Engine idles bad and is hard to start when near freezing

LBRY604

MEMBER
1990 MITSUBISHI MIRAGE
4 CYL
2WD
MANUAL
250,000 MILES

I have a 1990 Mitsubishi mirage. It is hard(Almost impossible) to start when temps are below 40 Degrees. When it starts it idles terrible(barely running) until the temp gauge starts to show the car is warming up. The warmer it gets the better it runs.

I replaced the Engine coolant temp sensor, rotor and cap and ran a scan on the engine. It gives me code 13.15.21. And 25. After replacing the Engine coolant sensor I unhooked the Negative post form the battery for a few minutes and then hooked it back up. For the first minute or more it just gave code 15 over and over and then added 13-21 and 25 again.
On your site it shows 13 is the intake temperature sensor, 15 is SC motor position Sensor, 21 is coolant temperature sensor, and 25 is barometric pressure sensor. Just wondered what I should replace next to see if I can get this car running.
If I put a heater in the engine compartment and warm it up it starts easier but still idles bad until it warms up.

1 Reply

HMAC300

MECHANIC
48,601 POSTS

First thing is to check that all vacuum lines are connected and not cracked or broken. For code 13 disconnect air temp sensor with key check dg/rd wire should be between 4 & 5 volts if ok then replace sensor. Code 15 may be a bad idle control solenoid or a wiring issue. But try cleaning throttle plate on both sides and remove solenoid and clean as well with choke cleaner. Code 21 remove connector check for voltage 4-5 volts if ok then check continuity on ground wire. If no continuity check to ecu or replace sensor if continuity. Code 25 see pics second pic for code 25

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