mExp
New Member
- Joined
- February 7, 2010
- Messages
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- Year, Model & Trim Level
- 2002 Explorer XLT 4.0
I've had my '02 ex for about 10 years now. It got a new engine (jasper) around 80k miles, a new rear end around about that same time, and a few other small bits here and there, but is completely stock no modifications.
It now has 132k miles on it and it has been giving me an absolute run for the money trying to solve a rough idle, poor mileage, intermittent stalling issue (more on that later).
I will give the long story now, but if you want scroll to the bottom and I'll try to make a bullet list of the problems and what has been done to try and remedy them.
It started late last year that I noticed I was getting really terrible fuel economy (worse than usual) averaging about 8-10 mpg in the city. I usually am just making short trips to and from work about 5 miles each way. On the highway it was also not doing so hot though I can't give an exact number there. On cold mornings it would throw a code, P0174 and usually have a P0171 code pending. I would drive with that for a few days and the light would turn off. At that point I take a simple minded approach and think well how about a do a little periodic maintenance items and see if replacing a couple of things will fix it, not a very educated first move. So I replace the coil, spark plug wires, spark plugs (had been replaced about 8 months earlier). I clean the MAF as well at this time. I also at the around the same time fix a coolant leak (plastic thermostat housing was cracked) that had been bugging me, but not causing any issues. I used all Motorcraft brand parts for all of this. Doesn't help the situation at all, plus on top of that I had a major idiot moment and crossed the 5 and 6 spark plug wires (why they couldn't just make the ignition coil pack go 1-2-3-4-5-6 instead of 1-2-3-4-6-5 I do not know). And because I'm an idiot I replace the MAF and IAC before realizing at work that afternoon what I had done (these were duralast brand parts, but I've looked at the live data from the MAF and tested the IAC and they both appear to be working properly).
Anyway so still no real improvement.
I replace the fuel filter (man what a pain in the ass those little red clips are). That does nothing, if anything it seemed like the car ran worse. Rough idle and poor MPG.
So now I decide okay I should perhaps be a little bit more scientific about this.
I purchase a OBDII scanner with live data so I can see what looks out of Wack and also because the codes are lean codes (Primarily P0174, but the other bank is also Lean, just not quite enough to throw a code). I find my fuel trim values both LTFT and STFT to be high (in the +20% range) at idle. I rev the engine to 1500 and 2500, trims level out. Okay it looks like its a vacuum leak. I will test this hypothesis. I make a little homemade smoke tester using a paint can, soldering iron, some copper wire, a tiki torch wick, mineral oil, some hose fitting, a little JB weld, and an air mattress pump. Works pretty well, smoke comes pouring out of the EGR valve. "AH HA I think; I have got it!"
New EGR valve, nothing.
At this point I will also note that it was actually the EGR valve housing itself that was leaking smoke not the gasket. There was also a little smoke coming from the throttle plate shafts where they go through the housing, but not enough to be a major concern. I also did the carb cleaner test and there was no change to the idle or O2 readings or fuel trims when spraying carb around that area. At the same time I replace the EGR valve (with a new motorcraft one) I also replaced the intake gaskets (with ford ones) as it seemed like these were often a source of headache for P0171/P0171 codes. But as I said before no improvement.
Also every time I did something major I would reset the PCM using the method FordMoko… (can’t remember his handle, but he’s made a lot of useful videos and posts so thanks).
I’m very disappointed at this point, and also totally perplexed.
I think hmmm, maybe this is a fuel issue not an air issue. So first thing I do is test the fuel pressure and the gauge reads 65 psi at idle and 65 psi with the engine rev’d to 2,500 rpm. Doesn’t seem like a fuel pressure issue, though I have to say this was a kit from my local FLAPs and the little Ford Schrader valve adapter was in sad shape, so I don’t know if I completely believe it. (I also did not check the fuel pressure with the engine off for leak down).
Then things seem to get worse. I’m driving home from work and its pouring rain outside. At stoplights the car will stutter and stall and then die. I think crap all I’ve done to this point is made things worse because the car certainly hasn’t done this before. I manage to get home and slowly slink back to my cave.
Next week I’m driving to work, car is running as it normally does (mildly rough idle, but fine at speed). It starts raining. Within about a minute or two of it starting to rain the car starts surging and sputtering and stalling out in the middle of the road. Not cool. I pull over and plug my OBDII scanner in real quick and I have a +20% fuel trim on Bank 1 and a -20% fuel trim bank 2. WTF!?!?!?! But then I realized hmmmm, rain. Had the issues in the rain last week with the car stalling. Okay maybe its electrical and water is getting in somewhere. I make it to work and home fine. Everything has dried at this point (gotta love crazy Houston weather). I take a giant bucket of water and just start pouring in various bits of the engine.
I’m thinking, "oh boy this is gonna be it!"
Nothing, not a flinch.
I poured water on everything I could find in there, including the crankshaft position sensor since I thought that could be prone to causing this stalling.
At this point I stop driving the car because I’m worried its going to leave me blocking traffic in a sea of angry armed Texans.
Fast forward to Easter weekend, I decide okay I’m gonna drive to my friend’s house, I didn’t want to take the bike. Get the car going, seems to be running especially rough at startup.
I go anyway.
I start to get on the highway about a mile from my house and I am giving it the beans its struggling to get up to 55, the engine starts shaking, CEL turns on, then starts flashing, and I say Frack. I pull off the highway real quick into a parking lot. Plug in scanner, codes come up P0171, P0175, and P0300. Yeah you read that right I had one bank of cylinders full lean and one bank full rich, fuel trim readings agreed. P0300 is random misfire and well yeah pretty sure an engine running ½ rich and ½ lean would cause that. This time no rain, just a little humid maybe.
Slump home, hop on the bike, and ride off into the horizon never to gaze upon the Ex again (or at least I wish).
At this point I revert back to mindless part replacement and replace the O2 sensors. Nothing, no change.
Then I think okay this has to be some weird fuel problem (not really sure why I think that, just do). So I take the Fuel Injectors off the rail to do the poor mans fuel injector cleaning. They all Ohm out at 15.4 on the dot. I forward and back flush them all with carb cleaner using a 9v battery and a momentary switch to pulse them. I’ve never done this before, but all the injector solenoids actuated as I’d expect and the fuel streams all looked fairly similar. None were leaking under pressure. Put it all back together with new fuel injector O-rings. And start her up. Same issue, high + LTFTs. Around about 20% LTFT or so on bank one the STFTs are able to oscillate around 0% and around about 15% LFTF on Bank 2 the STFT for bank 2 is able to oscillate around 0% at idle. Reving the engine the fuel trims all come down. I’ve also noticed now that on the highway, just cruising at a constant speed the fuel trims are about the same as at idle, and if I accelerate they go down. I drive around after getting things back together with the “cleaned” fuel injectors for about 30 miles of random highway, city driving. I have the scanner plugged in the whole time and the fuel trims are still showing lean at idle and cruising.
I pull up to my house and suddenly the SFTFs are in the negative and the LTFTs are slowly coming down from 20% to 0%. I think, “hey great this is looking promising!”
That thought lasted for about 30 seconds, LFTFs came and passed 0% and after about 2 minutes of just sitting and idling in my driveway they were now reading about -9% LTFT bank 1 and -15% LTFT bank 2. What is going on here?
I think to myself. That was last night, flash forward to this morning, I start the car up with the scanner plugged in, High + STFT fuel trims right away… But not just usual high, REALLY HIGH! 42.2% to be exact. I think this was because the LTFTs saved from last night that were really negative was forcing the pcm to dump tons of fuel to adjust, since after a minute or so the LTFTs started to rise up to their usual 15-20% and the STFTs came down to less heart-attack-inducing values.
I decide I’ll take the long way to work to see if I can simulate what happened last night.
I drive around for 20 minutes, pull up into the parking garage at work, idling, and BAM! STFTs start going negative, and negative, and the LTFTs start dropping and dropping and dropping and hit about the same -negative values as they did last night. Bank 1 2 LTFT < -10% and STFT < -4% I mean what is going on?!?!?
It could have been doing this the whole time from the beginning of my story and I just never noticed it, so I can’t be certain this is a new issue. Also it has not rained here lately and it’s not that humid out.
I’m just at a total loss of what any of this could possibly mean. I’m fine at taking things apart and putting them back together, but diagnosing is not my forte. I’m on the edge of finally throwing in the towel and taking the car into the dealer with the hope they’ll look at it and go, “Oh yeah we seen this all the time, it’s the residual schliber-schobler in the flux capacitor.” And they fix that part and that will be it. But I figured I would come here first to tell my story and see if there are any takers for what this could be.
So for those who don’t want to read this novella here is the short.
Initial Issue: P0171, very poor gas mileage, mildly rough idle. CEL would sometimes turn off on its own after driving a few days. Came up particularly on cold mornings.
Attempts to Fix Issue, which thus far have not resulted in any noticeable change:
Noticed it seemed to be exceptionally problematic in rainy or wet weather. In particular fuel trims would sometimes go full rich on Bank 2 and full lean on Bank 1 in the rain (as confirmed by live fuel rim data) and the engine would stall out. One time I got a P0171, P0175, and P0300.
Water tested engine for electrical shorts (i.e. I poured a bunch of water on things with the engine running). No results
Tested Fuel pressure. 65 PSI at idle and 2500 rpm, though equipment and user (me) was of questionable reliability.
Back to Fix Attempts:
I reset PCM using jumper wire from positive to detached negative batter cable every time a repair was made.
Current Symptoms:
Poor mileage, rough idle. High positive fuel trims when first starting the engine and still after about 15 minutes of driving when at idle or cruising (below). Fuel trims when accelerating are closer to 0% (<5% both banks).
Bank 1 LTFT ~20%
Bank 1 STFT ~4 to -4%
Bank 2 LTFT ~18%
Bank 2 STFT
After about 20-30 mins of driving at idle the fuel trims look like this:
Bank 1 LTFT ~ -9%
Bank 1 STFT ~ -2%
Bank 2 LTFT ~ -15%
Bank 2 LTFT ~ -4%
This morning when I start the car things look like this. I assume STFTs are like that since the LTFTs saved from last night (above) were so far off from what the engine is requesting upon cold start.
Bank 1 LTFT -9.4%
Bank 1 STFT 42.2%
Bank 2 LTFT -15.6%
Bank 2 STFT 42.2%
So with all that said does anyone have any ideas? Its fair to say parts were replaced properly though my diagnostic readouts (not the scanner readouts, but my home brewed tests) are of disputable reliability.
Also on a fascinating note I discovered yesterday you can use a bicycle pump with a built in pressure gauge to measure fuel pressure on the Schrader valve. I know this was probably not smart, but all the fuel pressure kits I could find at my FLAPs stores were missing the adapter.
It now has 132k miles on it and it has been giving me an absolute run for the money trying to solve a rough idle, poor mileage, intermittent stalling issue (more on that later).
I will give the long story now, but if you want scroll to the bottom and I'll try to make a bullet list of the problems and what has been done to try and remedy them.
It started late last year that I noticed I was getting really terrible fuel economy (worse than usual) averaging about 8-10 mpg in the city. I usually am just making short trips to and from work about 5 miles each way. On the highway it was also not doing so hot though I can't give an exact number there. On cold mornings it would throw a code, P0174 and usually have a P0171 code pending. I would drive with that for a few days and the light would turn off. At that point I take a simple minded approach and think well how about a do a little periodic maintenance items and see if replacing a couple of things will fix it, not a very educated first move. So I replace the coil, spark plug wires, spark plugs (had been replaced about 8 months earlier). I clean the MAF as well at this time. I also at the around the same time fix a coolant leak (plastic thermostat housing was cracked) that had been bugging me, but not causing any issues. I used all Motorcraft brand parts for all of this. Doesn't help the situation at all, plus on top of that I had a major idiot moment and crossed the 5 and 6 spark plug wires (why they couldn't just make the ignition coil pack go 1-2-3-4-5-6 instead of 1-2-3-4-6-5 I do not know). And because I'm an idiot I replace the MAF and IAC before realizing at work that afternoon what I had done (these were duralast brand parts, but I've looked at the live data from the MAF and tested the IAC and they both appear to be working properly).
Anyway so still no real improvement.
I replace the fuel filter (man what a pain in the ass those little red clips are). That does nothing, if anything it seemed like the car ran worse. Rough idle and poor MPG.
So now I decide okay I should perhaps be a little bit more scientific about this.
I purchase a OBDII scanner with live data so I can see what looks out of Wack and also because the codes are lean codes (Primarily P0174, but the other bank is also Lean, just not quite enough to throw a code). I find my fuel trim values both LTFT and STFT to be high (in the +20% range) at idle. I rev the engine to 1500 and 2500, trims level out. Okay it looks like its a vacuum leak. I will test this hypothesis. I make a little homemade smoke tester using a paint can, soldering iron, some copper wire, a tiki torch wick, mineral oil, some hose fitting, a little JB weld, and an air mattress pump. Works pretty well, smoke comes pouring out of the EGR valve. "AH HA I think; I have got it!"
New EGR valve, nothing.
At this point I will also note that it was actually the EGR valve housing itself that was leaking smoke not the gasket. There was also a little smoke coming from the throttle plate shafts where they go through the housing, but not enough to be a major concern. I also did the carb cleaner test and there was no change to the idle or O2 readings or fuel trims when spraying carb around that area. At the same time I replace the EGR valve (with a new motorcraft one) I also replaced the intake gaskets (with ford ones) as it seemed like these were often a source of headache for P0171/P0171 codes. But as I said before no improvement.
Also every time I did something major I would reset the PCM using the method FordMoko… (can’t remember his handle, but he’s made a lot of useful videos and posts so thanks).
I’m very disappointed at this point, and also totally perplexed.
I think hmmm, maybe this is a fuel issue not an air issue. So first thing I do is test the fuel pressure and the gauge reads 65 psi at idle and 65 psi with the engine rev’d to 2,500 rpm. Doesn’t seem like a fuel pressure issue, though I have to say this was a kit from my local FLAPs and the little Ford Schrader valve adapter was in sad shape, so I don’t know if I completely believe it. (I also did not check the fuel pressure with the engine off for leak down).
Then things seem to get worse. I’m driving home from work and its pouring rain outside. At stoplights the car will stutter and stall and then die. I think crap all I’ve done to this point is made things worse because the car certainly hasn’t done this before. I manage to get home and slowly slink back to my cave.
Next week I’m driving to work, car is running as it normally does (mildly rough idle, but fine at speed). It starts raining. Within about a minute or two of it starting to rain the car starts surging and sputtering and stalling out in the middle of the road. Not cool. I pull over and plug my OBDII scanner in real quick and I have a +20% fuel trim on Bank 1 and a -20% fuel trim bank 2. WTF!?!?!?! But then I realized hmmmm, rain. Had the issues in the rain last week with the car stalling. Okay maybe its electrical and water is getting in somewhere. I make it to work and home fine. Everything has dried at this point (gotta love crazy Houston weather). I take a giant bucket of water and just start pouring in various bits of the engine.
I’m thinking, "oh boy this is gonna be it!"
Nothing, not a flinch.
I poured water on everything I could find in there, including the crankshaft position sensor since I thought that could be prone to causing this stalling.
At this point I stop driving the car because I’m worried its going to leave me blocking traffic in a sea of angry armed Texans.
Fast forward to Easter weekend, I decide okay I’m gonna drive to my friend’s house, I didn’t want to take the bike. Get the car going, seems to be running especially rough at startup.
I go anyway.
I start to get on the highway about a mile from my house and I am giving it the beans its struggling to get up to 55, the engine starts shaking, CEL turns on, then starts flashing, and I say Frack. I pull off the highway real quick into a parking lot. Plug in scanner, codes come up P0171, P0175, and P0300. Yeah you read that right I had one bank of cylinders full lean and one bank full rich, fuel trim readings agreed. P0300 is random misfire and well yeah pretty sure an engine running ½ rich and ½ lean would cause that. This time no rain, just a little humid maybe.
Slump home, hop on the bike, and ride off into the horizon never to gaze upon the Ex again (or at least I wish).
At this point I revert back to mindless part replacement and replace the O2 sensors. Nothing, no change.
Then I think okay this has to be some weird fuel problem (not really sure why I think that, just do). So I take the Fuel Injectors off the rail to do the poor mans fuel injector cleaning. They all Ohm out at 15.4 on the dot. I forward and back flush them all with carb cleaner using a 9v battery and a momentary switch to pulse them. I’ve never done this before, but all the injector solenoids actuated as I’d expect and the fuel streams all looked fairly similar. None were leaking under pressure. Put it all back together with new fuel injector O-rings. And start her up. Same issue, high + LTFTs. Around about 20% LTFT or so on bank one the STFTs are able to oscillate around 0% and around about 15% LFTF on Bank 2 the STFT for bank 2 is able to oscillate around 0% at idle. Reving the engine the fuel trims all come down. I’ve also noticed now that on the highway, just cruising at a constant speed the fuel trims are about the same as at idle, and if I accelerate they go down. I drive around after getting things back together with the “cleaned” fuel injectors for about 30 miles of random highway, city driving. I have the scanner plugged in the whole time and the fuel trims are still showing lean at idle and cruising.
I pull up to my house and suddenly the SFTFs are in the negative and the LTFTs are slowly coming down from 20% to 0%. I think, “hey great this is looking promising!”
That thought lasted for about 30 seconds, LFTFs came and passed 0% and after about 2 minutes of just sitting and idling in my driveway they were now reading about -9% LTFT bank 1 and -15% LTFT bank 2. What is going on here?
I think to myself. That was last night, flash forward to this morning, I start the car up with the scanner plugged in, High + STFT fuel trims right away… But not just usual high, REALLY HIGH! 42.2% to be exact. I think this was because the LTFTs saved from last night that were really negative was forcing the pcm to dump tons of fuel to adjust, since after a minute or so the LTFTs started to rise up to their usual 15-20% and the STFTs came down to less heart-attack-inducing values.
I decide I’ll take the long way to work to see if I can simulate what happened last night.
I drive around for 20 minutes, pull up into the parking garage at work, idling, and BAM! STFTs start going negative, and negative, and the LTFTs start dropping and dropping and dropping and hit about the same -negative values as they did last night. Bank 1 2 LTFT < -10% and STFT < -4% I mean what is going on?!?!?
It could have been doing this the whole time from the beginning of my story and I just never noticed it, so I can’t be certain this is a new issue. Also it has not rained here lately and it’s not that humid out.
I’m just at a total loss of what any of this could possibly mean. I’m fine at taking things apart and putting them back together, but diagnosing is not my forte. I’m on the edge of finally throwing in the towel and taking the car into the dealer with the hope they’ll look at it and go, “Oh yeah we seen this all the time, it’s the residual schliber-schobler in the flux capacitor.” And they fix that part and that will be it. But I figured I would come here first to tell my story and see if there are any takers for what this could be.
So for those who don’t want to read this novella here is the short.
Initial Issue: P0171, very poor gas mileage, mildly rough idle. CEL would sometimes turn off on its own after driving a few days. Came up particularly on cold mornings.
Attempts to Fix Issue, which thus far have not resulted in any noticeable change:
- Replaced Spark plugs (8 months prior to the start of this tale, Motorcraft)
- Replaced Ignition coil pack (Motorcraft)
- Replaced Spark plug wires (Motorcraft)
- Replaced Fuel Filter (Motorcraft)
- Replaced MAF (duralast)
- Replaced IAC (duralast)
- Replaced Oil and Filter (quite a long shot)
- Replaced EGR valve
(smoke tested intake manifold and found smoke coming out of EGR valve housing, and a little around the throttle plate shafts in throttle body). Retested and still only a little around the throttle.
- Replaced Intake manifold gaskets at the same time as EGR valve. (Is it normal for the PCV to dump lots of oil into the intake manifold? I’m thinking of installing an air/oil separator inline there)
- Tested EGR vacuum solenoid for leaks and proper operation using vacuum gauge. Checked good
- Bench tested the web of red/green hard vacuum hoses for leaks. Checked good
- Replaced a tired looking hose going to EVAP purge solenoid valve (driver side engine bay) to intake manifold
- Replaced both upstream O2 sensors (I didn’t think this was really going to help, but it certainly wasn't going to hurt)
Noticed it seemed to be exceptionally problematic in rainy or wet weather. In particular fuel trims would sometimes go full rich on Bank 2 and full lean on Bank 1 in the rain (as confirmed by live fuel rim data) and the engine would stall out. One time I got a P0171, P0175, and P0300.
Water tested engine for electrical shorts (i.e. I poured a bunch of water on things with the engine running). No results
Tested Fuel pressure. 65 PSI at idle and 2500 rpm, though equipment and user (me) was of questionable reliability.
Back to Fix Attempts:
- Clean fuel injectors off the car (all 15.4 ohms and solenoid actuated properly, not apparent leaks)
- Recheck for vacuum leaks. None.
I reset PCM using jumper wire from positive to detached negative batter cable every time a repair was made.
Current Symptoms:
Poor mileage, rough idle. High positive fuel trims when first starting the engine and still after about 15 minutes of driving when at idle or cruising (below). Fuel trims when accelerating are closer to 0% (<5% both banks).
Bank 1 LTFT ~20%
Bank 1 STFT ~4 to -4%
Bank 2 LTFT ~18%
Bank 2 STFT
After about 20-30 mins of driving at idle the fuel trims look like this:
Bank 1 LTFT ~ -9%
Bank 1 STFT ~ -2%
Bank 2 LTFT ~ -15%
Bank 2 LTFT ~ -4%
This morning when I start the car things look like this. I assume STFTs are like that since the LTFTs saved from last night (above) were so far off from what the engine is requesting upon cold start.
Bank 1 LTFT -9.4%
Bank 1 STFT 42.2%
Bank 2 LTFT -15.6%
Bank 2 STFT 42.2%
So with all that said does anyone have any ideas? Its fair to say parts were replaced properly though my diagnostic readouts (not the scanner readouts, but my home brewed tests) are of disputable reliability.
Also on a fascinating note I discovered yesterday you can use a bicycle pump with a built in pressure gauge to measure fuel pressure on the Schrader valve. I know this was probably not smart, but all the fuel pressure kits I could find at my FLAPs stores were missing the adapter.
