QuestionQUESTION: Ted, I have a 1995 T100, v6, automatic, two wheel drive, 118,000 miles. Love it. Recently the check engine light came on. Truck was running fine no sign of a problem. After a few fill'ups I noticed I had lost my good gas mileage. I dropped from 19 to 21 mpg to 14.5 mpg constant. I had auto zone test it and it showed a code po 170. o2 sensors or maf. Not wanting to do it myself I took it to the Toyota dealer. They put it on their tester and told me it was the mass air flow sensor. 795.00 plus 45.00 for the diagnosis. I said duh. No thanks. Went back to auto zone bought some cleaner for maf's and tried that. It did'nt help. So I bought a remanufactured maf from auto zone for 220.00. Tried that for a couple tanks of fuel. Did'nt help. Back to auto zone, got tested again, this time it came up as a po 125. engine coolant temp sensor. I put on a new one. Did'nt help or change a thing. I put the old maf back on. I am guessing that it is running rich as I have noticed that smell. I have walked behind it and noticed the smell of alcohol, like that of gumout gas additive. I don'nt know what to do next but want to get my fuel mileage back. What can you suggest. Thsnk you
ANSWER: Since the p0170 code didn't come back it's safe to say that replacing the MAF solved that problem. The p0125 code is an oxygen sensor code, the description will say something like" insufficient coolant temp for closed loop operation" the problem is not the coolant temp sensor, the problem is that the signal from the O2 sensor is not within the parameters that the computer needs to go into a closed loop condition, more than likely replacing the O2 sensor will take care of the problem but only if there is not another problem with the engine such as a misfire, vacuum leak or a mechanical problem, from what you've said this doesn't seem to be the case, so before spending a lot of time diagnosing replace the sensor.
---------- FOLLOW-UP ----------
QUESTION: I am sorry. I failed to mention that the po170 code did come back,along with the po125. Even when I had the new maf on. I got the po170. thanks again
AnswerI'm beginning to think that the sensors are not the problem, there is something else causing the engine to run too rich, this could be an intake air leak, a vacuum hose off or intake hose air leak or possibly a bad fuel pressure regulator, it could also be caused by a leaking cold start injector.
