Fuel Pulse Width

[Chuck-AZ]

I have a 1999 Ranger 4.0 L vin code X engine - 2 wheel drive - AOD transmission
with 107K miles on it. The truck is new to me. No history.

The system sets P0172 and P0175 codes, rich left and right bank. The o2 sensors are working properly - in the .3 to .8 range. The fuel pressure is 65 psi and all other inputs seem operating properly. Or at least the scanner shows the proper information. I replaced the fuel modulator (the old one was good)

What should the fuel pulse width be. At idle and at driving about 75 MPH ?
Mine is 2.8/2.9 msec at idle and around 9 msec when driving.

How is the Engine Load Calc (on scanner) derived? Mine is at 30% at idle, a number I feel is not correct.

More questions: Can you explain these secret FORD failure codes?
TID CID
0x10 0x21
0x53 0x07
--"-- 0x08
--"---0x09
--"---0x0A

Thanks
Chuck-az

[70f100longbed]

Load is calculated in the PCM using TP and MAF. I would suspect you have a failing MAF (mass air flow) sensor. The o2s should switch between 0.1v and 0.8v and should have a even rollercoaster like pattern. I assume you have a scan tool capable of monitoring PIDs so look at SHRTFT1 & 2, LONGFT1 & 2, and BARO. Both fuel trims should be close to 0% and BARO for your location should be 149Hz.

[Chuck-AZ]

Thanks for responding

Please check out the threads under the "Ranger fuel issue" in the ranger fourm. I did replace the TPS, as it had a intermittent dead spot just off idle. This Ranger does not have a BARO.

Thanks again!!

[70f100longbed]

I didn't say anything about replacing the TP. There is a BARO pid. The PCM uses the MAF to calculate BARO and a good indication of a failing MAF is a wrong BARO value. Sorry if I wasn't clear it was kinda late when I posted.

[Chuck-AZ]

I replaced the MAF about a week ago, the voltage return was to high. The new MAF changed when the the codes are set, but still sets codes.

A NOTE to all this. The O2s go to .9v and the fuel pulse width goes upwards of 9ms at part throttle, returns to a normal condition under other driving conditions. Depending on the scanner (some don't find the BARO PID) the BARO the voltage return is .5v I'm thinking the ECU may be at fault. If the BARO is calculated by the ECU, I don't feel like this one is.

[70f100longbed]

Is the MAF aftermarket or did you get it from the dealer? I work at a dealer and have seen a few aftermarket MAF sensors not read right.

[Chuck-AZ]

The MAF is a new CarQuest part. - acts OK with scanner.

If I do a cold start, the ECM will set a code for (left & right bank rich) within two miles. If I reset the code (on the fly) I can drive 100 miles with no codes being set. If I stop, Engine off for (like to fuel) when I start driving it will reset the rich codes within 1/2 mile or less. Reset on the fly again, I can drive 200 miles with no codes. If I clear the KAM it takes 10 miles to set a code, but only after a restart.

[96_4wdr]

leaking injectors
pull and have professionally cleaned and spray tested

[Chuck-AZ]

Originally Posted by Chuck-AZ

I replaced the MAF about a week ago, the voltage return was to high. The new MAF changed when the the codes are set, but still sets codes.

A NOTE to all this. The O2s go to .9v and the fuel pulse width goes upwards of 9ms at part throttle, returns to a normal condition under other driving conditions. Depending on the scanner (some don't find the BARO PID) the BARO the voltage return is .5v I'm thinking the ECU may be at fault. If the BARO is calculated by the ECU, I don't feel like this one is.

I would agree with you on the injectors leaking, except the O2s indicate everything is normal at idle and the pulse width is low. Leaking injectors would be most noticeable at idle with high O2 readings. As NOTED above at part throttle the ECU is dumping fuel (pulse width at 9MS) The truck starts and runs fine and gets about 22 MPG.

Thanks for the post