Missing 4.6 V-8

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Brad Behm - 28 Oct 2006 17:02 GMT

Hi,

My '95 Town Car with 4.6 SOHC V-8 is missing on the # 1 cylinder. The
computer says so, and the spark plug indicates incomplete combustion as it
is pretty black compared to all the others. Sometimes it the engine
backfires into the intake plenum especially under acceleration. I have
eliminated the coil pack (swapped sides), spark plug (replaced all) , and
spark plug wire (replaced) as the problem. Should I be looking at fuel
delivery i.e. plugged injector, or even valve train problems or is there
something I have overlooked in the ignition sector? My gut tells me it's
ignition related, especially because of the intermitent "cough" up the
intake manifold...reminds me of crossfire. Is there an
electrical/electronic component that would only effect the # 1 cylinder that
I haven't already checked out, or should I move on to fuel or valve train?

Thank you in advance anjyone who can help me.

Brad

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Brad Behm - 28 Oct 2006 17:07 GMT

BTW, the post below "Cylinder Missfire" describes my symptoms very
similarly.

Thanks Brad

> Hi,
>
[quoted text clipped - 15 lines]
>
> Brad

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Backyard Mechanic - 28 Oct 2006 18:06 GMT

> Hi,
>
[quoted text clipped - 12 lines]
> only effect the # 1 cylinder that I haven't already checked out, or
> should I move on to fuel or valve train?

Remeber when you used to pour gas into carb throat to start an engine,
how it might 'cough'?

COULD also be sticky/leaky injector. But the OTHER plugs in that bank
should be whiter than normal, as the system tries to lean out based on O2
sensor feedback.

START with warming the engine then disconnecting MAF connecter to see if
it runs better. If so, clean or replace the MAF (clean should do it.)

Borrow a timing light to see if the coil is actually firing regularly.

Signature

Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!

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DeserTBoB - 28 Oct 2006 18:51 GMT

>Hi,
>
[quoted text clipped - 5 lines]
>spark plug wire (replaced) as the problem. Should I be looking at fuel
>delivery i.e. plugged injector, <snip>

No.

>or even valve train problems or is there
>something I have overlooked in the ignition sector? My gut tells me it's
>ignition related, especially because of the intermitent "cough" up the
>intake manifold...reminds me of crossfire. <snip>

If the plug wires are original with high mileage, there's a chance for
cross induction from one to the other if one of them goes high
resistance, but if the leads are all dressed the same way they were, I
don't think so. You should, just for drill, check the DC resistance
of your #1 and adjacent plug wires just to check.

This sounds like an intake valve hanging up, which I've seen on the
4.6L before. Compression will test fine at cranking and idle speed,
then the intake valve will start to hang up (or close late) at power
speeds, causing a backfire into the intake.

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Brad Behm - 29 Oct 2006 17:55 GMT

Bob,

Thank-You for the post

What specifically was causing the intake valve to hang up in the 4.6 you
saw this occur in? Was it a stem/guide issue,
or was it related the the valve actuating equipment? I swapped # 1 injector
with
the adjacent cylinder and cleared the codes hoping when "check engine" comes
back on it will indicate problem in the swapped cylinder rather than # 1. If
that doesn't pan out
I can't think of anything left but valve train malfunction. What do you
think?

Thanks Brad

>>Hi,
>>
[quoted text clipped - 24 lines]
> then the intake valve will start to hang up (or close late) at power
> speeds, causing a backfire into the intake.

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DeserTBoB - 29 Oct 2006 21:23 GMT

>Bob,
>
> Thank-You for the post
>
> What specifically was causing the intake valve to hang up in the 4.6 you
>saw this occur in? <snip>

There have been cam follower breakage problems on these. Why not save
yourself all this labor and just pop the valve cover?

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George Jaynes - 28 Oct 2006 20:12 GMT

Try some Sea
Foam in the tank

> Hi,
>
[quoted text clipped - 15 lines]
>
> Brad

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septicman@peoplepc.com - 29 Oct 2006 16:22 GMT

Brad,

These engines are prone to having the cam follower pop off, making
either valve inoperable. Do a compression test of the cylinder. If
there is zero compression, it could be because the intake is not
opening at all.

Land O'Lakes Fred

> Hi,
>
[quoted text clipped - 14 lines]
>
> Brad

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Brad Behm - 29 Oct 2006 17:47 GMT

Fred,

Thank-You for the post

Compression is fine...but that's at starter moter speed. Is there some
other valve train related problem that could be causing the intake valve to
hang up that may be typical with this motor? I swapped # 1 injector with
the adjacent cylinder and cleared the codes hoping when "check engine" comes
back on it will indicate problem in the swapped cylinder rather than # 1.
Short of that I can't think of anything left but valve train malfunction.
What do you think?

Thanks Brad

> Brad,
>
[quoted text clipped - 27 lines]
>>
>> Brad

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Bob - 30 Oct 2006 04:26 GMT

Even if the compression test looks normal it doesn't mean the intake valve
is opening.
Bob

> Brad,
>
[quoted text clipped - 27 lines]
>>
>> Brad

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Brad Behm - 30 Oct 2006 05:31 GMT

To all of you helpful gentlemen my problem has been solved!!

Last night I swapped injectors and then cleared the code, hoping a new
trouble code would
indicate a miss in # 2 where I put the injector from the troubled # 1
cylinder.
As an afterthought I swapped plug wire #1 and # 7 even though I had already
checked for a bad plug wire to #1 by substituted a plug wire off my son's
Escort a couple weeks ago when the problem first began. Back when I did
that, the car still missed with different plug wire, new plugs and new coil
pack installed on the right bank. I'd pretty much ruled out an obvious
ignition problem.

Well...To my delight this evening when I checked the new trouble code,
cylinder # 7 was missing. HAD to be that wire!! I installed a new set of
wires and presto! NO MISS!! Evidently my son's Escort needs wires
too...just my luck to use a bad wire off his car to test whether I had a
bad wire in mine!! Lesson learned: Take nothing for granted! THANK YOU ALL
for
the supportive posts!

Gratefully Brad

> Hi,
>
[quoted text clipped - 15 lines]
>
> Brad

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Steve Stone - 30 Oct 2006 14:22 GMT

>> My '95 Town Car with 4.6 SOHC V-8 is missing on the # 1 cylinder.

I had a similar problem with my 95 T-Bird.
The factory plug wires have gone thru at least 6 engineering changes.
Buy a set of OEM wires. They will cost between $100 - $130 depending where
you purchase them but the aftermarket wires for this car cause more grief
then they are worth, especially when you have to route the wires under the
alternator.
The under hood electronics of the 95 model year are very prone to picking up
noise from aftermarket wires resulting in some really weird problems, like
the car working fine until 45 mph and then bucking and missing over 45 mph.
In 96 Ford made some subtle changes to the module layout bolted to the inner
fender wells and that seems to have improved things. For a temp solution
until you get the wires try wrapping the plug boot of the failing wire with
black electrical tape (not too thick, you want to get it down that deep hole
and onto the plug). Make sure you use dielectric grease on the boots when
you install the new wires.

My results were on a 95 T-Bird, not a Town Car, but this is the same year
and same engine.

Steve

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