REDNECKISBOSS

I own a 94 5.7l z28. 156.000 miles. I have replaced: coil, ignition module, plugs, plug wires, fuel filter. I recently have had sputtering, poping, backfiring, and power loss. Can barely get it up to 55 mph. I figured it was my distributor so i took out my radiator, shroud, water pump and hormonic balancer pulley. I removed the distributor cap to find the metal on the rotary button ( the part futherest toward the edge) very wobbly. It wiggles so much while spinning that it left marks inside the cap. But here is my question. When i install the new distributor( im buying a whole new one) how will i set my timing? And aslo right before i removed the pump or anything it stopped cranking completely. And is there any suggestions on what distributor to go with?

GaryDoug

Are you referring to the rotor? Was that part loose in some way. How about the two screws fastening it down? They tend to come loose a lot. I would hesitate to but a new distributor unless you are sure it's defective and you get a top end one. Most of the Optispark distributors on the market are way worse than the original. Perhaps you just need a new rotor and cap.
There is no timing adjustment. Just be careful to get the shaft back in without forcing it out of keyed position.

Injuneer

Only 156,000 miles out of the original (???) distributor. Just don't make 'em like they used to. Sounds like the metal contact on the tip of the rotor came loose. Hard to understand how the qualifies it as "Opti-crap"

My recommendation would be full replacement with an AC Delco unit. As Gary points out, all you need to do is insure you correctly align the odd tooth on the splined drive shaft to the matching notch in the hole in the cam sprocket. Shoebox has a great alignment photo at shbox.com

REDNECKISBOSS

The rotor is self is not loose. The metal on top of the rotor that spins was very wobbly and loose from the plastic. I took the distributor completely apart and found rust within it in a few different places. How do you feel about MSD?

REDNECKISBOSS

One more question. How is it at autozone the ac delco cap and rotor costs 200$. But if you buy the whole distributor with cap and rotor its only 159$?

REDNECKISBOSS

I will be replacing the whole unit though. While driving the car to where i was going to work on it i heard a metal vibrating sound coming from the motor. Could my knock sensor also be bad? And could it also retard my timing?

REDNECKISBOSS

One more note. My ses light is not on.

Injuneer

Rust is common with the unvented (93/94) opti. The high voltage discharge generates ozone, which builds up and promotes rust. The only advantage of the MSD is the fact all years are vented to remove ozone. Disadvantages include erratic signal problems from the optical cam position sensor, and a mostly useless "timing" adjustment that can create problems, because there is no marked "0" point. Plus unjustified higher cost. You could put an MSD vented cap on an AC Delco unvented 93/94. Or you can add a vent to the Delco cap.


The "whole distributor" could not have been a real AC Delco unit for that price. Probably a store brand, a Chandler, or some other unit built with a Chinese sensor. The lower the price, the higher the failure rate. You can buy a complete unit on ebay for about $65. Often dead right out of the box.


If the knock sensor was bad, you would have code DTC 43. When DTC 43 sets, the PCM calculates a variable timing retard value based on engine operating conditions. If the metal contact on the end of the rotor is loose, the timing will be erratic and retarded. Erratic advance could cause more knock than the PCM can correct for (15* max retard).

How hard is it to turn the rotor? Could be failure of the friction bearing in the base of the Opti causing noise.


Then you don't have codes. There are no codes for misfires or problems on the high voltage side of the ignition in OBD-I. Transmission codes in general, do not turn on the SES light. There is DTC 16 for failure of the Opti's optical cam position sensor low resolution signal. Does not turn on the SES light. But if the code is active, the engine will not run because the PCM shuts down the fuel system.

REDNECKISBOSS

How would i clear that code? Disconect the batt for 30 mins after new distributor install?

REDNECKISBOSS

The rotor spun fairly easy. With a little resistance.

REDNECKISBOSS

And to explain the rotor problem further. There are two little white tabs that hold the rotor metal down. The outside one has broke of allowing the wobble. It also looks chared black due to bad conection.

REDNECKISBOSS

Is there any way to post photos via iphone?

REDNECKISBOSS

Also me being a stupid 18 y/o. I disconected my exaust from the back of my cat to see if it was clogged. Come to find out someone already gutted it. I cranked it and liked the sound. I figured since it does not have a o2 on the cat i left it disconected. Could that have burned a valve? Or bent a rod? Or caused any major issues?

Injuneer

You don't need to clear it, unless you have it. Wasn't the engine still running? If you had the active code, the engine wouldn't run. If it's a stored code from a past problem, you just leave it there. Every time you try to start the engine, the PCM looks for the low resolution signal from the Opti. As long as it finds the signal, it allows the engine to start. In general, to clear a code, pull the "PCM BAT" fuse at the end of the dash for 30 seconds.


Not an unusal problem in a high mileage distributor. My experience goes back to the days when you did a "tune up" every 15,000 miles, and you replaced the rotor, the points and the condenser in the distributor.

I have a dissected Opti sitting under my desk at work.

The metal strip on the rotor take the 20,000V spark from the coil, via the button in the center of the cap, and directs it to the buttons on the periphery of the cap that connect to the 8 spark plug wires. It takes a beating in 150,000+ miles.

This is the Shoebox photo that shows you how to index the splined driveshaft:

http://shbox.com/1/93-94_opti.jpg

You can't upload photos directly to post. You either have to have the photo saved somewhere on the internet, and post the address... or you need to upload photos to your CamaroZ28.com "pictures & albums" and embed the address of those photos in your post.

https://www.camaroz28.com/forums/sit...28-com-699204/

None of the above. Other than the possible hearing damage, shouldn't cause any problems. It's conceivable that the loud noise is triggering the knock sensor though.