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Misfire Cylinder 2

10K views 42 replies 6 participants last post by  Jeff K 
#1 ·
I have 170k miles on my 01 Taurus and about a year ago started having misfire problems. Since then and most recently have replaced the head gaskets, computer, coil, plugs, camshaft synchronizer, crankshaft sensor, fuel injectors and filter, radiator, water pump and just yesterday the o2 sensors on bank 2. I haven't timed them yet but the misfire begins and ends like clock work now. Sitting at idle or driving. I stopped driving it a couple of weeks ago as I have been trying to solve this problem. Please help?

Thanks, Roger
 
#3 ·
I know you said you replaced the head gaskets, but did you inspect the heads for flatness, burned valves?

Have you checked compression? This is important on a Vulcan.

Any pending codes other than the missfire code? Have you checked long term fuel trims at both idle and 50 MPH cruise? If so, what are the values?

What brand / type plugs, wires, coil pack? Use ONLY the correct Motorcraft or NGK plugs as others, especially Bosch, dont work. Use ONLY Motorcraft or BWD (Borg Warner) coil packs, other cheaply made in the third world ones are junk. Plug wires, spring for the correct Motorcraft ones, and be sure to use dielectric grease on both ends, and route them correctly. If not routed correctly, they tend to sag and hit the exhaust manifold on the bank 2 (firewall side) and burn up.
 
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#8 ·
Hey Jeff, I did a valve job and replaced all the seals, everything flat, valves and all looked great and the car actually runs great when the misfire is not present. I'll check the fuel trims tomorrow again on my day off. I work until 9 tonight. No other codes, just p0302. Coil is Motorcraft, wires are Duralast Gold, plugs are NGK. I only had a few minutes before work yesterday but checked the compression on #2 and it was only at 90 then #5 at 100. Seems lower than what I remember before the new head gaskets. I'll do some more testing tomorrow.
 
#11 ·
Chart nailed it...... Find and fix your vacuum leak.
 
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#12 ·
Hey guys sorry for the delay. I'm off today and will be looking for a vacuum leak. Also going to do a leak down test on cylinder #2. I checked the fuel pressure yesterday and with the key just on there is only about five psi. With engine running it over 50 psi, also when the misfire occurs there is no drop in pressure. Now it's kind of ironic that after I did this test and turned the car off and tried to restart it, it wouldn't start, just turning over and over. Had the pressure gauge on and there was only 5 psi and the needle was not moving while trying to start. Finally after several tries it cranked up. I'm going to do a smoke test to find the vacuum leak. Is there any other way that's better? Thanks for all your advice guys. I let you know what I find.
 
#16 ·
'01 is one year only fuel filter and pump. If the pump does not run with the key "on" but not to start, you have a bad pump. It should turn on for about 1 second and then turn off. When you key to "start" it starts pumping again. This year does not have a fuel pump module so no electronics involved, it just runs of battery voltage. All years turn the pump on with the key to "run' for about 1 second and they it quits. It will pump again during cranking or engine running. Intermittent pump means the pump is bad. Worn out. The filter is a 3 nipple with a bracket attached. In the rust belt, mine had the attachment bolt badly rusted and hard to reach. I popped the filter out of it's new bracket and did the same to the old filter on the car. Put the new filter in the old bracket, no need to mess with that hard to reach bolt. I put a hose clamp around the filter/bracket for good measure.

-chart-
 
#13 ·
In my opinion if you have a misfire on one cylinder it is not going to be a vacuum leak that feeds the whole manifold like a PCV valve elbow. I would think it is a manifold runner related leak like the manifold gasket or fuel injector o ring on manifold. Did you replace the upper manifold gaskets and injector o rings when you did the head gaskets? I had a #3 cylinder misfire on my 2001 and found a badly compressed intake manifold gasket on that runner. It showed signs of oil leakage from a bad valve cover gasket.



It was flush with the manifold and was not sealing effectively.
 
#14 ·
Yes all gaskets were replaced. I was just testing the fuel pressure again and no pressure with key on engine off. Turned the key on and off several times and I could hear the pump turning on but not every time. I went to start it for the first time today and it wouldn't start. While I was turning the key on and off the fuel pump was not coming on then finally I heard it turn on and the car cranked. There doesn't seem to be a leak at the regulator but is it still possible for it to be bad or do you think a pump issue. It has 50psi while engine is running though, so confused.
 
#17 · (Edited)
2001's have a special fuel system that was only used for one year. The EPA make the use of recycling fuel from the engine to tank as previous models not allowed. Ford used a mechanical relief valve in the fuel tank regulated the pressure at the fuel filter. There are two lines that run to the filter from the tank and just one to the engine which supplies gas at fuel filter pressure. I have two 2001s that had pumps go bad at approximately 100K each, like clockwork. Random no starts, then wait 30 minutes and they would start and run fine. Replaced the whole fuel pump assembly because the mechanical regulator could also have an issue. New models after 2001 use a modulated voltage to the pump to regulate pressure and seem to last a lot longer in my opinion. Never had a pump fail in any other year taurus even with 245k + miles.

This however it is not the reason for your #2 misfire unless that injector is plugged and your pressure is weak. Like I said, I never had an issue with the performance as long as the pump was running. You can try to change the fuel filter if you haven't already.
 
#19 ·
Hey thanks again for all the responses. Today I was planning on replacing the fuel pump until I found a couple of other issues. First the fuel pump inertia valve is showing no volts which should be at least 12 from what I have read. Second my fuel pressure gauge is showing no pressure which is really strange because it has been working fine. So I started looking and I found that the vacuum line from the EGR valve has no pressure in it at all. I'm not sure what the switch it is going to on the back of the intake but when I unplug it nothing happens and it's directly hooked up to the manifold so I'm thinking that the switch is stuck closed or it would be losing vacuum pressure. I'm not convinced yet that it's the fuel pump. It comes on and off with the key but not every time. I checked the relay and it works but the fuel pump cuts on then immediately cuts off. Is it supposed to keep running? I had the cover off of the relay and when I pressed on it the fuel pump stayed on, then took my finger off of it and it stopped again.
 
#21 ·
Sorry for my absence about the results guys. Changed the fuel pump and it's not the problem. I still have a misfire in cylinder 2. I replaced the egr valve control solenoid. I can't find any vacuum leak on this car. After all I have done mentioned in this post I don't understand why I have a misfire. How would vacuum cause a misfire anyway? I also did a leak down test on cylinder 2 and it's almost perfect at around 5%. I'm totally stumped on this car. Any comments are welcome. Thank you so much.
 
#25 ·
What does the #2 plug look like after the engine has run a minute or so? Wet with fuel? Dry?

Pull the #2 wire off the plug, and using a spare plug (any kind) put the plug wire on the spare plug and lay the plug so thet hreads are grounded to the engine. Start engine. Do you get a good blue fat spark? If so, either plug in the engine is bad, insulator carbon tracked, etc, the cylinder compression is way low, or you have an injector problem. If no spark, coil, even though new, is bad, or plug wire is bad.
 
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#28 ·
I tried that once but didn't have it laying like you are saying, it had spark though. That #2 plug is always wet when I pull it out. I will be testing all day tomorrow and post my results. It's a new injector and is getting good power to it and increasing with throttle up. Checking everything in detail tomorrow.
 
#30 ·
Please help...

Ok so all the cylinders are right at 120psi and 5% leakdown...except for #2 which is at 85 psi and 40% leakdown. The engine over heated a couple of months ago and that's when I did the head job and everything looked great and everything new from block up. However I didn't even think about the rings being bad at that point. It appears that the rings in cylinder 2 are bad after the engine over heating. What troubles me is that when the car is running it runs great and no misfire then at random it occurs then goes away again. It continues to do this back and forth. If the rings are bad how is there not a constant misfire? It almost seems as though it's being controlled by a switch. I'm baffled at this point. Any thoughts???
 
#31 ·
Ok so all the cylinders are right at 120psi and 5% leakdown...except for #2 which is at 85 psi and 40% leakdown. The engine over heated a couple of months ago and that's when I did the head job and everything looked great and everything new from block up. However I didn't even think about the rings being bad at that point. It appears that the rings in cylinder 2 are bad after the engine over heating. What troubles me is that when the car is running it runs great and no misfire then at random it occurs then goes away again. It continues to do this back and forth. If the rings are bad how is there not a constant misfire? It almost seems as though it's being controlled by a switch. I'm baffled at this point. Any thoughts???
I do a wet compression check on the bad cylinder. Tablespoon of oil in the plug hole, then do the check. If oil increases the pressure it is the rings. If not it is the valve, or valve train, as in rocker, lifter and such. A low compression misfire is not always a misfire. There are cases when overheat causes the rings to stick. You could even have a bad cam lobe. Not common but I have had that on old 272 ci V-8.

And the old school, easy to check compression: disable the spark and fuel. Crank the engine and listen. If each pulse sounds equal you are good. Any skip in the pulse sounds of the starter load indicates a low compression.

-chart-
 
#32 ·
You found the problem. No matter what, the rear head has to come off to see what is going on.

PCM doesnt directly measure missfire. PCM measures crankshaft acceleration. Every time a cyl fires, crank accelerates slightly, and the PCM measures this acceleration. Any cyl that doesnt contribute a crank acceleration equal to the rest of the cyls is flagged as a missfire. In your case, the low compression cyl doesnt contribute as much power, and therefore acceleration to the crank. You are probably on the verge of the PCMs decision point, based on crank acceleration, as to whether to set a missfire code or not. The low compression is less important at higher RPM where things happen faster than low / idle RPM. Does it set the P0302 when the car is idled a lot, driven at low speed compred to a run on the highway?
 
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#34 ·
Hey thanks for the input. I figured as much about taking the head back off, really sucks. The p0302 comes on pretty regular know matter at idle or driving then while driving the engine has no power at all then the code light quits blinking and it runs fine. It does this over and over. Will get back with you tomorrow with more info. Thanks so much.
 
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