Help! 1994 misses and backfires at all speeds

[gmjunkie]

OK, I think you may be judging the car too harshly. Optis go bad, that doesn't mean that the car is a hunk of junk. I understand your frustration I went through it too. Check this thread.

http://www.corvetteactioncenter.com/forums/c4-technical-performance/106269-sort-stumble-idle.html

But getting rid of it is being a bit rash. Once it is fixed you should have yourself a nice car. I love my 94, and as frustrated as I got with it I didn't feel the need to ditch it.

Now on the "new style opti" without changing out the cam/cam cover I don't believe that you can use the new style. (I could be wrong.....but I doubt seriously that I am). That is one of the reasons that I went with an MSD unit vs GM. And besides the GM opti that went bad had only 6k on it.

BTW if you are still set on selling that POS after you get it fixed, I'll give you $1000.

I believe your right Tom!! I don't know about changing the cam,but the timing cover and drive to the opti are different!! As far as $1000.00 to do it with Genuine GM Parts,I don't know!! The Opti with my discount is about $423.00 and the Genuine GM water pump cost's me about $235.00 and then there will be other things,Thermostat($20.+/-),Idler Pulley($32.+/-),Tensioner Pulley$32.+/-),Serpentine Belt ($47.+/-) Coolant($25.+/-),thats over $800. cost for parts now and then you'll probly find a leaking seal or two and who knows what else!! I know I won't change a Opti for $200. Labor!!

But I know what I'd do before I changed the Opti,I'd be checking ALL the grounds,Especially thous miserable PITA 3 on the back of the engine!!

My bid's $2000. and he don't have to fix it,Flowery Branch GA ain't that far!!

 

[strayrazor]

Thanks again for all the info. Pretty sure he knows his Corvettes. He owns one and works for a local dealer specializing in them. The labor is 5 hours @ $50 per hour, less than half the dealer rate. Good price for me, good for Matt who's happy to make a few extra $$. I said about 1K, OK so it may be a bit more. After this, I'll already have spent close to 2K in 8 months I've owned it. Its not that I'm complaining, even thought the miles are low, it's 15 years old, repairs are to be expected, but we've had some defaults on properties we've financed and the funds just aren't there for an expensive hobby car. Maybe a later model at a later date, I love Corvettes. Keep upping those bids, guys, but seriously about 12.5K will buy it.

 

[gmjunkie]

when i was having problems with mine i was hoping and praying it wasnt the opti and it turned out to not be i did a search on here and it seemed that alot of people have replaced them when they didnt need to i think JUNK was the guy who said something about if he had $1 for every opti replaced that was not bad hed have another vette .............

No,I said If I had $1 for every one that had been replaced that didn't need it,My and John Robinson's family would be in the Bahamas laying on the beach!!

I've only had to replace 3 in my Lifetime!!
1 From Collision Damage!!
1 That was Questionable because of Rust and Green Crud growing in it!!
1 On the 94 I just sold because the water pump started leaking and I changed it because I didn't want a customer to have any problems!!

I've Cleaned several up and put caps and rotors on them!

98+% of the time I've found corroded connections in wiring plugs,corroded fuses and grounds or bad coils and ignition modules!!

I've been roped into several jobs that someone else diagnosed as a bad Opti,changed it and it still wouldn't run right or wouldn't run at all!!
Ended up a Corroded Ground,Corroded Connection,Corroded Fuses,Bad Ignition Module,Broken Harness Wire or Bad or Weak Coil!!

 

[strayrazor]

Looks like it'd be quite a job to get the cap off.

 

[LT4man]

You have to go through the same amount of labor to replace just the cap & rotor, so a lot of folks replace the whole unit.

At 90,000 original miles on my LT4, I replaced the cap & rotor with one from Accel. They make nice gaskets to help keep the water out.

At 105,000 miles, still running strong with the original Optispark!

SAVE THE GOSH DARN !

 

[Kid_Again]

Thanks all. Out of curiosity, I pulled the passenger side #1 plug wire and to my surprise , no spark. Not to jump to a conclusion about bad Opti, I pulled wire #2 and put it in #1's position in the Opti and spark plug, and voila, sparky and strong, albeit engine was barely running on 6 cyl. Going to get a set of wires this afternoon and report later. Keeping my fingers crossed, and Matt on hold

Do you have time to ohm the wires before dropping bucks on new wiring??

BTDT

 

[strayrazor]

You have to go through the same amount of labor to replace just the cap & rotor, so a lot of folks replace the whole unit.

At 90,000 original miles on my LT4, I replaced the cap & rotor with one from Accel. They make nice gaskets to help keep the water out.

At 105,000 miles, still running strong with the original Optispark!

SAVE THE GOSH DARN !

Matt mentioned the labor involved, so I opted to go ahead and replace the unit and water pump even if it is only the cap itself now. Especially if we can keep it dry, just don't want the chance of needing to replace unit short time later, and have to go the labor again. Roll of the dice, but I've lost more in the casino in the past.:W