Hey all, back again with another possible blonde (or just new to cars) moment. ('94 LT-1)

Chugging on acceleration. I can feel it through the whole car, I can floor it past the problem into higher revs but anything other than cruising at barely above idle speed is getting a chugging / lurching from the engine.
It only started when I put in Chevron gas with Techron, which I noticed written on the pump simply because I've never seen it before, but thought nothing of it since it was 91 and I usually find myself at Chevrons whenever I'm out of town. After I left, it happened precisely once until two hours later on the return from my day trip when it lurched and stuttered every time I even thought about going for the gas. There isn't a noise associated with this unless you count the sudden jerking of the driveline.... just a feeling like its about to stall, and with the windows down, it's much more burbly from the exhaust.

Sounds like just a typical car problem I know, but the reason I bring this to the Corvette forum first is threefold : 1. My mechanic doesn't work weekends. 2. I understand that moisture in the distributor cap can cause this, and we all know what "OptiSpark" means. 3. Is Techron just a curse additive for our engines?

Nothing different at idle, and when I put the car in neutral and rev it out it shudders still though not as badly, so I believe spark plugs are still okay. We did have some harsh rain recently in Tucson but despite encountering a few puddles, none got any higher than the rocker panels. When I can I'll have the cat, fuel system, etc inspected. I really hope it's not a vacuum leak somewhere. No engine light.

Thanks as always.

 

I had this happen after getting bad gas with water in it once. Since water settles to the bottom it only took 5 minutes until it got bad. I don't think it is possible to go 2 hours with bad gas before the problems start. Dan

 

Do you know how old the ignition wires are? When you mentioned all the water from rain, group that with bad ignition wires that are old and or spark plugs with excessive resistance and you can get random misfires that will cause a chugging effect.

 

I don't know their age, no. Is it possible to have bad spark without any signs of it until a certain throttle?

 

Btw, I’ve had misfires caused by bad ignition wires on both my LT1 cars (94 and 96). Check engine lights (CEL) did not trigger in either case.

 

I had a misfire on another car caused by bad spark plugs. It would idle fine and under hard acceleration it was fine. It only acted up under light throttle load.

 

What better time to freshen them up, then. I'll add it to the list.

 

Plugs are not expensive and they’re relatively easy to replace. They’re a regular maintenance item as well. So if you don’t know their history it can’t really hurt to give replacement a try.

 

One thing I find funny is people with old style distributers would never go 150k miles without replacing the cap and rotor but people with opti's will. I wonder how many opti's have been replaced when it was just a cap and rotor. I do know what it takes to replace them. I also wonder how many people have never changed the dried out heat sink paste behind the ICM. If this was an 86 everyone would be suggesting to change the cap and rotor. Dan

 

Do you think the opti sensor can be damaged by cross firing inside of the cap? Thus, neglect to change the cap and rotate results in complete opti failure?

 

No I don't. But I don't have any data to really say that. I wish the old optidoctor was still active here. He would know. Dan Let me edit: Neglect to change the cap and rotor CAN cause complete failure but not by damaging the sensor.

 

That's not Techron in your gas!

Seriously, if you're worried about bad plug wires, run the car in a darkened garage and look at the wires for arcing which will be visible in the dark. Use an infrared heat gun on the exhaust ports where they meet the headers / manifolds, and you'll see the misfiring cylinder, as it will be the cool one compared to all the rest.