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Need some advise here. 96 LT1 70K miles. Been running great, but now twice in the last two weeks has taken a spell of running so bad that it won't run.

Both times this has happened after running great for several hours. Go out to start the car and it starts, but runs a little rough. Gets progressivly worse quickly and after about 300 yards, dies. Can be restarted, runs really rough, but has been able to limp back to the starting point. First time this happened was late at night, next morning it started and ran good, but threw a code for 'low voltage at TPS'. I replaced the TPS and replaced a cracked vacuum line from the valve cover to the TB and thought everything was fixed. Now 5 days and 400 miles later, same thing happened again. There are no codes being thrown, or at least no check engine light yet.

I haven't checked out anything else like fuel filter, plug wires, etc. I haven't owned the car that long, but I've never replaced any of that on this car.

Ideas?

Thanks in advance.
 

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Need some advise here. 96 LT1 70K miles. Been running great, but now twice in the last two weeks has taken a spell of running so bad that it won't run.

Both times this has happened after running great for several hours. Go out to start the car and it starts, but runs a little rough. Gets progressivly worse quickly and after about 300 yards, dies. Can be restarted, runs really rough, but has been able to limp back to the starting point. First time this happened was late at night, next morning it started and ran good, but threw a code for 'low voltage at TPS'. I replaced the TPS and replaced a cracked vacuum line from the valve cover to the TB and thought everything was fixed. Now 5 days and 400 miles later, same thing happened again. There are no codes being thrown, or at least no check engine light yet.

I haven't checked out anything else like fuel filter, plug wires, etc. I haven't owned the car that long, but I've never replaced any of that on this car.

Ideas?

Thanks in advance.
Just a guess maybe the opti-spark , There are alot of experts on this website and Im sure somebody will chime in.
 

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Can the Optispark be that intermittent? After stalling & stumbling for about 30 minutes tonight, it started running fine again. Drove it about 25 miles back to my house, parked in the garage, turned it off and when restarting immediately, it went right back into the stall & stumble mode then died.

Whatever the problem is, it seems to occur at a quick restart after running flawlessly for many miles.
 

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Is the water pump leaking from the weap hole at all? This is usually on way that the opti gets wet and runs like crap after sitting for just a few minutes after a good day of running? I would look real close at it....

JMO
 

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I haven't noticed anything leaking, but I haven't checked it out that closely. Thanks for the tip, I'll check it out.
 

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It sounds like you need to replace your PCV valve and fuel filter. Hopefully that's it, and it's a pretty cheap fix!
 

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Update - Can't find anything leaking moisture on the optispark. Took it to a local garage who had it for 2 days, during which it ran great. They couldn't diagnose the problem without experiencing the problem.

The shop wasn't a GM dealership.

If the problem was with the optispark, could a GM dealership diagnose the problem even with the car running right?

When it was running bad the last time, it never threw any codes.

Nothing like driving around waiting for the next breakdown! lol

Don't get me wrong, I love the car and drive it everyday, I just want it to be healthy!
 

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Did you replace the PCV valve? I had exactly the same symptoms until I replaced that. I still need to change my fuel filter but the idle/stalling problem hasn't happend since changing the PCV valve last weekend.
 

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I haven't replaced it, but I did check it and it seems to be fine. I'll replace it tonight to eliminate the possibility. I haven't replaced the fuel filter yet, but I will do that tonight too.
 

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I had a similar problem with my 94, not exactly, but similar. One of our resident DC experts suggested plugs, magnacore race wires, air and fuel filters which took care of it. 70k is not a lot of miles, but you are also dealing with age. your plug wires might only have 70k on them, but are 11 years old. Find a good mechanic and treat him well

neil
 

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Discussion Starter #11
Well, it's been just over a month since the last time the car gave trouble, but now it's happened again.

Since the last time, I've replaced the PVC filter, fuel filter and TPS. Last time it happened, I took it to a local shop and they couldn't diagnose the problem. (It was running great the whole time they had it.)

It's running today and same as before, if it starts, it usually runs good & strong for a long spell. One thing that was different was that the car would start, then run good for about 5 seconds, then die - like it was running out of gas. Something else slightly different, when it's cold, it seems to crank longer now before firing up.

I'm planning on taking it to a local Chevrolet dealership this week and letting them try to figure out the problem.

Do any DC members have any dealings with Jacksonville, FL area Chevy dealerships? Recommendations? Good experiences?

Last questions - is there any way to diagnose the condition of the optispark without replacing it? Will a GM dealer be able to accurately diagnose the problem if the car is running great? This car isn't throwing any codes at all.

Thanks in advance.
 

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average GM tech stays 3 years at the dealership, good chance that the ''mechanic'' who works on a 96 vette at the dealership has been trained to swap parts as recommended by his ''diagnostic tool'' on 2006 chevies, but has NEVER SEEN a c4 before...they will throw parts at your 96 until, with luck, the prob is solved -- then tell you that all eight+ major components were bad and charge for those.

in-tank fuel pumps last for 10 years or 100k miles...failure usually is intermittent to start before total fail occurs...change it,yours is due, even if not the cause of current prob...change the short elec ''harness'' ($20 item)for sure also, corrosion at the connector to the pump has stopped more than a few.

opti-spark is lovingly referred to as ''opti-crap'' by many techs...also a 100k expiration piece...''might'' be your prob based on symptoms reported...only good test is to try a known good one...as an lt1 owner (my 94 buick roaddie has a vette lt1 engine) i keep a spare ''good used'' opti on hand and do loan it out if you want to leave a substantial deposit, check local repair shops or j-y first.
 

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Need some advise here. 96 LT1 70K miles. Been running great, but now twice in the last two weeks has taken a spell of running so bad that it won't run.

Both times this has happened after running great for several hours. Go out to start the car and it starts, but runs a little rough. Gets progressivly worse quickly and after about 300 yards, dies. Can be restarted, runs really rough, but has been able to limp back to the starting point. First time this happened was late at night, next morning it started and ran good, but threw a code for 'low voltage at TPS'. I replaced the TPS and replaced a cracked vacuum line from the valve cover to the TB and thought everything was fixed. Now 5 days and 400 miles later, same thing happened again. There are no codes being thrown, or at least no check engine light yet.

I haven't checked out anything else like fuel filter, plug wires, etc. I haven't owned the car that long, but I've never replaced any of that on this car.

Ideas?

Thanks in advance.
Real simple if your 96 has a MAF sensor, Unplug it at the sensor,then see if it will start and if the engine starts and runs its the MAF sensor.
If the air filter was changed to a K&N the oil that they put on this filter messes with the sensor. if your lucky take the MAF out and clean it with electronic spray cleaner that won't melt plastic. Then put it back in and see if the engine will start and run. The members here on the forum helped me fix my 5 months headache.
 

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Mine is doing the EXACT same thing

Please tell me you've gotten this figured out. I am having the exact same problem. I suspected the K&N and the MAF but it seems to be ok. Its been at the shop for over a month now and they're trying to diagnose it without throwing parts at it.
 

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All I can say is GOOOD LUCK! I have had the exact same problem with my 93 for almost 2 years now. (not getting much done in the winters tho) I have changed everything to no avail.

NEW --> Optispark, water pump, injector O-rings, fuel pressure regulator, TPS, coil pack, ign module, swapped out PCMs. Alt and battery, EGR and it's solenoid, spark plugs and wires, air pump, checked all fuses and relays, even got me and OBD scanner but my car won't talk to it for some reason so I can't clear my codes. I have good fuel PSI at 42.

I even painted it and got new wheels but still stumbles and dies after warmed restart. :smack

Some times if it is stumbling I restart it again and then get a smooth run, sometimes.

If I ever solve my pro I'll let you know.
 
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