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PO306 MISFIRE 3.0L Vulcan

18K views 44 replies 5 participants last post by  soundu 
#1 ·
I am having trouble with my 2000 Taurus wagon. If you baby it, you can drive it but it sputters sometimes. It seems to do it under a load like going up a hill or on the throttle hard. Spread out over the past year I have replaced the plugs, then the coil pack and just recently the wires and I only did the wire since the misfire started. It is to the point that the check engine light will flash.
I pulled all the plugs and did a compression test
#1 = 165
#2 = 150
#3 = 165
#4 = 155
#5 = 155
#6 = 170 <-- smelled fuel
I smelled fuel as soon as I pulled the flug out of the # 6 cylinder.
I used a scanned and it says I have a misfire in #6.

What do you think, bad injector?

All of the plugs looked ok, kind of an oranginsh color but they have some miles on them
 
#2 ·
Check long term fuel trims on both banks at idle and at 50 mph cruise, and report back with the numbers. I am thinking a intake gasket vac leak on #6. Could be stuck injector on #6, but bad vac leak causing fuel to not burn because A/F is wacked would also result in unburned fuel / gas smell at #6.

Dont drive it with a flashing CEL unless you want to end up replacing the bank 2 cat for big $$.
 
#3 ·
You can test for a stuck open injector by checking if the fuel pressure drops after turning off the car. It really shouldn't drop at all when you shut the car off. If it drops quickly (within a few minutes, or few hours), that can indicate a stuck open injector.
 
#4 ·
Jeff K, how do I check the long term fuel trims? Will the scan tool give me that? The one I am using is borrowed because it is better than mine so I do not know its capabilities.
 
#5 ·
Scan tool will give you LTFT and STFT if it has the capabilities. My scan tool shows me them. If it shows fuel trims, it will show pressure too! So check for a leaky injector while you have the scan tool on! I don't actually know if it will give you a reading with the engine off though, so I may be wrong there. Could key on the engine off and then wait. Schrader valve on the fuel rail is the other way to do it.
 
#14 ·
Scan tool will give you LTFT and STFT if it has the capabilities. My scan tool shows me them. If it shows fuel trims, it will show pressure too! .
Depends on the year of the car. Not all years support the same PID's.
My 97 and 98 show fuel trims, but NOT fuel pressure.
 
#6 ·
Just to give an update, I put a new injector in #6 as a precaution since I have to drive the car every day. That wasn't it. Pulled the # 6 plug wire while it was running and no change. Then I pulled #5 & #4 one at a time and there was an obvious differance. I will read up on this scan tool but I guess its looking like some type of vacuum leak or maybe bad valve?
 
#7 ·
Pull the plug wire off and make sure you're getting a good spark. You should get it to arc about an inch or so or use a spark tester set to 25-30kV. Here's how to do it with a test light.



You have good compression, so it's probably not a bad valve. The extra fuel in the cylinder probably increased the compression a little bit.
 
#8 ·
While #6 was off I stuck an old plug in it and it appeared to get a good spark.

Here is what I got while driving home. The number fluctuated all over the place
ST FTRM1 (%) = 0.0 / -1.6
LT FTRM1 (%) = 0.0 / 1.6
ST FTRM2 (%) = 2.3/5.5/8.0
LT FTRM2 (%) = 17.2 / 15.6 / 16.0

When the CEL started flashing the ST numbers jumped up to 13 for FTRM1 & 15 for FTRM2
 
#9 ·
While #6 was off I stuck an old plug in it and it appeared to get a good spark.
This isn't a sufficient test because it doesn't stress the coil enough. It might spark fine in open air but under compression is a different story. Do the test so you can be sure.

Unfortunately the high fuel trims don't help much in this situation because they could be the result of no ignition, no fuel, or a vacuum leak.

It's interesting the fuel trims on bank 1 come up when it starts misfiring. That might point to a fuel delivery or coil problem.
 
#11 ·
One more bit of info, this car has 171,000 miles and every piece of plastic I touch under the hood cracks or breaks. Could the plastic upper intake be broken/cracked causing a vac leak? I don't hear anything. One of the diesel techs at work recommended I go around the intake with an unlit propane torch to see if the idle comes up but I am to chicken!
 
#12 · (Edited)
Still saying check the fuel pressure!!!! I don't know why this hasn't been done, it's very simple. Just rule it out.

You can do that to test for vac leaks, but you would have high trims at idle if you had a leak. Probably would be getting codes p0171 and/or p0174 if it was a large enough leak.

You can self smoke test with a cigar if you feel more comfortable that way. With the engine off blow cigar smoke into a vacuum tube and watch for it to come out of a leak. I doubt you have a leak though.
 
#13 ·
I don't remember seing fuel pressure but I will definetly check again. If I have to do it manualy I assume there is a tool kit that taps into the Schrader valve? What should the pressure be?
 
#15 · (Edited)
He is right. Some tools don't show it. Mine does. Yes, there is a gauge that can just be screwed onto the Schrader valve. 2000-2003 40 psi is ideal. My 2000 Duratec consistently sits at 39psi. I believe the 2004-2007's were higher than 40psi. IIRC 50psi was normal, but I think they can go as low as 25psi. Don't quote me on that. I just know what my car is for normal.

Also rev the engine and see what the pressure goes to under load. It should stay the same or rise slightly. If it drops a lot (5psi+), that could indicate a problem. Mine likes to go from 39 to 38 under load, but it never goes lower. The best way to tell is if the pressure has dropped when it starts to miss. If you can figure out a way to see the pressure when it is missing, that will let you know if it is fuel related or not. If it drops a ton when it misses, there you go!

Someone correct me if I'm wrong.
 
#16 ·
The 40/50 PSI figure sounds right for port injection. If it got as low as
25PSI (which would be OK for TBI), it would probably be lean.

One thing to check is the vacuum line going to the fuel pressure regulator.
make sure its not kinked, or have cracks in. As far as that goes, check
ALL the vacuum hoses under the hood for cracks or deterioration.

If you had a laser heat meter, you could laser the exhaust manifold runners
just outside the cylinder head on each cylinder for temperature variations.
They all should be close if they are all bringing the same.

On thing i did was make a ghetto vacuum leak detector.
I got a cheap small Halloween smoke machine and can fog the engine
compartment with smoke and look for any strange flow patterns.

One other strange possibility: that has the dual plane composite intake
runners? maybe there is a hole or leak on one of them.

After all else, i think the intake needs to come off, closely inspected
for faults and cleaned out, and re assembled with new gaskets.
 
#17 ·
Definetly no fuel pressure reading on my scan tool. I bought a cheap manual fuel pressure guage from Harbor Freight on my lunch. I won't be able to test it while I'm driving but I will do the best I can.
 
#18 ·
Okay, well it will be best if you can see it when it misfires, but if not, oh well. That would be the definitive answer for if it is fuel pressure related or not. If the pressure drops when it misfires then you know thats part of the problem.

I would check that pressure first. Just report back pressure at idle, as well as pressure under the max load you can give it. Try putting the parking brake on full and then put it into drive, turn the ac on max with max blower, high beams, and rear defrost on. Also make sure it's at operating temp too. Also try revving the engine a little (with it in park of course!), and see what the pressure does.

Just report back with your findings when you get them. Oh and lastly just because you already have the fuel gauge just ensure you don't have any leaky injectors by watching the pressure with the engine off. It should stay the same ideally. It shouldn't go down at all.

So report back with pressure at idle:
pressure under load at idle:
what the pressure does when rpm goes up (does it drop rise or stay the same):
does the pressure fall to 0 within 24hrs, (or maybe within a few minutes):

You can go ahead and check for vac leaks if you want, cigar smoke or propane torch is best way to go at it for almost free. Lets rule out fuel before we go on taking the intake off!
 
#19 ·
Well, I'm back. Hurricane Sandy threw me off for a while but now I am back to fighting with this car. My gauge had a small leak and I was doing this alone so I could only do the neutral no load fuel pressure test so far which was 52 PSI.
 
#20 · (Edited)
52 psi at idle?

That's quite high for a 2000. Is the vac line on the fuel pressure regulator?

There is a new sticky at the top of this forum called "how to understand and diagnose misfires". Give it a read.
 
#22 ·
Okay, that pressure is very high if the vac line is on the regulator. Should be around 40psi running at idle. It may jump up to around 50 if the vac line is not on the regulator.

Not sure what other reasons would cause it to be so high unless the sensor isn't working correctly.
 
#23 ·
Ok, so were the heck is the pressure regular? I looked all over under the hood, all the lines look good but cant find a regular.
I had to give my borrowed scanner back but before I did I scanned it again and now it has vacuum leak. I think it was P0442, EVAP system small lead?? going from memory.
 
#24 ·
The regulator is the little vacuum line that should be on the bottom of the fuel rail. Right near where the valve is to check the pressure. It looks like the line on top of the EGR valve.

Behlinla am I right?
 
#25 ·
The regulator should be somewhere on the passenger side of the intake manifold where the fuel line comes in. There should be a wiring harness going to it and a vacuum line with an elbow. This is from a DOHC engine but it should look similar on your car. Make sure the vac line is connected and you have vacuum coming through it with the engine running.

 
#26 ·
Mine doesn't look like that. My car just has the fuel line connected directly to one fuel rail, there is a cross over to the other rail were the schrader valve is.
I have tried to find a pic online but this is all I can find so far.
 
#28 ·
If you post high-quality picture of the area on your engine, we can probably point it out for you.

Part of the problem is that 2000 for the Taurus was sort of a "bastard year" because the engine designs only were used for that one year. So parts references and diagram are often wrong if they say 2000-2003 as the year.
 
#29 ·
My DOHC looks like the pic behlinla posted above, but you have an OHV so I don't actually know. Just look around the fuel rail and look for a vacuum line connected to it. Should look like the one above your EGR valve..

Posting a picture would help us point it out though.
 
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