Taurus Car Club of America : Ford Taurus Forum banner
1 - 19 of 19 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter · #1 ·
(first Post but have used this format before, part of the Turbo Dodge Forum as my other car is an 89 Shadow)

I am new to the forum and have a 2002 Taurus Wagon with a OHV V6 and an automatic. Has 47,000 miles and original parts everywhere. Recently had a constant misfire issue, pulled codes and got a misfire on cylinder 5 and 6, a multiple misfires within first 1,000 engine rotations, and an evap. code.

I have replaced the coil plugs and wires as all were factory. The coil had cracks in the resin on the underside. After replacing them the misfire came back but now it’s intermittent. It will start to run bad then it will go back to normal and it doesn’t mater if you are flooring it or idling. I switched #4 and #5 injectors and the problem didn’t move so I think they are fine. I did wipe off the ends as the injectors stayed with the rail and I fumbled it and it slid into the engine gunk in the valley between the valve cover and the intake.

Pulled up the data stream on by scan tool and both bank 1 and bank 2 O2 sensor fuel trims are pegged at 99.2%. I’d doesn’t change if you give it gas or not. (Will attach video soon)

Any suggestions.
 

·
Registered
Joined
·
556 Posts
Could be that you (or somebody else) accidentally interchanged the spark plug wires for cylinders 5 and 6. After all, they are numbered counterintuitively. The coil pack connections look like:

1 2 3
5 6 4

while the cylinders themselves of course look like:

1 2 3
4 5 6
 

·
Registered
Joined
·
3,831 Posts
What did the old plugs look like? Btw that fuel trim thing is just your scan tool misreporting that PID. There's no actual trim function for the downstream 02 sensors. If you look at the upstream ones (B2 S1 and B1 S1), the short term trims look completely normal. The limit is 30% I believe, and you'll get lovely P0171 and P0174 to accompany that if there's a problem there.

Given what you already replaced, and since the misfire is occurring in two adjacent cylinders, I'd go straight to a compression/leak down test here. The Vulcan really doesn't like sitting for long periods of time, and your vehicle is pretty low mileage. Head issues aplenty with that combination.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #6 ·
What did the old plugs look like?

Given what you already replaced, and since the misfire is occurring in two adjacent cylinders, I'd go straight to a compression/leak down test here. The Vulcan really doesn't like sitting for long periods of time, and your vehicle is pretty low mileage. Head issues aplenty with that combination.
They were pretty worn out. The gap was quite a bit bigger than it was supposed to be and with the now stuff in it ran quite a bit better.

From what I was told when I bought it it was driven regularly but it was a case of 5 miles down the road to church and 6 the other way to the grocery store.

I dont like the sound of “Head issues”.

If it was a blown head gasket between 5 and 6 why would it be an intermittent problem?
 

·
Registered
Joined
·
261 Posts
Kinda doubt you need to worry about a head gasket, nothing wrong with doing leak-down/compression checks though if you have the tools.
Taking it out on the highway and blowing the cobwebs out of it might help also.
 

·
Registered
Joined
·
7,592 Posts
I had a #3 cylinder miss fire on startup and thought maybe coolant leaking into the cylinder during periods of rest. Ended up being intake silicone rubber gaskets compressed over time and leaked air until engine warms up that area.
 

·
Registered
Joined
·
11,207 Posts
I had a #3 cylinder miss fire on startup and thought maybe coolant leaking into the cylinder during periods of rest. Ended up being intake silicone rubber gaskets compressed over time and leaked air until engine warms up that area.
From watching engine shows on TV where the build up and test lots of engines and dyno them. They said they always coat the mating surface with very light coating of silicone like the spark plug grease to preventing binding or pinching during installing. I never tried this but makes sense to me.
-chart-
 

·
Registered
Joined
·
3,831 Posts
They were pretty worn out. The gap was quite a bit bigger than it was supposed to be and with the now stuff in it ran quite a bit better.

From what I was told when I bought it it was driven regularly but it was a case of 5 miles down the road to church and 6 the other way to the grocery store.

I dont like the sound of “Head issues”.

If it was a blown head gasket between 5 and 6 why would it be an intermittent problem?
You're right, I missed that it was intermittent. Still worth a double check though.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #11 ·
Took it to a local shop, they said it was the intake plenum to intake manifold gasket. Handed the guy a $20 and said thanks. It makes sense now why I herd a sound reminiscent of a plastic bag or a fart coming out of the intake once while we were poking around. It was probably the gasket vibrating. I didn’t seem important to me before but it lines up well.

Any tips for taking off the intake plenum?

The gaskets are coming in a kit with the gaskets for the intake manifold too. Should we do that while it is all apart?
 

·
Registered
Joined
·
3,831 Posts
Took it to a local shop, they said it was the intake plenum to intake manifold gasket. Handed the guy a $20 and said thanks. It makes sense now why I herd a sound reminiscent of a plastic bag or a fart coming out of the intake once while we were poking around. It was probably the gasket vibrating. I didn’t seem important to me before but it lines up well.

Any tips for taking off the intake plenum?

The gaskets are coming in a kit with the gaskets for the intake manifold too. Should we do that while it is all apart?
It's not too bad at all. Worst part is dealing with the EGR tube. I've had more success than most by removing that giant nut that connects the valve to the tube assembly, but if you can't get that to break free, removing the nuts at the valve to manifold connection is fine, it's just a little tricky to get it lined back up on the reinstall. Double check all your vacuum lines after you reinstall everything.

As far as doing the lower gaskets, I'd recommend it, yes. It's not too hard, although some of the pushrods have to get removed to pull the lower intake manifold. Make that each pushrod goes back to where it came from. You also want some grey or black RTV to seal the corners of the "china wall" along with new end gaskets. Good time to toss in a new thermostat while you have it all apart.

When you put the pushrod/rocker arm back on, they're torqued 18-24 foot lbs, although make sure you rotate the engine until the valve isn't being held open by the cam to get an accurate value. You'll know because it will be really hard to tighten out of the gate.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #14 ·
If we do do the lower intake and have the valve covers off, that is the valve lash as we might as well check it while it’s apart.
 

·
Registered
Joined
·
556 Posts
But in a Vulcan engine there is no valve lash because the hydraulic lifters will automatically correct for that. So there is not much to check there. But it remains essential to tighten the rocker arm bolts only when the piston is at its TDC in compression because both valves are closed then, as ice445 said.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #16 ·
We did the upper intake gaskets, valve cover gaskets, and injector o rings. Decided not to do the lower intake because we weren’t up for it and it was supposed to rain the next day then get real cold.

The issue is still present, seems a bit les violent. I could see where the intake was leaking as the gasket had a dark spot and the intake runner had a lighter area that alighted with the spot on the gasket.

I will try to get a video of it doing the misfire. Just to restate the symptoms, misfire codes for 5 and 6, happens at any speed, rpm, or load at any engine temp or ambient temp or humidity. Will randomly come and go some times rapidly some times you can go 100 miles with no issue.

I did notice that if you are trying to accelerate when it is misfiring the check engine light will flicker and the engine will not seem to rev above 2500 rpm no matter how much you push the peddle.
 

·
Registered
Joined
·
3,831 Posts
We did the upper intake gaskets, valve cover gaskets, and injector o rings. Decided not to do the lower intake because we weren’t up for it and it was supposed to rain the next day then get real cold.

The issue is still present, seems a bit les violent. I could see where the intake was leaking as the gasket had a dark spot and the intake runner had a lighter area that alighted with the spot on the gasket.

I will try to get a video of it doing the misfire. Just to restate the symptoms, misfire codes for 5 and 6, happens at any speed, rpm, or load at any engine temp or ambient temp or humidity. Will randomly come and go some times rapidly some times you can go 100 miles with no issue.

I did notice that if you are trying to accelerate when it is misfiring the check engine light will flicker and the engine will not seem to rev above 2500 rpm no matter how much you push the peddle.
Unfortunately you're going to have to check mechanical causes next. Compression and leak down.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #18 ·
Update - it’s been ok for the past week or so but today there was a little sputtering. It also hapens to be the warmest day in the past week. Before today it stayed below 35º but today it was up to 45º. When it was misfiring before it was also warmer.

I’m thinking that maybe the intake air temp sensor is broken and it is stuck reading lets say 30º which is fine when it is around that temp but as it gets warmer the possibly faulty sensor is telling the computer to dump more fuel than the engine needed causing it to run like crap.

Is this a logical thought and if it is where is the part on the engine.

I saw it on rock auto and it looks like a longer and skinner metal price with some holes and a connector on the top.
 

·
Registered
Joined
·
556 Posts
I’m thinking that maybe the intake air temp sensor is broken and it is stuck reading lets say 30º which is fine when it is around that temp but as it gets warmer the possibly faulty sensor is telling the computer to dump more fuel than the engine needed causing it to run like crap.
Seems reasonable.
Is this a logical thought and if it is where is the part on the engine.
On my 2000 OHV it is integrated with the MAF sensor. Which -- as you must have seen -- is not directly cheap. So instead of throwing a new MAF sensor at the problem, you'd better invest in an OBD2 scanner and simply check the IAT value coming from the sensor.

And while you are doing smart investments anyway, you might consider a compression tester, because it seems there is something wrong with cylinders 5 and 6, as ice445 already mentioned.
 
1 - 19 of 19 Posts
Top