C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Several questions..

Thread Tools
 
Search this Thread
 
Old Sep 5, 2008 | 03:12 AM
  #1  
Emc-Icon's Avatar
Emc-Icon
Thread Starter
Heel & Toe
 
Joined: Aug 2008
Posts: 18
Likes: 0
Default Several questions..

So, i got my vette, and i have a few questions in order of importance.

1) The car is an 87 with a swapped in LT1, and it runs rich, and gets hideously poor gas mileage (4-5 mpg) and since the previous owner told me that he planned to slap on a supercharger on the car, he sent the ECU to be retuned for that. Obviously those plans didnt quite work out, so now i need to find a way to get back to the original Fuel map/tune.
How would i be able to do that?

2) Also, the car does NOT like city driving, gets warm after fifteen minutes of driving at 25-45, and once that happens, i lose power and the car runs like crap. Dont know if this is connected to the richness issue or not. Oh, and also, it seems to pull fastest if i give it like 1/4 throttle, and seems to bog out when i give it more.
Any ideas?

3) when the car was swapped, the iterior was also updated to a 92, except that the 87 wiring harness remains (i found a 92 harness for cheap) so the LCD screen doesnt work (tach, oil temp gauge and coolant temp gauges work but oil pressure doesnt.)
What would i need to make the LCD screen work?

I have a lot more questions, but ill wait until later to ask those..
Thanks ahead
Reply
Old Sep 5, 2008 | 05:52 AM
  #2  
REDC4CORVETTE's Avatar
REDC4CORVETTE
Safety Car
10 Year Member
 
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
Default

Ouch!!
Pull the motor and try an L98.
First off I would get a factory 93 LT1 manuel and start their.
You are tring to run an ob2 type system with a computer that can't keep up.
You are looking at the LT1 that needs diff map and o2 sensors along with a less restrictive exaust system,and the list goes on.I would change to a carb and save yourself alot of problems.
Don't get me wrong it can be done but for the beginner it will take you tons of $$$$ and most likely years to get it right.If you want to do it I would go to the fast system type computer and Lt1 edit or equilavent ,that would be a start .
Reply
Old Sep 5, 2008 | 09:26 AM
  #3  
MK 82's Avatar
MK 82
Melting Slicks
 
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
Default

Sounds like a cobbled up mess. Hope you got it cheap!
Reply
Old Sep 5, 2008 | 09:27 AM
  #4  
Emc-Icon's Avatar
Emc-Icon
Thread Starter
Heel & Toe
 
Joined: Aug 2008
Posts: 18
Likes: 0
Default

Originally Posted by REDC4CORVETTE
Ouch!!
Pull the motor and try an L98.
First off I would get a factory 93 LT1 manuel and start their.
You are tring to run an ob2 type system with a computer that can't keep up.
You are looking at the LT1 that needs diff map and o2 sensors along with a less restrictive exaust system,and the list goes on.I would change to a carb and save yourself alot of problems.
Don't get me wrong it can be done but for the beginner it will take you tons of $$$$ and most likely years to get it right.If you want to do it I would go to the fast system type computer and Lt1 edit or equilavent ,that would be a start .

I have a manual
I thought OBD2 was 96+, and the ECU is an LT1 ecu, and has all the sensors and even the EGR and emissions stuff, and a 3 inch exhaust to boot.
Reply
Old Sep 5, 2008 | 11:11 AM
  #5  
Keystring's Avatar
Keystring
Drifting
 
Joined: Aug 2006
Posts: 1,624
Likes: 2
From: Canandaigua New York
Default

Originally Posted by Emc-Icon
So, i got my vette, and i have a few questions in order of importance.

1) The car is an 87 with a swapped in LT1, and it runs rich, and gets hideously poor gas mileage (4-5 mpg) and since the previous owner told me that he planned to slap on a supercharger on the car, he sent the ECU to be retuned for that. Obviously those plans didnt quite work out, so now i need to find a way to get back to the original Fuel map/tune.
How would i be able to do that?

2) Also, the car does NOT like city driving, gets warm after fifteen minutes of driving at 25-45, and once that happens, i lose power and the car runs like crap. Dont know if this is connected to the richness issue or not. Oh, and also, it seems to pull fastest if i give it like 1/4 throttle, and seems to bog out when i give it more.
Any ideas?

3) when the car was swapped, the iterior was also updated to a 92, except that the 87 wiring harness remains (i found a 92 harness for cheap) so the LCD screen doesnt work (tach, oil temp gauge and coolant temp gauges work but oil pressure doesnt.)
What would i need to make the LCD screen work?

I have a lot more questions, but ill wait until later to ask those..
Thanks ahead
Sounds like the computer is responding as tho the supercharger was in place.

Might be a long shot, but try reprogramming the computer.
Reply
Old Sep 5, 2008 | 07:05 PM
  #6  
REDC4CORVETTE's Avatar
REDC4CORVETTE
Safety Car
10 Year Member
 
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
Default

If you have the LT1 computer I am thinking OB1 at least,you can use Lt1 EDIT and change the info in the computer yourself.If the car is running rich and It sounds like it is ,that means the engine is lean.Check the o2 sensors,intake gasket and egr.You can get some carb spray and use it around the intake to check for leaks.You can always get a used computer from the junk yard and install it.Just so you know any wiring on an 86 is not the best.Your oil line wire needs a sensor where the oil filter is,the wire should be at the back of the motor.
My 94 you program the computer it does not use a chip.

Last edited by REDC4CORVETTE; Sep 5, 2008 at 08:03 PM.
Reply
Old Sep 5, 2008 | 07:32 PM
  #7  
Aurora40's Avatar
Aurora40
Le Mans Master
10 Year Member
 
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
Default

You might try posting a location, and maybe there's someone nearby who can help you figure out the tune.

Or if the car has a swappable PROM (I don't know LT1's) perhaps someone nearby can lend you a stock PROM or ECM to see how it runs on the GM tune?
Reply
Old Sep 5, 2008 | 08:14 PM
  #8  
MK 82's Avatar
MK 82
Melting Slicks
 
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
Default

Originally Posted by Emc-Icon
I have a manual
I thought OBD2 was 96+, and the ECU is an LT1 ecu, and has all the sensors and even the EGR and emissions stuff, and a 3 inch exhaust to boot.
96 was first year for OBDII.
Reply
Corvette Stories

The Best of Corvette for Corvette Enthusiasts

story-0

10 Ugly Corvettes That We Still Kinda Love

 Joe Kucinski
story-1

Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer

 Brett Foote
story-2

10 Things Every Corvette Owner Needs (2026 Edition)

 Michael S. Palmer
story-3

8 Most "Only Corvette Owners Understand" Quirks and Problems

 Pouria Savadkouei
story-4

10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years

 Joe Kucinski
story-5

How Much Horsepower Every Corvette Engine "LOST" in 1972

 Joe Kucinski
story-6

Top 10 DOs and DON'Ts for Protecting Your Convertible Top!

 Michael S. Palmer
story-7

Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!

 Joe Kucinski
story-8

150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

 Joe Kucinski
story-9

8 Coolest Corvette Pace Cars (and Replicas) of All Time

 Verdad Gallardo
Old Sep 5, 2008 | 10:00 PM
  #9  
Emc-Icon's Avatar
Emc-Icon
Thread Starter
Heel & Toe
 
Joined: Aug 2008
Posts: 18
Likes: 0
Default

Originally Posted by Keystring
Sounds like the computer is responding as tho the supercharger was in place.

Might be a long shot, but try reprogramming the computer.

Thats pretty much exactly what i was saying. Is there anyone around Salem OR that can retune my ECU? or should i just buy a stock one from a nearby junkyard?
Reply
Old Sep 5, 2008 | 10:03 PM
  #10  
cv67's Avatar
cv67
Team Owner
15 Year Member
 
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Default

tjwong@qwest.net

He can straighten you out. Im guessing if the guy did some SC tune you may have an injctor which is WAY too big in there also.

Sounds lke the conversion is done just needs some details sorted out.
Reply

Get notified of new replies

To Several questions..





All times are GMT -4. The time now is 03:05 PM.

story-0
10 Ugly Corvettes That We Still Kinda Love

Slideshow: 10 ugly Corvettes that we still kinda love.

By Joe Kucinski | 2026-06-03 10:34:17


VIEW MORE
story-1
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer

A lot of money has changed hands at the online auction house over the years.

By Brett Foote | 2026-06-03 10:21:50


VIEW MORE
story-2
10 Things Every Corvette Owner Needs (2026 Edition)

Slideshow: 10 great gifts Corvette enthusiasts actually want for Father's Day!

By Michael S. Palmer | 2026-06-03 15:43:40


VIEW MORE
story-3
8 Most "Only Corvette Owners Understand" Quirks and Problems

Slideshow: These are the quirks, annoyances, and oddly lovable problems that every Corvette owner eventually learns to live with.

By Pouria Savadkouei | 2026-05-28 09:31:39


VIEW MORE
story-4
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years

Slideshow: 10 reasons why the C6 Z06 is still a performance benchmark after 20 years.

By Joe Kucinski | 2026-05-27 17:20:09


VIEW MORE
story-5
How Much Horsepower Every Corvette Engine "LOST" in 1972

Slideshow: How much horsepower every Corvette engine lost in 1972.

By Joe Kucinski | 2026-05-27 16:54:53


VIEW MORE
story-6
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!

Slideshow: How to Protect A Convertible Top: 10 DOs & DON'Ts

By Michael S. Palmer | 2026-04-03 00:00:00


VIEW MORE
story-7
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!

Slideshow: The 10 most explosive Corvettes ever built based on power-to-weight ratio.

By Joe Kucinski | 2026-05-20 07:23:03


VIEW MORE
story-8
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

Slideshow: From C1 to C8 we compare every Corvette generation by the numbers.

By Joe Kucinski | 2026-05-12 16:54:12


VIEW MORE
story-9
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE