I am a newbie here, but have been reading just about every post for the past 4 months. I want to understand why the consensus is that the Opti is a bad design. What makes it unreliable?
I bought a 93 A4 with 29K for my wife for mom's day, and it runs very strong. Do I have to be concerned with it going out on her? At what point should i look into replacing it? Should I go with one of the aftermarket Opti's?

Just want to make sure the car is reliable for her.

 

Just my opinion here... but I wouldn't worry about it until it becomes a problem. I had the same concerns about the opti when I first got my car, but there are many people on this forum who have not had terrible experiences with the opti. Just know that it will eventually need to be replaced. Just like the water pump, the brakes, the u-joints, the shocks... see what I mean???

Relax and enjoy your car!

 

You shouldn't have to worry for a long time! My stock opti on my 94 went 70K! I think it would have gone longer but a detail shop steamed my engine! Thats a NO NO with the optis!! Mine puked a few hours after I picked it up from the detail shop! So don't wash your engine with water and with 29K on the clock you should be fine for a good amount of time!

BTW You must be one hell of a nice guy!

 

The opti is a horrid design. Why GM did it, I haven't a clue.

Don't be lulled into believing tha mileage is the only cause of failure. Moisture is the real killer. Letting the car sit, then only driving it a short distance can wreck havoc on the high voltage side.

If the car was in a huge rain, hosed, the water pump leaked(leaks). Take your pick.

You don't mention where you are from, if the car came from, say, FL, don't be surprised if the humidity kills it early.

 

Drive it and have fun, they generally give a little advanced warning before going. ike the posts above try to keep it dry and don't hose off your engine you should be fine, mine went 103,000. I offered my wife a C4 for her birthday, she coose a Mustang GT

Mo

 

Mine was still going strong at 93,000 when I replaced it anyway while doing a cam swap. I wash my engine frequently but am careful in that area, albeit my '95 has the improved vented and better sealed design. I find the opti to be a rather amazing bit of engineering, in function anyway, as it can adjust timing on individual cylinders as needed to prevent detonation as well as always allowing maximum timing for conditions optimizing power.

 

What are the symptoms? Rough idle....and what else? And couldn't other things cause rough idle?

 

I appreciate all the comments. We did encounter one issue this summer. We sprayed off the engine the day before a large show in Ohio. The car died on the way to the event. My wife was driving and is very quickly lost just about all power. She pulled to the side, and had trouble even getting it to fire again. After 30 minutes it re-fired, but did not have enough power to move. Was acting like blown head gasket, backfireing through the exhaust. Had it towed home, topped off the tank with Sunoco 94, and fuel injesctor cleaner. One hour later, running like a top. i am assuming this was moisture in the opti. Could have this event caused any perminant damage? Is the opti ok once it dries out?

You guys are great.

 

The Opti is a weak spot on most C-4s but many run for well over 100000 miles before a replacement is needed. They tend to fail from moisture. Especially when they are sprayed with or by coolant. Coolant tends to corrode and short out the system. They need to be replaced like any other older part. C-4s are between eight and twenty years old so some parts do go south.

 

Your "car crapping out on the side of the road after we hosed off the engine" sounds like a classic case of Opti failure to me. Do yourself a favor, and don't ever do that again. No running water or steam cleaning under the hood....bad idea on an Opti equipped car.

My Opti failed at 25,000 miles and fortunately was symptomatic vs. suddenly leaving me on the side of the road. The culprit turned out to be a bad water pump (the bearings were shot). GM, in it's infinite wisdom, placed a moisture sensitive component beneath a moisture source. Makes sense, right?

As far as your concern about future reliability based on your past experience, my opinion is this: you have shortened the life span of the Opti by getting it wet like you did. Sort of like a battery that gets run down....it will probably take a charge, but it's not going to be as strong as if it were never run down to begin with.

Introducing water like you did causes the formation of corrosion on the internal disks, which makes the Opti's "reading ability" rather weak. Enough corrosion and you'll have bucking, stuttering, backfiring and stalling. Over time, the seal that surrounds the Opti shrinks/retracts and allows that moisture in.

You may also want to check for codes on the DIC. Keep an eye on it since it's already symptomatic.

 

It's not so much a "rough" idle, as a wildly flucuating idle.

It will go from like 600rpm, to 1000 back to 700 up to 1100, see?

Another symptom is a high RPM miss.

The death nell is an error code, dependant on year, referring to low or high res pulses.

 

Gloom and Doom, Gloom and Doom, Gloom and Doom. The Sky is Falling!

The Opti is not that bad of a design. It is a much more accurate and precise distributor than the L98's traditional HEI design could ever dream of being.

And the failure is usually like many said, not until advanced mileage and then it is typically gradual and not a bang all at once deal.

 

you are funny.

the opti is a POS... it's a marginal design, sensitive to moisture, located in an exposed area.

At the time, GM had lost spark systems available, why the hell didn't they use it? Bobo Buicks with 3800 V6s got'm... LT5's got'm, why not the Gen II?

Sure, it's "better" than a HEI, but do you have to tear down half the motor to replace an HEI distributor every 80k miles? No.

 

I apprecitate the info. What could cause a slight miss at idle ...vacum leak...but from where? Any ideas?? Thanks

 

how many miles?

A slight miss? I would think a bad plug or wire. also, make damned sure the plugs are snug in there! if one is loose, it will make a funny missing sound.

 

 

Thank you. I endeavor to instill mirth.

 

You done good.

 

97k right now. I replaced the plugs, wires, fuel filter, and O2 sensors (they threw a lean code...but after pulling the fuel filter, which was never changed, I am pretty sure that was the source of the O2 problems). Anyway...I did all of that probably a month or two ago. I am contemplating pulling a plug to see what it looks like. By the way, it did have a slight miss before I changed plugs and wires. Any ideas....Thanks.
Jeff

 

At that mileage?

Could be an opti, surprised it's lasted that long down in the land of humidity!

Coil??

I would replace the opti, if only to eliminate the miss.

My bigger concern is a burnt valve.