QuestionDear Autohelp,
I have a 1994 GMC Sierra pickup that I purchased about 3 years ago. It ran great when I purchased it but it has gone down hill since. It started out with bad gas mileage and seemed to have a hesitation in it (like the older cars that had electric chokes that didn't work properly). I brought it in and they replaced the exhaust (put a larger one on it which made it noisier and my wife has hated it ever since), they also gave it a tune up and replaced the plugs, wires, cap and rotor. This helped a bit but the hesitation was still there. The service engine light started to come on at times and the codes in it said it needed an EGR valve - so I replaced it. It ran a bit better again but started to get worse. It not only has the hesitation but it sometimes seems like it is missing when I stop at a traffic light. The Service engine light kept coming on - the engine would run great then it would go off and a short time later it would start running rough again. The codes that I was getting where the EGR valve and Oxygen Sensor. I took the EGR valve off (the one I purchased less than a year before) and cleaned it (what I thought was cleaning it) and put it back on. It ran a bit better again for a while. The engine light stayed off but it started to run rough again and then the engine light came on and now stays on while I'm driving (it takes a couple miles before it comes on after shutting the vehicle off but when it comes on, it stays on). I checked the code today and I am getting the Oxygen Sensor code (13). I have also noticed this past week (when the light came on) that my gas mileage seems to have gotten even worse (you can almost see the fuel gauge drop as you drive). This may sound long winded but I'm getting fed up with it and everytime I bring it in, they tell me it could be this or may be that and I don't have the money to keep replacing parts and have it run the same after or shortly after replacing them. My question I guess is "should I change the Oxygen Sensor or bring it back in again for more diagnosis"? (or maybe just shoot it and bury it in the back yard!?!). Anything you could suggest I would appriciate.
Thanks
Dave
AnswerA code 13 (Oxygen Sensor can set under TWO conditions:
1. A fuel to air ratio being to LEAN.
2. A fuel to air ratio being to RICH.
There is a procedure for testing the oxygen sensor, But usually in most cases the code 13 means the oxygen sensor is either PLUGGED and or faulty.
My experience has been that is it faulty and should be replaced.
I need to know the COMPLETE past and current repair history of the vehicle. Everything from a new engine to changing a light bulb.
Every time the CHECK ENGINE light illuminates the computer goes into a BACKUP MODE so as to allow the vehicle to run, Although not very well, But enough so that you can get to a facility who can properly and professionally diagnose and correct your problem.
The NEXT thing I recommend is that your remove ALL of the spark plugs and see if they all look the same, As a visual inspection should show a light color on the elctrode porcelin portion of the spark plugs. This inspection of the spark plugs is VITAL for providing me with just how efficiently the fuel is being burned.
I need to know EXACTLY what color per above shows on the spark plugs.
Your original EGR problem may NOT be the actual EGR valve but the EGR VALVE CONTROLLER. The EGR has a vacuum line attached to it that goes directly to the controller.
Make sure that there are no kinks, splits and or a softness to the touch of this vacuum line. If you are NOT sure of it's integrity, Replace the vacuum line with the EXACT same inside diameter hose as is on the vehicle NOW.
NEVER EVER install a smaller inside diameter hose.
Let me know, As your problem(s) appear to be minor problems.
autohelp
autohelp
