Can anyone help me interpret scan tool data for rough idle?

Maintenance/Repairs
61

So I have been driving the car (with the check engine light on constantly) for the past several months. I installed a new fuel pump, fuel pressure regulator, and camshaft position sensor more than a month ago, and it made no difference, other than getting the fuel gauge to work properly, and the pressure to be what it should be. I have a new crankshaft position sensor and another set of fuel injectors, but have not installed them yet.

Every time I connect my code reader, it showed the same codes: P0442 and P0456 as “active” and P1618 as “pending”.

Today, I decided to try clearing the codes to see if there is a distance I could drive that would set enough monitors to “ready” so that I can pass emissions when the time comes, without triggering a CEL.

I discovered that the code P1618 cannot be cleared–it immediately comes back as an “active” code, and when I tried driving the car after clearing the codes, it misfired a lot, the check engine light was blinking, and the transmission would not shift out of 1st gear. Prior to this, the transmission has always worked fine. Also, with the engine running, I looked at the datastream, and the long-term fuel trim was jumping around from 0 to -27.2.

The Factory Service Manual defines code P1618 as “PCM/ECM SPI Communications Diagnostics”.

Does this sound like a defective PCM, or is there something else I am missing? Should I get a used one from a junkyard?

62

So today, I disconnected the battery, pulled the fuel rail assy, and saw that one injector had a drop of gasoline at the tip, and another had a lot of corrosion on the nozzle. I installed the fuel rail assy that I bought from the junkyard (obviously, I cleaned it up, pulled the injectors from it, and replaced all the O-rings).

The performance has improved somewhat, and the idle quality is better, though there is still a vibration at idle, it’s not nearly as bad as it was before. I made two trips in the car, and so far the check engine light has not come on. I checked with my code reader, and there are no current or pending codes at this time.

However
the long-term fuel trim is still about -19. Does this mean the new (used) fuel injectors are leaking somewhat, or nothing to be worried about?

63

Give it a few more drive cycles for the fuel trims to adapt on their own

Or you could reset the fuel trims yourself, with a scanner. But even if you do that, the fuel trims won’t necessarily stay at 0 over time

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