Intake? Crankshaft Position Sensor? Vacuum Leak? | Ford Explorer Forums - Serious Explorations

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Intake? Crankshaft Position Sensor? Vacuum Leak?

maksimfa

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Year, Model & Trim Level
2003 Explorer XLT
Good day everyone. New member here.

Just picked up an 03 Ford Explorer 4.6. It has a few issues.

The main one is this.

Car starts however it has a low RPM, around 500 to 600 and is a bit lumpy.
Engine sounds fine, no abnormal ticking I believe, but there is a bit of hesitation. There is the rattly catalytic converter however.

After a while, the car will just die/stall. Will not immediately restart and would need to wait a while to restart it, about 10 mins. It does crank over, just does not start.

When it is running, giving it gas the car starts running rough then dies.

No codes yet... but it may have to do with battery was dead and I just replaced it.

Live data shows the O2's are fine... the catalytic converters seem stable.
The short term fuel trims however are in the 20's and 30's... no long term fuel trims yet.

Unplugging the MAF did not seem to make much difference.

Battery voltage is 12.6 so is fine. The alternator, at idle the voltage is at 13.7 or so... perhaps a tad low?

I just changed the oil, it was a bit dirty/old and a tad low but otherwise looked clean.

So.... ideas?

Vacuum leak? Bad intake manifold? It is a 2003.... or thinking bad Crankshaft Position Sensor?

I know in the past it with a different car it would die at idle when it got too hot then you had to wait for it to cool down to get running again.

Not sure if a regular vacuum leak or a bad intake would cause the same issue start immediately after stalling.

Thanks!
 



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Bad cat(s) or fuel pump (and/or filter) issue is my guess. Check fuel pressure at the rail. Those are not normal short term fuel trims, as I suspect you know.

How many miles? If not a fuel or cat issue, I'd check the coil packs next.
 






Bad cat(s) or fuel pump (and/or filter) issue is my guess. Check fuel pressure at the rail. Those are not normal short term fuel trims, as I suspect you know.

How many miles? If not a fuel or cat issue, I'd check the coil packs next.

129k, was a fleet maintained vehicle so most of the stuff was done on time, the coils do look original but that would throw a code? I do have new plugs which I will do.

I did suspect plugged cats however their voltages were not consistent with plugged cats, ie the voltage on those secondary o2 remained constant instead of jumping up and down as they have with other failing cats.

The IAC looks like it was done a bit ago however the TPS looks original as is the Maf. I will spray out the maf and clean the iac and throttle body too, can’t hurt right? And I do have a new TPS that I bought to see if it will resolve the issue.

Appreciate your help.
 






129k is not old for this truck--cats are supposed to last twice that long. And the V-8's don't have the premature timing chain issue. Still sounds like fuel system issue to me. But vacuum leak or IAC could be possibilities. Smoke test would be good.
 






Thanks for the help.

So had some time, cleaned up the MAF and throttle body. Tons of gunk on TB. I figured may be TPS so tried getting it off, original sensor and bolt got stripped so ended up taking off tb plate and will try to get it off later today. While all that stuff was off figured do the plugs. Did 6 out of 8 before got too hot out and had to run out to finish work. 3, 4, and 5 looked okay, just old. 6, 7, and 8 were really fouled and had crap on the boots and in the plug well, 7 was the worst. Smelled like fuel but may have been burned coolant.

So the plugs were an issue the question is the cause, I suspect either fouled injector or perhaps cracked or leaking intake. Have to see if the funk on plugs is oil or coolant but don’t think it is valve cover gasket?

But would fouled plugs make the truck run rich?
 






Doubt it. Vacuum leak would, though (trying to compensate for the extra air). There's supposed to be a coating on the TB plate; supposed to use TB cleaner, but I've used kerosene w/o issue. I'm not seeing seeing how a "fouled injector" fouls a plug. You can run some Techtron fuel system cleaner (in a high concentration) through there.

You removed the plate from the TB? I did not know that was a service option . . . .
 






you have a vacuum leak. you have to find it. that is not a guess. the 20-30 stft numbers indicate it.
 






Hope everyone had a great weekend.

So... replaced the plugs, cleaned the MAF and TB... it did run a tad better but still the issues. LEAN at idle and gets better at RPM.... BUT then when it warms up the car does not go above 2,000 RPM and then just dies.

Was thinking clogged cat which would be consistent with perhaps the clunking drivers side cat.... if it was more than the heatshield.

At night I was browsing and realized.... "wait... there was no vacuum cable that went on top of the EGR."

Went to look at the car today and I did not leave it unplugged... because there was none!

Will post pics in a few mins but...

There is no cable attaching to the top of the EGR.
The EGR vacuum solenoid looks brand new or newer... BUT... there were also no vacuum cables attached to the two nipples on it... just the ecu/power connector was plugged in.

Then... looked closely at another cable... which I thought was just a bad ziptie but it turns out the zip tie was put into the cable to plug the vacuum hose. This is the one with a yconnector. No clue what it is.

Also... attaching a pic.

So... I am assuming this would account for the vacuum leak.... question is... anyone have a diagram? What kind of vacuum hoses? Where do they plug in.

Also... IAC looks brand new...
 






Here are the pics.

As you can see... no cables to the EGR.
9ofyBQu.jpg


The two tubes are into the DPFE sensor and cables seem to be there as they should.
jxWQtf8.jpg


Solenoid is there, but nothing running to it besides ECU connector.
i6UNpn2.jpg


This is the Y cable running from I believe firewall to the throttle body. You can see the plugged in zip tie... no clue where that goes...
kvT6BcC.jpg


You can see that braided cable here... resting on the coolant overflow tank.
jV4Fw86.jpg


And also in this pic.... also, what is that thing with the grey vacuum cable plugged into back? There is an exposed nipple on top too... something supposed to go there?
tXWhWCo.jpg


This is where the zip tie cable goes into the throttle body. You can see the red wire going in BUT... there is an empty spot at the top... where does that go?
SD92AM0.jpg


Thanks all!
 






and yes.... I unplugged the vacuum cable into the IAC to get the pics. =)
 






I'm afraid I have the 4.0L SOHC V-6, not the V-8, so have limited advice to offer.

I can tell you that in your photo #6 (second-from-last), that's the heater control valve. A vacuum line should run from there through the passenger side lower firewall. When you turn the knob on your dash to move from cool (blue) to hot (red) temp mix, a vacuum supplied by the engine (intake) is used to regulate that valve. there should be two very tiny vacuum tubes (please don't call them "cables"--its confusing) should pass through the firewall under the ECU connectors--one is a vacuum line that runs along the top back side of the engine and is eventually connected to engine vacuum; and the other goes to that valve that is inline with the heater hose from the front of the engine/water pump.

When I had my engine out (twice) to do timing chains (two different engines), I remember scratching my head on these vacuum lines until I figured it all out.

I would suggest you take you VIN to your local Ford Dealer parts department, explain to the counter person you picked up a used 'sploder with missing vacuum lines, and ask him/her to pull up the diagrams for the parts. Even if you don't buy them from the dealer (they may no longer be available), this could help you sort things out.

Other ideas: scour this forum and YouTube for photos/videos of your model V8. Even if the posts have nothing to do with vacuum lines, detailed photos of the top, back of the engine may help you sort it out. Another idea: spend a Saturday surveying yoru local auto salvage (junk) yards for Gen 3 Explorers with a V8 that you can inspect. You will likely learn the vacuum line routing, and may even be able to buy some complete lines.

I found a kit at a my local O'Reilly's Auto Parts that helped me splice some of those thin, hard plastic vacuum lines that broke. I also used plastic cement (from model shop) to seal some torn rubber grommets that the lines passed through or connected at. Got everything (including the heat/A-C) working just fine with a little TLC. Good luck.
 






...Also, you might want to see if you can find a diagram at fordparts.com (type in your VIN).
 






... and a big vacuum leak it was!

So got a big issue solved.

As it turns out the EGR vacuum harness that goes from firewall to EGR solenoid to throttle body, EGR valve and the brake booster was partly missing sections on my truck! lol.

Could not find one at a local junk yard and the dealer did not have this discontinued part.

Found a person on craigslist parting out a 2002 V8 Mountaineer and was able to pick up the harness for $10.

Plugged it all in and now my fuel trims at various RPMs are just in line. Engine sounds pretty good and is quiet. Although I have not done a compression test on it yet, seems pretty good.

But alas, still issues... while the idle is now pretty much good, as the truck warms up, it does not seem to want to go above 10 mph. Once warmed up, seems like it is really struggling for air and backpressure almost nonexistent out of the tail pipe.

While the Bank 1 Side 2 o2 reads steady, the Bank 2 Side 2 o2 keeps jumping up and down (indicative of plugged cat)

Also seems a bit of liquid or so out from tailpipe.

So either a blockage somewhere in the exhaust past the cats... ie someone made a nest, or more than likely a bad cat.

Ideas?
 






Glad you got the vacuum thingy worked out.

I'm a little confused by the O2 problem description. There are two banks, each with two O2 sensors: upstream (designated 1 or zero 1 ("01"); and downstream (designated 2 or zero 2 ("02"). So, Bank 1, sensor 2 would be the downstream on bank 1. Bank 2-01 would be the upstream sensor on bank 2. Various code readers will display these values differently, but on a given bank, sensor 1 is always the upstream and sensor 2 is always the downstream.

The upstream sensors, once warmed up (in open loop; only takes a minute or two), should constantly be "jumping around" (volts reading between 0.01 and 0.9). This is NORMAL. The upstream sensors are constantly reading oxegen (unburnt air) in the exhaust on each bank and adjusting the fuel trims accordingly.

The downstream sensors should change much more slowly, and less frequently. They are there only to detect whether a catalytic converter is failing. Honestly, I forget what reading you get when this happens (failed cat), but there should be a DTC (diagnostic trouble code) triggered if they sense a bad cat.

I'm guessing that you're saying that one of the two downstream sensors is fluctuating rapidly, a sign of a bad cat. Keep in mind that a cat can be "bad" (i.e., not removing the chemicals its supposed to) and still not be plugged up. So you might not pass inspection (if your state has one), but there might not be a resulting drivability problem.

If my guess is wrong, and one of your two upstream sensors is not "jumping around", then it is a bad sensor (or has bad wiring to it), and needs to be replaced (or repaired) before further diagnosis. (However, if you have a bad upstream O2 sensor on one bank, I doubt you'd be getting normal fuel trims on that bank.)

As mentioned before, 129k miles is awfully soon for a cat to fail, unless there was a serious fuel problem.
 






Hey Drew,

So yes, Side 1 is the upstream, Side 2 is the downstream.

Side 1 jumps around as it is supposed to, side 2 is supposed to be fairly constant.

In my case Bank 2 Side 2 is jumping around... indicating a cat issue.

I do not have a history on the vehicle as it is a former county government vehicle but... plenty of stuff on it was replaced.

Having pulled the plugs, quite a few of them were quite fowled and I suspect such abuse is what lead to the cat going bad.

Only other thing I think is if some mud or something got into the exhaust. The vehicles were stored in a easy to flood area and could have gotten in.

Also, because the battery was dead... it reset all of the emissions monitors, including the O2 ones. AS such, it will not give you a bad cat code while the monitors reset... hence one of the main challenges of finding out what the codes or issues were as the entire history was wiped clean by the bad battery.
 






Re-read the thread. You stated a couple of times early on that yomu were getting normal 02 readings for the downstreams. I wonder what caused that to change?

Seems to me your symptoms at this point (with the possible exception of the now-fluctuating downstream O2 sensor on one side) could be just as consistent with a clogged fuel filter or failing fuel pump, which are not all that uncommon on these trucks. Can you figure out a way to measure your fuel pressure at the fuel rail?
 






Re-read the thread. You stated a couple of times early on that yomu were getting normal 02 readings for the downstreams. I wonder what caused that to change?

Seems to me your symptoms at this point (with the possible exception of the now-fluctuating downstream O2 sensor on one side) could be just as consistent with a clogged fuel filter or failing fuel pump, which are not all that uncommon on these trucks. Can you figure out a way to measure your fuel pressure at the fuel rail?

Humn, good point on the fuel issue again.

I do have a pressure meter but did not have the fitting for the Fords. I will go and buy one from Advance Auto and double check.

Question is... if it was fuel... wouldn't it just not work at all?

Never had a clogged filter or fuel pump on any prior vehicles.

I did smell a bit of foul sulfur smell but you are right... unless really clogged should at least still run a tad.

Will re-read my post... but

fuel trims are now fine.

Upstream 02 behaving normal.

Bank 2 Side 2 cat 02 not behaving properly, (now that vacuum issues were solved).
 






Fuel pump producing insufficient flow, or restriction of flow from clogged filter, would starve the engine at higher demand, but may produce enough flow for idle/low speed.

Does the alternator check good? (Higher rpms/power would draw more current from coils; if alternator cannot supply, might also explain lack of power?)
 






Fuel pump producing insufficient flow, or restriction of flow from clogged filter, would starve the engine at higher demand, but may produce enough flow for idle/low speed.

Does the alternator check good? (Higher rpms/power would draw more current from coils; if alternator cannot supply, might also explain lack of power?)

Alternator is not great but it is okay, high 13's last I checked... will double check.

Fuel... it surely can be... jsut thinking why it had no issues reving up when cold but then would have issues once warmed up a bit.

Will test fuel pressure anyway but... will also unplug the o2 when I can get in under it to see if it comes to life.
 



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