CEL on and driving me crazy!!!!
 

Ok so I have a 97 Ford Ranger XLT 4.0 V6. My CEL came on a week ago and I have been diagnosing since. Had the codes read and came back P0171 and P0174. So I changed the Mass Air flow sensor and reset the codes. Drove it three days and nothing and then on my way home the CEL comes back on. Gas mileage has dipped a little but nothing great. Truck starts and runs fine. Only "odd" noise I hear while its running is a low pitch siren. I know horrible description but it will have to do for now. Anyone had this problem or have suggestions? Thanks

Re: CEL on and driving me crazy!!!!
 

YES, GOD YES!!! I just posted a thread aboout it. I have purchased 2 MAFS since monday! The CEL keeps coming back on. There is also a knock under my driver side floor board in between the steering wheel and seat. I am going to run a full diagnostics check on it around 12:00 today. I will let you know what happens to see if I can help you too. Good luck!

Re: CEL on and driving me crazy!!!!
 

just as i posted in johns thread, check for a vacuum leak, those two codes together usually indicate a vacuum leak and that whistling sound you are hearing is probably the leak its self. check over all vacuum lines and elbows for cracks or damage.

Re: CEL on and driving me crazy!!!!
 

I have a 97 with the 4.0 in it and the check engine light has been on forever with those 2 codes. the bulb finally burned out the other day so im content but the codes are still there, so i look forward to seeing if anyone has an answer for this.

Re: CEL on and driving me crazy!!!!
 

I will around noon today. I think Patrick is right. I think it is a vacuum leak. I will let everyone know later on today what it is, when I run a full diagnostics check on my truck.

Re: CEL on and driving me crazy!!!!
 

I have a 97 with the 4.0 had the same issue a few years ago no one could give me a definite answer. I took it to the dealer for the high dollar diagnosis. they said it was the upper intake plenum gaskets and the fuel rail gaskets, and they wanted $600.00 to do it. I said no thanks took the printout to my mechanic friend ,he printed out step by step for me.I done the job on Saturday afternoon for about $20.00 worth of gaskets,and a few cuss words. That was a few years ago a the cel has not came on again. Google what I am talking about and you will find it is a common problem on those 4.0s.