97 tacoma issues.

Ok first post some what of a regular lurker. I have a 2wd extended cab tacoma with 2.7 ( i believe), auto trans with overdrive and 17inch steel wheels with lopro tires. No big stereo system or big drag on the motor. I have been some what happy with the truck but i have been dissapointed with the mpg (keep reading). I am averaging 19-20mpg and was really hoping it would get 25 or more. I have changed plugs, filters, checked for a coal filter(no), tire pressure is good and all the basics and then some. I have cleaned the MAF sensor and it actually worked great for a few days, crisper throttle response and even started better. Heres my pickle that is making me wondering, I have exhaust soot on my bumper. So it tells me i am not getting a "clean" burn (correct me if i am wrong). Does this mean that i need a new MAF sensor, could it be exhaust or both? I am asking because i dont want to drop a good chunk of change and have no gains. I have even considered an electric fan kit to help boost it but i cant see the gains being that great either.
Any help or ideas would be most appreciated.

 

If your getting sooting on your bumper you are definately excessively rich. Many different things can cause this. If cleaning the MAF made a noticeable difference you very well could have one out of range. Cleaning can sometimes make them worse depending on what cleaners your using. Some other things to check: O2 sensors, thermostat operation ( one running to cool can drive the system rich), vacuum leaks, exhaust system leaks upstream from the O2's. Find a reputable independent shop that has the equipment to read the data stream and check the sensor parameters. More than likely you have a sensor that is out of range far enough to drive the system rich but not bad enough to trigger a check engine light.

 

Are your tires and rims larger than stock? If so, are you accounting for the mileage error when calculating your mpg? Oversize wheels will make your mpg seem lower unless you calculate in the error.

 

What do you mean by mileage error. I have factory 17" wheels and my mileage is about 16mpg and I drive very easy. Could be mostly around town driving that does it.

After all it is a truck.

 

I know I should get better mileage. My Tacoma is one that sits low no 4 wheel drive and all that stuff. I did not put the wheels on but the wheels on but they look te same for overall size. Far as sensors go I am going to look into that because the sooting does have me concerned. It is a truck but dang my 1990 chevy got 16mpg and my 1989 Mazda pickup gets 29! Something wrong.

 

I dont know what stock tire and rims are for a 97, but if they have been altered in size it will cause the speedometer and odometer to be incorrect. If you calculate mileage from incorrect odometer mileage, you get the wrong mpg. Like I said, I dont know what is stock for that truck. Just throwing that out there for a thought. My 86 had oversize tires, and caused the readings to be off by 7%. To get the correct mpg, I would have to add 7% to my mileage when calculating mpg.

 

I believe that stock tires and rims are 14 inch rims and tires are 205/70/R14. That is what came on my '96 Tacoma 2WD reg cab. I average 27 or so running conventional oil and slightly closer to 30 with 0W30. Mine is a 2.4L engine.

 

I was getting 18-20 also, I did a bunch of things(which needed to be done anyway..plugs, wires, one coilpack(had a misfire), cleaned air filter, etc).....I got like 21-22,
then I ohm'd my MAF sensor because for some reason I had a feeling it was runnin all weird on the fuel trims..

Ended up being out of spec...so I replaced it..got a genuine Toyota one for $68

and my truck gets like 25-27 now..

1999 2.4L 5 speed.