Electrical Alternator (91 Mustang GT & 89 Lincoln Mark VII)

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Jhp84

Member
Mar 2, 2019
62
8
18
california
The verdict is in....the Mustang did NOT pass emissions.

Told the idle was borderline high, just under 1,000 RPM. And, the NOx levels were too high.

Below are the readings for the different test points:
At 15 mph, it measured 1348 RPM. Emission levels were
--HC (PPM) : Actual 40 (max allowed 85)
--CO (%) : Actual 0.01 (max allowed 0.54)
--NO (PPM) : Actual 838 (max allowed 629)


At 25 mph, it measured 1158 RPM. Emission levels were
--HC (PPM) : Actual 30 (max allowed 67)
--CO (%) : Actual 0.01 (max allowed 0.45)
--NO (PPM) : Actual 785 (max allowed 686)

So, it looks like it failed because NOx were too high and the idle rpm were accelerated.
The technician suggested I look into vacuum leaks to lower the idle RPM, or possibly retarding the timing.

Looks like we have bit more reading to do to figure out the issue here.

Jhp & son (slightly disappointed)
 

Mustang5L5

Mod Dude
Feb 18, 2001
30,785
7,235
224
Massachusetts
Drop idle via the "baseline idle reset procedure" should be easy fix.

As for high nox, could be a few things. Verify the egr function. Set baseline timing to 10 degrees. Could also be bad/aged o2 sensors. Might be worth a pair of new motorcraft sensors.