2000 Mercury Mountaineer, Idle issues.

[Idaho_Dave]

Ok guys, I have tried nearly everything I can think of or find related to this issue. With some luck in resolving my problems. I am hoping you guys can help me get this truck back to 100%. The patient is a 2000 Mountaineer with the 5.0 motor with 131 thousand miles on it.

The history on this mountaineer is too lengthy to explain here, but I will try to be as detailed as possible in order to hopefully get the correct diagnosis.

Symptoms
1.) The truck has an issue idling. (idle intolerant) The problem is intermittent and does not seem to be able to be reliably reproduced. The truck will start every time, and rev to about 1200 RPMs and then settle to about 500/600 RPMs and repeat that pattern for about three to five times and then it will idle for a few min and do it again three to five times, sometimes it will die when it is going through this process and has to be restarted. Some times it has stalled when putting the truck into gear (Drive or reverse) It will also stall at stop lights from time to time, just to remind me it isn't fixed yet. None of these symptoms happen every time just on occasion ... to make it fun.

2.) The truck will surge forward and then the engine will stumble (very slightly) and then surge forward again at 40 to 65 MPH. Again this problem is very intermittent, it is also very subtle but can be felt through the pedal and noted on the speedo and RPM gauge.


History

I have been working on some form of this problem for almost two years (don't judge me) . It all started with the fuel pump (according to the dealership) they diagnosed it and replaced it and a few weeks later the problem came back. Now I could have taken it back to the dealership and had them rip me off some more, but I didn't (it would probably be fixed if I had, Of course I would be bankrupt, but it would be fixed) I started reading to find out what the problem might be. It didn't take me long to figure out that is could be almost any number of sensors, or vacuum hoses, leaks, oxygen sensors, gas cap, valves, plugs, wires ... ect. So I began troubleshooting. My methods are somewhat unique as this is an un-needed vehicle. (in fact I have tried to sell it but no one wants a broken mountaineer it seems) So I began replacing parts that seemed logical (MAF, IAC, TPS, PLUGS, WIRES, OXYGEN Sensors(before the cats) EGR, and two vacuum hoses that had obvious leaks.)

List of replaced parts;
1. Fuel Pump (dealership I assume motorcraft)24 mos
2. Water pump (irrelevant)24 mos
3. Plugs (bosch platinum) 12 mos/3000 miles
4. Wires (napa) 2 weeks
5. TPS X2 (duralast) one year ago and again 1 week ago
6. O2 sensors (Duralast i think) one week ago
7. IAC (can't remember) 12 mos/3000 miles ago
8. MAF (can't remember)12 mos/3000 miles ago
9. Fuel filter X2 (motorcraft) 22 months and 12 months ago.
10. DPFE (can't remember) 10 months
11. EGR (can't remember) 2 weeks ago


So here we are two years down the road, and having replaced almost everything I can think of the truck still has issues. With each part replacement the issue has become less and less (or gone for short periods) but it REMAINS! Last week I made a few modifications to the fuel to help clean out any crap that might be in there. I ran some seafoam 1/2 of a can, and 2 oz of two stroke motor oil. It made a difference and the truck seems to be slightly improving (no stop light stalls or stalls when the transmission engages since) It is my intention to run out this tank of gas and do it again to see if the improvement continues.

I would prefer to not change any of the previously mentions sensors, unless I can prove they are the problem. So if you suggest a sensor change please include some instruction on where I can find information to test the proposed sensor so I am not throwing any more money away. Also please if you suggest a vacuum leak include the place for me to look that I may have overlooked, as I have looked at all the obvious places, and hosed the engine compartment down with carb cleaner looking for them with no luck. (slight exaggeration. )

My next move is to wait a week and see if the symptoms are continuing to improve (Computer re-learning and the seafoam breaking down any fuel restrictions). After that it is intake gaskets upper and lower, unless I get a better idea from this forum (possible test fuel pressure and verify the pump is doing its job after 24 months). I also may see about removing the cats on the off chance they are plugged. Last on my list is transmission torque converter/valve body as that has proven to be the problem for some people.

It should be said, I am not a mechanic I have some experience with machines and have even fixed a few (accidentally). Any help given will be greatly appreciated.

Engine codes:
None at the moment,for almost 100 miles of driving,

Most recent(one week ago)
02 says Lean on both banks. (changed pre-cat o2 sensors)
MAF out of range. ( I unplugged the sensor to see if it helped, it didn't)
TPS out of range. (changed TPS .. slight change if any)

 

[koda2000]

sounds like a vacuum leak to me. this would cause idle problems and lean codes. best way to try to find it is with a smoke test.

 

[Idaho_Dave]

I am thinking the same thing,

I tried to make a smoke canister and after hooking it up the egr was smoking a bit so I replaced it. It turns out that the issue was that one of the DPFE hoses had fell off and I think the smoke was coming out of that ( I think) . I may try to repeat it, before the intake gaskets get replaced, If I can remember how to run the hillbilly smoke canister I made.

Thanks Koda

 

[2000StreetRod]

Bosch plugs?

Many members have reported problems when using Bosch spark plugs although I have no logical reason why. Try a search for the numerous threads about spark plugs. Your ignition system is a waste spark system - plugs are paired to reduce the number of coil sections. When one plug in the pair fires on the compression stroke the other plug is firing on the exhaust stroke. Because one coil fires two plugs current flows in opposite directions for the plugs in the pair. That's why double platinum or double iridium plugs should be purchased. Single platinum or iridium plugs work fine in one bank but not the other. When your vehicle was assembled at the factory there were different plugs in one bank than the other.

Since you have no DTCs it will be difficult (and expensive) to solve your issues by parts replacement. There are reasonably priced electronic "gadgets" that I'm not familiar with that can read OBD pids (i.e. fuel trims, TPS, MAF sensor, etc.) that can identify abnormalities.

 

[Idaho_Dave]

Good advice,

I have a set of autolites I bought but have not put in, because I cannot convince myself that they need replaced. I will read up on it, and likely change them this weekend. Is there a brand that is more reliable in your opinion? I am trying to change my thinking from the cheapest part...to the best part, It has been a hard lesson, but I have always said you only have to hit me with a brick four or five times and then I will learn to do things differently.

I am hoping it will throw another code in the near future, but I have only been able to drive it for 15 min to work and then back again, I will have to run it this weekend and see if I can get it to throw another code, I doubt it will be too hard to make it happen.

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EDIT

Holy crap there are a ton of stories about bosch plugs fouling up a system. I will change them tonight, and hope that is the issue, THANKS!

 

[koda2000]

most here use Motorcraft or Autolite brand plugs. personally i use double platinum's but you could also step up to iridium's. i have no idea why some plugs work well while others seem to repeatedly cause problems, but i figure why mess with success. go with what seems to work. BTW, i don't see where spark plugs would be the cause of your specific problem, but if they're due to be changed it couldn't hurt.

 

[Idaho_Dave]

Sure koda steal my hope with your reality.

OK so changed the plugs, and little if any change is noted. The truck is running great... with the exception of the rare stumble. Also, I was able to run the truck for 160 miles and it threw some new codes. I will get them read this afternoon and post them as soon as I get them.


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Edit: NEW CODES

0455
Evap Large leak (already changed Gas Cap less than a year ago) and replaced one of the hoses on the evap system that had a huge hole in it. I will check them again (can I just plug the evap off? I live in Idaho and we have way too much environment already so we have no vehicle inspections.)

p1100
MAF reading out of bounds (supports vacuum leak theory) Maf was changed a Year ago and the truck was parked so after so it doesn't have very many miles on the MAF.

P0401
EGR system fault. (egr too little flow) ( EGR has been replaced less than 500 miles ago)


Let me hear the theories, my next step is to get it on a smoke machine... Maybe tomorrow if a guy I know will do it for me.

 

[Bobmbx]

I'm thinking vacuum leak somewhere.

Its the intermittent issue thats most troubling. That would point to an electrical issue, either with a harness shorting or grounding, or with the PCM itself.

I think you've done just about everything that would generally be offered as things to check. You're fuel-injected, right? It could be one or more of your injectors are not operating, which again, could be mechanical or electrical. Do you get any misfire codes?

 

[koda2000]

i'm still thinking vacuum leak. let's see what codes you pull. vacuum leaks are P0171 and P0174 (lean on banks 1 &2).

if you do have a vacuum leak it can be anywhere past the MAF sensor. this includes a lot of territory, that's why i suggested a smoke test. to list just a few areas where vacuum leaks may happen...

intake manifold gaskets/o-rings, PCV grommet elbow and hoses, any & all vacuum lines, brake booster, vacuum reservoir ball, HVAC controls, intake tube between MAF and throttle body.

one way you know you have a vacuum leak is if you set your HVAC controls to the panel and while climbing a steep hill the air flow switches to the defrosters. i found that this test will show up even a tiny leak. if the air flow is always coming out the defrosters you have a large vacuum leak.

 

[Idaho_Dave]

I have had a misfire code in the past, but not the last two times the codes were checked. (Three weeks or so )

I replaced the EGR recently and am wondering how vigilant I was in making sure which line went to which port on the DPFE. It is possible I got them switched, and I will check that this evening just to be sure.

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Koda,

Smoke test seems like the most obvious next step. I will report back once I have the results.

 

[Macgiobuin]

My 2000 Mountaineer had electronic problems that baffled me. I kept getting P0340--camshaft position sensor. To make a long story short, I found that the alternator was putting out stray voltage that the PCM was picking up in the camshaft position sensor circuit. At least there is a good diagnostic procedure. Clear out all the codes. Charge up the battery. Run the car with no loads on it--with the alternator electronically separated from the system. Drive it on one trip (just in case you have to restart it with a depleted battery.) See if there is an improvement, and if the drive cycles complete. If it's cured, then you are no longer spraying stray voltage thru the electric system, being picked up thru your low voltage sensors, any more. Replace the alternator--it's probably putting out the stray voltage from a bad diode plate. Good luck.

 

[Idaho_Dave]

Fuel Pressure?

Ok I know I said I was going to do a smoke test next, but I am waiting on a friend that owns a shop to fit me in I decided to change the fuel filter. The vehicle had sat for about 12 months and I though maybe it was gummed up so I decided to change it.

For the record if I ever meet the fellow that made the ford connector to the fuel filter I will kick him right in the nuts as pay back. Three different part stores assured me that I did not need a special tool to remove my filter. Apparently they were trying to get me to commit suicide my ex wife may have been involved ..investigation on going.

OK so I also decided to check the fuel pressure before and after the change to see if there was a difference. SO before the change the pressure was between 25 and 30 at idle .. say 27, and after it was .... wait for it ... 27 at idle. Which seems really low. SO I repositioned the gauge and revved the engine to see what the pressure did ... it dropped in the high 20's say 21 when I revved the engine... Sounds like I need a new fuel pump?

I tested using the best tools harbor freight could provide, and I connected to the port near the front of the engine on the passenger side of the engine on the fuel rail. If I remember right the pressure can start in the 30's but is supposed to climb when the engine is revved or put under load is that right?

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This thread says I should start in the 30's and go up to the 60's

http://www.explorerforum.com/forums/showthread.php?p=2359055

 

[koda2000]

your fuel pressure is way to low. for a 2000 model (return-less system) you should be around 65-67 psi.

could be the fuel pump. could be the fpr (in-tank) or it could be you have a leak in the hose between the fuel pump and the fpr.

BTW, changing the fuel filter (while not easy) has a lot to do with technique. the right tool also helps. the first one i changed took me over an hour. now i can do them in about 1 minute.

 

[Idaho_Dave]

No leak !

There is no significant external leak... This car sits in my garage and the garage does not smell like gas, and there is nothing dripping. for it to be losing 40+ psi it would be a fairly big leak, and I am getting 16 to 18 mpg with no external leaks.

So FPR? what is this? Fuel pressure relay?

So I have a wedding this week for my daughter, and will not have much time to work on this for a few weeks grrrr. I am still going to try to get it smoke tested if the opportunity arises but the fuel pump/fpr just jumped to the top of the list. It amazes me that a fuel pump (installed by the dealership) would go bad in so short a time, I am sure stranger things have happened.

I haven't thought of this for some time, but there is one symptom I forgot to mentions. (every mechanic loves that phrase) after the pump was changed the fuel gauge was off, and the truck would run out of gas just before the E on the fuel gauge usually on a left turn, I corrected this by filling it up at half a tank, and no issues since..

Is there a brand of pump that is better than whatever is sold at the local parts store without having to shell out all the cash for a Motorcraft?

 

[2000StreetRod]

Harbor Freight tester

I had problems getting an accurate pressure reading using Harbor Freight's fuel injection pump tester.

The fitting on the test adapter did not depress the Schrader valve core adequately. I had to remove the valve core to get an accurate reading. If your readings are accurate, then I agree with koda2000 that your fuel pressure is very low. My 2000 Explorer shop manual states that the fuel pressure for the returnless system should be 65 psi +/- 8 psi. My stock pump pressure was about 62 psi and did not vary with engine speed. The fuel pressure regulator (FPR) is part of the fuel pump assembly and is about midway in the photo below.

Sometimes the hose above the FPR will rupture causing loss of pressure. It is often not replaced when the fuel pump is replaced. The dealer technician who replaced your pump may have bent the float arm when removing/installing the assembly causing the incorrect reading. Or the sliding contact material may just be worn off with age.

 

[Idaho_Dave]

Very good information,

I will retest tomorrow without the schrader valve just to be certain. (My gauge is the exact same as yours) I am suspicious of the gauge because it is running so well with so low of pressure.

But it is not out of the realm of possibility that the bulk of my problems are fuel pump related.

1. Lean codes (fuel pump) low fuel pressure
2. Idle issues (fuel Pump) low fuel pressure
3. slight hesitation (fuel pump) low fuel pressure
4. Intermittent issues (fuel Pump) low fuel pressure
5. MAF misread? (dunno)

seems reasonable... we will see what tomorrow shows. Thanks for all the help

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When I replace this I am replacing the entire unit with the DELPHI HP10135

http://www.rockauto.com/catalog/moreinfo.php?pk=3642294&cc=1363991

 

[2000StreetRod]

PCM compensation

My Volvo 850 turbo wagon would start and idle with only .5 psi but did not run well. The PCM adjusts the fuel trims to compensate for decreased fuel pressure until the fuel trim limit is reached. There is no fuel pressure sensor on the 2nd Generation Explorer so the PCM can't determine why the trims have to be adjusted. It only knows (via the O2 sensors) that the air/fuel ratio is lean.

The MAF sensor code may be unrelated to the low fuel pressure. Make sure the intake and MAF sensor airflow path is clear. There could be a mouse or wasp nest in the intake if the vehicle was parked for a long time. I suggest cleaning the MAF sensor with MAF sensor cleaner aerosol.

 

[koda2000]

FPR = fuel pressure regulator. in the pic provided by streetrod2000, it's the round thing half way up the fuel pump assembly. it is mechanical and dumps excess fuel pressure back into the tank. if it goes bad it might release pressure too soon. also notice the rubber hoses between the fuel pump before and after the FPR. if the clamps are loose or if the hose splits you will lose fuel pressure. the issue with your fuel gauge was probably due to a bend rod on the float. that has nothing to do with the fuel supply. if you find the pump is the issue, you can replace just the pump (not the whole assembly) for under $100. Bosch makes a good pump.

BTW, any leaking would be internal/inside the fuel tank, so you wouldn't see anything. and before you do anything else, remove the schrader valve from the fuel rail connector and retest the fuel pressure.

 

[Idaho_Dave]

I think I fixed it.

I realize this is a bit old, but I thought the feedback might help someone else.

I realize I was supposed to remove the Schrader valve (for further diagnostics), before I removed the pump, but I had the part and I felt like doing it so I did. I purchased the entire assembly because I did not want anything else to break. First thing I did was remove the filter on the engine side and looked at the fuel output while starting the engine. The stream was very small with little force, think old man with prostate issues urine stream.

So I dropped the tank and I noticed the Vapor return valve was broken, I don't think I broke it, but it is possible. I got a replacement return valve and put the new pump assembly on and put it back on. Check the fuel coming out of the fuel filter and it is much better. Think race horse after a keg of beer.

Get everything hooked back up, and the truck is running ... awful. Blowing black smoke, and stumbling. I figure the computer is trying to relearn the new pump, so I reset the computer by removing the battery cable, it helps but not much. I disconnect the MAF, and tada! the truck runs like new. There is a slight hesitation when fuel is applied, but it is running better than ever. (20+ MPG)

My conclusion. MAF and Fuel pump, or fuel regulator (replaced the entire assembly) are causing my problems. The fuel pump could not keep up with demand, and when it could the MAF tried to drowned the engine. Perhaps the fuel regulator was a party as well. Not sure if the vapor return might have been causing issues as well.

What I learned;
Don't use cheap parts. Cheap parts are going to break sooner than good parts. Thus you will get to replace them over and over again.

I hate ford fuel lines, but I learned to take them off with a reasonable amount of effort.

The dealership does not always do good work. I strongly suspect the Vapor Return was damaged when the pump was removed the first time which is why I was getting the EVAP leak code (gas cap loose). The in tank filter was not attached to the pump when I removed it. All being said the work seemed shoddy.

Lastly listen to your brother in law when he suggests to replace the already replaced fuel pump, sometimes he knows what he is talking about.

Hope this helps someone else. Thanks for the help I still have the check engine light, but the MAF is still unplugged, I will get a new one and I hope to be finally set up I will update if there are any issues.