I am having typical 89 K5 hesitation problems at idle and driving. I have replaced the fuel injectors, o-rings on the injectors, all gaskets, tps (throttle position sensor), fuel regulator, oxygen sensor,pcv valve, fuel filter, air filter, spark plugs and wires, radiator, transmisson, and rear-end. The last three due to failure. However, I have checked all vaccum lines as well and they all appear to be fine. I have checked for the code readings and I get Code 43 and 44. My next step is to go for the ECM.......where is it located? OR any suggestions would be much appreciated!!!

 

If I remember right, the ECM is behind the glove box.

Have you checked the throttle body base gasket for vacuum leaks?

Also, have you checked the operation of your EGR system?

 

Thanks for the location for the ECM!

I have checked for vaccum leaks around the TB base, seems to be ok.

I have not checked the EGR system, will do.

Thanks for the help.

 

No problem. Let us know what you find!

 

I have changed out the ECM, which cleared code 43. I still have code 44 and my problems haven't really changed much. Maybe I have a bad fuel pump? The EGR system is okay. Suggestions?

 

How did you determine that the EGR system is ok?

There is something causing a lean condition as suggested by the code 44. You don't have an exhaust leak somewhere before the oxygen sensor do you?

 

I rechecked the EGR valve and noticed the GM Rochester logo which led me to believe that this had never been changed, original EGR valve. I took it off and discovered charcoal had nearly closed the ports, so I replaced it along with a new O2 sensor, a coolant temp sensor and put in GM recommended spark plugs (replaced NGK platinum split fire). Problem solved!............until I took it for a test drive. Idled great, ran great and then I heard a loud knock, knock, knock. My tach was not idling at 800 RPM and then it was, it kept trying to stall and then it wasn't. The knock sounded like there is a marble or hard object bouncing around in the motor. The guy at the part store informed me of the for sale signs in aisle 3. LOL! This Blazer must think I am made of money!!! Of course it is almost 20 years old. I haven't checked the truck after I test drove it, will do tomorrow. Suggestions?

 

You may have knocked a piece of carbon into a cylinder. I would suggest pulling the plugs again and looking into the cylinders with a pen style flashlight. Then if you have air pressure blow out the cylinders or crank the engine several times with the plugs out.

 

Thanks for the advice. Will give it a shot.

 

I did what you recommended and the problem still occurred. So, I pulled the valve covers off and noticed a plastic ring from the cap of a quart of oil wedged into the spring below the lifter. Pulled it out and the knock went away. However, test drove it and service engine soon light came on and it started to hesitate again. I checked for trouble codes and I am still getting code 44. I have replaced everything the Haynes manual recommended. What next? new fuel filter? knock sensor? what else is there?