Supercharged LS7 will not idle

[WallinAuto]

I'm working on a 2006 Z06 Vette that has a starting/idle issue. It has a blower with an intercooler and a sniper intake.

It will only start at 20% throttle and idles really rough. I get a DTC for the MAP sensor but nothing else. The MAP signal pulsates and looks wiered. I will attach a messurement so you can see what it looks like.

Any ideas what could be the issue?

[blindsquirrel]

I notice that BARO is reported as 90kPa, but key-on MAP is 99-101. They should read the same, a mismatch there will cause P0106. A broken MAP will also cause P0106 though, and could also cause the mismatch shown in the log.

Circuit/System Verification

If DTCs P0641 or P0651 are set, refer to DTC P0641 or P0651.

1 Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust.
2 Verify that the engine is in good mechanical condition. Refer to Symptoms - Engine Mechanical for the 6.0L engine.
3 Ignition OFF for 90 seconds, determine the current vehicle testing altitude. Ignition ON, observe the scan tool BARO parameter. Compare the parameter to the Altitude Versus Barometric Pressure table. The BARO parameter should be within the specified range indicated in the table.
4 A skewed MAP sensor will also cause the first and second intake manifold models to disagree with the actual MAP sensor measurements. Use the scan tool and compare the MP Sensor parameter to a known good vehicle, under various operating conditions. The readings should be within 3 kPa of the known good vehicle.
5 Ignition ON, observe the scan tool MAP sensor parameter. Start the engine. The MAP Sensor parameter should change.
⇒ Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.


Circuit/System Testing

Important: All electrical components and accessories must be turned OFF and allowed to power down.

1 Ignition OFF, disconnect the MAP harness connector at the MAP sensor.
2 Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit and ground.
⇒ If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3 Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.
⇒ If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
⇒ If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4 Verify the scan tool MAP Sensor parameter is less than 12 kPa.
⇒ If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
5 Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify the scan tool MAP Sensor parameter is greater than 103 kPa.
⇒ If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
6 If all circuits test normal, test or replace the MAP sensor.


Component Testing

Important: You must perform the Circuit/System Testing in order to verify the integrity of the MAP sensor circuits before proceeding with the Component Testing.

1 Turn ON the ignition, with the engine OFF, and remove the MAP sensor.
2 Install a 3A fused jumper wire between the 5-volt reference circuit and the corresponding terminal of the MAP sensor.
3 Install a jumper wire between the low reference circuit of the MAP sensor and ground.
4 Install a jumper wire at the MAP sensor signal circuit.
5 Connect a DMM between the jumper wire from the MAP sensor signal circuit and ground.
6 Install the J 35555 (vacuum tester) to the MAP sensor vacuum port. Slowly apply vacuum to the sensor while observing the voltage on the DMM. The voltage should vary between 0-5.2 volts without any spikes or dropouts.
⇒ If the voltage is not within the specified range or is erratic, replace the MAP sensor.

You can also monitor reported voltage in the scanner during the vacuum test instead of measuring with a DVOM at the sensor harness. Only resort to the DVOM as a double-check if the scanner reading doesn't do what it should.

I would actually bypass all their initial circuit tests and go straight to the vacuum test first, as if it works there the rest of the items are automatically proven good.

[WallinAuto]

Thank you for taking the time to reply. I will perform the vaccuum test as suggested.

Do you have any thoughts on the pulsating MAP signal? The car has a boost gauge and it also shows a pulsationg pressure.

[blindsquirrel]

I think you should evaluate the known problem first before wasting time speculating what else might also be wrong. If the MAP checks out OK with the vacuum test I'd say probably a broken engine (holed piston, valve hung open or gone missing, etc.).

[WallinAuto]

OK, thank You.

I will update this post when I know more.