davkenrem

Hello all, looking for some help. I have a 97 Chevy K1500 Suburban w/ a 6" lift. This summer I installed a L31-R crate engine. It has been modified with Chevrolet Performance Hydraulic Roller Camshafts 12677151 (Duration at .050 in. 215/223, Lift .473/.473), Doug Thorley Tri-Y Headers and the upgraded MPFI Spider.

I just had a new exhaust installed with 2 - 2-1/2" highflow Catalytic Converters into a 2-1/2" Y-Pipe into 3" Turbo Muffler and 3" Tail Pipe.

It's running on the stock computer badly. and throwing the following codes:


Current Fault Log
------------------
P0101: Mass or Volume Air Flow Circuit Range/Performance Problem
P0300: Random/Multiple Cylinder Misfire Detected

Pending Fault Log
------------------
P0108: Manifold Absolute Pressure/Barometric Pressure Circuit High Input
P0134: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
P0154: O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)


So, I knew the changes would be allot for the stock tune but it runs pretty badly with a misfire and very poor idle.

I have everything to do the 411 Swap, but thought it might be wiser to get it running on the stock computer before making the big change to the 411.

Maybe that was not the best choice.

For some reason the muffler shop did not plug in my new 02 sensors and only installed the 2 front ones stating "the back 2 don't tell the computer anything."

Once it stops snowing I'll get under there and plug in the front 2 sensor and hopefully that will clear at least 2 codes.


So my question you guys who have much more experience with this than I:

Will the stock computer be able to handle the changes and increased air flow of the engine, or should I send out my 411 PCM and get a tune on it based on the changes I've made?

This my first attempted at a mild upgrade of a modern engine, have much more exp with carbed engines.


Thanks in advance for the help.

davkenrem

More info

Things replaced with new build:

distributor
AC Delco cap & rotor
Ignition module
crank sensor
cam sensor
ac delco plugs
Summit 8mm wires
new MPFI Spider`

Also Cam Retard set to .02 at 11-1200 rpm

RB04Av

Sensor 1 on each bank is the front one. Sensor 2 is the rear. If your ECM is complaining about sensor 1, it's not seeing the signals it expects from the front ones.

Sounds like you have the rear connectors plugged into what should be the front sensors.

The only thing the rear ones do, is to provide the ECM, and the smog *****, a measurement of catalyst activity. A tune can eliminate the code that comes from not having them. They don't really affect how the engine runs.

The front ones however, DO affect how the engine runs. EXTREMELY. Those are what the ECM uses to get feedback on its mixture, and other, commands to the engine. Without those it reverts to pre-programmed (lookup table) guesses about how much fuel to put in and where to set the spark timing and so forth. Trying to run an EFI motor without O2 sensors is like trying to drive with a blindfold on: no matter how well you have the road memorized, you can't compensate for even the most minor deviations that occur. You are GOING TO end up in a ditch. That's where your setup is now; in the ditch.

Hook your O2 sensors up right, then get a tune. You are HOPELESS without those 2 things.

I'd also recommend ditching the spider thing altogether and getting a port FI setup. The marine one is popular. There are also others. Any port EFI manifold that will bolt to Vortec heads will fit your motor. A Holley Stealth Ram for example. While probably not the ideal choice, that should give you some idea as to how wide-open your choices are, once you ditch the CPFI spider.

Last Call

iTrader: (4)

I suggest upgrading to the 411 PCM before going any further. I have a copy of the required calibration if you have HPT or EFILive.

Front O2s need to be connect or you are operating in open loop (no O2 feedback/correction applied). Rears should be disabled if there are no cats.

The misfire is likely from the cam of the new engine. You will need to add misfire counts in the idle region of the calibration to prevent the code.

davkenrem

I would love to do that but it will be after mid January before I can swing the $$$ for a programmer setup and license. About $500 I think for HP Tuners which is the way I'm leaning. It is supposed to be in the 40s this weekend so I will try to get out and do the O2 sensors (sucks working outside) and check for vacuum leaks.
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2xLS1

iTrader: (25)

Only tuning option for a 97 Black Box is Tunercat OBD2. HP Tuners support on Black Box PCMs starts at MY 98. What is your location? I have Tunercat. And figure out what is wrong with the MAP sensor causing the P0108.

davkenrem

I live in NW Ohio. Not looking to stay with the Blackbox. Have everything but the tuner to do the 411 Swap.

davkenrem

After hooking up 02 sensors and fixing 2 wires not fully seated on spark plugs, I'm down to one code P0101 Mass Air Performance. I started looking for vacuum leaks but got rained out. Will tray again tomorrow. Will also look into testing MAP Sensor.

Thanks for the help so far, will report back.

davkenrem

Ok, finally getting a chance to report back. I did not find any vacuum leaks but the P0101 code is cleared. Took the truck for a short drive today started right up but will not idle well. It drops below 1000rpm. Slight backfire when accelerating and not much power. Cam Retard was at 1.7 at 1100rpm. The PCM Stored P0108 and P1106 both dealing with Manifold Absolute Pressure, but I replaced the MAP sensor a few weeks ago. I guessing the Cam and headers could be confusing the PCM at this point. I also looked at the PIDs for misfire and it was show as misfires on at least 3 cylinders, I can only hear them at idle. they seem to disappear above 1800 rpm. The only other thing I can think of is the Valves are adjusted too tight.

Anyone have any thoughts?

1slow99