Bad ECM?

[TJ79Cheyenne]

How do I tell if my ECM is going bad or is bad? I have an 87 R10 that will not idle right. I set the timing to 0 and plugged the computer back in. Plug the computer advance in and the idle goes up and down.. Any ideas to help me out would be awesome!

 

[highdesertrange]

a few different things could cause that. first thing would be to check for codes. if that checks ok, check your sensors to make sure the ecm is receiving the correct data. do this though your diagnostic port. if all this checks ok I would clean the tb is it dirty. I have seen them so carboned up that the throttle plate will not close all the way. if you do this remove anything that carb cleaner will hurt, like the throttle position sensor, injectors, after that you really don't need to take it apart just blow everything out. if all this fails can you get your hands on a known good ecm module? to test on your vehicle. let us know how it goes. highdesertranger

 

[TJ79Cheyenne]

Yeah its not throwin a code. It just seems like the computer advance isnt doing its job.. my buddy that builds hot rod motors took a listen to it today n said he heard a timing knock from not being set right.. my throttle body is pretty darn clean for how old it is.. guess ill have to bring her back to a friends garage to have him run a diagnostic check on her since i wouldnt know what data id be lookin for on the scanner