For several weeks, my 1995 camaro z28 with 125,000 miles has slowly gotten worse with pinging and loss of power while throttling in high rpms, stumbling while at idle, and sometimes having trouble starting. Before it would only ping slightly and if i gunned it, it would come out of it and rev like normal. Now that isnt the case. With the trouble starting, if it doesnt start right away, I can give it gas, or wait about 30 minutes, and itll fire as if nothing was wrong. I assume it is the opti since their is no code being shown, and my fuel pressure was a steady 38psi without disconnecting any lines or vacuums, but I figured if it was the opti it would have fully been done for by now. Another thing I found odd was I can get a little more throttle when shifting from overdrive to drive. I have taken a couple videos to show the pinging with throttle. I just wanna know what others think may be the problem before I go down the optispark rabbit hole. Any advice will be greatly appreciated.

 

I tried the videos, with my high end Sennheiser earphones, and really couldn't detect the pinging. Note the I do have the typical hearing loss of a senior citizen, particularly the heigh frequency bands. But I have compensated for that in me audio system. But over the 30 years I've been doing this, I have never solved a problem by listening to a video.

Power seem to be cutting in and out over the whole pull. What grade (octane) fuel are you running? Is the engine stock or modified? Stock tune? You would most likely be hearing "knock" (detonation)..... the creation of a second burn front in the cylinder that collides with the initial burn from the spark plug. Causes extreme, damaging pressure waves in the combustion chamber. Common problems could be low octane fuel, running lean, running too hot, carbon buildup causing excessive compression, too much spark advance.

You should never hear knock, because the knock sensor hears it before the human ear can hear it, and retards the ignition timing. The maximum timing the PCM can pull is 15-degrees.

I looked at your past posts, and found the AIR piping problem and a possible clogged cat. You advised you did find a blown fuse for the AIR pimp and were gong to replace it. What did you do about the broken AIR supply pipe? How did you repair it, or did you block off the connection at the manifold.

Your second problem was a stumble you attributed to a possible clogged cat. You indicated you took down the exhaust and examined the end of the ceramic substrate, and it looked very clean. That was the last info you posted. Did you ever solve that problem, or is this a continuation of the stumble issue? To fully evaluate the condition of the cat, you need to have a mechanic or an exhaust shop do a pressure test - very simple, unscrew the pre-cat O2 sensor and attach ha pressure gauge.

 

Sorry for the audio, it was just basic videos from my phone while driving. It is a fully stock engine besides a couple of basic bolts on like an underpulley and an air foil. It is also the stock tune. I run 87 octane. As for the secondary air, i unplugged the pump and put a new fuse in like someone advised and it did fix the code it was throwing. Should I have also blocked it at the manifolds, because i just left it all connected? As for the cat, I gutted the ceramic inside.

 

Did a little more work on it. I have a misfire on cylinder 1. Switched the plug and wire out, and it was still misfiring. I'm assuming the opti isn't sending spark on 1, but all other cylinders seemed fine. I unplugged a couple more and each one made the car stumble worse. Is it common for the opti to work on some and not others? This is my first rodeo with optispark trouble and just trying to understand as much as I can with it.

 

I was the one that advised replacing the fuse to get rid of the code for the AIR system. You had a problem with the passenger side connection pipe between the check valve and the manifold - it was broken at the threads for the check valve. You indicated you didn’t want to spend the $400 for replacement parts. If you did not replace the pipe, broken at the check valve threads, you needed to disable the pump and delete the AIR system. Did you do that?

If you left the pump running when commanded by the PCM, and did not remove the broken pipe, and plug the connection on the exhaust manifold, you might have a problem with the A/F mix on the passenger side. You might also have caused a problem with poor AIR flow to the cat, allowing fuel to build up and overheat (possibly melt) the cat when hot exhaust gasses caused it to burn.

The pump shuts down after the first couple minutes of “cold start”. Now you would have the possibility of the exhaust gasses from cylinder #2 “educating” air into the exhaust, causing the O2 sensor to report a false lean condition, and the passenger side could run rich, fouling the spark plugs.

I’m wondering if the”tick” you hear under hard acceleration could be the exhaust leak at the broken AIR pipe.

 

I did not do the full delete. Should I have? I just unplugged the pump and tossed a new fuse in there so it would no longer throw the code. It could be possible that is where the noise is coming from. It only does it while in drive while revving past a certain point. I do not hear it at an idle. I'll have to pull a couple plugs tomorrow to see if they are foul on the passenger side.

 

The answer is in the first paragraph:

“If you did not replace the pipe, broken at the check valve threads, you needed to disable the pump and delete the AIR system.Did you do that?”

You aren’t going to hear knock at low engine loads. It shows up when you get on the throttle.