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idle starting surging stalling vac-leak
There are three things to check out. And a good inspection of vac lines is always in order.
There is a larger vac line that does to an electric air flow valve attached part way down on the HR strut tower. This inturn goes to the charcoal evap control canister in that fender. I want you to find a method to pinch off that hose when the problem is occuring. If doing that affects the idle, then the valve is bad. The ECU never activates it at idle to avoid problems. It opens at part throttle, and never on boost! Unless something else affects idle and the ECU then makes bad decisions about the evap valve.
We had a report of a vac-leak in the evap hose, where is attached to the TB, and there was a circumferential crack on the bottom of the hose where it attached to the TB. Watch for this. This damage could easily occur when one is manipulating the vac lines while looking for damage. Be sure to check for this when doing the pinch off test. A leak at the TB end would defeat the purpose if the test.
The idle air control valve could be dirty or defective. Most likey is dirty. It attaches to the throttle body with aprox 3/4" hoses, to control bypass flow across the throttle plate, to allow the ECU to control the idle. It might be fouled to the point of sticking. Remove one electrical connector and two hose clamps and pull it and its rubber boot off of a mounting pin that sticks up from the intake manifold. Spray it with the extension tip of a can of carb cleaner. Work in open air and note that the carb cleaner might work quite well as paint remover. Some of the deposits will be stuborn. The cleaner is a good degreaser and I think that is not a good idea to return the valve without lubrication. I suggest putting a lot of oil into it and allowing it to seep into where ever it wants to go, with the valve up and downward. Oil the exposted bronze bearing exposed on the end of the unit top. Let the oil drain and wipe a bit. Don't worry about any residual oil getting into the intake air. You might want to poke into the unit and swing the valve a bit to see what you are doing when cleaning and oiling. Note the arrow and orientation when putting it back. Wires and connectors look ok?
Also clean the throttle body, open the throttle plate to see what you are doing. A cloth works well. No need to flood this area with carb cleaner. If you use carb cleaner spray on the TB, a drop of oil on each end of the shaft from the inside would be a good idea. At worste it will not hurt.
As with many problems, make sure that the battery connections are clean and tight, electrolyte levels are good, spark plugs look ok and are gapped, injectors cleaned with a fuel system cleaner. Techron Concentrate recommened in the US market. Don't look defective expensive parts until you are certain that the problem is not cause or being aggrevated by a bacic maintenance issue.
We have see seen a few starting issues caused by fuel pumps or fuel pressure regulators. These are quite rare, at least in the current age of the ng900 fleet. A fouled fuel filter must also be considered. A bad DI can cause starting and idling problems, but usually with running problems as well. A defective throttle position sensor could cause problems, but the TechII can be used to check that out. We have very few cases, perhaps one, where the throttle posistion sensor was replaced. Look for general wiring damage, then get out the mouse traps and posion. If you ever find evidence of mice damage under the hood, you better have a look in the air filter box, especially with a paper filter!!! A K&N filter is mouse proof.
For the turbo engines: NGK BCPR6ES11's have been found to run the cleanest. Any use of 'magic plugs' will most likely lead to problems. That includes Bosch platinums of any type.
posted by 208.24.179...
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