Taurus Car Club of America : Ford Taurus Forum banner
1 - 15 of 15 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter · #1 ·
I have a long history with this car. I will try to condense it, but please bear with me. I have 1997 Mercury Sable with 3.0L 12V Vulcan engine.

First, the list of symptoms:
The car misfires on cylinder 2, darn near consistently, and creates a very noticeable engine shake at normal idling speeds (900-1100). Upon starting the car, it revs up to 2000 rpms, then takes up to nearly a full minute to come down to 1000. From there, it slowly climbs back up to to 1500.

What happened before this:
About a year ago, I had a mechanic replace the cylinder head on bank 1 (cyl 1-3) and replace the head gaskets. He also replaced my water pump and fixed the wiring to my VSS. After running it for about 6 months, I moved for the summer, during which it sat. I came back, found it had a dead battery and a bad water pump. I replaced the battery and drove it. The engine shake started around this time. I replaced the water pump, and the shake remained until a few weeks later, the MIL came on showing Misfire, cylinder 2.

What I've done so far:
I have replaced the fuel injector on cylinder 2, and tested for good spray. Looked great. High idle started to show up around this time. I replaced the IAC, high idle still remained. Took it to a mechanic that said my PCM was bad, because it was powering the fuel injectors and IAC with 12V and not 5V, so I replaced it, which did absolutely nothing. It sounded cockamamie to me after I looked at the wiring diagrams. Checked for spark, which I had plenty of, but decided to test the coil pack anyway. Tested, seemed normal on the primary windings, but secondary windings showed 13.5 kOhms, so I replaced it, the new one only showed 10.5 kOhms. Awesome. Still misfiring. Performed a compression test, all cylinders show great compression (150, 150, 150, 150, 145, 148). Performed a leakdown test, on which no cylinder lost more than 10% after 5 minutes. Any hissing was heard solely through the dipstick tube or oil cap, and it was VERY faint. It sounded the same on ALL cylinders, none louder than another.

What I suspect now:
Possible restricted catalytic converter or other exhaust restriction. Or leaky intake manifold.

Additional Information:
The spark plug on #2 is soaked in gas (except the electrode) when I pull it out, especially when compared with other spark plugs. The car smells like it is running rich. The lower intake manifold is definitely, but SLOWLY, leaking coolant. No coolant is being burned. The car is also leaking oil from an unknown location, where it hits the exhaust and burns. I have tried using starting fluid to find vacuum leaks, but I have not had any success. The car doesn't sound like it has a vacuum leak that's anywhere easily accessible.

Any other ideas?
 

·
Registered
Joined
·
197 Posts
Did you check the EGR? A bad EGR valve can cause misfiring or detonation, which can cause your rich condition as well.
 

·
Super Moderator
Joined
·
8,732 Posts
IAC and injectors ARE powered by 12V, as are ALL activators, like EVAP solenoids, etc. The 5 V is VREF, the regulated referenece voltage the sensors (IAT, ECT, TPS, etc, etc) use to report parameters to the PCM. You mechanic is an idiot!!!! Run away as fast as you can and find someone who has a clue on how to diagnose problems on a modern car.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #4 ·
Josh, I will test the EGR valve today and let you know how it goes. The EGR valve was replaced about two years ago, but that was before the head gasket job. But I will give it a shot.

Jeff, yeah, I agree. At least I picked up the computer pretty cheap (~$45) from a local junk yard. That mechanic wanted about $200 for another USED PCM and $90 for diagnostics. I'm not going back to him.

Oh and I should specify that the mechanic that did the head gaskets is different from the one that thought my PCM was bad.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #5 ·
Just tested the EGR valve, it works well. The diaphragm moves and seals right, and it holds a vacuum well. Any other ideas?
 

·
Registered
Joined
·
13 Posts
Have you done a compression test? I had a noticeable misfire on cyl 3 with my 97 Vulcan Taurus, turns out i had a bent valve... Ended up doing a complete valve job and shaved heads. Compression went from 5 cylinders having 120psi and 1 having 0psi, to all 6 having AT or damn near 200psi.

I'm not sure what would be causing the high idle though.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #7 ·
Lakai, I have done a compression test, where nearly all of them were 145-150 PSI. The impression that I have been given is that that is plenty of compression for a gas engine to fire. Cylinder 2 happened to be one of the higher ones. I also performed a leakdown test, and all cylinders are fine in that regard as well.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #9 ·
Tried that too. It didn't follow. It stayed on cylinder 2. Even went through the trouble to switch fuel injectors, and it is still on #2.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #11 · (Edited)
That's a good question. I don't know why either, but it was extremely cheap, according to the mechanic. He got it for $20 new. All I know is when I started driving it after the summer, it made a lot of bearing noise and the pulley showed noticeable wobble. It was also leaking coolant through a little hole near the bearing. So far as moving coolant through, it worked, but it was killing the serpentine belt.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #12 ·
Well, from what it sounds like, I think it is some sort of hidden vacuum leak in the lower manifold. I'm going to try and redo the lower manifold gasket and probably the upper plenum gasket as well on my day off this week. If it's not a gasket problem, then maybe I will find something else that catches my attention in the process. Plus, the intake manifold gasket is leaking coolant, so it would at least fix that. I will let you all know how it goes.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #13 ·
Well, I spent nearly 12 hours yesterday taking apart the top of the engine to replace both the intake manifold gaskets and the valve cover gaskets, and guess what? There was a HUGE split in the gasket on bank 1, centered right on cylinder 2. In fact, the gasket was completely split down the middle, so it came out in two pieces. The gasket was leaking vacuum into the valve cover, creating vacuum inside the valve cover and crankcase. In hindsight, confirmation was found in the fact that when either the PCV valve was removed while running, or the breather hose was disconnected from the air intake tube, the engine would suddenly drop in RPM, and a loud whistle would occur when the vacuum leak pressure was relieved on the crankcase.

After spending LOTS of time cleaning and removing gasket crud, I was able to replace the gaskets. The end result being an engine that no longer misses, and idles lower as the car warms up. At operating temperature, it idles at 850 RPM. Hopefully now I will see the fuel mileage that I'm used to with this car.

Thanks everybody who replied. I hope this information might help some future schmuck who had a crappy head gasket/intake gasket job from a disreputable mechanic.
 
1 - 15 of 15 Posts
Top