Sorry this is going to read like a book. I posted on another forum and nobody with a brain responded. I was a diesel mechanic in the late 1980’s and OBD systems were out while I was in school, so I have some tech skills. LolMy son US ARMY has a stock 1994 Firebird TA GT auto trans - 58,000 miles,.We bought the car in 2021 from a mechanic with a new water pump installed. After driving car for 500 miles we heard ignition detonation knock under hard throttle. After reading this forum I thought Opti was bad and replaced it. I got from Autozone with lifetime warranty car ran perfect with new one. Because of Covid no good ones you guys spoke of were available (Petris) 3 months after replacing I got email from Petris saying they were available, just a bit late. Kid took the car DEC 2021 to North Carolina from Wisconsin with no problems.
May 2022 Son was discharged to go to West Point so I drove car home for him. North Carolina to Wisconsin, car ran great 25mpg and no problems. A 2 weeks later he’s driving & engine started loosing power after it warmed up, car was Non Operable at this point. I took it out for a drive a few times after it sat overnight multiple times. Car started and ran great for a few minutes then a couple blocks from my house the thing just lost all power 15mph max and goes funny shifting. I've read 100+ posts, watched YouTube videos but can’t seem to find issue.
**OK so the story changed a bit - things got worse -Car did runs great when cold, could spin wheels. Even when car is warmed up it did idle perfect, when in park you could rev engine. It did not miss or backfire.
**SEPT 2022 OK so a little change in problem, I just fired up the car after 2 months of sitting. It started fine but 2 minutes into running it won't go over 1800rpms and stinks out the tailpipe. It sounds like a diesel - not like rod knock just a bit out of time and doesn’t idle good - bad miss firing.
**I put in new Opti July 2021 which was 2500 miles ago, and I did replace Opti again OCT 2022 with wire harness pigtail up to plug next to intake. Again Autozone because of lifetime warranty.
**June 2022 I tested O2 sensors- (they tested fine but out of caution put in 2 new AC Delco sensors), Tested tps, maf, fuel pressure is 43psi and held 30psi for hours after. Fuel injectors all 12.4 ohms, also Noid lite on all injectors was solid pulse. I did test engine running and disconnected each injector and there was no change in RPMs from passenger side, but Driver side definitely could tell drop in RPMs, I took out the PCM and checked all the pins to see if there was corrosion also. I checked EGR and fuel pressure regulator,
**When we got car I replaces OPTI, fuel filter, intake gasket, ground strap,rad coolant sensor.
**New parts June 2022 - knock sensor, water pump coolant sensor
OCT 2022 Got the OBD1 cable and downloaded Scan9495 for PC it had 2 DCT codes 16 & 18,
NOV 2022 new spark plugs - the old ones looked good and ICM, ignition coil
12/5/22 Now again today tested voltage and ohms at pins for Opti and ICM all normal 5v 12.3v and continuity. Injectors raised fuel rail and battery tested each one Spray was perfect and no leaks. Tested fuel pressure again same as before. Barely idles now and hard to start. I did smell oil to be sure there isn’t a stench of gas in oil. It seems ok.
I saw today in a post about oscilloscope testing- I will buy one but I'm not sure if the car runs (be it badly) that I need to test Opti with it. And I don’t even know how to use one (but I can look it up if needed)
The answer may be here on forum I just haven’t seen it, Any help would be appreciated, My son is home in 2 weeks for Holidays from West Point and I would like to have Car repaired if possible for him. Thank you guys

 

When you clear the codes, how fast do they come back?

DTC 16 prevents the engine from running at all. When it sets it doesn’t turn on the SES light.

DTC 18 sets when the PCM detects the wrong voltage on one of the injector circuits. There is no indication of which injector set the code. If you have 12 volts on the pink wire at each injector, could be an intermittent open in the ground supplied by the PCM to fire the injector.

When the starter is cranking the engine, does the tach needle move upwards ABOUT +/-200 RPM.

When you installed the Opti did you Loctite the rotor screws? Are you sure you indexed the splined Opti drive correctly? Sounds like the timing may be off. You should never hear knock (detonation) with correct timing and a functioning knock sensor.

There are other tests to make before investing in an oscilloscope.

 

Is engine totally stock?

Not much stands out in the screen shots. But screen shots do not provide the insight that a correctly run data log can show.

Idle is way low and the IAC valve is maxed out open. High MAP probably due to misfires.

At idle the long term fuel trims (LTFT) are adding an appreciable amount of extra fuel, but misfires can cause that.

 

Thank you, I just came in frozen chosen from garage. I cleared codes just now - engine was running with them but they weren't active? Codes never came back on either. There were no lights on dash ever. All stock - it was a older ladies car like a 9 out of 10 garage kept.
Tach goes up and down +200 but engine starts right away. It continues to stall when cold I didn't push on throttle at all.
When it stalls out it does start right up but takes a second to catch.
Fuel pressure is 36psi running @ idle but I have a cheap Chinese gauge, it's 43psi when key turns on- I disconnected vac hose on regulator gauge jumped to 45psi - when I disconnected regulator I pushed throttle open and it bogged out still.
O2 sensors are way off from each other on start up, both leveled out at 100f
Battery voltage is 14.5 but on log it shows 13v, my guess that's computer leveling?
Once it was warmed up it didn't stall just no power. When I pushed throttle it revs and bogs then stalls as I'm releasing throttle. Not enough fuel?
As for Locktite I did open this distributor this time but rotor didn't seem to have any fasteners. It looked as though they had it set in plastic molded buttons, like a rivet pressed down. I never removed the rotor so I would think manufacture did that. I opened it to verify position to drill because I installed 2 vented lines and one vac line out of distributor. A Mopar Tech on YouTube had a very detailed video showing how he did his LT1 so I copied that. The Opti has a notch in the spline so you can only install with notch perfectly lined up so timing is right.
It ran fine after the first replaced Opti. It's only when it started running rough when son got home in summer. It runs I would say just the same with this Opti I just installed. The detonation sounds more like a diesel maybe valvetrain noise but it's on the passenger side. I took oil fill cap off and gave a listen but it didn't sound noisy. I may pull valve cover tomorrow to see if the rocker lash is tight.
Here attached are the CVS reports from October and now
Thank you

 

I also meant to say I checked voltage pulse for all 8 injectors they ranged from 0.11v - 0.28v while running at idle.

 

You need to verify steady 12 volts at each injector pink wire, key on. The voltage is always present key on. Something is apparently setting an intermittent DTC 18. The question is, why? Does the pulsed ground from the PCM occur each and every time the injector is supposed to fire? Issue could be the injector driver in the PCM, the connection at the PCM, the wire from the PCM to the injector, the injector connector. These are not common faults. You mentioned DTC 18 and posted a screen shot showing it. But I have no way to know how “intermittent” the fault is. From your new comment, appears it might not be very common.

I'm assuming you were measuring the voltage across the two wires in the connector, and the only way you would see these numbers is if the injector was receiving the ground pulse. But it's not a number I've ever looked for. So I have no way to know the significance of the data. Sort of like looking at the 'noid light. If it flashes, you assume the ground is being received. Question is, when is DTC 18 setting? And how often? A data log might catch it, might not if it is infrequent.

I know the Opti drive shaft has an “odd” spline to facilitate alignment. Problem is, by my experience here for 24 years, at least 10% of the installs fail to achieve proper alignment. I've had people who were 100% certain they did it right. They insisted it was “impossible” to do it incorrectly. They were wrong.

Similarly, when does DTC 16 set, and how often. It isn't uncommon to see it set when cranking the engine, if the PCM does not immediately see the low res pulse from the Opti. And for the code to set, the PCM has to be receiving the high res pulse. Again, that is apparently an intermittent problem.

Have you verified the correct sequence of the plug wires on the Opti? Another item people insist is 100% correct, and end up saying “oooops”. Has happened.

ICM could be a problem, even if fairly new. The cheap Chinese junk can be defective right out of the box, or soon thereafter. Might want to have a shop test it, making sure they get it good and hot.

You mention the O2 sensors are “way off from each other at startup”. On cold start the injectors aren’t working because they are cold. They have to reach ~600°F before the work accurately. On cold start they should both be ABOUT 0.450 volt. That's the bias voltage supplied by the PCM. As they warm up the should track each other. But it may take one longer to heat up than the other. If the vehicle still has a functioning AIR pump the voltage should drop as they warm up, reflecting the high O2 content due to the air being injected into the exhaust manifolds. If the AIR system is not functioning the sensors will move the other way, reflecting the very rich cold start A/F mixture. After the O2 sensors warm up, coolant reaches (variable) minimum temperature, and 206-second timer times out, the PCM enters closed loop, and the sensors should cycle rapidly over a range of +/-0.100 to +/-0.900 volts, and can differ widely since each bank of the engine is controlled independently. What do yours do?

What brand are the O2 sensors? Again, doing this for 24 years (on this site) there seems to be poor results with O2 sensors other than AC Delco. Even Bosch seem to cause problems, and the $17 Chinese sensors on Amazon are a complete disaster.

Battery voltage - the dash gauge reads the voltage direct from the alternator/battery. The PCM reflects the voltage loss through the wiring, fuse blocks, etc.

I can take a quick look at the data logs, but I can’t commit to a full-blown review. I don’t know if you ran across my guide to running a data log, but a while back I edited the procedure to indicate I am no longer reviewing the data logs. It takes a lot of time, and many of the people resist things like giving me the details about modifications to the engine, resist answering ALL my questions, resist doing suggested follow up diagnostic work, and eventually drop off the edge of the earth, because they didn’t get an immediate, one sentence answer of how to fix their problem. Unfortunately, I haven’t seen anyone else on this site who is willing to take on the task. But I will take a quick look at what you posted. That's all I can commit to at this time.

https://www.camaroz28.com/forums/com...-guide-886891/

 

PLASTIC RIVETS??? Never trust an AutoZone Opti!

AutoZone Opti may run 1000's mile then die or be dead right out of the box.
I would get rid of it!

 

You might have other issues, but have you checked for a clogged cat (could have been caused by fueling problems)?

 

Im sorry, I didn't clear codes after testing with noid light. I started new test 1st with clearing codes. Shoebox, I also was thinking last night after posting could it be the cat. I will try and get it apart or drill a hole and check with scope camera.
Car runs, it just sounds like a diesel knocking like valve train noise. (Not pre ignition detonation)
Voltage is solid 12v on all 8 injectors pink wire. I checked negative pulse also all 8 were same so I'm assuming they are ok.
O2 sensors are Delco. Now makes sense .453 cold start and they bounced all over til it got to operating temp.
Car is completely all stock, minus all the new $$$ parts.
New scan - engine kept stalling til warmed up. Then ran noisy and no power. I have more scan pics just didn't want to put in to many. Also Added Pics of voltage from injectors

 

I wanted to say thank you guys for posting all this help. I've read thru so many posts and used so many diagnostic pages you admins have written. It gets tough with some of these threads get stupid replies and fill the page with nonsense. Have to read thru 10 replies to get to answer. Or as you have pointed out people don't search old threads. I've got so many relevant pages in bookmarks so I can get to the ones that are clear and helpful. I've been working on and off since June on this car and not being current on this tech is a learning curve. I'm ordering diagnostic tools that a newer mechanic would take for granted. My 4 car garage is full of contractor tools and not so much automotive tools. My kids have been filling up toolbox / hand tools for Christmas gifts the last couple of years. Lol
Again Thank you

 

Rob/Shoebox raises an excellent point.

The high MAP readings (~50+ kPa at idle, vs. a typical value of ~30+kPa w/ stock cam) could be caused by a plugged catalytic converter. That has to be diagnosed by hooking a pressure gauge up to an O2 sensor bung.

 

Good one! that will cause lost of power.
my ElCamino ran great till I had to go over a mountain pass and had to turn around and limp home.
I remember of the days of putting a potato in the tail pipe.

 

On Scan9495 where does the RPM's come from? is the computer getting it from the Opti?
I see on one of the pics it showed 'Engine RPM' 420 but "Target Idle Speed" 900
420 RPM seems real slow, is that true RPM or error reading?

Thanks!

 

The PCM reads RPM from the Opti cam position sensor pulses. The PCM controls the RPM using the idle air control (IAC). As I pointed out in post #3 the idle RPM is way low compared to the target idle, and the IAC is maxed out at 160 counts. First thought might be that the engine is starving from air, but the high MAP reading (50+ kPa) is possibly due to misfires, preventing the IAC from controlling idle.

Fortunately Shoebox pitched in with the comment about a plugged cat. Could cause the high MAP, low RPM, and loss of power. I overlooked that possibility, instead suggesting it is a timing problem.

 

Well here it is. Bad catalytic converter.



I'll post once I get it back together.