Erratic high idle help, please!

[franklin2]

Your carpet wet over there? The rangers like to rust out in the corner right below the computer where the kick panel is located. Water from the wiper grille area runs down behind there and is supposed to run out through some drains in the bottom of the firewall/cowl area. But that joint at the bottom likes to rust out and it will start leaking inside the cab floor.

 

[ActuallyaMazda]

It does appear to be a bit rusty. Especially around the parking brake mechanism.

 

[Josh B]

I'd also spray that board off good with an electrical cleaner and let it air-dry, they have a large can at wmart, after you get the weather blocked

 

[ActuallyaMazda]

Sounds good. I’ll grab one on my way home. I just left the junkyard and to my dismay, all the PCMs were already yanked. I did grab an OEM Ford IAC valve and an OEM FPR just for testing purposes. I know those old ford systems are really picky about aftermarket sensors, so I thought it could be good to grab those just in case.

 

[ActuallyaMazda]

Just bought some CRC Quick Drying Electronic cleaner. I confirmed that it was safe for computer components from their website. Since I couldn’t find a new ECU I will try cleaning the old one given how crusty it was. Also cleaning the junkyard IAC and installing that in lieu of the aftermarket one.

 

[alwaysFlOoReD]

Which o2 are you missing? You have 3? 2 before the cats and 1 after? They are a consumable, only sensor that wears out. Good for 10 years or 100,000 miles.

 

[ActuallyaMazda]

Bank 2 o2 sensor is missing and plugged. It only has one currently. Could that have helped with this condition? It also doesn’t have a cat anymore

 

[alwaysFlOoReD]

With only 1 of 2 front o2 sensors in place (and presumably only 1 working) the computer is probably confused. It needs 2 o2 sensors to work correctly. And I'm pretty sure there is a 3rd o2 after the "cat", which is used to check cat performance. Not as important but may have some input to drivability, and will cause a cel when missing.

 

[ActuallyaMazda]

With only 1 of 2 front o2 sensors in place (and presumably only 1 working) the computer is probably confused. It needs 2 o2 sensors to work correctly. And I'm pretty sure there is a 3rd o2 after the "cat", which is used to check cat performance. Not as important but may have some input to drivability, and will cause a cel.

It’s definitely had some confusion I’d say relating to fuel trims, but nothing so far that has affected the idle. I’ve had the truck for about a year and never messed with the O2 sensors yet. What could come from running with no O2 at all?

 

[alwaysFlOoReD]

My best guess (again) is that the computer will default to open? closed? loop. The one using the default fuel maps when cold. But with 1 working o2 sensor I'm not sure what would happen when the ecu expects 2. Maybe the cleaner killed the last working o2 and its gone to default cold engine?

 

[ActuallyaMazda]

My best guess (again) is that the computer will default to open? closed? loop. The one using the default fuel maps when cold. But with 1 working o2 sensor I'm not sure what would happen when the ecu expects 2. Maybe the cleaner killed the last working o2 and its gone to default cold engine?

Update: I reinstalled the PCM, installed the cleaned IAC, and fired it up. It did the same thing where it started cold at 1200 rpm, dropped to about 900 for a few seconds and rose to almost 2000. I let it run for a few minutes to get it close to temperature and turned it off. On trying to restart it, it struggled hard to start and seemed like it was bogging down. It ran like crap for a few seconds and then ran right up to 2000. Started it with the one O2 sensor unplugged and it ran terribly, backfiring heavily. Still ran itself up to 2000 rpm after about 20 seconds of being on. It just backfired even more than it did before upon warm restart. I’m going to replace both o2 sensors tomorrow to see if that makes any difference, but I’m losing it over this high idle that seems to just happen whenever it sees fit to piss me off.

 

[SenorNoob]

I can't see the sudden appearance after cleaning being a coincidence... Seems something there caused a change.

 

[ActuallyaMazda]

I can't see the sudden appearance after cleaning being a coincidence... Seems something there caused a change.

You’re very correct in that being probably the case. I’ve been going after mainly everything after the Throttle body since that’s where I cleaned. The only two things that haven’t really been replaced or at least checked, are the O2 sensors and the Ambient Air Temperature sensor. Getting new O2’s today and installing a used OEM FPR.

 

[superj]

white powdery/crusty on aluminum is the aluminum returning to its original state. instead of red oxides, it becomes that white powder. you can brush it off with a wire brush and treat with baking powder in water, i believe is the baking part. and then spray clear coat paint on it or put a light layer grease on it. just make sure its a electric non-conductive grease like you use under the heat sinks and stuff.

 

[ActuallyaMazda]

white powdery/crusty on aluminum is the aluminum returning to its original state. instead of red oxides, it becomes that white powder. you can brush it off with a wire brush and treat with baking powder in water, i believe is the baking part. and then spray clear coat paint on it or put a light layer grease on it. just make sure its a electric non-conductive grease like you use under the heat sinks and stuff.

Thank you! That is really helpful! I’ll make sure to do that.

Next update: I yanked the one O2 sensor out today and not only was it the original one dated to 1993, but when I pulled it, it basically fell apart in my hand it was so brittle. Replacing both banks and seeing what happens.