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RandyBSmith

Guest
I have a 93 6 speed. I have had the following things done:
Corsa Cat Backs
JBA shorty headers
K&N Filter
It supposedly had 160 degree thermo when I purchased it
drilled HP 13" rotors
52mm throttle body Eddlebrock
adjustable fuel pressure regulator: set to 32 lb
Jacobs Performance coil
I have a stage II Performance Chip purchased through Mid America.
8mm performance plug wires

Once engine is hot, service engine light comes on and stays on, you can feel the timing being retarded and it back fires.

Same problem with hypertech chip and stock chip.

Any idea about what could be causing the problem?

WOuld like to purchase a set of hoses to replace all under engine compartment, any suggestions
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
I'm curious about the fuel pressure regulator being set at 32 psi. I know on the earlier C4's, stock pressure was 37 PSI and the recommendation was to make it higher (like 42). I'm fairly sure that TPIS states on their website that GM increased the base pressure to 39 or 41. You might want to bump that up 8-10 PSI and see if the low pressure is causing you to run a bit lean. What codes are being thrown when the SEL comes on?

[RICHR]
 
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RandyBSmith

Guest
fuel pressure

I apologize. It is set at 42 psi.
When service engine soon light comes on, you can smell the raw fuel. Corvette mechanic at Chevy dealership said that nothing is showing up on the codes. I had someone stopped behind me who said they could smell the raw fuel. I believe that whatever is causing this is what is making it backfire. This was also happening with another performance chip.
 
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Shadowing1985v

Guest
umm

O2 sensor maybe
but i would think the comptuer would detect that,,

your o2 sensor control's how rich to burn the car


what is your car idling at
in N should be 600
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Ouch. If you're dumping raw fuel out the exhaust, your cat is going to be toast soon. Have you had the injectors checked? Perhaps one or more are stuck open.


If the engine light is on, there HAS to be a code. It wouldn't trip otherwise.
[RICHR]
 
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RandyBSmith

Guest
Code

I believe that the tech told me that he was seeing an intermittent code. I think it was a code 43.
When I had the covers off I could hear the injectors clicking. Is this normal? I am use to carbs.

How easy or difficult would it be for me to replace these myself. I have the manuals.
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
43 is the knock sensor. Make sure it's connected (mine wasn't when I bought my Vette, but it had the opposite problem of yours) and working. Too sensitive?
[RICHR]
 

compyelc4

Well-known member
Joined
May 1, 2002
Messages
607
Location
Dayton, Ohio
Corvette
'95 LT1 Coupe, Comp Yell; C6 Roadster, Vel Yell
Could it have been a code 42. My 95 was doing that recently and it proved out to be the opti-crap. The backfiring was due to false firing signals being sent to the ECM. Plugs were intermittantly firing when they should not have been.

You really need to find out what codes are being set. You must be setting something. Try something the next time your dash light come on. Try turning on your air conditioning. Does it work? During this interval are the fans on? I'm playing a hunch here.
 
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RandyBSmith

Guest
I am afraid that it could be the opti-spark. Not knowing that it was not suppose to get wet, I washed the engine and when I went to start it, it backfired and something up in that area popped real loud.

If this is bad, I don't understand why the car doesn't skip at idle.
 
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Shadowing1985v

Guest
umm

does L98's have opti spark

what is a opti spark is that your advance spark

those cost like 40 bucks to replace,,i replaced mine
i get code 43 right now

and i dn't know how to clear it yet

and i replace the advance spark square comptue rthing
and the knock sensor and i still get 43
 

Geof180

Well-known member
Joined
Mar 2, 2002
Messages
69
Location
Ohio
Corvette
94 ZR-1 and a 96 LT1 coupe
no.. L98 does not have the opti-spark.... that is LT1/4 equipment.....
 
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RandyBSmith

Guest
The cost of an opti-spark for a 93 is 398.00. The water pump has to come off so if that hasn't been replaced you might as well replace it too.

It looks like I am going to have mine replaced in the next couple of weeks.
 

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
be careful who does your work on that stuff. Mine has been throwing belts ever since one of the Denver dealers replaced my opti spark and water pump. :hb
 

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