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Missing 4.6 V-8

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

Reply to
Brad Behm
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BTW, the post below "Cylinder Missfire" describes my symptoms very similarly.

Thanks Brad

Reply to
Brad Behm

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.

Reply to
Backyard Mechanic

No.

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.
Reply to
DeserTBoB

Reply to
George Jaynes

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

Brad Behm wrote:

Reply to
septicman

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

Reply to
Brad Behm

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

Reply to
Brad Behm

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

Reply to
DeserTBoB

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

Reply to
Bob

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

Reply to
Brad Behm

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

Reply to
Steve Stone

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