Service Engine Soon (MIL) on GM 5.7L??

[AnthonySS]

Thanks to Lambton Park Auto (Airpacker) and McCulloch Engines (Jeff) for the replacing the 5.7L (throttle body) in my 1991 K1500 Extended Cab.

Motor is 0.030” Over and has a tow cam. Engine idles real low.

Just one little glitch… The Service Engine Soon (MIL) light comes on when truck down shifts on grades or is stepped-on to get up to hiway speeds. Light is off when vehicle is restarted but will come on during downshift again. It happens around 2100 RPM

Scan codes revealed Knock Sensor…so Knock sensor was replaced. Light still came on…then Spark advance module code…. Connector was cleaned and truck was ok for a day.

Now it’s happening again.

Any thoughts guys?

Your input will be appreciated. THANKS

[1BadAction]

if you don't already have you own code scanner, get one. they are only about $30 from a discount auto type store. also, make sure to check the o2 sensor, map sensor, and cap/rotor. the o2 sensor was reading bad in my 94 blazer, and the engine was throw all kinds of weird trouble codes (spark advance module, and knock sensor) , not to mention running real rich. i changed the o2 sensor and it cleared up the problem.

[eautosales]

you need to pull the code & then get a flow chart & physically & scientifically troubleshoot pulling codes & changing parts only works 50% of the time you need a troubleshooting guide like alldata or mitchell on demand & follow every step of the flow chart for the code you get

[AnthonySS]

THANKS GUYS,

Sounds like we are headed in the right direction.

I appreciate your inputs