97 chevy tahoe service engine light blinks and idles rough

A high idle is common with a vacuum leak. Ive done plenty of chevy intake manifold gaskets due to the gasket failing.

It is hardly ever the spark plug or only the spark plug - generally for some reason there is a weak or lost spark and the reason must be found and rectified by carefully checking and then replacing any components found to be edfective - plug wires, coil, distributor cap, rotor (if fitted), wiring, connections and could conceivably even be the ECU. Perhaps the misfire is due to injector trouble...

Sometimes a fault with persist even after it has been "cured" until the fault code is erased with diagnostic equipment.

P0300 random misfire, slight rough idle good , by the way your repair is good you dont want a identified misfire, Lets start by what it is not. Not a misposition sparkplug wire you would of gotten that cylinder code, as misfire, Oh try this got carburator cleaner? spray safely along the intake gasket, How about inspecting the vacuum hoses especailly at the map sensor. Here the thing you got. a vacuun leak. on a 5.7 a vacuum leak causes random misfire, by definition P0300 means 2 cylinders or more. By experience its a vacuum leak

Sounds like you might have gotten some bad gas, Try a bottle of HEAT. good luck

I would do a full tune up first. Plugs, wires, rotor, cap and coil. If your idle is still rough consider MAP sensor, idle position sensor, or any other emissions sensors maybe suspect. They usually set codes that would trigger your "check engine" light. On the other hand check belts and tension pully if you have one. Lastley, change the fuel filter put in some injector cleaner. A good shop can test the fuel pressure from the fuel pump. I hope this can help.

Flashing check engine light is missfire, fuel pump probably causing multiple tries to start.Having to build fuel preasure,vac leak on one side of intake probably causing rich/lean condition.Also check back preasure to cat ,Sound like you are moving down right track.Mas air flow would probably set lean code bank1 and lean code bank2

P0300 is random multiple misfire. If its been more then 3years since the last tune-up, do one. Usually it is caused by debris inside the distributor cap but could also be plugs wires, fuel and air filter.

Code p0300 is the code for "random missfire detected". The "check engine" light is flashing to warn you that severe damage is being done to the catalytic converter.(very expensive)..

Check your exhaust. If the vacum is not complete, the truck may idle like ****. Same for your catalytic converters and O2 sensors. do a system check at a garage.

here is a diagram of the map sensor #5.