dgascho

Redid several things on the Cobalt, working on getting the tune dialed in (KM043).


First thing I noticed was a faint stutter/misfire, randomly. Startup, acceleration, cruising, not much pattern. Started throwing only p2188 and p0191. I've seen p2188 before, too rich at idle, still getting it tuned in, no big deal.


I've never seen p0191. Fuel rail pressure? Injector? regulator? Has a new HPFP.


Final variable is that I'm pretty sure the oil level is increasing, and it smells like gasoline. I know a gasoline smell is normal for these cars. Combined with the codes and the oil level, is fuel somehow washing down piston or something? Could a bad injector do this? I'm not getting any cylinder-specific codes.

Looking for ideas.....

Kolt

idk if you can change hpfp pressure with a tune but if your smelling gas in the oil most likely the hpfp is leaking. Pretty common on the equinox di engine. It will cause rich concerns as well since it will be sucking fuel vapors in the pcv system.

From gm service information

Conditions for Setting the DTC
P0191 Low Rationality Test

The fuel pressure during engine cranking is less than 120 kPa (17.4 psi), then the engine continues to run for 30 seconds after the start occurred and DTC P0087, or P2178, or P2188 is set.

P0191 High Rationality Test
•The fuel pressure during the initial power up is greater than 1.5 MPa (218 psi), and P0088, or P2177, or P2187 is set.
OR

•The fuel pressure during the initial power up is greater than 1.5 MPa (218 psi), and the fuel pressure increase during fuel pump prime is greater than 385 kPa (56 psi). The condition exists for more than 4 seconds or a cumulative of 50 seconds.

dgascho

Just put a brand new hpfp on, but I suppose it's possible I got a bad one. could a stuck/leaking injector do this? maybe flood a cylinder? would have thought if that bad, it would throw a cylinder-specific code?

I have hptuners if there's some way to use it to diagnose. I'm obviously not an expert with it.

dgascho

If reading your post correctly, the combo of p0191 and p2188 is triggered by low pressure at startup?

I wonder if it would be possible for a leaky injector to wash fuel down a cylinder while engine is not running, causing rich condition, fuel in oil, and then resulting low pressure at startup?

Kolt

Its possible you got a bad pump, or a leaking injector. Usually you would see a leaky injector cause a specific cylinder misfire so if hp tuners has it I would watch your misfire when running first then if you don't find anything check fuel pressure during cranking, should go up to around 60-70 on key on and should not drop more than 5psi in 1 min. From that pressure it then should increase to around 3-600 as you crank. Idling it should be around 5-800psi.

I don't know anything on hp tuners unfortunately but being a dealer tech I know tech 2 and gds.

Kolt

idk how diag savvy you are but here is the important stuff from gm si diag page for p0191

DTC P0191, P0192, or P0193
Diagnostic Instructions
•Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
•Review Strategy Based Diagnosis for an overview of the diagnostic approach.
•Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0191Fuel Rail Pressure (FRP) Sensor Performance

DTC P0192Fuel Rail Pressure (FRP) Sensor Circuit Low Voltage

DTC P0193Fuel Rail Pressure (FRP) Sensor Circuit High Voltage


Circuit/System Description
The fuel rail pressure (FRP) sensor detects fuel pressure within the fuel rail. The engine control module (ECM) provides a 5-volt reference voltage on the 5-volt reference circuit and ground on the reference ground circuit. The ECM receives a varying signal voltage on the signal circuit. The ECM monitors the voltage on the FRP sensor circuits. When the fuel pressure is high, the signal voltage is high. When the fuel pressure is low, the signal voltage is low.

Conditions for Running the DTC
DTCs P0097, P0098, P0099, P0117, P0118, P0128, P0192, P0193, P0627, P0628, P0692 are not set.

P0191 Low Rationality Test
•The engine speed is greater than 25 RPM for greater than 0.5 second.
•The engine run time is greater than 30 seconds.
•DTC P0191 runs the low rationality test during engine start only.
P0191 High Rationality Test
•The engine speed is greater than 25 RPM for greater than 30 seconds.
•The engine block heater is not active.
•The engine coolant temperature (ECT), at shut down, is warmer than 72°C (161.6°F).
•The ECT, at start-up, is colder than 54.8°C (130.6°F).
•At start-up, if the ECT is warmer than the intake air temperature (IAT), the difference must be colder than 35°C (95°F).
•At start-up, if the IAT is warmer than the ECT, the difference must be colder than 10°C (50°F).
•The engine OFF time during soak is greater than 4 hours 27 minutes.
•DTC P0191 runs the high rationality test during engine start only.
P0192 and P0193
•The ignition is ON or the engine is running.
•The DTCs run continuously within the enabling conditions.
Conditions for Setting the DTC
P0191 Low Rationality Test

The fuel pressure during engine cranking is less than 120 kPa (17.4 psi), then the engine continues to run for 30 seconds after the start occurred and DTC P0087, or P2178, or P2188 is set.


P0191 High Rationality Test
•The fuel pressure during the initial power up is greater than 1.5 MPa (218 psi), and P0088, or P2177, or P2187 is set.
OR

•The fuel pressure during the initial power up is greater than 1.5 MPa (218 psi), and the fuel pressure increase during fuel pump prime is greater than 385 kPa (56 psi). The condition exists for more than 4 seconds or a cumulative of 50 seconds.
P0192

The ECM detects that the signal circuit voltage is less than 0.3 volt for greater than 4 seconds.


P0193

The ECM detects that the signal circuit voltage is greater than 4.7 volts for greater than 4 seconds.


Action Taken When the DTC Sets
•DTC P0191 is a Type B DTC.
•DTCs P0192 and P0193 are Type A DTCs.
•A message center or an indicator displays Reduced Engine Power when DTC P0192 or P0193 sets.

Conditions for Clearing the DTC
•DTC P0191 is a Type B DTC.
•DTCs P0192 and P0193 are Type A DTCs.
Diagnostic Aids
A poor connection, improper terminal contact, or improper terminal retention at the X162 multi-way harness connector may set DTC P0191 or P0193.

Circuit/System Verification
 1. Engine idling, observe the Actual Fuel Rail Pressure parameter with a scan tool. The pressure should be approximately 3.5–5.5 Mpa (508–798 psi).
 2. Command an increase and decrease in fuel pressure with a scan tool. Observe the scan tool Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure parameters. The Desired Fuel Rail Pressure and the Actual Fuel Rail Pressure should closely match in all the commanded states.
 3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
 1. Ignition OFF, disconnect the harness connector at the FRP Sensor.
 2. Ignition OFF, test for less than 2 ohms between the low reference circuit terminal 1 and ground.
⇒ If greater than the specified range, 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 terminal 3 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. Install a 3A fused jumper wire at the signal circuit terminal 2. Toggle the jumper wire between the low reference circuit terminal 1 and the 5-volt reference circuit terminal 3. Verify the scan tool Actual Fuel Rail Pressure toggles between 0.1 MPa and 20.1 MPa.
⇒ If the specified parameter does not toggle between the minimum and maximum values, test the signal circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the ECM.
 5. If all circuits test normal, replace the FRP sensor.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•Control Module References for ECM replacement, setup, and programming
•Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement

Kolt

Here is p2188

DTC P2097, P2178, or P2188

DTC P2097Post Catalyst Fuel Trim System High Limit Bank 1

DTC P2178Fuel Trim System Rich at Cruise or Accel

DTC P2188Fuel Trim System Rich at Idle

Circuit/System Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open Loop and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During Closed Loop, the ECM adds HO2S inputs to calculate the short and long term fuel trim (FT) adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. If the HO2S indicates a rich condition, the FT values will be below 0 percent. The short term FT values change rapidly in response to the HO2S voltage signals. The long term FT makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.


Conditions for Setting the DTC
P2097
•The post catalyst FT weighted average value is greater than a calibrated value.
•The DTC sets when the above condition is met for 4 seconds continuously, or for 50 seconds cumulatively.
P2178 or P2188
•The long term FT weighted average value is less than a calibrated value at idle, cruise or during acceleration.
•The DTCs set when the above condition is met for 4 seconds continuously, or for 50 seconds cumulatively.
Action Taken When the DTC Sets
DTCs P2097, P2178, and P2188 are Type B DTCs.

Conditions for Clearing the MIL/DTC
DTCs P2097, P2178, and P2188 are Type B DTCs.



Circuit/System Verification
Important: Disregard any transmission symptoms, antilock brake system (ABS) indicators, and traction control system (TCS) indicators until any fuel trim faults are repaired. A fuel trim fault may cause default actions such as harsh shifts and illumination of the ABS/TCS indicators.

 1. If any other DTCs are set, perform those diagnostics first.
 2. Operate the vehicle within the parameters described in Conditions for Running and Conditions for Setting. The DTC should not set this ignition.
⇒ If the DTC sets this ignition, proceed with Circuit/System Testing.
Circuit/System Testing
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

Allow the engine to reach operating temperature. With the engine running, observe the Long Term FT parameter with a scan tool. The reading should be between −20 and 0 percent.

⇒ If not within the specified range, inspect for the following:
•With the engine idling and the transmission in the Park or Neutral position, observe the manifold absolute pressure (MAP) sensor parameter. The MAP sensor parameter should be between 19–42 kPa.
⇒ If the MAP sensor parameter is not between 19–42 kPa, refer to DTC P0106 or DTC P0107 or P0108.
•With the engine idling, observe the mass air flow (MAF) sensor parameter. The MAF sensor parameter should be between 2–6 g/s at idle.
⇒ If the MAF sensor parameter is not between 2–6 g/s at idle, refer to DTC P0100-P0103 or DTC P0101.
•Vacuum hoses for splits, kinks, and improper connections
•The air intake duct for being collapsed or restricted
•Leaks in the air induction system between the turbocharger outlet and the throttle body inlet, including the charge air cooler
•The air filter for being dirty or restricted
•Objects blocking the throttle body or MAF Sensor
•Excessive fuel in the crankcase due to leaking fuel injectors
•The evaporative emissions control system for improper operation
•Excessive fuel pressure—Refer to Fuel System Diagnosis.
•Malfunctioning fuel injectors
•Fuel contamination—Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
•Missing, loose, or leaking exhaust components from the HO2S forward—Refer to Symptoms - Engine Exhaust.
•The HO2S for improper installation and for electrical wires or connectors that may have suffered corrosion, water intrusion, or contacted the exhaust system
•Incorrect terminal tension at electrical connectors
•Loose, corroded, or mislocated electrical ground connections
•A restricted exhaust system—Refer to Symptoms - Engine Exhaust.
•The HO2S signal circuit shorted to voltage
•Malfunctioning engine components—Refer to Symptoms - Engine Mechanical.

dgascho

Wow, a lot of help. Thank you. Gives me something to work with.

Kolt

np man, good luck with it. If you need any more help just ask

dgascho

The car is my wife's daily driver, occasionally. I set the Aeroforce Interceptor to monitor misfires while she drove, and let me know what she saw. She text me today saying all of the cylinders are 2 or less, except for the last one,...……….. its in the 40s.

Think I may have found a problem lol. Time to get the opels, anyway

umrdyldo

iTrader: (1)

Misfires could be spark slugs, injector issue or a compression issue. Especially dirty valves.