First I'd like to apologize for posting this here but I'm a little desperate and running out of ideas. Most 4th gen camaro forums seem entirely focused on LS1s, so I've found the most knowledgeable people for the 3.4l are on third gen and fiero forums from doing swaps. The engine is in a 95 Camaro and is essentially stock.


I have a 95 3.4l Camaro. It's got 220k on the body but the engine is a pull out from another 95 with around 80k on it and has been in the car for a few years.

Some background: I took my car to its first track day and during the third session I lost power exiting a corner. I thought it was a misfire, did some basic diagnosis, and everything seemed fine. Got on the track again, same issue.

What seems to be happening is the car will start, idle, and rev fine. When it's in drive if you stay under 2000rpm it's fine, though it's really difficult to do this so I haven't been able to see if it's a open loop startup related thing or not. As soon as you go over 2000rpm in drive it will studder and continue to do so at any rpm until restarted. I've done additional testing to confirm that the misfire happens just after 2000rpm in drive. It does not happen in park or neutral. I can put it in drive and do a brake stand and once I hit 2k it misfires.

I have changed the plugs, wires, coils, icm, pcm, 7x (3x? the one on the passenger side of the block) crank position sensor, and map. It behaves exactly the same.

When changing the plugs i noticed 1/3/5 look normal to lean and 2/4/6 look rich, with 4 being wet with fuel or oil.

In researching this problem I've seen people suggest injectors, fpr, fuel filter, and fuel pump. I'm willing to do those, but if anyone has any insight on how to diagnose this it'd be greatly appreciated. I've also seen the camshaft position sensor and the 24x crank position sensor suggested. I'll try those as I still have the ones from my 220k block and that ran fine.

Did I read you replaced everything but the O2 sensor? Almost seems like when it's switching from sequential to batch firing that you are having an issue with a bank of injectors staying on.

You might want to download TunerPro RT and get an ALDL usb cable do some datalogging and try to figure out what's happening...
http://www.tunerpro.net/

About 1/3 the way down the page you'll see the datastrean definitions for your car:
http://www.tunerpro.net/downloadBinDefs.htm

If when logging it seems everything is skipping every so often there's a trick you have to search for on youtube for converting the V4 .ads file to a V5 .adx file.

[This message has been edited by lou_dias (edited 06-27-2018).]

Yeah I've replaced more or less everything but the O2s at this point. I cant remember if it's just the two in the manifolds or if there are any downstream.

I have a Tunercat/Datacat cable and tried monitoring it with Datacat and to be honest I have no idea what I'm looking at. The knock count doesn't go up, retard stays at 0, and my spark advance hovers around 20-30. I have no DTCs and I THINK all the bits are normal but I can't say for sure. The cam position sensor detected flips on and off. The only other thing that seems suspect is that the 6x ign value stops after 2000rpm. Is this normal? Is there anything specific I could be looking for with Datacat?

I think you'd really need to determine what is fouling the plugs. Fuel and oil are two very different things with some different troubleshooting approaches. What's the O2 sensor data look like between the two banks?

I wouldn't say anything is specifically fouling the plugs as in causing them to not work. The engine's behavior is identical before and after changing the plugs, and after turning it off and on again, will always idle and run normally as long as you don't go above 2000 rpm in drive.

o2 sensor data looks like this. the first part of the data is all in drive to trigger the misfiring condition.

I'm tackling lean issue with my 3.4 too.
Did you check fuel pressure during: key on, engine off?
idle?
2000 rpm while driving?
What is your BLM and INT during : idle?
2000rpm?
Does your EGR work?

That PCM was also used in the 96 Grand Am with the 3100 V6. You may want to check those forums. It's actually what I'm running in my 3100->3400 conversion in my Fiero. Runs silky smooth.

I've forgotten the specifics of the data I recorded so I'll try to record new data later or tomorrow and get better answers but BLM left and right are hovering around the normal 128. I see it dip as low as 110 and as high as 131 but it seems to quickly correct itself. I think this is all after the misfiring condition starts. I don't have a lot of premisfire condition data to look at.

The bits for EGR 1, 2, and 3 flip on and off and no check engine light comes on so I believe it to be working. I had a malfunctioning EGR valve on a separate 3.4l and it never behaved like this.

I haven't checked fuel pressure, that was my next step. The pump has 220k on it so I wouldn't be surprised if it's suboptimal. It just seems unlikely since the condition always goes away after turning it off and on again until you hit 2k again, and then it persists at any rpm. When my fiero had a bad fuel pump it just didn't run.

I rebuilt the fuel rail with new injectors and fuel pressure regulator (probably didn't need that) and it seems to be back to normal.

I want to give a shout out again to scan9495 and everyone else that offered suggestions.

I'm happy that you seem to have gotten it sorted.

The "cam signal missing" doesn't sound normal, however. The cam should provide a pulse/signal every time it turns, I would think. (Unless there is some set of parameters that causes the ECM to "not care".).
With that said, I'm not familiar with your ECM, at all.
Best of luck.

The cam signal goes on and off, which to my best guess, is indicitave of when it's signaling TDC for piston 1, which is all it does. In other words, I think that's normal and expected.