My wife’s aunt gave me a 97 blazer LS 4x4
my father in law and I have done the following. Rotor and cap, plugs and wires, tranny fluid filter and gasket change, oil and filter, air filter, I’ve replaced the ICM, the crankshaft sensor and tested the ignition coil. The blazer starts fine cold and idles pretty smooth but runs rough when it’s warm and starts hard after it’s warmed up and seems to have a miss. It smells like it’s running rich so I don’t think it’s a fuel issue. It also doesn’t shift if I put it in OD or 3rd it only stays in 3rd. Weird thing is that there is no check engine light. Any input would be great!

 

FYI, there are error codes that can be set that wont' set the "Check Engine Light." Best thing is to rent an OBD checker or take it to an autoparts store to get all the codes read.

If it is running rich when warmed up, perhaps there is a temperature gauge/sensor not working so that the ECM is not seeing that it is warmed up?

 

i didn’t know that I’ll definitely see if there are any codes. And just not sure which sensor would do that any recommendations? Thanks

 

As for the sensors, there is the inlet air temp I think that could be an issue. But this is not a problem I've had. Hopefully someone else will chime in with more advice.

Good Luck!