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

Poor running '94

Thread Tools
 
Search this Thread
 
Old Apr 10, 2010 | 03:51 AM
  #1  
caseyjones125's Avatar
caseyjones125
Thread Starter
3rd Gear
 
Joined: Apr 2010
Posts: 3
Likes: 0
From: Letcombe Regis Oxfordshire
Default Poor running '94

Hi there, new member here,
I've got a worsening problem with my car and I was hoping that you could point me in the right direction to fixing it.
Some history:-
It's a 1994 with a manual gearbox. When I bought the car it was fitted with a Hypertech (Non-adjustable) piggy-back chip.The car was running as though the timing was slightly out and the 'SYS' light was flashing continuously.On advice of a mechanic friend, I removed the chip and the fault disapeared.Iwas told by the previous owner that the person that HE had bought the car from had fitted the chip along with larger injectors, I have the receipts for the chip plus quite a lot of other bits bought at about the same time but not for the injectors which seems a bit odd so I have to take the larger injector story at face value only.
I replaced the standard headers with some " Shorty" ones and, on the advice of the same mechanic friend, removed the EGR pipework and blocked off the intakes in the headers and back of the plenum chamber. I also reversed the intake/output pipework on the air pump so that it now draws from atmosphere and blows into intake manifold,post filter (Working on the 'why not' principal)
Because the headers made the car sound so much better than I was expecting, I then had the centre silencer replaced with 2 straight pipes making it a true dual system.
The car has recently started missing slightly under part or light throttle openings (Cruising at 50/60 MPH or accelerating gently)Occasionly the car will suddenly start juddering whilst cruising along at a steady 50/60 MPH in sixth as though trying to climb a gradient in the wrong gear.If I push the throttle harder or drop down a gear, the problem goes.
When I get back from a run, I have noticed that the right hand tailpipe is black whilst the left one is a very pale grey.
On starting up from cold, the sound from the tailpipes is very even and properly "V8", as the engine warms up, the right-hand pipe starts to sound more and more "Woofly" ending up sounding very flat and un-"V8ish"
I have changed the plugs (Cheapest option first,of course!) and, although it now starts better, it hasn't cured the poor running.
I have cleared and then checked the engine diagnostic (Paper clip) and it has stored fault codes 4.63 and 4.64.
I have been on several sites and it has been suggested that it could be either the dredded Optispark or that the exhaust pipe now has no balance pipe.
Any thoughts would be very welcome.


Andy Crosby.
Reply




All times are GMT -4. The time now is 03:33 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