P0171 and P0174 again with a twist.
#46
03-30-2009, 02:04 AM
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If the MAF is dirty, the fix is easy enough: just clean or replace the MAF sensor. In many instances, the MAF sensor can be successfully cleaned by spraying the sensor element with electronics cleaner. Do not use any other type of cleaner as this may damage the sensor.
Disconnect the air inlet tube just ahead of the sensor, and then spray the electronics cleaner through the screen at the wire element in the center of the little MAF sensor. Let the cleaner soak in for several minutes, then give it another shot of cleaner. Let it sit another five minutes, then reconnect the air inlet tubing and start the engine.
If the lean codes keep coming back, the MAF sensor may have to be replaced if the engine does not have a vacuum leak or fuel delivery problem.
VACUUM LEAKS
Another common cause of Ford P0171 and P0174 ean codes is an engine vacuum leak. Ford TSB 04-17-4 details procedures for checking fuel trim and looking for vacuum leaks.
On 3.8L Fords with a split-plenum intake manifold, the port gaskets and isolator bolt assemblies for the upper plenum can deteriorate over time and leak air, often as a result of oil being sucked into the intake manifold through the PCV system. Also the vacuum hose that connects the fuel pressure regulator to the intake manifold can swell and leak vacuum where the hose connects to the manifold. Ford TSB 03-16-1 says the fix involves several steps: remove the upper manifold plenum and replace the original gaskets and bolts with revised ones, replace the front valve cover with a revised valve cover that reduces the amount of oil vapor sucked into the PCV system, inspect and replace the fuel pressure regulator hose, and finally, reflash the PCM so it is less sensitive to lean fuel conditions.
BAD DPFE SENSOR
Ford p0171 AND p0174 lean codes can also be set by a bad EGR differential pressure sensor. These sensors have a very high failure rate once a vehicle has more than about 60,000 miles on the odometer or is more than five or six years old.
The DPFE sensor is mounted on the engine, and is attached with two rubber hoses to the tube that routes exhaust gas to the EGR valve. The original equipment sensor has an rectangular aluminum housing about three inches long. Corrosion inside the sensor reduces its sensitivity to EGR flow, causing it to under-report EGR flow. The PCM responds by increasing EGR flow, which may keep the EGR valve open longer than usual creating a lean condition in the engine. Thus, a bad sensor may set a P0401 code (insufficient EGR flow), or it may not set an EGR code but a P0171 and/or P0174 lean code instead.
The cause of the P0401 code in most cases turns out to be a bad DPFE sensor, not an EGR valve problem or an EGR valve that is plugged up with carbon (though this can also set a P0401 code). An afterma
rket replacement DPFE sensor costs less than $50 and usually gets rid of not only the P0401 code, but also the P0171 and P0174 codes, too.
Disconnect the air inlet tube just ahead of the sensor, and then spray the electronics cleaner through the screen at the wire element in the center of the little MAF sensor. Let the cleaner soak in for several minutes, then give it another shot of cleaner. Let it sit another five minutes, then reconnect the air inlet tubing and start the engine.
If the lean codes keep coming back, the MAF sensor may have to be replaced if the engine does not have a vacuum leak or fuel delivery problem.
VACUUM LEAKS
Another common cause of Ford P0171 and P0174 ean codes is an engine vacuum leak. Ford TSB 04-17-4 details procedures for checking fuel trim and looking for vacuum leaks.
On 3.8L Fords with a split-plenum intake manifold, the port gaskets and isolator bolt assemblies for the upper plenum can deteriorate over time and leak air, often as a result of oil being sucked into the intake manifold through the PCV system. Also the vacuum hose that connects the fuel pressure regulator to the intake manifold can swell and leak vacuum where the hose connects to the manifold. Ford TSB 03-16-1 says the fix involves several steps: remove the upper manifold plenum and replace the original gaskets and bolts with revised ones, replace the front valve cover with a revised valve cover that reduces the amount of oil vapor sucked into the PCV system, inspect and replace the fuel pressure regulator hose, and finally, reflash the PCM so it is less sensitive to lean fuel conditions.
BAD DPFE SENSOR
Ford p0171 AND p0174 lean codes can also be set by a bad EGR differential pressure sensor. These sensors have a very high failure rate once a vehicle has more than about 60,000 miles on the odometer or is more than five or six years old.
The DPFE sensor is mounted on the engine, and is attached with two rubber hoses to the tube that routes exhaust gas to the EGR valve. The original equipment sensor has an rectangular aluminum housing about three inches long. Corrosion inside the sensor reduces its sensitivity to EGR flow, causing it to under-report EGR flow. The PCM responds by increasing EGR flow, which may keep the EGR valve open longer than usual creating a lean condition in the engine. Thus, a bad sensor may set a P0401 code (insufficient EGR flow), or it may not set an EGR code but a P0171 and/or P0174 lean code instead.
The cause of the P0401 code in most cases turns out to be a bad DPFE sensor, not an EGR valve problem or an EGR valve that is plugged up with carbon (though this can also set a P0401 code). An afterma
rket replacement DPFE sensor costs less than $50 and usually gets rid of not only the P0401 code, but also the P0171 and P0174 codes, too.
Not the EGR or DPFE, the engine idles smooth as silk @ 750RPM and holds there once warm. Stuck open EGR would give codes but would do so at idle resulting in hesitation, miss, bad idle, etc.. Bad DPFE would result in the same across the board.
The MAF is still suspect as it is an aftermarket replacement I did not put in. The hot wire has been cleaned multiple times using the correct cleaner. That one was put on the side burner as the fuel pressure readings were believed to be suspect. The lean codes (the engine is really running lean so it's not just a code being thrown) happens @ >50% load, low speed, and low RPM. When the engine is torquing over is when the code goes. This should be from fuel delivery. The more I think about it, the manifold vacuum should be lower than @ idle when i'm at 1800 RPM and TB butterfly opened. If this was a vac leak then why wouldn't it throw a code on decel rather than on accel???
#47
03-30-2009, 03:10 AM
Idunno - Your idle is @ 750 rpm. I have the same motor/same year, I can't recall ever seeing 750 @ warm idle. 730 steady, but the PCM was re-flashed with an updated calibration in fall of 2000. If I was at 750, there would be something definitely going wrong. If yours was re-flashed at any point in time, it should say so - outside of the PCM housing or thru the scanner.
How fast does the DTC appear after re-boot ?
Well, the Fuel Monitor runs all the time that the engine is running correct. Although the Monitor is running, in Open Loop - no adjustments are made to the fuelling trims. When the Entry Conditions are met the FUEL Monitor checks that the Fuel Trims have not exceeded their limits, which would indicate a deterioration in the HO2S sensors, or perhaps an intake or fuel pressure fault. BUT, an HO2S always shoots a code if @ fault or failing. So look for slow switching and/or flatlining HO2S sensors can push up the LTFT to compensate. The HO2S sensors (forwards) should be monitored and checked for periods of inactivity, slow switching, or low and high voltages.
Leaks in the inlet system can admit unmetered air which leans the mixture. This will also cause a rolling/uneven idle. However, your not experiencing an uneven idle that a very small leak in the inlet can cause. That said, that really isn't enough to upset the fuel trims without setting any DTCs. It requires a larger leak to drive the Fuel Trims high enough to set a DTC.
Points to check are:
Leak by loose/split inlet trunking, leak around MAF O-ring seal that we covered already.
Split or loose Idle Air Valve bypass pipe, covered that.
Split or disconnected engine breather pipes, I'm sure you been their. - PCV system etc...
A faulty fuel pressure regulator can produce severe negative and positive LTFTs at idle speeds, been there - This usually causes starting problems anyway.
Mentioned injectors before, but dirty/gummed injectors can deliver fuel as a dribble rather than a spray, and this effects combustion efficiency.
Some~MAF Data:
A failing MAF sensor can also cause Fuel System DTCs. Lean side, running DTCs P0171 and/or P0174 along with consistent very high Long Term Fuel Trim (25% is common) - then log the MAF reading carefully at idle and at higher revs. No load idle reading on the 16V should be ITRO 0.657 llbs/min - less than that and the LT fuel trims will react to compensate. If your getting a reading of 0.235 at idle is enough to provoke the LTFT to maximum without causing a DTC for a failing MAF. If this is seen then the MAF must be replaced even though no MAF fault has been registered.
BTW - Does the OD on/off illuminate once in awhile? On it's own and out of the blue? Honestly, it's usually something simpler, like a leak or the filter,- I know , I keep saying that lol, it's true.. The only sensor on the 98 here that wasn't right, was the TPS. I had to modify the TPS angle in order to set it right with spec, but I wasn't having any problems before doing so.
How fast does the DTC appear after re-boot ?
Well, the Fuel Monitor runs all the time that the engine is running correct. Although the Monitor is running, in Open Loop - no adjustments are made to the fuelling trims. When the Entry Conditions are met the FUEL Monitor checks that the Fuel Trims have not exceeded their limits, which would indicate a deterioration in the HO2S sensors, or perhaps an intake or fuel pressure fault. BUT, an HO2S always shoots a code if @ fault or failing. So look for slow switching and/or flatlining HO2S sensors can push up the LTFT to compensate. The HO2S sensors (forwards) should be monitored and checked for periods of inactivity, slow switching, or low and high voltages.
Leaks in the inlet system can admit unmetered air which leans the mixture. This will also cause a rolling/uneven idle. However, your not experiencing an uneven idle that a very small leak in the inlet can cause. That said, that really isn't enough to upset the fuel trims without setting any DTCs. It requires a larger leak to drive the Fuel Trims high enough to set a DTC.
Points to check are:
Leak by loose/split inlet trunking, leak around MAF O-ring seal that we covered already.
Split or loose Idle Air Valve bypass pipe, covered that.
Split or disconnected engine breather pipes, I'm sure you been their. - PCV system etc...
A faulty fuel pressure regulator can produce severe negative and positive LTFTs at idle speeds, been there - This usually causes starting problems anyway.
Mentioned injectors before, but dirty/gummed injectors can deliver fuel as a dribble rather than a spray, and this effects combustion efficiency.
Some~MAF Data:
A failing MAF sensor can also cause Fuel System DTCs. Lean side, running DTCs P0171 and/or P0174 along with consistent very high Long Term Fuel Trim (25% is common) - then log the MAF reading carefully at idle and at higher revs. No load idle reading on the 16V should be ITRO 0.657 llbs/min - less than that and the LT fuel trims will react to compensate. If your getting a reading of 0.235 at idle is enough to provoke the LTFT to maximum without causing a DTC for a failing MAF. If this is seen then the MAF must be replaced even though no MAF fault has been registered.
BTW - Does the OD on/off illuminate once in awhile? On it's own and out of the blue? Honestly, it's usually something simpler, like a leak or the filter,- I know , I keep saying that lol, it's true.. The only sensor on the 98 here that wasn't right, was the TPS. I had to modify the TPS angle in order to set it right with spec, but I wasn't having any problems before doing so.
Last edited by jbrew; 03-30-2009 at 06:23 AM. Reason: crap load of info
#48
03-30-2009, 10:49 AM
Senior Member
#49
03-30-2009, 03:39 PM
#50
03-30-2009, 06:55 PM
Senior Member
The needle sits a hair under the 700 RPM line.
No joke, I can't believe how accurate my dash gauges are to my Equus Scantool. The MPH is real close as well according to the Equus.
My MPH dash gauge is real close to our Garmin GPS Unit as well.
I bought the Garmin so I didn't have to keep riding with the wife as a map source.
I don't mind riding along if I am up to it. I have actually gotten calls from her before, and she would be angry and crying
because she was lost in the city.
Syracuse, NY and the surrounding area is not that complicated.
No joke, I can't believe how accurate my dash gauges are to my Equus Scantool. The MPH is real close as well according to the Equus.
My MPH dash gauge is real close to our Garmin GPS Unit as well.
I bought the Garmin so I didn't have to keep riding with the wife as a map source.
I don't mind riding along if I am up to it. I have actually gotten calls from her before, and she would be angry and crying
because she was lost in the city. Syracuse, NY and the surrounding area is not that complicated.
#51
03-30-2009, 07:37 PM
Yea , that GPS is pretty close. I have that on the phone (iphone). I like that, used it allot when driving home once a month. I was talking to ONELOWF (member here) - I think JMC as well - while I was driving across two states last year. Thought my clutch fan bearing was fried.
Was having problems towing an empty 1900 trailer at the time. That was before and the reason why I tore the truck down the last time. No problems now.
There's software for this phone that converts it to scanner. It's expensive , but it is released. - Yea, it's around $250 tho.
Was having problems towing an empty 1900 trailer at the time. That was before and the reason why I tore the truck down the last time. No problems now.
There's software for this phone that converts it to scanner. It's expensive , but it is released. - Yea, it's around $250 tho.
#52
03-31-2009, 11:36 AM
Join Date: Mar 2009
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Alright guys, this will be the final post I have in this thread related to trouble shooting this. This issue is resolved, she passed inspection this morning and I still have a couple things to tighten up not related.
So I believe this issue was related to fuel flow, and not pressure at heavy load. I reset the ECU totally the night before last by pulling the battery connection. This made all of the base maps reload so it wasn't going from its previous lean settings. After this, the wife put about 60 miles on it, and no more CEL. Last night I found a bad o-ring in the AC system, evaced it at idle and recharged. No code while the AC pump was cycling. It went for inspection this morning and passed with no monitors in the not ready state.
I want to thank everyone for their help on this one. Your time is very much appreciated. Just so you know, I have $3000 total invested in this vehicle at this point. Purchase price $2K, new tires $500, New bank1 cat $80, Fuel pump, sock, and regulator $175, Plugs $20, Replacement COP Free. One was in the glove box when I got it. And the rest is misc. parts (new tail light lens, recycled working CD changer, detailing chemicals. I will put another $50 into 134a freon, oil, and the new o-ring.
Thanks to the fuel pump replacement, I also discovered a crack in the frame above the trailer hitch which was repaired and I boxed the rear portion of the frame so that won't happen again.
All in all, I am still in the black on this one. Someone is going to get a nice reliable truck out of the deal and i'll be able to sleep at night knowing it's running well and safe once again.
So I believe this issue was related to fuel flow, and not pressure at heavy load. I reset the ECU totally the night before last by pulling the battery connection. This made all of the base maps reload so it wasn't going from its previous lean settings. After this, the wife put about 60 miles on it, and no more CEL. Last night I found a bad o-ring in the AC system, evaced it at idle and recharged. No code while the AC pump was cycling. It went for inspection this morning and passed with no monitors in the not ready state.
I want to thank everyone for their help on this one. Your time is very much appreciated. Just so you know, I have $3000 total invested in this vehicle at this point. Purchase price $2K, new tires $500, New bank1 cat $80, Fuel pump, sock, and regulator $175, Plugs $20, Replacement COP Free. One was in the glove box when I got it. And the rest is misc. parts (new tail light lens, recycled working CD changer, detailing chemicals. I will put another $50 into 134a freon, oil, and the new o-ring.
Thanks to the fuel pump replacement, I also discovered a crack in the frame above the trailer hitch which was repaired and I boxed the rear portion of the frame so that won't happen again.
All in all, I am still in the black on this one. Someone is going to get a nice reliable truck out of the deal and i'll be able to sleep at night knowing it's running well and safe once again.
#53
03-31-2009, 12:04 PM
Alright guys, this will be the final post I have in this thread related to trouble shooting this. This issue is resolved, she passed inspection this morning and I still have a couple things to tighten up not related.
So I believe this issue was related to fuel flow, and not pressure at heavy load. I reset the ECU totally the night before last by pulling the battery connection. This made all of the base maps reload so it wasn't going from its previous lean settings. After this, the wife put about 60 miles on it, and no more CEL. Last night I found a bad o-ring in the AC system, evaced it at idle and recharged. No code while the AC pump was cycling. It went for inspection this morning and passed with no monitors in the not ready state.
I want to thank everyone for their help on this one. Your time is very much appreciated. Just so you know, I have $3000 total invested in this vehicle at this point. Purchase price $2K, new tires $500, New bank1 cat $80, Fuel pump, sock, and regulator $175, Plugs $20, Replacement COP Free. One was in the glove box when I got it. And the rest is misc. parts (new tail light lens, recycled working CD changer, detailing chemicals. I will put another $50 into 134a freon, oil, and the new o-ring.
Thanks to the fuel pump replacement, I also discovered a crack in the frame above the trailer hitch which was repaired and I boxed the rear portion of the frame so that won't happen again.
All in all, I am still in the black on this one. Someone is going to get a nice reliable truck out of the deal and i'll be able to sleep at night knowing it's running well and safe once again.
So I believe this issue was related to fuel flow, and not pressure at heavy load. I reset the ECU totally the night before last by pulling the battery connection. This made all of the base maps reload so it wasn't going from its previous lean settings. After this, the wife put about 60 miles on it, and no more CEL. Last night I found a bad o-ring in the AC system, evaced it at idle and recharged. No code while the AC pump was cycling. It went for inspection this morning and passed with no monitors in the not ready state.
I want to thank everyone for their help on this one. Your time is very much appreciated. Just so you know, I have $3000 total invested in this vehicle at this point. Purchase price $2K, new tires $500, New bank1 cat $80, Fuel pump, sock, and regulator $175, Plugs $20, Replacement COP Free. One was in the glove box when I got it. And the rest is misc. parts (new tail light lens, recycled working CD changer, detailing chemicals. I will put another $50 into 134a freon, oil, and the new o-ring.
Thanks to the fuel pump replacement, I also discovered a crack in the frame above the trailer hitch which was repaired and I boxed the rear portion of the frame so that won't happen again.
All in all, I am still in the black on this one. Someone is going to get a nice reliable truck out of the deal and i'll be able to sleep at night knowing it's running well and safe once again.
#54
03-31-2009, 05:20 PM
Senior Member
Alright guys, this will be the final post I have in this thread related to trouble shooting this. This issue is resolved, she passed inspection this morning and I still have a couple things to tighten up not related.
So I believe this issue was related to fuel flow, and not pressure at heavy load. I reset the ECU totally the night before last by pulling the battery connection. This made all of the base maps reload so it wasn't going from its previous lean settings. After this, the wife put about 60 miles on it, and no more CEL. Last night I found a bad o-ring in the AC system, evaced it at idle and recharged. No code while the AC pump was cycling. It went for inspection this morning and passed with no monitors in the not ready state.
I want to thank everyone for their help on this one. Your time is very much appreciated. Just so you know, I have $3000 total invested in this vehicle at this point. Purchase price $2K, new tires $500, New bank1 cat $80, Fuel pump, sock, and regulator $175, Plugs $20, Replacement COP Free. One was in the glove box when I got it. And the rest is misc. parts (new tail light lens, recycled working CD changer, detailing chemicals. I will put another $50 into 134a freon, oil, and the new o-ring.
Thanks to the fuel pump replacement, I also discovered a crack in the frame above the trailer hitch which was repaired and I boxed the rear portion of the frame so that won't happen again.
All in all, I am still in the black on this one. Someone is going to get a nice reliable truck out of the deal and i'll be able to sleep at night knowing it's running well and safe once again.
So I believe this issue was related to fuel flow, and not pressure at heavy load. I reset the ECU totally the night before last by pulling the battery connection. This made all of the base maps reload so it wasn't going from its previous lean settings. After this, the wife put about 60 miles on it, and no more CEL. Last night I found a bad o-ring in the AC system, evaced it at idle and recharged. No code while the AC pump was cycling. It went for inspection this morning and passed with no monitors in the not ready state.
I want to thank everyone for their help on this one. Your time is very much appreciated. Just so you know, I have $3000 total invested in this vehicle at this point. Purchase price $2K, new tires $500, New bank1 cat $80, Fuel pump, sock, and regulator $175, Plugs $20, Replacement COP Free. One was in the glove box when I got it. And the rest is misc. parts (new tail light lens, recycled working CD changer, detailing chemicals. I will put another $50 into 134a freon, oil, and the new o-ring.
Thanks to the fuel pump replacement, I also discovered a crack in the frame above the trailer hitch which was repaired and I boxed the rear portion of the frame so that won't happen again.
All in all, I am still in the black on this one. Someone is going to get a nice reliable truck out of the deal and i'll be able to sleep at night knowing it's running well and safe once again.
How much do you want for it and will you deliver to Central NY.....
Just kidding. I am very happy with my 1998 F150 5.4L 4x4. Someone is going to be very fortunate to get that vehicle.
Stay in touch, you have alot to offer to this forum.
Job complete, now you can do the
dance.