I am currently back to square one with this car and not far from striking a match and setting it on fire. If someone has a few minutes to look over what I am forgetting/missing here it would be greatly appreciated!


Symptoms:
The car starts without hesitation and only takes about half a crank to fire up. When started cold it idles okay due to the higher RPM. Once it warms up and the RPMs lower it shakes a little bit. Driving around city the car acts okay but when stopping at a light I can feel a misfire. Driving on the highway I have a vibration around 65 MPH that seems to be motor related because if I throw it in neutral and coast down from a higher speed I do not get the same vibration. The motor seems to make good power for the most part. Data logs show a random misfire across multiple cylinders.

The Car:
1996 Chevy Camaro – 4 speed automatic – lt1
Mods worth mentioning: Borla cat back and K&N intake

History:
I took ownership of the car in June 2013 and it has not been right since the beginning (which I already knew). From all the issues I have sorted out so far it seems like previous owners just drove it into the ground. There were 7 or 8 DTCs that have been situated. The car was spitting and sputtering and harder to start before all of this.

List of what has been done in the last 3 months:
-New plugs/wires/coil/ICM
-Different Opti with new cap/rotor (old one had excessive bearing play) – idle quality got better and overall performance increase
-New serp belt
-New Thermostat/Radiator cap (had a 7lb cap on it) – operating temperature is much lower
-New upstream O2s (replaced 2 days ago)
-New EGR solenoid/Valve (stuck open/carbon buildup causing it to be held off its seat) – idle quality got better
-New lifters/pushrods/intake manifold gaskets – I could hear a lifter noise and was getting massive amounts of timing pulled – after replacement and reassembly noise is all gone and still getting some knock retard but NO WHERE near as bad (10 – 15 degrees before and most of the time – now maybe 1 – 2 degrees once and a while)
-New secondary injection check valves
-Re-bent pins on MAF and Bank 1 sensor 1 O2 harness – they were not making contact so MIL light was on

Things I have checked:
-Checked bank 2 exhaust for excessive backpressure and need to do bank 1 hopefully today
-Pulled fuel rail to check injectors – no leaking and cone shape spray
-Fuel pressure is good at idle (don't have a long enough hose to drive and observe)
-Compression checked cylinders all around 170 (cold engine/dry)
-No wire arcs
-No crossed wires
-Can’t find anymore vacuum leaks (there were some before) – sprayed ether around possible leak areas and nothing
-Sealed throttle body upper plate and lower plate (breather passage and IAC passage)

My observations:
-IAC counts are pretty low at idle (less than 16). I closed the throttle blades as much as it would allow and they did come up (was sitting at 0 when warm at idle). Currently the blades will not close any more than they are.
-Pulling the intake manifold revealed felpro gaskets so I guess it is within the realm of possibilities that there is an aftermarket cam in the car but it has stock rockers.
-Currently there are 0 DTCs set and no MIL light on.
-Unplugging MAF or resetting PCM makes LTFT bank 2 go -100% (not sure if that is usual for the PCM)

Data Log:
https://docs.google.com/file/d/0B0EB...it?usp=sharing


Sorry for the longer post but I am sure I still left things out. Thanks in advance for any help/support that can restore my sanity!

 

Opened your data log, and it's huge. What software are you using? Does it offer the ability to select what you want to log? Can you delete the "time stamp" on each bit of data? That almost doubles the number of columns of data, and doesn't provide anything useful. And, as a result of logging a large number of items, the cycle time between frames of data is 2.06-seconds, which is not really useful. For example, the PCM is toggling the STFT's almost 10 times per second, so you are only capturing a fraction of the data.

I'm deleting or moving off to the side the data that I don't usually consider. I do notice the EGR system, O2 heaters and O2 sensors monitors shows "not complete". Any idea why? If there are no codes, it should eventually indicate "complete". Only the fuel system shows "complete".

Many columns are duplicates, with just the units of measurement revised. I generally prefer kPa (MAP), G/Sec (MAF), *F. You don't need to record data that doesn't exist, like the oil temperature (only on Corvettes).

Some columns, like "Throttle Position Sensor" do not show units of measurement, only (). I'm assuming that is volts???

I'll let you know what I find after making the changes to the presentation, so it is limited to the critical parameters.

 

Thanks for taking a look at the data log!

I am using autotap for data logging so I am pretty sure I can not remove the time stamps but I can do so manually before posting a new one back up today.

The system monitors not being complete were because I reset the PCM because my LTFT on bank 2 were not changing from -100% after driving around for a while. I decided to hit the inspection station anyway yesterday and she passed so I assume the monitors have completed by now.

 

Fred,
Awesome catch on the sample rate for the data log! If you would not mind still taking a peek I would be grateful!

Now that the sample rate is faster it looks like the offending Cylinder maybe Cylinder 3.

A trimmed log:
https://docs.google.com/file/d/0B0EB...it?usp=sharing