myoriginal77

Hello everybody,

I have a '77 Corvette (i bought new) that I put a 2004 LS1 motor and 6 speed trans in.

It runs fine up to about 3300 RPM and then it sputters, it shows codes 171 & 174 showing right and left bank lean. It also showed a MAF code (i forget the number.)
I'm running a Walbro in the back of the car, C5 Corvette regulator and then through the stock line to the front, braided line to the rail. Like I said, really strong until 3300, no popping or backfires, more like sputtering and with the lean codes it has to be running out of fuel.
I have a solid 60 pounds fuel pressure. I'm only running the 2 -O2 sensors on the stock manifolds and the ECM has been modified for this.

All the connections around the MAF are tight, PCV is all OK (it's a LS2 system with no PCV valve), exhaust OK. I have the engine and everything else well grounded.

Any ideas would be appreciated,
Thanks,
Frank

P.S. here is my car at the Bonneville Salt Flats, scroll down, it's the black one on the trailer; http://www.saltflats.com/2009_photos_1.htm
before the salt attack. Went 125 when I had the problem. Didn't have time to test it before I left, got it running on thursday, left monday.

brian g

iTrader: (1)

Is the pcm tuned for a manual trans, see an lq4 swap having the same issue in this forum.

Problem with conversion using 2005 LQ4, will not run off idle

Hope this helps.

Reckless

iTrader: (9)

Does your fuel system have a regulator and return line to the tank?

JAY ROD

iTrader: (1)

Check your fuel pressure,then check to see if your oxygen sensors are working correctly.

myoriginal77

Thanks for the replies,
The ECM is tuned for a manual (thanks for the link) fuel pressure is a solid 60 pounds while it sputters, as far as I can tell O2's are ok, I'm running a C5 regulator / filter with a return to the tank which looks likes it's working.

I'm stumped,

thanks,
Frank

50chevy

iTrader: (2)

Check out the MAF sensor. These would be the questions I would ask myself: It is installed in the correct direction? Are all the wires good? Has the screen been removed and might be affecting the tune? Hope this helps, I had a MAF act up and it will create popping, hesitation, and other issues.

Marky522

iTrader: (8)

Is your MAF mounted directly after a 90 degree bend? I have seen this cause issues on other cars, the air has mass and going around the corner causes it to miss the Sensor of the MAF.

Mark

myoriginal77

Hello,

MAF is OK as far as I can tell, the motor only had 625 miles on it and it's first in line after the air cleaner so no bends.

Also, at the suggestion of a friend, I dis-connected the battery and then un-plugged the MAF, re-connected battery and then started it. He said it would then by-pass the MAF in Speed Density mode, and I still had the problem, so that should rule out the MAF.

Still stumped,
Thanks for the replies,
Frank

CalEditor

iTrader: (1)

It sounds like the PCM is limiting Torque.
Make sure you have a Good VSS signal. Scan it
Make sure all of your abuse or limits are set correctly.
Disable the column lock
Set the Column lock MPH to 255
Make sure the Fuel cuts are correctly set
Make sure the ETC RPM limit is correct.

Make sure your Stoich is set for the proper Ethanol Mixture. you may have 2 problems. E10 is about 14.1


Not the issue, but
You may want to look at the ETC setting also and increase the rate.

post your tune.

myoriginal77

Thanks Answer Man;

I have no tune, just the stock program modified for the install in the '77, no VATS, only 2 O2's etc.

When you say VSS signal, I have nothing hooked to the trans (T56) I know there is a VSS wire in the harness under the hood but it was my understanding that it did not need to be hooked up to anything.

I am assuming all the locks and limits have been disabled or set when they did the PCM and harness mod (waitforme performance.)

I'm only running regular gas right now and I'm not hip to the ETC setting so I need some help.

I'm an old carb and distributor guy and not up to speed (no pun, sorry) on this stuff although I'm reading everything I can and trying to catch up.

You're not close to Joliet Illinois by chance are you ???

Thanks for your help,
Frank

CalEditor

iTrader: (1)

Hey do you have the clutch switch wire connected?
If it is not hooked up the PCM thinks that the clutch pedal is depressed.

myoriginal77

I do not have the clutch wire connected - I think there was 2 of them in the remaining wires of the harness.
Do they go to the same switch that locks out starting unless the pedal is down ???

Thanks,
Frank

CalEditor

iTrader: (1)

Battery voltage is supplied from the Engine Ignition 1 fuse to the clutch switch. The clutch switch is a normally closed switch. When the clutch pedal is released, the clutch pedal position switch signal circuit is pulled up to B+. When the clutch pedal is applied, the switch opens, and the voltage drops to 0 volts.

If the powertrain control module (PCM) detects a specified number of vehicle speed transitions without detecting a clutch switch transition, DTC P0833 sets. DTC P0833 is a type B DTC.

The DTC's reporting may be shut off.

You may want to contact Jesse and see what he says

Jake Harsha

Something like that. Here's how I have mine set up:



Yours should look like that, but probably without the clutch start cancel (manual bypass switch). I have that in there because it's a rock crawler Jeep and it's often useful to start it with the clutch engaged when you kill it on a climb. Wire colors and pin-out numbers are for a 2007 LQ4 out of a 2500 Silverado. Your colors/numbers may vary.


HTH,
Jake

myoriginal77

Thanks for the ideas,
I guess the question I have now is; If the VSS is not hooked up, does the PCM even care about the clutch switch not seeing any mph at all ???

The other trans wire that was left in the modified harness was the 1 inch diameter round plug, which I assume went to the trans.

I will check with Jesse and see what he thinks,

Thanks again guys,

Frank

CalEditor

iTrader: (1)

PM me your email and I will get you a set of Schematics for the M6 and the A4. I will have some additional info with them.

myoriginal77

OK thanks answer man, you have a PM,

Frank

CalEditor

iTrader: (1)

The Extended Brake Travel Switch need to be connected or 12V need to be supplied to Terminal #62 of the PCM Connector #2. If not the PCM will retard timing, shut off up to 4 cylinders, and on ETC (DBW) car it can close the throttle if the throttle is opened


The VSS need to be connected for several reasons. IAC or TAC positioning of the throttle on decel. Some Torque management or limiting also. Also you need it on M/T to switch to different tables as the gear selector would on the A/T






Not sure if this is just for Cruise on not. I will look at the PCM Calibration tonight and see what I can find out.











I will post the rest of them later today

gofastwclass

iTrader: (2)

People like this are why I love this site!

CalEditor

iTrader: (1)

I am under the impression from GM documents that the PCM needs to see the fuel level change as in filling up the gas tank to switch back to the High Octane Spark Tables from the Low Octane Spark Tables. If not you will be stuck on the Low Octane table.






The Fuel Strategy has been assembled with Fuel Vapors from the EVAP System in place. It is very easy to install a EVAP Canister and install a new plastic line from the purge valve to the EVAP canister. You don't have to do this. It you can have the car tuned around this by adding fuel to the program in some areas. This is more detailed than just shutting off the EVAP DTC's




On the Corvette's Calibrations you will need to have the Real Time Dampening and the Traction Control Torque Management's turned off
I see about 8 RTD Torque Limiting parameters and about 100 possible Traction Control parameters. I bet you tuning software doesn't list all of them.


If you are running an Auto Trans the PCM need to know what gear you are in. Many of the PCM's functions rely on this input. Even the Rev limiter


The Brake switches need to be connected
The TCC switch for the TCC to engage
The Extended brake switch so the PCM doesn't go into Brake Torque Management.
On some Operating Systems or Calibrations the TCC Brake switch failure can limit Torque or cause BTM to be enabled


The Clutch Switch as I discussed earlier