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Discussion Starter #1
Hello Guys,

New member but have used the site as a visitor with good results many times. Am experiencing some drivability issues without an MIL on my 00 DOHC wagon.
I have a scan tool and have been monitoring Live Data, however I can't seem to find the expected ranges for the PIDS I'm concerned with anywhere.
Here's what I've seen for the MAF at Idle and at Highway speed or about 2500 RPM's.

MAF Lbs/min Idle .795 LBS/min 2500 RPM 10.5 LBS/min
CALC LOAD
TPS

If anyone can supply a place to find the ranges for these PIDS on a properly running vehicle or the factory specs it would be greatly appreciated.

Thanks in advance for any input.
 

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There aren't any defined ranges because those ranges can vary widely depending on many factors.

For the MAF, you generally want to see about 0.5 lb/min at idle (~700 RPM). At 2500 RPM cruise the value may be around 3.7 lb/min. And at WOT you should be able to hit 15-17 lb/min passing the torque peak.

This image should sum up TPS readings:



Fully closed it should read just under a volt or about 18% and at full travel it should hit about 4.5 volts or 90%.

If you can post a data log in spreadsheet form I can take a look at it.
 

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Discussion Starter #3 (Edited)
Thanks Behlina
The wagon has 112,000 miles. Symtoms include rough idle, at times especially when cold there is very little power, MAF and the STFT's both go very high. This happens for about 10 minutes and then seems to clear up.

Have had an intermittent PO306. Have done a dry and wet compression test, 4&5 were 135psi, 6 was 110 which is borderline. Vacuum gauge was a steady 17WC. Have tried to find vacuum leaks with brake cleaner and smoke with a cigar without much success.

Both of the S1 O2 sensors do flucuate when graphed but I do believe they may be lazy, sometimes the oscillation looks pretty good, but sometimes goes flat line for a few seconds.

Have also, pulled the main wiring harness connector in the engine cpmpartment and also the blue silicon gasket, there was a small amount of moisture or oil which was thoroughly cleaned and dried.

Note, only after purchasing an Autel graphing scantool did I realize the MIL PO306 was on but the dash light was burnt out. The car seemed to have a slight miss when I bought it at 110K but overall ran quite well until Dec.


This is my 5th Taurus or Sable wagon and we've owned three sedans as well Most have had many miles and mostly just normal replacement part issues.

Howerver, have been struggling with this one for sometime and any input you can provide would be greatlly apprecitated.

Here are the scantool readings at Idle and 2500 plus RPM. Most of the the driving data was a recorded screen, but if there are multiple numbers, they were flucuating.

Idle 2600
Fuel sys CL CL
Load % 14.9-11.6 43-48
ETC F 205 208
STFT1 .8-4.7 0
LTFT1 10-12.5 2-3
STFT2 12-12.5 -.8
RPM 890 2792
VSS 0 72
FRP 37.9-40 37.9-40
SPARK ADV 5 38-42
IAT 50 64
MAF .718 3.9
TPS 18.8 22.7
O2B1SI .08-.9 .785
O2B2S1 .06-.9 .405

Have replaced the following:
PLUGS new Motocraft
COPS
UIM GASKETS
LIM GASKETS
1 FUEL INJECTOR, CLEANED THE REST
FUEL PUMP
FUEL FILTER
IAC
DPFE
MAF
GAS CAP
PCV
PCV ELBOW
TPS
 

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Whoops, looks like you forgot LTFT2.

Your idle is a little high (900 RPM instead of 700). If you unplug the IAC what happens to the idle speed? If the IAC and TB are both completely closed and the engine still runs at a normal speed you definitely have a vacuum leak.

MAF numbers look pretty normal considering the elevated engine speeds.

Without having all the FT numbers it seems like the trims are higher on bank 2 at idle, right? That points to something specific to that bank like a fuel injector, misfire, gasket, or manifold. Do you have any exhaust leaks (they can cause high fuel trims as well)?

Did you replace injector #6? Yes, compression on #6 is borderline so you might have a mechanical problem. Can you do a leak-down test on it (inject shop air listen for where it leaks)?

O2 sensors might be suspect considering the milage. Make sure they are hitting 0.1 and 0.8 volts or more while they're switching. Flatline is okay coming off a throttle snap or closure, but they should not flatline with the engine at a constant speed. They're old enough it might not be a bad idea to replace them anyway.

You're also replaced so many parts we have to consider you might have gotten a bad part unless you've used only Motorcraft replacements? I don't like random part changing for that reason.
 

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Discussion Starter #5
Wow, you are fast and thorough too, thanks so much. The columns looked a lot better before hitting send, sorry about that. No Excel at home.

Should've mentioned the original issue was when cold and sitting at a stop light, engine running quite normal, it would all of a sudden start running very rough for a few seconds and then straighten out and run fine. That started this journey.

Idle 2600
LTFT 2 2.5 5.5

I did raise idle speed some time ago as it seemed to run better a little higher. Will back that down tonight.

I will also the IAC to check idle speed and will buy another cigar for a smoke test, how do I confirm the TB is completely closed? Or do you mean at the normal idle setting?

I did replace #6 injector as I heard the original quit while listening with a stethescope. All injectors Ohm'd the same on the bench. However, later I heard the new one quit as well. this happens for 10-15 seconds or so and it starts back up. It was an aftermarket injector, if the LIM is pulled agian was going to replace the A/M injector with the #5 and put the OEM back in.

Have not done a leak down will need to investigate that process to accomplish.

This morning when the engine stumbled I noticed the Load % was at 60% and the MAF was 5.5 lbs/min and was only going 25mph or so.

Also, checked the IAT temp before start up and it seemed accurate, 29 outside and it was at 41 in the garage which iI suspect is correct.

Have not used OEM replacements and most parts were changed only after cleaning or testing if possible and only one at a time. Have not pitched ony of the OEM parts as other than the MAF, none really made any noticeable change.

Because of the fact it seems worse on a cold engine before the O2's are active, had discounted them as the main culprit. Had also thought possibly temp sensor(s) but they both seem accurate and change up and down on the scanner as they should.

Note, have also confirmed the EGR functions by putting a slight vacuum on it to make the engine stumble or die which I've read confirms OK but am starting to suspect it may not be fully seating at idle. I did run it with the vacuum line plugged yesterday, it may have been a bit better stumble wise but there still was a stumble.

Also thought maybe plugged CATS but there was only 1-2lbs pressure at the DPFE tube, which I believe is normal.

And lastly thought about the PCM being funny and heard about reflashing but wanted eliminate the easy items first.

Thanks again Behlinla for your valued input.
 

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If the car detects a bad enough misfire to cause catalyst damage it will turn the injector off. Is that what's happening here?

If the EGR isn't completely closed at idle you would get a P0402 code pretty fast.




Sent from AutoGuide.com App
 

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Discussion Starter #7
Thanks much Sam,

I did read that the PCM could shut down and injector and that may well be happening, of course read it after changing the injector out. Not sure how to determine if that is the cause though.

Also felt if that was happening with the #6 cylinder being somewhat low on compression, if any vacuum issue was resolved and if fuel delivery and spark were optimized, it would minimize or eliminate the misfire and keep the injector engaged.

And yes, good point on a leaking EGR should throw a code, but I drove it 20 miles with the EGR vacuum line plugged this week to see if it would change anything on the low power episodes or point a finger or not at the EGR.......shouldn't that have thrown a code too?

If I haven't mentioned this, at times the vehicle seems to drive without issue except for the somewhat rough idle.

Thanks again for your thought's and input, and any more you may have. Am sure looking forward to getting this behind me.

The studder hasn't been the only issue with this car, have also replaced the oil pan gaskets, yes of course the back Y-pipe bolts busted , the water pump, the lower radiator hose was replaced due to rust ($20 all rubber, no more steel nice), inner and outer tie rod ends, driver door lock actuator. All of this because it's a really decent 12 yr. old car.
 

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If your lucky, the leaking PVC elbow and other vacuum leaks before you
got the car did not fry some of your valve seats. Not a uncommon problem
with a TEC. The leak down test might shed more light on the situation.

You also need to verify that your fuel pressure is up to snuff when your
having issues.
 

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Discussion Starter #9
Well Behlinla, just lowered the Idle to 700 and pulled the IAC plug as directed and the idle dropped slightly but seemed to idle just about the same.

Looks like there's a big cigar in order for (to try to find a leak) tonight.

When trying to smoke the engine in the past, I have removed the MAF housing and plugged the intake boot directly attached to the throttle body. But it seems there is very little resistance when blowing smoke into the intake and haven't seen any smoke leakage before but was unsure the test was correct.

In the past have used the larger hose on the vacuum block above the master cylinder and plugged it's hole in the boot.

It seems some intake and exhaust valves have to open but should there be some resistance when trying to smoke the engine? Should the tailpipe be plugged during the process?

Will update with the results tomorrow, thanks all.
 

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Discussion Starter #10
Thanks Soundu,

Yes, as I understand a valve job on the TEC is pretty much out of the question.

Regarding fuel pressure, have seen differnet minimum numbers online.

Almost the first item changed was the pump, as I recall it had enough pressure or about 40psi but didn't hold it for long enough after the key was turned off.

Changed the pump because of that but now that I have a scantool and can see what's happening, it seems to flucuate between 37.8-40psi continuously. Have not checked it to see if it drops pressue like before. Will do that tonight as well.

Thanks much for your input.
 

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I would not use the cigar method to smoke test. Only works for very large leaks. You seem competent enough to not overlook those before the test. Use carb cleaner or NON CHLORINATED brake cleaner and spray it around vacuum hoses and the UIM/LIM. You should notice a change in idle when it hits a leak. To be more conclusive, watch the scan tool at the same time. The STFT will suddenly change drastically when you hit a leak.

When you plugged the EGR Vacuum tube, did you drive more than one cycle? AKA did you plug the tube, turn the car on, drive, turn the car off, drive more, then un plug it? If you only did one driving cycle it won't set a code I'm pretty sure.
 

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Discussion Starter #12
Thanks Sam,

Have tried the brake cleaner method and smoke methods more than once, however that was before the scanner. Could not hear any difference but will give the scanner method a try. Being a non-smoker, that's pretty good info and even better timing.

Believe it was actually three cycles for the plugged EGR, two less than 5 miles and one 15 or so and have not ever had a EGR code.

Thanks much for the input.
 

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I am a non-smoker as well and after failing a cigar smoke test I did the carb cleaner method. I remember wanting to vomit at one point because of the nastyness :p As soon as I sprayed it on the failed LIM gasket, I noticed the idle change. Watching your fuel trims will help. When you think you have found the spot, wait a few seconds then spray again to confirm the same change in the STFT happens.

It sure should have set a code at that point. I need to actually go back and read this entire thread before I start to ask more questions! Which vacuum tube did you plug exactly? I'm happy you have a 2000 DOHC, it's the motor I understand the most!

So just really quickly to make sure you and I both understand. I'm guessing you just pulled the vacuum tube off of the top of the EGR and plugged it? That would make sense. If you did that and no code was set then something really weird is going on. P0401 for sure should be set at that point. If that wasn't the vacuum line you used, which one? There are two vacuum lines that go into the regulator. One comes from the UIM and one goes to the top of the EGR. There is another vacuum tube that comes from the UIM and goes to the FPR in the same bundle. Any chance that was unplugged or plugged or anything?
 

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Discussion Starter #14
Hey Sam,
Great input on using my new favorite toy the scanner showing just STFT's and RPM's and spraying brake cleaner. Spraying the EGR gaskets cause the STFT's to both goto -5 and settled solid at -3.1 for a few seconds before going active at just over and under .00.

I did see some smoke from under the EGR body one time but read that it was normal under pressure as the holes were vents but would not leak under operating condition which would be vacuum. Maybe it was not the vents at all, but it sure looked like it.

The RPM flucuates around 50 RPM all the time on the scanner and with no connection to the change in fuel trims, so no wonder I could not hear the RPM change as expected before.

Regarding plugging the EGR vacuum line, it was the line on top of the EGR valve. As I think about it, have had that plugged before without throwing a code before replacing the DPFE, which showed a higher than recommended voltage of 1.2V I believe.

Off to get gaskets or maybe a new EGR and gaskets now.


Thanks for your input, will keep posting progress or lack there of, especially with a positive conclusion.
 

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Discussion Starter #15
OK, changed the EGR gaskets, there are two that are different materials with no indication of which one belongs where. Placed the thin one on the bottom and it had a worse leak. Swapped gaskets positions and still had a leak showing on the STFT's, no better.

Replaced the new thin gasket with the (not very) old thicker gasket, so there are now two thicker gaskets in place, one at each opening.

EGR leak is now gone, but who knows for how long.

That said, with no minor vacuum leak at the EGR, the scanned MAF reading dropped from about .8 lbs/min to .52 lbs/min. This seems more in line with what little info I could find on this specification.

Motor was still warm but seemed better, so the next test will be tomorrow morning with a cold motor to see if there is any change in the drivability.

Will update tomorrow.
 

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Okay, I need to explain something about the idle speed to you. On your car, the idle speed is not supposed to be adjustable! If you were using the idle stop screw on throttle body to adjust it (and it worked) something is wrong. That screw should never be touched unless someone already messed it up. The PCM uses the IAC exclusively to control the idle speed to the desired value and to compensate for changing loads and engine temperatures. If the IAC is working, changing that set screw will have zero effect on the idle. In your case it appears it has, so that tells me the IAC is not working properly. If the PCM can't raise the idle speed enough when the engine is cold, you will have cold stalling issues. When you first start the car the idle needs to stay up at about 1500 RPM for 20-30 seconds before it starts coming down.

Take your new IAC off and compare it to the original one. It should look exactly the same inside. If they look different, then you got an incorrect replacement part (which seems to be very common with the IACs lately). I would play it safe and just by the Motorcraft part so you can be sure it works as designed. You should also make sure you are using the correct gasket. If the gasket that came with the aftermarket IAC is different than the original gasket, it's wrong—use the original one or buy a new OEM one.

That brings us to setting the idle stop screw back to where it was originally. If there are witness marks or shiny exposed threads on the screw, you can use those as a guide. You can reset the screw by using the idle speed under specific circumstances. Those conditions are fully warm engine (ECT ≥180ºF), zero accessory loads (turn off climate, radio, all lights, etc), zero throttle bypass air, and zero vacuum leaks. When you unplug the IAC, it's supposed to close all the way and the idle will drop down low to something like 500 RPM. However if you have the wrong IAC or the IAC is sticking this might not happen. So in your case I think you're going to have to take the IAC off cover the IAC holes with something smooth and flat like a piece of sheet metal, making sure you get a 100% seal (you might have to hold/press on it). Now adjust the screw until you get a low idle of about 500 RPM (open and close the throttle after each adjustment). Again, I think you need to do this, but you need to wait until all your vacuum leaks are fixed since they will affect the setting.

Here's a video that shows the set screw adjustment process on a Ford V8: https://www.youtube.com/watch?v=ayjhL9jpFH8

Like Sam said, the PCM will disable fuel injection on a cylinder to save the catalytic converters it detects a bad enough misfire. I'm guessing the original fuel injector is probably fine.

As for the EGR, take a look at the DPFE voltage with your scan tool. With KOEO (engine not running), you should have a voltage right around 1.0 volts. If you start the engine with the EGR valve unplugged that number shouldn't change. Now put the vacuum line back on the EGR valve and see if that makes a change. With a cold engine it really shouldn't. Now pull a vacuum on the EGR valve and see if the voltage rises as the EGR valve opens. The engine should want to die, so open the throttle to keep it running. If you have enough vacuum on the EGR valve and the throttle open enough you should be able to get 4.5 volts or more on the DPFE. Let me know the results of these tests so I can interpret them for you.

You said you had 1-2 psi of exhaust back pressure? At what engine speed? At idle you should have essentially zero pressure. 1-2 psi would be okay if you were at 2000-2500 RPM though.

Fuel pressure should always stay right around 39 psi with the engine running, so I think that's okay. If you do a key cycle without starting it should be higher (45-50 psi) and it shouldn't really drop more than a few psi in 5 minutes. Pull the vacuum line off the IPS on the fuel rail and make sure you feel a vacuum there with the engine running (put it back after).

FYI, the PCM may not run the EGR monitor if you have a misfire.
 

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I have had good success on the EGR gasket with some high temp rtv silicon to help seal. +1 about adjusting the throttle plate.
 

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Discussion Starter #20
Thanks Belinla,

This morning the car ran quite a bit better than it has in a couple of months, That's with the EGR gaskets repaired as stated. Want to reiterrate how small this vacuum leak was. There was no lasting stutter and lack of power on the drive this a.m.. All is not perfect but much better.

I pulled the battery cable for 10-15 minutes to clear KAM and then ran it through it's paces per the op. manual. The MAF numbers have come down significantly.

I lowered the idle with the screw last night just as I had raised it a month ago and it worked, so something may well be up there. It is the same as the old unit but could be defective. The idle is not a steady idle on the scanner but it's unnoticeable by ear or tachometer.

Tonight I will search for any more small vac leaks, and also change out the IAC for the previous one as it may well have been fine. And will monitor STFT's and LTFT's next week.

Believe bank 2 O2 sensor is weak and will monitor and more than likely change that out.

Will also check back pressure again at the DPFE tubes, was going from memory on those numbers. However as I recall I could feel pressure at the time and was convinced I'd found the problem, but putting a gauge on it and researching results told me was actually OK at the time. However it's easy enough to recheck those findings.


I do understand about the silicon and O2 sensors and appreciate all the input. You guys are very helpful. Thanks much.

Tom
 
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