 2014 08:25 PM ------

And through this summer she is my daily driver unfortunately lol. We have a love/hate relationship lol.
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  #8  
Old April 18th, 2014, 06:20 AM
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Unless you put some cats back in or get a custom tune it will probably never run right. Nature of the beast with computer controlled fuel management. Now if you put a carb on it that's a different story
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Old April 18th, 2014, 06:24 AM
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Have you dared check your mpg?
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  #10  
Old April 18th, 2014, 09:32 AM
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I have not dated check my mpg. Judging from our last trip from MI to MO I think I was getting around 13 mph highway. I'm thinking I'm around 10 mpg city. That is about normal right? I'm running 255/85/16 with stock gears.

------ Follow up post added April 18th, 2014 07:32 AM ------

Dared*
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  #11  
Old April 18th, 2014, 09:46 AM
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Get a high flow cat from Summit, replace them both... I had one of mine replaced on my NRP system a few year back... Easy and runs great.
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Old April 18th, 2014, 11:53 AM
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not having a cat would certainly convince your engine that the system is running lean, without that restriction so the unspent fuel can heat up the engine management generally throws more gas at the problem. I wouldn't use MPG as a barometer for you engine running rich, especially not in a rover v8

Also, I'd consider replacing the o2 sensors, my 2000 Jeep just needed all 4 o2 sensors replaced in the last few years. Also have someone check your ECU (even without an engine light on). I have (in my younger years) removed the bulb in the dash to pass inspection (airbag light on a vw, CEL on a toyota). not saying that is the case here I am just saying it happens. Sometimes they throw intermittent codes as well...
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Old April 18th, 2014, 12:11 PM
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My check engine light was on until I reset the ecu a few weeks ago... The light had been on since around 2002 when it was restored. I hate the idea of having catalytic converters especially on a low HP v8 that already feels so boggish but I guess if they will actually make it run Better maybe I'll get new cats soon.
The only light on is the service engine soon light which like I said has something to do with an intermittent bad ground and also is probably the cause of my intermittent non-idle as well.
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Old April 18th, 2014, 12:34 PM
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Not having cats means you need to select the european programming on the ECU, which can be done via the tuning resistor (long thread on this elsewhere). There are several reasons for 4 O2 sensors, they essentially look at pre-post cat for determining how much fuel to dump into the system and how to run the fuel trim.

There is another lurking culprit in overly rich engines. The Temp sensor, not the gauge one, but the coolant one. This is kind of a master fuel map selector. Your ECU isn't an advanced computer, but more of a lookup table. There are several different fuel maps stored in memory and they are selected first off based on coolant temp. The start program is rich until warm up. If the sensor gives bad data, the engine will run rich or poorly at start, depending on how the resistance has skewed. Corrosion on the connector also changes the resistance. You can look at the data it puts out if you have a 97, with an OBD system. The sensor is under $20 and is fairly common. You can get the OEM version off ebay or get an aftermarket one from the likes of O'Riely (Part # 17-1263).

I get between 13-15 mpg on my 1997 up here at 7,000' urban driving.
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  #15  
Old April 18th, 2014, 12:36 PM
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I hate to say this, but what is wrong with you? You asked the forum why you have 'black exhaust' after having a engine light on since 2002?! Who the hell cares what the truck sounds like, you are losing more 'performance' out of the tail pipe then you are gaining making the truck louder. And clogging your injectors, your exhaust manifold, your exhaust valves, your cylinder walls while you are at it.

'resetting' the CEL just forces the ECU to re analyze information and eventually your CEL will come back on. Since you reset it you have to wait for it to come back on to figure out which o2 sensor (or MAF) is bad, or since you clearly haven't done anything involving emissions since 2002 (aka a decade) I would replace all the o2 sensors anyway, they aren't that expensive.

Sorry for the rant I just hate when people ignore problems instead of solving them; "Don't do anything if you're going to do it half ass". Most secondhand rover owners will attest to this frustration

------ Follow up post added April 18th, 2014 10:40 AM ------

Quote:
Originally Posted by Dogpilot View Post
There is another lurking culprit in overly rich engines. The Temp sensor, not the gauge one, but the coolant one. This is kind of a master fuel map selector. Your ECU isn't an advanced computer, but more of a lookup table. There are several different fuel maps stored in memory and they are selected first off based on coolant temp. The start program is rich until warm up. If the sensor gives bad data, the engine will run rich or poorly at start, depending on how the resistance has skewed. Corrosion on the connector also changes the resistance. You can look at the data it puts out if you have a 97, with an OBD system. The sensor is under $20 and is fairly common. You can get the OEM version off ebay or get an aftermarket one from the likes of O'Riely (Part # 17-1263).
I had an audi with this problem 'cold weather sensor' it was called, essentially its a 'choke' for gas engines on cold day starts. I didn't realize the rover utilized this, essentially it 'switched off' after the engine reached temperature (even though the sensor was bad) but it did leave noticeable black soot on my exhaust pipes
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Old April 18th, 2014, 03:02 PM
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Quote:
Originally Posted by Jtomchik View Post
I hate to say this, but what is wrong with you? You asked the forum why you have 'black exhaust' after having a engine light on since 2002?! Who the hell cares what the truck sounds like, you are losing more 'performance' out of the tail pipe then you are gaining making the truck louder. And clogging your injectors, your exhaust manifold, your exhaust valves, your cylinder walls while you are at it. 'resetting' the CEL just forces the ECU to re analyze information and eventually your CEL will come back on. Since you reset it you have to wait for it to come back on to figure out which o2 sensor (or MAF) is bad, or since you clearly haven't done anything involving emissions since 2002 (aka a decade) I would replace all the o2 sensors anyway, they aren't that expensive. Sorry for the rant I just hate when people ignore problems instead of solving them; "Don't do anything if you're going to do it half ass". Most secondhand rover owners will attest to this frustration ------ Follow up post added April 18th, 2014 10:40 AM ------ I had an audi with this problem 'cold weather sensor' it was called, essentially its a 'choke' for gas engines on cold day starts. I didn't realize the rover utilized this, essentially it 'switched off' after the engine reached temperature (even though the sensor was bad) but it did leave noticeable black soot on my exhaust pipes
Well this thing has had black exhaust as long as I can remember. This is a 2 owner truck-my dad bought it in 97. I bought it in 2004. This is not a new problem. Let me be clear-it has ALWAYS has a black tail pipe and spewed a puff of black when hammered (which is very rare). She runs fine. I have not done anything to try and make it louder? I have always thought of catalytic converters as a waste because they restrict air flow. There are no emission codes coming up and the only one that was flipping the check engine light was my wheel sensors. I do agree I should replace my 02 sensors. However, I really like the idea of removing the cats if I can re-program the computer to run without! I'm going to look into that more.
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  #17  
Old April 18th, 2014, 03:23 PM
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TJ Spencer
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I'm sure the ecu could be the culprit considering the multiple times this thing has been under water and also the fire back in 1999 lol.
I really appreciate everyone's feedback on here. This forum is great. The only thing id like to say is try not to get all butt hurt over how I treat my D90. Currently she is my DD but really guys/gals for the most part she is a nice toy I beat the crap out of and tinker with on the weekends. She happens to be worth lots of money but that means nothing to me. I treat my rover the way rovers are made to be treated. I do very regular maintenance and store her in the winter. She is NOT a mall crawler, status symbol or anything else. She's pure utility. Yeah, I have neglected the emissions part but with all the issues this thing has had over the years it's the least of my worries. Currently she's up and running darn good and this is my latest gremlin to diagnose. Also, I do 98% of my own work because I do not have the money to pay someone else and most mechanics are too scared to work on it anyways even though in reality they are much more simple than most cars. Sorry for MY rant....now back to the possible reasons my exhaust is black! :-) Cheers!!
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  #18  
Old April 18th, 2014, 03:43 PM
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Quote:
Originally Posted by Spenc1tj View Post
The only thing id like to say is try not to get all butt hurt over how I treat my D90.
No one is 'butt hurt' aka I don't care if you drive your truck into the ground, but noting that your truck is blowing carbon and not mentioning that you've had a CEL on since 2002 is wasting board members time when they are trying to help you out. Hence my frustration.
It's why you'll often see people respond to new threads about importation, customs, just about anything that has been discussed at length, with instructions on how to use the search line on this site, great community but generally we are efficient with our time.

You said you 'hollowed' the cat, I presume to make it louder or 'unrestrict the exhaust' which is is meant to improve output on mechanical engines but does not work with engines that are utilizing electronic fuel management, high flow cats and new o2 sensors would be a better solution then removal, and retain value should you decide to sell down the road.

Also if you don't have the money for a mechanic then I wouldn't recommend treating a rebuilt rover as a beater; though I appreciate your utilitarian sentiment. It might be one of the few 'modern' cars on the road that actually hold their value; be smart, take care of it, think of the next potential owner when you perform any modification or maintenance (or lack thereof) because it just might be the cash you need for your next hobby (or next rover) down the road.
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  #19  
Old April 18th, 2014, 04:08 PM
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Ok I still don't get it. The exhaust was black well before I had the cat hollowed . The exhaust shop hollowed it because it was clogging up. I would not think of hollowing it to make it louder . The hollow one actually sounds like crap because you can hear the exhaust flowing through and almost makes it sound like a leak. So throwing the hollow cat out of the equation and the only code I'm throwing is the ecu having communication problems from a twitchy ground what are the other possibilities? I was thinking plugs, wires and coils would be a good idea but this engine only has 20k miles on it and was installed by LR so that's probably nothing to do with it. I still plan on doing coils,wires and plugs since the engine was installed back in 02 or 03.
I guess I've always figured that all defenders had dark exhaust. Any other suggestion out there?
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  #20  
Old April 18th, 2014, 04:19 PM
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Quote:
Originally Posted by Spenc1tj View Post
the only code I'm throwing is the ecu having communication problems from a twitchy ground
Fix that problem first
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