Consistently shuts off at stop signs/stoplights.
The idling fluctuations also manifest themselves when driving, particularly at low speeds (under 45 mph) but also at highway speeds when the accelerator is not pressed down (so on slight downhills). At high speeds it’s just a mild hesitation. At low speeds it actually jerks.
It performs extremely well when accelerating from zero to 60, or when climbing hills at speed. In other words, when the accelerator is pressed beyond a certain point (about 1/4 of the arc) it does fine, and the problems seem to disappear.
The idle fluctuation tends to be less pronounced when the engine is cold, but doesn’t disappear completely.
Big clue: When the air flow meter is disconnected, the idle fluctuation disappears, and it idles steadily. (Haven’t tried driving with it disconnected). (There is no mass air flow meter on these things, rather it’s an air flow meter on the throttle body itself).
Did self diagnosis on ECU, it said that there was a problem with the air flow meter. But we tested the air flow meter and it seems to test fine (voltage increased when air was blown across sensor).
What we’ve tried so far:
Replaced the air filter.
Replaced oxygen sensor.
Replaced the ERG valve.
Cleaned contacts on sensor connectors (air flow meter, idle control valve, throttle position sensor).
Cleaned the air flow meter sensor.
Cleaned out the throttle body.
Tested the voltage on air flow meter (tested fine).
Replaced the PCV valve.
Replaced the coolant temperature sensor.
Replaced cracked hosing.
Tested fuel pressure (at fuel filter, pre-fuel-pressure regulator). It tested high. Plenty of steady pressure.
Eyeballed the fuel injector spray. Seems fine.
Replaced timing chain tensioner.
Tried two different idle control valves (made no difference, but they both seem to be functioning).
Checked timing (fine).
Arggggh! What else to do?
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Tuesday, March 10th, 2020 AT 7:07 AM
