2001 V70XC - struggles to idle when coming to stop light Topic is solved

[abscate]

Remember, you cant test for boost by just revving the engine. THese cars manage torque, so revs without load wont boost.

A very good friend of mine spent a long time troubleshooting this before he learned it.

[xHeart]

Do I check for vacuum at MAP sensor riding on the hose to ETM? Probe for opening and closing?

Unfortunately you can only reliably test it by swapping with a known good one and driving through the pattern which was causing problems previously.

Thank you vtl!

It appears that the new Bosch 0261230029 MAP sensor has stabilized when coming to stop -- hesitation is absent, idle feels normal and smooth.

[vtl]

Glad to hear you finally had it sorted out.

[xHeart]

Remember, you cant test for boost by just revving the engine. THese cars manage torque, so revs without load wont boost.

Revs without load won't boost.

This phrase is relevant to what I see in the freeze frame data. While under load and around 2700 rpm it stores ECM-6806, even after replacing large hose between MAF and turbo, MAF, TCV, MAP, and replaced the green, yellow, red, and blue vacuum lines. The wastegate (yellow line)) and bypass valve (green line) hold vacuum.

Why would MAF jump to 370kg/h at 2700 rpm -- is this too high?

[vtl]

Was it happening during gear shift?

[xHeart]

Was it happening during gear shift?

I was looking at the freeze frame to determine when and where by narrowing on mileage data. Indeed, I recall, there were 2 occurrence of gear shift stalled and delayed.

[vtl]

Do you have more data freezes for ECM-6806? With every sensor replaced.

So basically the TCM asks ECM to reduce torque for the longevity of the shift. ECM does it by reducing fuel, boost and throttle. For some reason ECM thinks it has no control over air flow and has to compensate for too much air by reducing the fuel injection. The pressure buildup can happen, for example, if ETM turns the plate more than it has been asked for. Or if the turbo does not respond to TCV quickly enough.

[xHeart]

Do you have more data freezes for ECM-6806? With every sensor replaced.

So basically the TCM asks ECM to reduce torque for the longevity of the shift. ECM does it by reducing fuel, boost and throttle. For some reason ECM thinks it has no control over air flow and has to compensate for too much air by reducing the fuel injection. The pressure buildup can happen, for example, if ETM turns the plate more than it has been asked for. Or if the turbo does not respond to TCV quickly enough.

The ECM-6806 Counter data was adding confusion. For some reason the ECM-6806 freeze frame data was 600 miles old, i.e. before the recent turbo diagnostic and service -- replaced MAF, TCV, MAP,and blue, yellow, red, and green lines.

The 2 TCM delays, I mentioned, was during the previous drive cycles of 20-80 miles. I did a ERASE ALL to reset since this pix below.

MVS_ETM100720.png (25.87 KiB) Viewed 1123 times

[xHeart]

Do you have more data freezes for ECM-6806? With every sensor replaced.

A voltage reader is plugged into the cigarette lighter port. It read a drop to 13.1v when it struggled to idling -- coming to stop. The response is a jolt vs hint when the foot is removed from the gas pedal verses just taking the pressure off the pedal.

Following freeze frame data is 600 miles old, i.e., before replacing MAP sensor.

[vtl]

So, is it good now or still the same problem?