Running Lean - Dynograph attached

[DHMag]

last Saturday, i dynoed the car for the first time in 2 years. not as impressive as i had hoped for but it did raise a question with me. from start to finish on the dyno, it ran lean. anywhere from 14.4:1 to a spike of 16.3:1 at 5K RPM. all thru the range it stays lean. look at the dynograph for better description (sorry, no flatbed scanner, just a digital cam).

HP curve is nice though. ran codes today and no codes returned. no known issues with the engine. stock motor, high-flow cats, bigger exhaust, Fram air filter. O2 sensors havent been changed since i have owned the car. 28-30MPG on the highway, 16-18 in the city.

any ideas where i could start ?

 

[AutoSHO]

Bad MAF.

Edit: Have you ever changed the fuel pump? How old is the fuel filter? ECT? TPS?

 

[DHMag]

Bad MAF.

Edit: Have you ever changed the fuel pump? How old is the fuel filter? ECT? TPS?

fuel pump was changed right after i bought the car, now a 155. fuel filter is 3K miles old. TPS was replaced several years ago, ECT has never been changed but i could prolly benefit from it. MAF was swapped out a few years ago as well. cant i backprobe the MAF and check the voltage ?

 

[SHOKYLE1]

ford manual says the computer will try to maintain the optimal fuel ratio of 14.7 to one looks alright to me.

 

[Ishodu]

ford manual says the computer will try to maintain the optimal fuel ratio of 14.7 to one looks alright to me.

For simply and quietly running down the hwy maybe. Not for WOT high horsepower running.

 

[SHOKYLE1]

the ideal ratio would not change at wot. the computer sees the increased air flow the drop to a lean voltage signal of the 02 sensor. as long as you are in closed loop your computer will attempt to maintain the optimal ratio by increasing the pulse width of your injectors.

 

[DHMag]

my dyno from 2 years ago shows a nice flat A/F at 13:1 with no jumps or erratic behaviour.

ford manual says the computer will try to maintain the optimal fuel ratio of 14.7 to one looks alright to me.

 

[AutoSHO]

ford manual says the computer will try to maintain the optimal fuel ratio of 14.7 to one looks alright to me.

Not at high load. The commanded values for his run start out at about 13:1 and drop slowly to redline at about 11.5:1 if the car is running exactly as programmed.

Dale, I don't know of any way to backprobe the MAF accurately, because no two cars run exactly the same voltage.

I would try replacing the ECT first, as it has some effect on mixture and load calculation... But typically a lean mixture at WOT is either low fuel pressure or a bad MAF sensor.

 

[DHMag]

off the top of your head, would you happen to know the O'Riellys part number for the ECT ? me no longer shop at Auto-Zone.

Not at high load. The commanded values for his run start out at about 13:1 and drop slowly to redline at about 11.5:1 if the car is running exactly as programmed.

Dale, I don't know of any way to backprobe the MAF accurately, because no two cars run exactly the same voltage.

I would try replacing the ECT first, as it has some effect on mixture and load calculation... But typically a lean mixture at WOT is either low fuel pressure or a bad MAF sensor.

 

[SHOtimer]

I think the Ford ECT is recommended because it is brass instead of the plastic ones sold from advance, AZ, napa.....

Doug

 

[DHMag]

brass contacts with a plastic connector...thats how all of them are made.

I think the Ford ECT is recommended because it is brass instead of the plastic ones sold from advance, AZ, napa.....

Doug

 

[SHOKYLE1]

you can back probe your maf blue with red strip maf signal. the voltage here should be .7 to 1 volt at idle. if you have a scope you could watch the signal. the voltage should go up with the throttle with no drop outs.wot should be around 4v

 

[Redline]

Another simple thing to try would be cleaning the MAF. That has made a difference for a lot of people, myself included.

 

[DHMag]

you can back probe your maf blue with red strip maf signal. the voltage here should be .7 to 1 volt at idle. if you have a scope you could watch the signal. the voltage should go up with the throttle with no drop outs.wot should be around 4v

thanks, can i do this with key on, engine off ?

 

[SHOKYLE1]

no it needs to be running. Sorry for opening my mouth about the a/f ratio. I did some investigating and I was wrong. I am now smarter thanks everyone.

 

[Sho-Driver]

When you talk about WOT being around 4 volts, is that at 7000rpm? Since it measures air flow, it will need to see a max amount of flow to get the highest reading. The reading will also suffer from altitude.

 

[SHOKYLE1]

yes. the sensor just mesures the amount of voltage it takes to keep the hot wire 200 degrees above the temperature of the refrence wire. I live at 6000 feet and get a high reading of right around 4v. low is around .8 as far as i know alt has no effect on this sensor the heat loss of the hot wire is effected by the air flowing over it. the volume of air shold be the same the density diffrent for diffrent altitudes.

 

[wood_e]

off the top of your head, would you happen to know the O'Riellys part number for the ECT ? me no longer shop at Auto-Zone.

O'Rielly's will try to sell you a plastic ECT.

Wells SU201... just go to auto-zone...

 

[AutoSHO]

yes. the sensor just mesures the amount of voltage it takes to keep the hot wire 200 degrees above the temperature of the refrence wire. I live at 6000 feet and get a high reading of right around 4v. low is around .8 as far as i know alt has no effect on this sensor the heat loss of the hot wire is effected by the air flowing over it. the volume of air shold be the same the density diffrent for diffrent altitudes.

Altitude absolutely affects air density. This is why your car runs so much slower at elevation than at sea level.

However, the difference will be around .2 vDC at this altitude vs. sea level. Like I said before, you cannot accurately measure the MAF voltage and get any useable data.

 

[SHOKYLE1]

Altitude absolutely affects air density. This is why your car runs so much slower at elevation than at sea level.

However, the difference will be around .2 vDC at this altitude vs. sea level. Like I said before, you cannot accurately measure the MAF voltage and get any useable data.

I said the volume of air is the same I also said "density is diffrent for diffrent altitude. and a .2v diffrence is why they have approx numbers not a set number. if you see numbers way out of range by back probing you know where you problem lies. if i was to back probe it and see idle numbers higher than range and wot lower than range i would look for contamination if none i would replace sensor. if you go from idle to wot and you see a drop out but it still goes all the way up around 4v you know you have a problem. this is all usable to me.