Is it time to replace the Opti-Spark?
Thread Starter
Cruising
Joined: Feb 2003
Posts: 12
Likes: 0
From: ISLAND HEIGHTS NJ
Is it time to replace the Opti-Spark?
My '93 LTI, 60K miles, 6sp. runs fine when oil & water temps get up to normal; However, this toy is taken out once every week or so, and if it goes for a short trip (<2miles) it is hard starting or running rough when turned off and back on. (i.e. quick trip to the store, hard cranking like fuel is there but no spark, or missing on accelleration). Prior owner changed the water pump @ about 30K-50K miles. I wonder if moisture worked its way into the opti-spark when the pump went bad? Maybe once the engine warms, any moisture dissipates? But why no problems when cold starting? Plugs have never been changed, and I plan to put in OEM AC-Delcos, but this does not seem to act like a fouled plug.
Saw an article @ Corvette Fever home page on modifying the '92-'93 Opti to use vacume off the intake manifold to keep moisture out, as the '94-'95 unit does. Anyone have experience with this mod? :confused:
Saw an article @ Corvette Fever home page on modifying the '92-'93 Opti to use vacume off the intake manifold to keep moisture out, as the '94-'95 unit does. Anyone have experience with this mod? :confused:
Burning Brakes
Joined: Apr 1999
Posts: 1,161
Likes: 0
From: Texas
Re: Is it time to replace the Opti-Spark? (skohl)
Regarding the mod and opti prob, do a search. The subject has been pretty thoroughly flogged recently. I have similar prob's but after reading Bill McDonalds response to a stumble post prob I think mine *could* be an exhaust manifold leak. I'm going to check it out tomorrow. I'd suggest you do the same, as well as check for a leaking intake manifold and broken/leaking vacuum fittings under the F/I rail covers. I found two leaks under mine last weekend. It's a '96 with 82K on it.
Good luck.
dr
Good luck.
dr
Thread Starter
Cruising
Joined: Feb 2003
Posts: 12
Likes: 0
From: ISLAND HEIGHTS NJ
Re: Is it time to replace the Opti-Spark? (DavidR)
Thanks for the reply. I had searched the topic last week. Where was the
"Bill McDonalds response to a stumble post prob"? Good luck with your
manifold.
"Bill McDonalds response to a stumble post prob"? Good luck with your
manifold.
Elite Torch Red Member
Joined: Sep 1999
Posts: 57,805
Likes: 23
From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
Cental/South NJ Events Coordinator
CI 1-2-3-4-5-6-7-8-9-10-11-12 Vet
CI-II Burnout & Drag Champ
St. Jude Donor '03-'04-'05-'06-'07
Re: Is it time to replace the Opti-Spark? (skohl)
Since you are in Island Heights, you should pay me a visit and see what I'm doing about my optispark problem. Shoot me an email, I'll be home all day tomorrow.
Burning Brakes
Joined: Apr 1999
Posts: 1,161
Likes: 0
From: Texas
Re: Is it time to replace the Opti-Spark? (skohl)
Check out this thread...
http://forums.corvetteforum.com/zerothread?id=581611
later
dr
ps
definitely visit Mr Mojo... he'll fix you up.
[Modified by DavidR, 10:53 PM 6/14/2003]
http://forums.corvetteforum.com/zerothread?id=581611
later
dr
ps
definitely visit Mr Mojo... he'll fix you up.
[Modified by DavidR, 10:53 PM 6/14/2003]
Melting Slicks
Joined: Jul 1999
Posts: 2,875
Likes: 0
From: Olive Branch (Memphis suburb) MS
Cruise-In II Veteran
Re: Is it time to replace the Opti-Spark? (skohl)
From Purp Plastic vacuum tee under passenger fuel rail cover
One of the most commonly overlooked, yet easily recognized vacuum leak occurs with a plastic vacuum “T” under the LT1 passenger side fuel rail cover. Located about mid-way between the front and back, and situated very closely to the top of the intake manifold, the “T” is subjected to enormous heat.
Visual inspection often doesn’t reveal that the vacuum “T” has failed. The vacuum “T” tends to slowly disintegrate over a period of time. The best method for inspection is to actually turn the “T” over and look at the underside. What you find may shock you. Due to heat, the “T” fitting actually decomposes on the side toward the intake manifold and develops large holes similar to Swiss cheese. Replacement is cheap and easy.
GM calls that vacuum “T” a "valve". The GM part # is 14056648. You can pick one
up from your friendly Chevrolet parts man for cost + 10% + tax = $3.00
If you don’t have easy access to a dealership, you can call Jeff Kopp at 1-800-728-8267. Jeff can help you get the part.
Purp :steering:
One of the most commonly overlooked, yet easily recognized vacuum leak occurs with a plastic vacuum “T” under the LT1 passenger side fuel rail cover. Located about mid-way between the front and back, and situated very closely to the top of the intake manifold, the “T” is subjected to enormous heat.
Visual inspection often doesn’t reveal that the vacuum “T” has failed. The vacuum “T” tends to slowly disintegrate over a period of time. The best method for inspection is to actually turn the “T” over and look at the underside. What you find may shock you. Due to heat, the “T” fitting actually decomposes on the side toward the intake manifold and develops large holes similar to Swiss cheese. Replacement is cheap and easy.
GM calls that vacuum “T” a "valve". The GM part # is 14056648. You can pick one
up from your friendly Chevrolet parts man for cost + 10% + tax = $3.00
If you don’t have easy access to a dealership, you can call Jeff Kopp at 1-800-728-8267. Jeff can help you get the part.
Purp :steering:
Instructor
Joined: Jan 2001
Posts: 138
Likes: 0
From: Seattle WA
Re: Is it time to replace the Opti-Spark? (skohl)
I've also heard that leaky injectors can cause hard starts when already warm. With a cold start the rich mixture doesn't hurt, but too much fuel when already hot causes starting problems. Might be something to check before diving into the Opti. Though at your mileage it's deffinately possible your Opti has had enough. good luck! :cheers:
Race Director
Joined: Mar 1999
Posts: 16,950
Likes: 0
From: Stafford, Virginia Kittah, Kittah, Kittah...
Re: Is it time to replace the Opti-Spark? (Onyx)
I've also heard that leaky injectors can cause hard starts when already warm. With a cold start the rich mixture doesn't hurt, but too much fuel when already hot causes starting problems. Might be something to check before diving into the Opti. Though at your mileage it's deffinately possible your Opti has had enough. good luck! :cheers:
Only reason I mention this is because I think it's still the old style injector design in 93... I think 94 was the change over year with the new sequential fuel injection...
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Thread Starter
Cruising
Joined: Feb 2003
Posts: 12
Likes: 0
From: ISLAND HEIGHTS NJ
Re: Is it time to replace the Opti-Spark? (DavidR)
Mr. Mojo, thanks for the offer. Let me know whatever time is good for you.
David R, thanks for the reply.The stumble post problem does'nt match the symtons I have. Your '96 has an improved Opti-Spark design, where vacume draws air from the intake manifold through the distributor. The modifcation in the Corvette Fever article gives the '92-'93 Opti Spark this feature.
Ramrod 92, thanks also. Couple of weeks ago I had the Passenger side fuel rail off, just looking around, and I broke the bottom end of that vacume T/Valve. Replaced it with new GM part; My situation was the same before and after replacing it.
Onyx, Wake: How can you test the injectors for leaks?
David R, thanks for the reply.The stumble post problem does'nt match the symtons I have. Your '96 has an improved Opti-Spark design, where vacume draws air from the intake manifold through the distributor. The modifcation in the Corvette Fever article gives the '92-'93 Opti Spark this feature.
Ramrod 92, thanks also. Couple of weeks ago I had the Passenger side fuel rail off, just looking around, and I broke the bottom end of that vacume T/Valve. Replaced it with new GM part; My situation was the same before and after replacing it.
Onyx, Wake: How can you test the injectors for leaks?
Elite Torch Red Member
Joined: Sep 1999
Posts: 57,805
Likes: 23
From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
Cental/South NJ Events Coordinator
CI 1-2-3-4-5-6-7-8-9-10-11-12 Vet
CI-II Burnout & Drag Champ
St. Jude Donor '03-'04-'05-'06-'07
Re: Is it time to replace the Opti-Spark? (skohl)
skohl, I'll be doing stuff around the house in the morning, I may be gone for the afternoon, but I don't know yet, I'll probably be around until teh evening.
I'll shoot you an IM with my phone #, if you are free, take a cruise out.
I'll shoot you an IM with my phone #, if you are free, take a cruise out.
Race Director
Joined: Mar 1999
Posts: 16,950
Likes: 0
From: Stafford, Virginia Kittah, Kittah, Kittah...
Re: Is it time to replace the Opti-Spark? (skohl)
Testing fuel pressure leakdown with a gauge is the first step... It will either point to the regulator or the injectors...
On an LT1, you should be able to pull the fuel rail up and away from the intake to see if any of them are leaking once you establish that you do have pressure leakdown...
Kind of a shadetree method, but on my old TPI setup, I pulled the plugs and stuck some tubing down into the cylinders and took a big whiff to see if I could smell gasoline... As funny as that sounds, I actually found my 3 bad injectors on my old IROC that way... :lol:
On an LT1, you should be able to pull the fuel rail up and away from the intake to see if any of them are leaking once you establish that you do have pressure leakdown...
Kind of a shadetree method, but on my old TPI setup, I pulled the plugs and stuck some tubing down into the cylinders and took a big whiff to see if I could smell gasoline... As funny as that sounds, I actually found my 3 bad injectors on my old IROC that way... :lol:
