Okay, any time I'm driving along on the highway for a while, I get my check engine light come on after several minutes. It comes and goes. The error code indicates rich exhaust. I changed my air filter and I've ran fuel injector cleaner through the system but I was without success in nailing the problem. The car seems to run great, but it's majorly guzzling gas and I can't get this light to go away. Ideas?

 

It maybe somthing minor, have you mad sure it has anafreez, and stuff? plenty of oil?maybe its just broken that happend to a friend it just mest up and started stane onall the time. just take t to somboyd to fix it...no big

 

Lance,

What engine/fuel system?

If you have a TPI,you may have a leaking FPR. On TBI or TPI, you may have a leaking injector or grounded injector circuit. On a carbed engine you could have a float, choke, or MC adjustment problem. On any engine you could have a plugged PCV system or saturated EVAP canister.

 

It's the 305 TPI.

Would any of these contribute to both the check engine light AND horrible gas mileage?

 

Any of those could contribute to both the check engine light and the bad gas mileage. Also, if it's been going on for any length of time, chances are that your catalytic converter is plugged, and possibly spark plugs are fouled. First thing I would check would be all vacuum lines, spark lug wires, distributor cap, and charcoal canister hoses , then fuel pressure. The fuel pressure should be between 40 and 46psi, unless you have an 85' where it would be 37.5psi. If all that checks out, then a cleaning of the throttle body and adjusting the minimum air and Throttle position sensor on the throttle body would be a good idea. If none of that fixes the problem, then chances are you have an injector that is staying open. There are a few ways to check for that. One is to disconnect each injector electrical connector and then replace it while the engine is running. There will be a drop in idle speed if the injector is working correctly. If there is no change, then either the injector, or the electrical circuit is no good. Fuel injector electrical connection testers can be bought at Pep Boys fairly cheaply. Also, you could pull the plugs and see if one or more are loaded with carbon. Good luck.

 

This happened to a friend once. As mentioned above his fuel injectors were faulty. The code would come on and off on the highway and then just like that the car died then restarted when cool. upon further examination of the injectors ,all were shot. we got a set of SVO 19's for his 305 iroc and the car runs beautiful now.

 

I believe that the previous owner had the cat cut out and put a straight pipe on. I've yet to visually inspect though. But that's what he said.

How do I check this?

Already did that

Good idea; thanks a lot! I have some stuff to work with now. Anyone else who has suggestions please post...

 

Have you checked the specific SES code? Is it code 45? First thing I would check is the actual O2 sensor if it hasn't been replaced in awhile. They don't last forever and generally one of the more common sensors to replace.

Start there before getting into "expensive" fixes. Without an AFPR you can do nothing about your fuel pressure, and if you could, you'd need to lower the pressure.

Since you have SD, there are a variety of other things that can cause a Code 45 - Rich O2 condition. Like a relocated MAT in cold weather.

But without a scan tool, the best you can do right now is get a code and change the O2 sensor to start if that is what the SES code is suggesting. Go with the obvious.