HELP!! 95 Z28 running horrible!

[Sacius]

I have a 95 Z28 and it has just started in the last couple weeks to have no power and it feels like it is missing really bad. The car does have to original optispark in it with 126K on the ticker. I am wondering if that could be the problem. It might be going out and causing the car to have a rough idle and no power with quite often annoying backfiring. Please help me. If you have any ideas anything would help.

[Injuneer]

How old are the plugs and wires? Has the IC Module ever been replaced? Have you had it scanned? Have you checked fuel pressure? Have the injectors ever been cleaned? Have you checked the plug wires, coil wire and Opti harness connector and Opti wire terminals for corrosion?

[Sacius]

What is the ic module? I had it flashed and its not throwing a code or anything, it just said the 02 sensors were reading off of each other when we did it. The wires are new 2 years ago as well as the plugs. I have not checked my opti connections or anything like that. What do you think?

[Sacius]

Oh and the fuel pressure is good. It was a little low when we checked it, but I changed the filter and now it is perfect.

[Joe 1320]

I would bet that the original optispark is toast. They are designed for 100K trouble free miles. some fail a little sooner, others a little later. With 126K, I'm suprised it lasted this long.

[Injuneer]

What is the ic module?

Takes the signal from the PCM and tells the coil when to fire. Similarly, has the coil been checked? Both of those are critical components of the ignition system.

Courtesy of Shoebox:

I had it flashed and its not throwing a code or anything, it just said the 02 sensors were reading off of each other when we did it. The wires are new 2 years ago as well as the plugs. I have not checked my opti connections or anything like that. What do you think?

You lost me there..... did you attempt to "flash" the codes by shorting the ALDL pins, or did you connect the correct OBD-I scan tool, with the correct adapter plug that allows it to connect to your OBD-II style ALDL connector?

What do you mean by "the 02 sensors were reading off of each other"? Do you mean the readings weren't the same for the left and right side O2 sensors? They are never the same, since the two banks of the engine are individually controlled.

[Joe 1320]

Forgot to add......

If it were me, the entire ignition system would be replaced. Optispark, plugs, wires, Coil and driver module all as a complete set. That should last you another 100K.

[Sacius]

Yes I was meaning that we used a hand held unit to diagnose the system. There were no codes and I did use an OBD2 plug with the tool set for an OBD1 system. I was pretty sure that was why the O2 sensors were reading different so I really was not concerned with that.

Next up, all these parts are a couple of years old
Plug wires (MSD)
Coil (MSD)
Plugs

Now I havent changed the opti and was thinking that would be smart to do. I really just need to get it running good again so I can sell it. I bought a new toy to tinker with (06 GTO).

You think I should change the Opti and supporting components correct? Also do you think I should clean the injectors? I have had a few problems with them sticking open on me in the past, but this does not seam like that.

Lastly if the Opti was going out why wouldn't it just quit. I have never heard of it doing something like this.

[Injuneer]

Yes I was meaning that we used a hand held unit to diagnose the system. There were no codes and I did use an OBD2 plug with the tool set for an OBD1 system. I was pretty sure that was why the O2 sensors were reading different so I really was not concerned with that.

The connector adapter has to be the specific one made for a 95. You can't just plug a standard OBD-II connector in. I already explained why the O2 reading were different (assuming you mean they were not the same on both sides, a question you never answered).

You think I should change the Opti and supporting components correct? Also do you think I should clean the injectors? I have had a few problems with them sticking open on me in the past, but this does not seam like that.

I think you should check all the things I've mentioned so far. The MSD coil has not proven to be all that reliable. But it appears you want to start playing parts replacement roultette. It that is your prefered approach, go for it, but you don't really need our advice to do that.

Lastly if the Opti was going out why wouldn't it just quit. I have never heard of it doing something like this.

Then you haven't heard to much about LT1 engines. Its a distributor. The cap and rotor has metal contacts that erode with use. As they wear, the ability to transfer the spark GRADUALLY reduces.... just like any other conventional distributor. The cap has thin conductors buried in the epoxy of the cap that routes the buttons in the cap to the correct plug wire terminal. The dielectric strength of the epoxy breaks down SLOWLY, and the conductors start to cross-fire. The interior is susceptible to moisture. The moisture causes carbon tracking and carbon buildup. As the tracking worsens, performance it GRADUALLY degraded. The bearing in the rear of the case is a low-grade friction bearing. It GRADUALLY wears and starts to cause the rotating components to wobble, causing intermittent irregularities. The optical sensor relies on the light from two tiny LED's passing through 360 extremely thin slots in the rotating wheel. As dirt and rust builds up on the LED's and receptors, the sensor starts to lose the correct count as the wheel rotates, causing timing errors. The wire terminals and the harness connector are susceptible to corrosion and moisture buildup, just like any other distributor. As this happens, the electrical conductivity is GRADUALLY affected. Simply checking all the terminals for corrosion might reveal a problem like this and solve the missing.

But... its your money, spend it any way you want.

[formula_gramps]

Sacius,

Just to add a real life, case-in-point to what Injuneer is telling you.......

I actually had my opti-spark replaced at just under 20k miles. For months the car's performance was deteriorating at such a slow pace that it was really unnoticable from day to day. One day I was driving down this particually nice straight, and punched the throttle really hard and the car began to miss badly. It finally hit me: "this thing feels like it's trying to pull a dumpster behind it".

Took it in, still under warranty and they replaced the opti. Full performance was back immediately.

So yes, the opti's like any other electro-mechanical part are subject to a sudden catastrophic failure, but most people's experience is with a gradual loss of performance due to the reasons that Fred outlined. When you consider what a POS the opti is, it is amazing that it lasts up to 100k.

It stinks having to replace it now when you want to sell the car though.

[Sacius]

I did know how the Opti works and had heard about it causing things like this, but most times you hear about the story of someone starting there car and then bam it dies and does not live again.

I still have my stock coil and I did decide to buy an Opti and cap/rotor for the car today. Since I am selling the car I went with the cheapest way possible and it ended up costing me $215 for the entire setup. I will replace them this weekend and see where that gets me.

Thanks so much for all your help guys its greatly appreciated. Also what other parts do I need to replace the Opti? I know water pump gaskets and all that (should be ok since I have replaced that once) but are there any other gaskets or parts needed to do the change?

[BrdWAtti2d]

There is an o-ring on the water pump driveshaft but that "should" come with the water pump gasket set.

[Joe 1320]

If you want to do everything right..... change the oil control seals in the front cover for the optispark, water pump and crank. There are two o-rings on the water pump shaft.

If you don't replace them, some time reasonably soon, they will start to leak.

[Sacius]

Sounds good. Thanks for the help guys.

[00 Ragtop Z]

If teh 95 has a MAF sensor (I assume it does) have you cleaned it? As I have noted on this board in teh past, my ragtopz became a brand new car when at 112,000 I cleaned teh MAF. 10 minutes and $7 for a can of MAF cleaner at OReillys and I was on the road with no more stumbling or power loss.