P1416 code & warmup stall problems

[ejguillot]

All,

I'm getting an intermittent P1416 code (sets about once every 5 driving cycles). The code will set when the engine is warm, and when driving at a steady speed, usually over 35 mph.

The computer is not setting any other codes. I hear the AIR pump (vacuum cleaner sound) on startup, and have checked the vacuum lines going to the check valves (they were in place and looked OK)

Other symptoms: When starting from cold, the car will either stall or near stall when idling (like at a traffic light) and the temp gauge is at the first mark (1/8). The car will not do this again for the rest of the drive, or when started warm/hot. This only happens when the car is almost completely cool.

Also noted: an intermittent hesitation to accelerate (like a bog) when cruising and light to moderate throttle input is requested. Almost feels like the transmission is taking its time deciding whether to unlock the torque converter or not. Heavier throttle input does not show this behavior.

What I've replaced on the car since I got it 6 months ago @ 91,250 miles (car now has 100,750 miles):

Spark plugs (used AC Delco 41-950), no wires to replace (coil on plug)
Pre cat O2 sensors, AC Delco parts
Center engine mount (by radiator)
Crankshaft position sensors (was getting p0385 error code)
Coolant drained and refilled with DexCool mix
Oil changed, now at 70% life remaining
Fuel Pressure regulator
MAP sensor (was getting intermittent MAP too high error)
Throttle body cleaned, GM TEC used on engine as per procedures listed elsewhere on these forums.

Any ideas on how to proceed? I don't have a tech 2 to use.

[FrankT]

P1416 code is the AIR Bank 2 insufficient airflow.
This is what you need to do.

When the AIR pump is running make sure that both shut-off valves have vacuum. If they don’t have vacuum then repair the vacuum lines or AIR solenoid that is located under the engine cover. Now, if the vacuum tests are ok you have a bad shut –off / check valve. They can be tested with a hand held vacuum pump, they should hold vacuum for at least 15 seconds. Wthout proper vacuum they will not open up and allow airflow from the pump to the exhaust manifolds.

The AIR Pump system will not cause a stall or hesitation problem. Look elsewhere for your stall, its possible your throttle body needs cleaning, or your fuel injectors are dirty and need to be cleaned. Also check your fuel pressure and fuel pressure regulator for the stalling and hesitation.

[ejguillot]

Follow up: Went under the car and removed the panel to get to the AIR system, and found that the pump in question was silent. Removal of the AIR pump found a little water dripping from the intake. After dismounting it, letting it dry and spinning the impeller (got a little bit of hesitation, then it was spinning fine) I remounted the pump and it worked! No more codes.

Regarding the misfire: I pulled all the spark plugs, and found 1 (the rear bank, plug closest to the brake master cylinder) where the boot on both ends showed a buildup (looked corroded). I cleaned up all the plugs, coil ends and boots, using 2000 grit sandpaper on the coil pack tips and the boot end of the plugs to remove the deposits. Result: no misfires so far!

Thanks all for the advice.

[Ranger]

I think there is a TSB out on that AIR system which tell the mechanic to install a shield to prevent water ingestion.