Junkyard Day...30APR24

[XR7-4.6]

Contrary to what the California air resource board may think of the rest of the country our cars do in fact run at stoichiometric fuel ratios too. Don’t overthink it, all CA spec means in modern terms is bureaucracy. There’s no real difference in 97 between 49 state and golden state in any component, earlier years yes.

 

[1997ThunderbirdLXV6]

So...let's assume I'm not just dreaming this: it has a smoother idle. What could possibly cause that benefit?

One thing I also noticed: when starting the engine (warm), there's a distinct 2-step rpm drop. Say I start the engine and do nothing ( = stay in Neutral): with the junkyard PCM, it first revs at 1,200 very briefly, then drops to 1,000, then drops to 800 or so. These two drops are very distinct.

With my original PCM, the drop after initial startup rpm was more of a gradual settling down. I also think that (with an already warm engine) it didn't stay above 1,000 for any duration.

 

[Kenz]

@Kenz
As long as the non-CA PCM doesn't do anything that could negatively affect the CA catalytic converters (?).l

Mine still has the original EPA converters, also a high octane tune, and revs to 6500 rpm... Been fine for years now, you will be fine.

 

[1997ThunderbirdLXV6]

First time starting the cold engine with the "new" PCM. It starts up remarkably quickly (compared to my personal norm which is usually at least twice as long).

This could be a total coincidence...but it's encouraging.

 

[GRWeldon]

What is axle code "F5"?

From the info I found on the web last week when I was researching the diffs in my cars, F5 is the same as 5. Unfortunately, I can't find the website that showed this. I will look more. Only reason I know this is that one of mine is also F5.

 

[theterminator93]

I updated the gears and axles tech article here as well.

 

[Grog6]

There's a sticker under the hood, at the hood gasket on the pass side. It's slightly under the gasket. it's a 4 digit alphanumeric code. Mine is mbe2.

 

[1997ThunderbirdLXV6]

@Rodeo Joe

Just saw this on Facebook. May be another opportunity to get a PCM, though possibly with an older tune.

 

[Rodeo Joe]

I searched that name on Facebook and didn't find this.

Joe

 

[1997ThunderbirdLXV6]

Update: the junkyard PCM doesn't do anything appreciably better/worse than my own PCM, except for one thing: the car starts up noticeably faster. I'm not just dreaming that! That alone makes it worthwhile for me.