1990 Chevy Silverado Miss Fireing

Ok need some information first if you could. How old is the O2 sensor? When was the fuel filter last changed? How dirty is the air filter? I know this sound simple but you would be very supprised as to how often the simple is over looked thinking it must be something else. I would also like you to take a timing light if you have one and check the timing and check the injector spray with it too. To check the injector spray you hook up the timing light like you normaly would and with the air cleaner off you point it to the injector and look at the spray pattern. It should look like a fine mist if you see any droplets or streams then you will need to do some cleaning. Let know what you find with this and give the needed info and we will go from there. You might need to do a seafoam treatment and I will let you how to do that after you get back to me ok.

It could be a temp sensor too. This is the sensor that tells the computer how warm it is and when they go bad they do weird things and usually don't set codes either. Let me know what you find with the injector spray with this timing light first and we will go from there. I will look up what the ohms should be on the sensor today at work and then you test that next.

Ok good that means less money to spend gotta love that. Now do you have a manual on this? If you do ohm out the coolant sensor and see if it is in range if you don't know what the specs are let me know I will find them for you. You could also do the seafoam treatment. What I mean is buy some seafoam and get some vacuum line and find a cup you don't care to keep. Pour about 8 oz into the cup and as the truck is running slowly using the vacuum line a smaller vacuum port off the throttle body slowly suck up the seafoam and put the rest of the bottle in the tank.