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My ’92 K1500 stumbles when it starts to warm up (@ 150 degrees) and acts like it’s leaning out. So far the fuel pump has been changed, the fuel filter and the spark plugs. Spark plug wires were tested & the resistance in them is fine. New distributor cap & rotor, timing was checked & corrected (a little too far advanced). New TPS, new ignition coil, new coolant temp sensor. EGR was stiff but we were able to clean it up. MAP sensor & wiring has been checked.
When it’s cold the engine runs awesome. But when it starts to warm up it stumbles. When running on OD (5 speed manual) the “Service Engine Soon” light will come on after 5-10 minutes, but goes away after driving in a lower gear for a few minutes. It’s low on power when it does this, runs rough & backfires on occasion when decelerating. The OBD code points at the O2 sensor, but it’s intermittent.
What else can we look for? My Haynes manual isn’t a big help here, we’ve changed or checked everything it’s suggested. Does anyone have any suggestions?
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Just spit ballin’ it here …
Have you checked for vacuum leaks.
Perhaps smoke the system.
Have you checked the operation of the fuel pressure regulator.
Possible injector issue…
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