My daughter has a 1996 Mitsu Eclipse that without ...

Does the check engine light come on at all? The first thing I would do is go to AutoZone and have them check for codes. They will perform this service for free for you. If there are no cades I would check for vacuum leaks. With the idle going high one time and shutting off another it could very well be a leak. Take some 2+2 gumcutter carb spray and spray it around the intake manifold and throttle body gasket to see if the car dies or the idle increases at all. If it does either of the mentioned items you have a vacuum leak and whatever gasket is leaking needs to be replaced. If you have codes in the computer I can help you more from there. Mitsubishi does have a Technical Service Bulletin out for what you are decribing, but it usually is accompanied by a check engine light and codes. I will attach a copy of the TSB for you to read. I hpe this helps. If you have any other questions feel free to ask.

No.: TSB-03-13-006
DATE: May 2003
MODEL: 1996 Eclipse

SUBJECT:
ECLIPSE PCM REPROGRAMMING (420A ENGINE)

This bulletin supercedes TSB-96-13-022, to include additional conditions that Reprogramming Cartridge MIT992012 will correct.

PURPOSE

On some affected vehicles, poor driveability and/or certain false trouble codes may be due to software programming in the Powertrain Control Module (PCM). Reprogramming the PCM using PCM Reprogramming Cartridge MIT992012 will correct the condition.

This bulletin describes diagnostic and PCM reprogramming procedures for several conditions. Use PCM Reprogramming Cartridge M1T99201 2 to recalibrate the PCM to correct any of the conditions described below:

PCM does not store OBD-II Readiness Codes

Generic scan tool cannot read all DTCs

Rough engine idle

Hard to start; runs rough, unstable, or flares when at idle

Engine stalls at idle during warm-up

Poor driveability at any time and at any engine temperature

Long cold engine start time in ambient temperatures above 30 degrees F

Engine rpm undershoot right after cold start, or after releasing the clutch, or with gear engagement, A/C engagement, power steering input, and/or heavy electrical load after cold start in ambient temperatures above 30 degrees F

Engine rpm flare or surge while driving at low speeds, or when stopped with light brake application

Engine rpm flare after power steering input with the A/C and blower motor switches in the "ON" position

Slight hesitation during shifting on manual transmission models

Sharp acceleration in 3rd gear while climbing a hill with the auto speed control activated

False DTC P0401 "EGR System Failure"

False DTC P0703 "Brake Switch Stuck, Pressed or Released" (M/T only)

False DTC 106, 107, 108, 109, and/or 110 is set and the "CHECK ENGINE" light comes on

False DTC 46 is set and the "CHECK ENGINE" light comes on

CHECK ENGINE" light intermittently comes on and DTC 129 and/or DTC 104 is set

AFFECTED VEHICLES

1996 Eclipse 2.0L DOHC non-turbocharged models

PROCEDURE

1. If any Diagnostic Trouble Codes (DTCs) are set, follow the appropriate troubleshooting steps in Section 13 in the 1996 Eclipse service manual. Make any necessary repairs described in the service manual, then continue with Step 2.

2. Gather the following equipment which is contained in Reprogramming Kit MIT992000-A:

Do not install the cartridge into the Reprogramming Unit at this time

3. Attach the EATX III/Engine harness to the Reprogramming Unit. Refer to the Reprogramming Unit Instruction Manual.

4. Set the switch on the harness black box to the side labeled ENGINE.

5. Connect the EATX III/Engine harness 16-pin and 12-pin connectors to the vehicle's data link connector.

6. Install the Reprogramming Cartridge into the Reprogramming Unit.

7. Follow the displayed instructions on the Reprogramming Unit screen.

8. The display will ask if you want to change the controller part number. Select Yes. Reprogramming will begin.

NOTE :If the PCM has already been reprogrammed for this condition, the displayed current and replacement part numbers will be the same, or the message "BREAK NOT SEEN" will display. If so, do not continue with this procedure.

9. Current and replacement PCM part numbers will display. Record the replacement part number displayed.

NOTE :The displayed PCM part number should be 04887051 for M/T models, and 04887050 for A/T models.

10. When completed, disconnect the reprogramming unit and EATX III/Engine harness.

11. Using a ball-point pen, enter the replacement PCM part number (noted in Step 9), your dealer code, and the current date on the Control Module Label.

12. Affix the Control Module Label to the side of the PCM.

Using a ball-point pen, enter the replacement PCM part number, this TSB number TSB-O3-13-xxx), your dealer code, and the current date on the Engine Compartment Label.

Edited by autodoc_2000 on November 24 2005 at 12:12pm

Thanks. I will accept your answer. I'd just like to ask a bit more on the issue. It has been too cold here to try to work on the car. (I don't have a heated garage.) I will check as you instructed for vacuum. One thing more I noticed: When car will not idle, I can unplug the vacuum line that leads to smog pump. Check engine light just started coming on, but did not for several weeks. Now the car will begin to rev cruising down the road.

I have cleaned throttle body accelerator cable & butterfly.

Is there an electronic accelerator sensor to replace.

Thanks,
Clifford

From everything I am reading on this vehicle it does not have a smog pump. I'm not sure what you are unplugging the vacuum hose from.There is an idle speed throttle actuator that controls the idle. It receives the signal from the engine computer as to how far it should open to control the rpms. If the actuator is not working correctly it could cause the idle to go high or low usually not both though. If the plunger gets dirty it will usually cause stalling and low rpm reading. If the actuator goes bad it could do either one or the other. The idle speed actuator is located under the throttle body. I am including a picture of the actuator. If I can be of anymore assistance please ask.

The idle air control motor maintains idle speed by compensating for loads placed on the engine by regulating the amount of air taken in through the bypass circuit of the intake manifold by opening and closing the motor valve located in the air passage. The powertrain control module supplies Voltage in one polarity direction, which turns the motor in a particular rotation. The motor shaft is connected to a screw that when turned, opens the passage by moving the pintle. When the PCM reverses polarity, the passage is closed in the same manner. The PCM uses several sensor inputs to determine the operating condition of the engine and the loads being placed on it. The PCM adjusts the idle for air conditioning and automatic transmission loads, and controls fast idle for cold start. The PCM uses the IAC motor to make all of the adjustments to idle speed.

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