I have a 2000 mitsubishi eclipse gs stuck in 3rd gear with neutral light blinking

SOURCE: I have a 2001 Mitsubishi Eclipse GT Neutral light blinking

Could be a wiring issue if you already replaced the speed sensor. I believe there are 2 speed sensors on that tranny though, and both are usaully replaced at the same time.

SOURCE: 2000 Mitsubishi Eclipse will not idle, all else OK, just repl bat

I can only offer these few ideas.

1. The TP throttle position sensors for this year group fail often Pin 1 to Pin 4 resistance should be 3.6 to 6.3 ohms but you need to remove the two 7mm bolts that hold this sensor on the front side of the throttle body, then rotate the two bolstered center and see a change in resistance from low to high. If the resistance remains fixed, the sensor is rusted out and must be replaced.
2. The IAC motor is mounted on th LH side (driver's) of the throttle body. It should make a clicking sound when the key is turned from Lock to Run. Pin 2 to Pin 1, Pin 2 to Pin 3, Pin 5 to Pin 4, and finally Pin 5 to Pin 6 must all have continuity at 38 to 52 ohms.
3. Check for any vacuum leaks.
4. Remove clean and check EGR.
5. If this is a Cranks but will not start problem, check the owners manual for Theft Deterant UNLOCK proceedure. If there is power at the rear fuel pump relay coil and no power at the MFI/ASD front relay coil and no spark, then its the security system.

SOURCE: i have a 1999 gs mitsubishi eclipse my check

It appears that there might be a TSB (technical service bulletin) issued on this vehicle by Mitsubishi. Check with your local dealer to verify for certain. One link with brief summary of this on a 1998 model (yours might fall into this class too?) can be seen here and is as follows:

1998 Mitsubishi ECLIPSE 98 - Transmission TCM PCM > POWER TRAIN : AUTOMATIC TRANSMISSION : CONTROL MODULE (TCM, PCM) [Part 103100 ]
TSB No: 01 NHTSA ID: 622435 , May 01, 2001 : Replacement:
Summary: subject regarding diagnostic trouble code p1390 pcm relearn.

A fuller discussion on a 1996 with this code can be seen here. Scroll down to the answer.

Perhaps these will provide a bit of information prior to contacting your dealer. I've never worked in a dealership that charged for looking up & providing info on TSB's. Good luck.

If this helps to solve your problem then please take a moment to rate this post. - Thanks.

SOURCE: Where is the fuel filter located on a 1999

HI. The fuel filter is located in the engine compartment, mounted to the firewall. Extraction will be easier if the air inlet hose and upper air cleaner housing is removed from the vehicle. This will expose the filter and allow for a better extracting experience.