1990 GMC S15 Q&A
1990 GMC S15 Question: My truck is a 1987 4cyl and when i turn the key on the throttle body fills up.
Leaking injector o-ring seals. Most likely! Unplug injector wire connector to see if it still does it. Post the test results for more info. - pushrod
A defective ignition module was a common cause for this. They would falsely send a very fast pulse on the ref wire to the PCM even without the engine cranking. - cardocIII