Hi all. I have a 92 s-10 blazer 4.3L vin W and my problems started with running rough with a high idle and code for running rich. While checking with a scan tool i noticed the throttle position sensor was not reacting right. With no throttle the scanner shows 1.8v - 2.2v and 18% - 22% open throttle. At WOT the scanner shows around 2.2v- 2.6v. I thought my tps was bad so i replaced it. Im now having the same readings so I checked voltage at the sensor itself. With no throttle, at the sensor, the voltage is .49v and at WOT it is around 4.9v. So I think the sensor is working ok. Next I checked voltage at the pinout on the ecm for the tps. These readings correspond with the readings taken at the sensor. So I think the wiring from the sensor to the ecm is ok. I have checked all grounds, all vacuum lines, all electrical connectors. I tested the MAP and oxygen sensors. IAC and EGR are new as of 2 months ago. Fuel pressure is good and not leaking down. My question would be - Why is the scan tool showing such off the wall readings?? could this be a bad ECM?? Any constructive help would be appreciated. Thank you in advance..

 

Did you change the temp sensor?When they are not working right the engine will run rich and idle will be high and or erratic.

 

I have not changed the temp sensor. The scan tool is showing that it is working normally. I may be wrong, but I'm thinking it is running rich with a high idle because the computer is thinking the throttle is open 20% - 22% when in reality the throttle is fully closed.

 

how is the vacuum reading, also wouldn't hurt to do a fuel pressure an leakdown test

 

Im dealing with a similair issue on my 94 gmc truck right now.I have changed every sensor but the tps.Im also wondering if my ecm is going bad as Im told it will cause the problems me and you are having.Is there a way to test it?I can easily fix mine by changing the prom.

 

I don't know of any test I can perform on the ecm itself, so I disconnected the tps while the engine was running. This SHOULD have set a code off. It DID NOT set any codes. As a matter of fact, the scan tool still shows throttle is open 17% - 18% - and this is with the sensor disconnected. ( Yes - I disconnected the correct sensor )I'm believing there is a fault in the ecm - almost as if it is stuck. Anyone have any experience or thoughts on this matter?? I may be way off base and would like to hear your thoughts..

 

Im going to change my tps today and see if my problem gets any better.Now one thing I didnt mention ealier is my exhaust has wrap around it which maybe causing the o2 sensor to get too hot so Im going to unwrap it and see if it makes any difference.Im surprised Capatain Hook hasnt chimed in to help he knows a ton about these kinda issues.

 

I've got a new ECM coming in today - that's my only option right now. Once I get my hands on it I will throw it in and see what happens. Keeping my fingers crossed. Thought I would've gotten some other ideas to check out but everything leads me back to a faulty ECM.

 

Put in new ECM and it fixed my problem Now the fuel pump just went out....