Misfit74

The car: 1995 FIrebird Trans-Am, 5.7L LT1. Engine is from 1996 Caprice. Rest of car is stock.

What's happening:

When cold: seems to idle well enough and can push the pedal and get power that one should expect with this car. Drives and accelerates well in all gears. Will go sideways if not careful . While cool/cold, it rarely stumbles or misses until car is warm, temp gauge starts moving to normal operating temps.

When warmed up: car will stumble from 0-35 or so and may miss if given too much pedal. On the highway, typically bogs down when accelerating from low RPMs - like 55 MPH and need to get to 60-65 MPH it's almost mandatory to downshift and achieve higher RPMs in order to have the requisite power to accelerate properly. The longer the car driven the worse the performance, it seems, though it's a pretty consistent level of suck when car is fully warm. Does not overheat. Fans kick on as they should.


What's been done:

2010, last 3 months: Pontiac dealer diagnosed DOA alternator, leak in cooling system. Fixed. Asked them to diagnose the tuning/stumbling problem and they said do the distributor/optispark/cap/rotor stuff. Not for eleventy-million dollars at their shop, no. Also should be noted that most or all of those spark-related things were done in a shop in 2007 (see below). Coolant-system flush, Oil-change.

2010, in the last 6 months (car sat for 2 years or so): new plugs, wires, PCV, EGR valve, EVAP purge control solenoid, Alternator, Battery, ECU/PCM, Oil Pressure sensor.

2008-2010: car sat after needing trans work (lost 3rd gear).

Mid-2007 a shop did: Plugs, Air duct assembly 25147186, Hose 9807, Seal assembly 10217886, Seal35072, TPS Sensor 2-19072, Dist & ign kit RR218 (Note: RR = Refurbished? I hope not but maybe so! Grrr). Drove okay but problem persisted - the shop tech could never solve the low-RPM stumbling issue.

Early-2007: Removed stock 1995 Firebird LT1, installed 1996 LT1 from Caprice. Fuel pump (used) was replaced at engine swap time, Starter.

Technology: It was suggested that I get the cable and software to connect to my car through a laptop. Have cable (AKM Electronics), DataMaster software, and being somewhat of a computer guy the Laptop was the easy part. I've recorded some data including a.) cold start to warm idle, b.) various closed loop driving conditions - backroads, highways, interstates and c.) stopped to redline-RPMs in 1st gear. I've also looked around at the Dyno (where is the horsepower?) and tried to assimilate the info using a great read by InjuneerZZ here: Scanner readings article .

In Summary: Through all that I'm stumped and though I have several friends that are mechanics and work on my car - this is also beyond their experience and understanding. If anyone who I'm not already talking with would like to review the logs/recordings I'd be happy to send them. I also have data exported to excel spreadsheets available. Basically in the area I live, my resources have been mostly exhausted. Mechanics/Shops in the area can't solve this or diagnose with accuracy. This ongoing issue has be very frustrating. Help is greatly appreciated. I really want to get this car where it should be performance-wise. To the store and back; great. Any significant distance and we have 'bog-city'.
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Note: recent replies on other boards have implored me to check/replace the ICM (and/or Coil). AC-Delco parts best for this? Try this first? I fear it's the Optispark (again?). Thanks in advance!

Guest47904

So in my mind I could see 2 main causes of hot running bad but cold is ok. Either from poor closed loop control or something is changing (breaking down) when hot.

So eliminate the control from the equation since it is easiest. Unplug either of the O2s and see if it runs good once warm. If so, you have a closed loop control problem.

If not, then it's possible something is breaking down once hot. What I find strange is you never said the coil was replaced. The coil is considered a tune up item. It is common for it do what I call "side firing" where spark jumps from the insulated body to the laminations. This can be seen at night when it's dark and in the light by tell tale white spots on the insulation. Any brand coil will do, no need to buy a particular brand unless you want to step up the power with a higher voltage from an after market type.

If the problem is indeed from a device breaking down, then even after disconnecting the O2, it will continue to run crappy.

Usually it is from an electrical device. Rarely is it the PCM. So what are some of the others? Coil, ICM and the low voltage feedback side of the opti. All of which can be tested for the problem BEFORE you buy them.

Remember the opti is composed of 2 sections. The high voltage distribution side. This side, if it were the problem, is likely to be the problem whether it's cold or hot. The other side is composed of a shutter wheel and sensor which provides two 5 volt square waves of differing frequency. If these are changing, they can be tested BEFORE replacing it.

Misfit74

I replaced the ICM and Coil yesterday. I included the cooling mod from shbox.com, which was adding space between head and cover-plate with washers, basically. Made little-no difference in how it runs, esp. how it runs warm. Several folks thought heat could be stressing those components, which made sense. Also made sense to do that (myself) before the Opti.

Question on 02 sensors: some have said that they could be culprits here. One suggestion was to unhook one and see how it runs. I'm wondering which one first? Does it matter? Also, with DataMaster software and cable to run to my laptop, I can monitor the readings of the sensors in mVs and there are no huge red flags with the readings during driving conditions or otherwise - that I can tell. If it was an O2 sensor, wouldn't I be able to detect that in the readings? And what of there being no 02-related DTCs (codes)?

Guest47904

Wish I had money to throw at my vehicles. I been wanting new carpet.

I had an O2 wire that was burned in 2. The PCM thought it was running rich all the time. As soon as it went into closed loop, the PCM kept pulling fuel until it ran so bad it jumped back out to open loop. Then it would jump back to closed loop, go through the whole process all over again. It NEVER threw a code.

You will set a code when you unplug an O2 but it will go away as soon as everything is normal.

Injuneer

I posted a response on the other site you posted this on. Looking at your data logs, you have a lot of problems, including massive knock retard every time you push the throttle, driver's side O2 showing way lean in PE mode (WOT). Driver's side adding a bunch of fuel with the long term fuel corrections. Passenger side adding about 1/2 as much. After hard driving, even though the TPS sensor returns to 0.65V, the idle stays up around 1,000RPM, the MAP is too high (48kPA) and the IAC is commanding full open, even though its idling way above the programmer idle speed. That's the part I can't figure out.

Are you running premium fuel? Are you absolutely sure you aren't running the aluminum head program with the iron heads? What MAF sensor are you using?

Misfit74

I will call the dealer to verify the program - I think it's the aluminum heads/stock program.

Everything in the car except the motor is stock '95 stuff, including the MAF sensor.

I added 12 gallons of 92 octane fuel today - no change, yet.

Update: replaced thermostat (stock 180-degree). I bled for air. Car still took 350-450 seconds to reach closed-loop temp. It is about 40 degrees outside, though.

Also checked the MAF and boot for damage or un-tight seals. Everything is good and tight and properly fitted.

Checked EVAP vacuum line that wraps around the throttle-body and found no cracks, holes or damage. I still have to get behind one of the wheel-wells to access the rest of the line between the EVAP solenoid and the canister.

Now that it has been pointed out in the data recordings, it's beginning to make some sense as far as there being so much activity with the CCP DC and EGR. Both of those are VERY active and always active anytime I'm pressing the gas. There is spark-retard, CCP DC and EGR activity coinciding with throttle. CCP is more frequent, I believe. I'm not sure what is supposed to be 'normal'. Here are a couple of screen-shots (last one is at idle):





Here is one more of today's idle after driving 10-15 mins into closed loop:

Injuneer

Were you goosing the throttle to get those RPM spikes, or are they data errors? You have the same problem in the hot data logs you sent me. At the end, the throttle is fully closed, but the RPM spikes from the 800/900RPM idle speed to 4,000 or 5,000 RPM for a single data frame, and there is no indication of "DATA ERROR". Could be erratic signal from the cam position sensor in the Opti, including possible interference from a high voltage wire running too close to the Opti harness, or spark jumping to the Opti case. Have you ever open the hood in the dark and looked for arcing around the distributor?

Misfit74

Sounds like I can check the Opti harness and spark-plug wire route on the passenger side of the motor. I need more info on what's being called the High-voltage wire. Part of Opti plug-in harness or coming off the Coil? I'm curious what you think of the RPM spike at idle. It's pretty consistently spiking. Perhaps there will end up being some truth to the Pontiac dealer recommending the Opt-stuff being done to solve the issue.

Is it going to be important to dig into the rest of the vacuum line from the EVAP to the Canister? I was going to do that today or in the next day or two but if it's not necessary, the wheel well can stay on. Again, thanks for the feedback. Much appreciated.

Guest47904

"A" high voltage wire is either the coil wire or one of the 8 plug wires. As was previously explained.

When looking at the spikes in your waveform, what is the time separation between the spikes?

It looks like spark plug wire signals. I believe this is what he may be alluding to about a high voltage wire. So knowing the frequency of the spikes would help determine that.

Misfit74

No, I was not touching the trottle at all.

I'll try the dark thing. (Im posting another update below, and sent a fresh log/spreadsheet).

Misfit74

A couple screenshots yesterday's driving/recording data (below). If anything strikes anybody, please feel free to chime in!

This is recording (rather than monitor and screenshots like also-recent images above) after adding 12 gallons of hi-octane fuel (I learned that's a MUST), replacing the thermostat, ICM, and Coil. I re-checked all the intake stuff and re-routed a couple wires in case they could have been causing interference (someone's suggestion also). I re-seated a number of connectors and made sure the intake/MAF stuff was tight as could be. I found no cracks in any lines under the hood. I did find, and I'm not sure why, that the car ran better yesterday with less knock counts and less spark retard than the day previous. Perhaps the fuel is that important. Maybe it wasn't quite a hot as before, though this did encompass 12-15 minutes of driving. I did get a couple of solid 'misses' that I noted driving. It's definitely still not 'right'. Here are the screenshots from yesterday's driving (the second one is same as first but graph is zoomed):

Misfit74

Problem resolved!

After installing a new Delphi cap/rotor front-half Opti kit and it NOT fixing the problem, I bought a new, ready to bolt-on entire Optispark unit that included everything: new optical sensor, bearings, back metal cover, etc. - the whole unit. And...

FIXED!

Thanks to everyone who helped.

Injuneer

Glad you figured it out.