Need help diagnosing '97 Camaro issue

Hello all,

Long time lurker here so bear with me.

I purchased a 1997 z28 in Feb 2019. 3rd owner. Car sat in garage for 12 yrs and then 2 yrs in a backyard. Had 56,xxx mile on it. Now had 62,xxx miles on it. when purchased did the usual, fluids, plugs, wires, hoses, belt, etc...

The current issue appeared 7 months ago. with now warning. 

When I first start the car in its cold condition it runs fine but when it reaches operating temp, 180 degree t-stat, it dies. i bought a scaner and began chasing codes. Well, there where so many issues because it sat so long untouched I replaced just about every electronic sensor, ICM, Ignition coil, plugs, wires(again), fuel pump. The only codes I have now are for O2 sensors. 

I am at a loss as to why this will not stay running once warmed up. Nothing was changed before this began to occur. 

the car, 350, 6sp hardtop base model.

Thanks for any help, Jack.

Without really thinking about, my first guess goes to Otispark!

no clue the steps to troubleshoot that; only one I ever worked on still worked. But, if your not familiar with the location, it gonna be fun learning...

03Panther said:

Without really thinking about, my first guess goes to Otispark!

Leaking water pump screws those IIRC.

Most cars ignore O2 sensors while warming up and once the coolant passes a certain temperature it starts to use the O2 sensors for feedback. If your car idles fine but starts to act funky when it gets up to temperature I'd check for exhaust leaks before the O2 sensors and barring any issues, test your O2 sensors.

Not exactly the same car,  but my 95 9C1 had a MAF go bad and a ECM (brain box) go bad on me in separate occasions.  

I had 3 E36 M3ty water pumps fail, but it never effected the Opti. Those are expensive if you just assume it's bad and throw parts at it.

I am unfortunately very familiar with these cars as a friend track day one for 17 yrs and helped him maintain it all those years. 

 The opti is dry and no water pump leaks. I have replaced the MAF and the elbow after. The original was cracked and chunks missing on bottom side. The car idles so smooth now with all the air/vacuum leaks fixed and fresh plugs/wires.

I will confess this as I was incorrect in that I had changed the plugs & plug wires and then this began to occur. I ordered the larger 8.8 wires by accident but believe it shouldn't make a difference, I hope.

No exhaust leaks I can hear or feel. I did not replace the O2 sensors yet. Tried and broke the HF socket in the O2 kit.  

I gave it another run and after it died I fired it up and could keep it running by pumping the gas pedal. I just replaced the fuel pump as the last time I drove it, it acted like it was not getting gas. Got a nice new Delphi complete assembly installed after I cut the access hole.

Something controlling the fuel pump in the ECM being affected after warm up?

Im pretty familiar with these but I never experienced these symptoms. Most GMs have a base map they can revert to if they are missing certain inputs, so the first thing I would try is just unplugging the o2s and seeing if it runs better. If that doesnt help you can check back pressure pre cat. I have seen cats clog that really only shows when warm, but normally the car will still run just wont rev or will run poorly. if you dont have a back pressure tester just unthread the o2s and see if removing the restriction makes it run.

The common runs bad when warm is the ICM but you have already replaced that. 

The larger wires wont affect anything but routing, I also ran 8.8 wires on mine for many years.

Also what do fuel trims look like when it is running?

I will get out there this morning and hook up the scanner and get the readings. 

It just seems as I began fixing the issues, vacuum leaks - tuneup - etc, this issue began.

Have you replaced the fuel filter? 

Yes I replaced the filter, twice. Once when I first acquired the car 2 yrs ago and just 7 months ago as a just in case.

I have a HF Zurich ZR11 scanner, so may not the best, don't know. It has a few options for reading codes.

Global OBD2: code P0372 is only code shown.

OEM Enhanced PCM: 0101, 0107, 0108, 0121, 0125, 0372, 0400, 0410

The codes related to O2 sensors. P0131, 0132, 0133, 0134, 0135, 0137, 0138, 0140, 0141, 0151, 0152, 0153, 0154, 0155, 0157, 0158, 0160, 0161

When viewing live data on the O2 sensors the difference between pre-post cat sensors: These are at idle, 870rpm.

B1S1 0.785v  0.0%

B1S2 0.900v 99.2%

B2S1 0.570v 4.7%

B2S2 0.785v 99.2%

MAP 11 inHg

spark adv 17.0

IAT 37 F

fuel sys 1 CL

fuel sys 2 CL

Calc load 3.5%

ECT 111 F

STFT B1 1.6%

In reply to JBruin :

Is it dying without throttle response, or with it?

I had a car that once it warmed up would try to die on me with all the classic vaccum leak symptoms but I couldn't find it. 

Finally I figured out that it was a slightly loose spark plug that would only be loose when it warmed up. That was odd

Without throttle response. After it dies I can start it back up but have to hold throttle pedal to the floor.  I can keep it running by pumping throttle. 

I should have just kept driving it instead of fixing all the issues. frustrating. 

Sometime new sensors can be E36 M3. Do you out have a manual or a good forum to run diagnostics to check them?

The reason I ask is that on my 22RE 4Runner, the throttle position sensor would get dead spots on it and computer would spaz trying to keep it running. These were on cheap Vatozone sensors, because we were all to cheap to spring for the OEM Densos, even after I was told they were crap. (Not saying you're cheap, but new sensors can be bad out of the box leaving you stumped because "it's a new sensor." I've been bit by that.)

Is it possible that the fuel pressure regulator chokes out the flow once its warmed up?

After some reading in the Haynes manual and whats happening it's got to be the 02 sensors. 

When cold the sensors are ignored and run in open loop, when sensors reach operating temp goes in closed loop and adjusts air/fuel mixture to O2 signals. The elbow between the MAF and throttle body was cracked and a chunk missing underside so extra unregulated air intake. Also a few vacuum leaks all fixed at same time. 

After these fixes once reach operate temp, gets choked out too lean/rich.

I will unplug the O2 sensors as advised to try above. 

That P0372 is either bad optispark (optical sensor issues) or malfunctioning PCM according to the googles.  I'm with 03Panther on this one.

If this all started when it was being worked on, I'd be going back to the areas I worked on and figure out what I have connected wrong or not connected at all.

Check the PCV system. Leaks there are a vacuum leak.

I've thrown $1500 worth of parts so far chasing codes. I have bought GM/AC Delco parts when available to purchase. 
I buy through Rock auto but don't go cheap. 
Things I've worked on, replaced, were vacuum lines, plugs/wires, ICM, coil, MAF, throttle position sensor,IAF. 
I have AC Delco O2 sensors but broke O2 socket attempting to remove a sensor. So none replaced yet. 
I am hoping against the optispark being bad. LOL

I thank all of you for your help and suggestions with this issue. 
This on hold until next weekend as this weekend is work and these cold temperatures. 
I didn't move to southern Ky for 25 degree days and snow/ice. I would have never left Wisconsin. 

Bad PCM code and runs fine in open loop then dying as soon as it hits closed loop plus a million other codes? I'm thinking try another PCM if unplugging the O2 sensors leads to no change. Unplugging stuff really is the way to diagnose '80-'90s GM

And yes Kentucky can be very cold.

Open loop or closed loop shouldn't affect Optispark operation, no? Unless it retards it to the max thinking there is something wrong when it doesn't get the signals it wants in closed loop?

With the rest of the info., you are prolly right in it not being the distributor. But remember the Optisparks failed for many reasons other than water pump leaks. Road water, condensation ( but I think it had a drain by 97 for that, but wouldn't the drain let road water in easier?) And I've heard ozone from the high voltage inside can cause problems. And general neglect, due to the location! Like I said, the only one I worked on (97 also) has almost 180K miles on the original, so only remembering what I've read, and sounds like you've got that part covered.

So I was thinking about this a little more last night and reviewed the data you posted.

So it sounds like it runs fine in open loop and like crap in closed loop. If I remember correctly the LT1s take info from most sensors for open loop except o2 sensors.

If you unplug the o2s it's going to force it to always stay in open loop so it will run fine but that doesn't necessarily tell you if that's the problem.

From the PIDs you posted It looks like the Map reading is fine for a cold idle.

The fact that you show a p0101 and you should diagnose from the lowest numerical code up and MAF failures are very common in these makes me suspicious of the MAF. Although I've never seen a failure of them present quite like this, most people just unplug it and if it runs fine replace it. I would be curious to at least see a maf reading at idle and how it responds when revved.

I never bothered to actually test an o2 I always replaced them preventatively on my junk, so I don't know the actual test procedure, but if you already have them I'd probably throw them in and see how it responds, especially since that is the major change when moving from open to closed loop and that appears to be when you are experiencing problems

Yes, it discards the O2 sensor data until they reach 600-700 degree operating temp then use the data for air/fuel mix.

The MAF questioning makes me Grrrrr. I replaced it, it is a new part. But with that most of the codes above are new quality replacement parts. New parts can be bad though.

I have a snow day monday so will spend some time in the garage. First up is unplug the O2's and run until hot and see what happens. I'll try with the MAF unplugged first and plugged in with the scanner.

I don't consider the optispark as it would not run as good as it does cold.  These opti's are vented but from my experience takes a lot to get water up inside the vent hole.

An update as I finally had time to get out in the garage.

I unplugged the MAF and ran the car. It ran the same until operating temp and died. I attempted to restart and it produced the same results, wanting to stall out but could not keep running with gas pedal.

I will let cool and unplug O2 sensors next and see what happens.

We close on the new house March 2nd so it's begin packing, keep rental house respectable for showings, work on the car but states in rental agreement no auto repairs of any kind in garage or yard. I go from one car to two + car garage.  

Consider changing the ECM Coolant Temp Sensor (if applicable). That era of GM vehicles often had two separate coolant temp sensors (i.e. cool temp gauge/warning light sensor and a ECM CT sensor.

Good luck and hang in there.