Mitsubishi Galant A sporty mid-sized sedan offering the perspective buyer a change from the normal mid-size sedan class.

Rough idle - throttle position sensor?

Old 12-15-2013, 12:01 AM
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Join Date: Dec 2013
Location: NZ
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Smile Rough idle - throttle position sensor?

Hi all, this is my first post here, I'm sorry to be asking for help so early.

I have a 1997 Legnum, 2.5L 6A13, JDM model, with 205000kms on the clock (127000 miles for you Imperial folk), which I bought a couple of weeks ago with failed water pump.

Just finished cambelt and water pump swap, and now the car idles really roughly when in gear and has occasional misfire, runs fine in neutral or park or when at speed.

First thing I did was to pull the manifold and throttle body and run a compression test, which checked out (165+psi in all cylinders). While I had the throttle body off, I manually tried to turn the butterfly valve, which seemed locked shut. It took some force to move but eventually gave and now has free travel.

Today I had CEL come on. My OBD-II scanner won't communicate with the ECU (I guess it is a different protocol?) so I grounded pin 1 of the connector as instructed by the service manual to get the code. However, the flashes I got don't really make sense. I got 1 long flash, followed by 10 short flashes, repeating, which doesn't match any trouble code.

I pulled the TPS afterwards and I think this is the problem. Tested resistance between pins 1 and 2 and got a gradual climb from 50 ohms to 70 ohms through the first quarter of throttle operation, and then a jump to 20000+ohms. Continuity tests for pin 3 and 4 were fine. Does this indicate a faulty sensor? Did I wreck it when I forced the throttle plate? Has anyone ever seen that CEL code sequence before and know what it means?

Appreciate any help I can get. Thanks!
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