ECM Location

[vsassano]

Could someone tell me where the ECM (Engine Control Module) is located on a 1996 Cavelier Base Model? I think it needs replacement since it hasn't been running quite right and is getting lousy gas mileage 12-15 MPG down from the 25-30MPG. I pulled the plugs and they were covered with black soot indicating a rich mixture. I checked the air filter and it wasn't bad. I changed the plugs as an interim solution but that won't last. I changed the MPS (manifold pressure sensor) and that seemed to help for a while. Any other ideas on the cause of the problem would be helpful.

[jdthewrench]

the computer is in the passenger front fender well, ahead of the wheel. I'd be looking at ignition and fuel delivery before I jamed an ecm in it. O2 sensor as well. 2.2 or 2.4? check for vacuum leaks. delco or Ngk plugs are a must. NO BOSCH PLATINUM in a chevy!!!!!!

[vsassano]

Thanks buddy. It's a 2.2L with AC Delco Plugs and 87K miles. I was thinking the same thing about the 02 and vacuum in addition to the ECM. Fuel system should be fine because I got a new fuel filter and new fuel pump last year. I've used injector cleaner and fuel system cleaner. If it is the injectors, how could I find out without pulling or replacing them? Although would a failing injector cause a rich mixture? I could understand if it injected at the wrong time (a.k.a timing) but I would think failing to inject during a cycle wouldn't cause a rich mixture. When I pulled the plugs all of them were black sooty so if the ignition is failing, it's failing on all of plugs. I'll also check for vacuum leaks. Why no platinium in Chevy's?

[rallyaddict]

Why do you think it's the ecm and why would you change the MAP sensor?

[vsassano]

I took it to the dealer and they wanted $650 just to replace the sensors. They told me that they wanted to replace the temp sensor, MAP sensor, and the ECM before they could tell what the real problem was. I replaced the O2 sensor in the exhaust manifold and noticed exhaust leaking from the pipe closer to the manifold in the pipe running from the manifold to the converter. I tightened the pipe connection and patched what I thought was a hole in the pipe and it ran great for a day. Now the car is making muffler sounds most of the time during idle (like heavy put-putting), it is still sluggish at times but not always, and it is still spewing black smoke when I press on the gas when it acts sluggish. The engine is shaking more than I'd like it to during idle. I don't know if it is the ECM but it's something. My next guess is to replace the O2 sensor after the converter and maybe replace the entire exhaust system. The car is 10 years old and has never had any exhaust work done on it. But it's still running rich and my gas mileage has noticably dropped 30-50%. Funny how when I replace a sensor it seems to fix the problem and then it comes back a day or two later. It's like the computer is re-adjusting to purposefully run worse. The same thing happened a couple of weeks ago when I changed the plugs. Ran great for a day, then not. But each time I change something it does seem to get better over all but I guess that just kind of makes sense when you replace new parts for old. Any suggestions?