I own a stock '85 auto and it started to miss. Also acting like its loaded up and doesnt wanna run right with fresh gas. I changed the timing chain and injectors. I am thinking it might be the throttle posistion sensor? Has anyone else had this problem or know what this could be? Thank you, Don

 

Have you checked all the plug wires and plugs? I think I would start there. The fact that it's missing and you feel it's loading up sounds like one hole might not be firing. Hope you find the problem.

 

yes Im sorry I didnt say that. I had already checked the plugs and wires. I ordered the throttle posistion sensor and am going to try that. Anything else it might be? thanks.

 

Seriously doubt the TPS has anything to do with it. A miss usually means either one or more cylinders isn't making the same power as all the others. Combustion takes air, spark and fuel, so you need to isolate it to one or the other. If you think it's a random misfire, take a stab at the air part first. The MAF is the device that measures what's getting sucked into the engine, so disconnect it and let the ECM use a backup value for air flow. If the problem goes away, you usually need a new MAF. Also make sure all of the connections are tight and leak free - particularly the rubber hose.

If air isn't it, try to isolate fuel or spark by cutting some 1/4 inch vacuum hose about an inch in length and inserting a piece between the distributor and each spark plug wire. Start it up and touch each piece of vacuum hose with a grounded test light. That will kill the cylinder and any cylinder that doesn't have an RPM drop the same as the others has a spark or fuel problem. You can ohm out spark plug wires and also check for a problematic injector by checking the resistance across it's terminals. Specs are above 10 ohms, all should be within a couple of ohms of each other.

Hope this helps - replacing good parts is frustrating (and obviously expensive).