High Mileage Hauler
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High Mileage Hauler
I just purchased a beautiful 2003 convertible in millennium yellow. The car runs really strong but I noticed that the tail pipes are a little black as if it's running rich. The car is completely stock as the one owner car was purchased from was a senior citizen who didn't abuse the car in any way. I figured with 150,000 miles it's time for injectors, coils and plugs. It does have a twin filter high flow intake which I just installed new filters as the others were original to the car. Also what else can I do as far as freeing up HP? I plan on doing a complete sevicing including all the fluids and possibly a shift kit for the automatic transmission. This is my first LS engine as I'm experienced in the chevy small block of yesteryear. I absolutely love the car and I don't want to mess with it too much. Would a ECM tuner be worth the money? If so which one would you recommend? What# injectors should I get? I like to get on it once in a while but I'm not racing it. I like to know that the power is there when I want it. I'm new to this site and I'm still getting used to finding my way through it so be patient with me if I mess up, LOL . Thanks for any help and guidance you can give me.
Last edited by My1stONE; Jul 7, 2018 at 02:13 PM.
Melting Slicks
Joined: Sep 2012
Posts: 2,222
Likes: 798
From: Fort Myers Beach Florida
I find it difficult to imagine anyone needing more than 350 horsepower for driving on the street. I get a kick out of owners with high mileage older vehicles that find the need to "improve" a reliable design. It appears you would like to create a MONEY PIT. SO start with more horsepower, rebuild the transmission, upgrade the suspension and brakes. Don't forget new wheels. By then you'll be a favorite in the club with $28,000 invested in a $14,000 car. Have fun and enjoy the ride if you're headed that way. The supporting vendors will appreciate your contribution. 
Melting Slicks
Joined: Nov 2014
Posts: 3,399
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From: Havre de Grace Maryland
Normally, people buying Convertibles do so (like I did) for cruising, not showing off who has the bada** HP. If HP and racing is your focus, coupes usually are bought. But if you want to do, as DDaaryl opines, go for it the supporting vendors are there to help. It is your car.
Last edited by Vetteman Jack; Jul 7, 2018 at 04:27 PM.
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From: Chandler AZ
I would hold off replacing stuff and find out what is making black in exhaust pipes, is this just normal carbon, or is it excessive?
Pics of black exhaust?
Does it still have catalytic converters, I hear taking those off make black exhaust.
Maybe do a compression test while changing the spark plugs.
I have heard that the coils don't really go bad that often since there is one for each cylinder, if one was bad you would have a misfire and get a check engine light.
Are there any codes in current or history, these cars don't need code scanners, you can pull codes, just look up pull codes C5 Corvette and should be instructions online.
I want to know if this black stuff is normal or excessive.
Pics of black exhaust?
Does it still have catalytic converters, I hear taking those off make black exhaust.
Maybe do a compression test while changing the spark plugs.
I have heard that the coils don't really go bad that often since there is one for each cylinder, if one was bad you would have a misfire and get a check engine light.
Are there any codes in current or history, these cars don't need code scanners, you can pull codes, just look up pull codes C5 Corvette and should be instructions online.
I want to know if this black stuff is normal or excessive.
Last edited by Vetteman Jack; Jul 7, 2018 at 04:32 PM.
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Joined: Jul 2010
Posts: 4,004
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From: Chandler AZ
I would hold off on injectors also, and only add bigger injectors if doing upgrades that call for it, such as putting in a more aggressive cam and heads, headers, even then the stock injectors might be fine, the tuner (a expert tuner with a dyno)might just change the injectors open time, etc, I'm not sure though.
From what I have read, a real custom tune from a professional with a dyno is better than a "canned tune" you get when buying a programmer.
It might even cost the same or even less than the one you would buy and do yourself, and they can probably do more for your car's tune than the kind you just buy.
From what I have read, a real custom tune from a professional with a dyno is better than a "canned tune" you get when buying a programmer.
It might even cost the same or even less than the one you would buy and do yourself, and they can probably do more for your car's tune than the kind you just buy.
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Safety Car
Joined: Jul 2010
Posts: 4,004
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From: Chandler AZ
Also I believe a shift kit would not be used on these cars, the tuner changes the transmission shift points and pressures etc during the tune, all in the programming.
I have read people with C5 with automatic can really step up the way the car drives and feels by replacing the differential gears from the 2.73 or optional "performance factory automatic 3.15 upgrade option" to the manual 6 speed 3.42 ratio.
Another upgrade while swapping out differential while it's out, is add a high stall torque converter, they say it really perks the car up.
Of course you will lose some MPG.
People with 6 speeds and factory ratio of 3.42 sometimes step up to 4.10 ratio, or 3.90 if the car is a Z06 as that transmission is geared differently than base C5 manual.
It may be possible to buy a used 3.42 differential to make this upgrade.
You can supercharge your car, and/or put on better heads and cam, but being a automatic, usually means you need to have your transmission built up to handle these mods. $$$
I say keep your engine stock internally, hopefully that air intake you have is a cold air intake, if not buy a Vararam air intake, install long tube headers and high flow cats, swap to 3.42 rear gears, and a high stall torque converter, then get a real dyno tune done by the best tuning shop in your area, you should be good to go.
But first figure out your engine's black exhaust.
I have read people with C5 with automatic can really step up the way the car drives and feels by replacing the differential gears from the 2.73 or optional "performance factory automatic 3.15 upgrade option" to the manual 6 speed 3.42 ratio.
Another upgrade while swapping out differential while it's out, is add a high stall torque converter, they say it really perks the car up.
Of course you will lose some MPG.
People with 6 speeds and factory ratio of 3.42 sometimes step up to 4.10 ratio, or 3.90 if the car is a Z06 as that transmission is geared differently than base C5 manual.
It may be possible to buy a used 3.42 differential to make this upgrade.
You can supercharge your car, and/or put on better heads and cam, but being a automatic, usually means you need to have your transmission built up to handle these mods. $$$
I say keep your engine stock internally, hopefully that air intake you have is a cold air intake, if not buy a Vararam air intake, install long tube headers and high flow cats, swap to 3.42 rear gears, and a high stall torque converter, then get a real dyno tune done by the best tuning shop in your area, you should be good to go.
But first figure out your engine's black exhaust.
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Joined: Apr 2017
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From: Hickory NC
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Welcome and congratulations on your C5!
It's hard to tell from just a basic discussion whether your car is running rich. Several factors can cause the black on the exhaust.
You mentioned you just changed the air filter elements which is good. Do you still have cats on the car? If these are removed you’ll not get the extra burnoff which cats do to reduce emissions and this could cause some soot.
Is your driving primarly short trips or low speed stop and go? If so, you are probably getting incomplete combustion of the fuel that happens then while the engine is still a little cold. Also, if you are accelerating hard and then abruptly let off the gas this can cause some soot.
Of greater importance is the exhaust composition. Your concern is if the exhaust pipes have wet or oily looking black soot. This could indicate oil usage.
1999corvettels1 raised a good question – are you getting any codes on your DIC? If you aren’t sure how to pull your codes, watch this short video from forum vendor Zip Corvette Parts: https://www.google.com/url?sa=t&rct=...x-JW18j-ZNRMJH.
You may only need to clean up your exhaust pipes and then clean them on a regular basis. I use Simichrome Polish and know others have had good results with Rejex and Never Dull.
I would hold off on a shift kit for your A4 unless you are going to rebuild the transmission at the same time. A good tune would correct any possible richness in your stoichiometric (air-fuel) ratio and the tune could also adjust and firm up your shift points as well as changing temps for fans to turn on, etc. As far as a tuner to recommend; there are good ones around the country. Your signature does not indicate your general location. You could ask that question separately in the Tech with your location or you could check the Upcoming Events Regional Discussion section of the forum at https://www.corvetteforum.com/forums...-discussion-9/. Go to your area in that section and see if any Corvette clubs meet, or if there are any Cars and Coffee, in your area. Meeting other Vette owners there may help give you insight into a good tuner.
Please realize on the forum you’ll always have other members who disagree with what you do or don’t do. There is no perfect answer to anything except for the fact we all like our Corvettes. After that, adding or not adding stripes, chrome or black wheels, modding or not modding and whatever else will meet with some agreement and some disagreement. And as DDaryl points out, you don’t really need more than 350 horsepower for the street. However, the Prius site would point out you don’t need more that 121 horsepower and a battery for the street.
We all have our own idea of what we like.
Best wishes with your car. Hopefully the soot is not a major issue, and hope you enjoy your ride for many more years.
It's hard to tell from just a basic discussion whether your car is running rich. Several factors can cause the black on the exhaust.
You mentioned you just changed the air filter elements which is good. Do you still have cats on the car? If these are removed you’ll not get the extra burnoff which cats do to reduce emissions and this could cause some soot.
Is your driving primarly short trips or low speed stop and go? If so, you are probably getting incomplete combustion of the fuel that happens then while the engine is still a little cold. Also, if you are accelerating hard and then abruptly let off the gas this can cause some soot.
Of greater importance is the exhaust composition. Your concern is if the exhaust pipes have wet or oily looking black soot. This could indicate oil usage.
1999corvettels1 raised a good question – are you getting any codes on your DIC? If you aren’t sure how to pull your codes, watch this short video from forum vendor Zip Corvette Parts: https://www.google.com/url?sa=t&rct=...x-JW18j-ZNRMJH.
You may only need to clean up your exhaust pipes and then clean them on a regular basis. I use Simichrome Polish and know others have had good results with Rejex and Never Dull.
I would hold off on a shift kit for your A4 unless you are going to rebuild the transmission at the same time. A good tune would correct any possible richness in your stoichiometric (air-fuel) ratio and the tune could also adjust and firm up your shift points as well as changing temps for fans to turn on, etc. As far as a tuner to recommend; there are good ones around the country. Your signature does not indicate your general location. You could ask that question separately in the Tech with your location or you could check the Upcoming Events Regional Discussion section of the forum at https://www.corvetteforum.com/forums...-discussion-9/. Go to your area in that section and see if any Corvette clubs meet, or if there are any Cars and Coffee, in your area. Meeting other Vette owners there may help give you insight into a good tuner.
Please realize on the forum you’ll always have other members who disagree with what you do or don’t do. There is no perfect answer to anything except for the fact we all like our Corvettes. After that, adding or not adding stripes, chrome or black wheels, modding or not modding and whatever else will meet with some agreement and some disagreement. And as DDaryl points out, you don’t really need more than 350 horsepower for the street. However, the Prius site would point out you don’t need more that 121 horsepower and a battery for the street.
We all have our own idea of what we like.Best wishes with your car. Hopefully the soot is not a major issue, and hope you enjoy your ride for many more years.
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