High RPM issue when clutch engaged
 

I have this 2003 Mazda truck below. Every time I push in the clutch the RPMs float higher. I've already replaced Air Filter, Mass Airflow Sensor, Idle Air Control Valve, and cleaned throttle blade. I also changed the PCV valve. There are no vacuum leaks. I tested with a cigar and by unplugging the IAC while engine going. I tried putting on a new Throttle Position Sensor, but my vehicle ran real fast and made the issue worse. RPMs ripping at 3000 at a stop. So I went back to original TPS. Last I reset ECU by unhooking lead battery for 15 minutes and turning on the headlights. I seems to run fine now, but I'll report back by end of day. An auto shop tried a Hytachi IAC, but it didn't solve the problem. The dealership said someone messed with the factory set screw on the throttle body, but no one has. I have adjusted it now to where I think it will work best.
https://cimg3.ibsrv.net/gimg/www.ran...2345e5333.jpeg
2003 Mazda B3000 DS, V6, Manual Transmission

Welcome to the forum

The anti-diesel screw is the one on the throttle linkage

To adjust it correctly you need to warm up the engine first
Let it idle
Unplug the IAC Valve, same as testing for vacuum leaks
Idle should drop to 500rpm or engine may even stall either is OK

If idle stays higher turn screw counter clockwise until engine is barely running, its now set
Plug IAC Valve back in and idle should come up to computers "target idle" RPMs

Turn off engine, turn key back on
Use a sewing needle to pierce the CENTER wire on the TPS
Test voltage with ground to engine or battery
Should be .69-.99, under 1 volt
Now open throttle all the way, WOT(wide open throttle)
Should now be 4.5-4.9volt
needs to be 4.5v or higher at WOT
Under 1volt closed throttle



Its normal for 1995 and newer Rangers with manual transmissions to HOLD RPMs when shifting, its an emissions thing
When speed is above 5MPH the computer will use the IAC Valve to hold RPMs high for 5 to 8 seconds when clutch pedal is pushed down, but if you keep holding clutch pedal down RPMs should drop to 1,000 or so, not idle, and hold there until speedometer drops below 5mph, then it will drop to idle RPMs

But RPMs should not go up, unless engine was under heavy load when you pushed in the clutch

There were software issue in the early 2000's computers and high RPMs between shifts was one of them
Get your VIN and call dealer to see if there was an updated software available

It appears resetting the ECU by unplugging negative power cable and turning on headlights has solved my problem. It must be true that draining the ECU’s capacitors resets the program. Seriously, everything mechanical on my truck is working smoothly. It’s come to being the dreadful ECU! Not something normally replaced or reprogram for that matter.

To reset the idle control screw I lubed it up really well and held the throttle up to the sky looking through the throttle body. I adjust the screw back and forth to get a feel for where the throttle blade is. Then I adjust to the max point the least sunlight passes by the throttle blade.