Grand Marquis feels like misfiring - transmission?

[Black_Thunder]

I would start with plug wires before anything else.


the 4.6's were very sensitive on what kind of wires that they had on them, and if they get old etc.


See if it has the original wires on it or if they are aftermarket, I would put motorcraft wires back on it and go from there.


I've own several 4.6's with the 2 coil system mounted one on each side and haven't ever had one go bad so I would firstly start with the wires.

 

[Linctex]

Originally Posted by clinebarger
Ford's are notorious for NOT setting misfire trouble codes, I see them come in all the time with DEAD holes....


AGREED!!!!!

And having those molded coil packs fail is also very, very, very common

 

[Lubener]

Don't do anything until you atleast check for codes. If you had a misfire, a code may have been initiated, pointing towards the affected cylinders. My G.M. issued a misfire code when I had a coil pack break down. I hope you took the tranny out of O.D. when you were driving up those mountains.

 

[irad]

Uphill misfire is a sign of a bad ignition coil/ pack. Could be a bad wire or spark plug too.

 

[MuzzleFlash40]

I had a 1994 that was doing the exact thing and it was a bad mass air flow sensor. You'd punch it and it would act like the trans was slipping and wouldn't accelerate and sometimes backfire. Turned out it had a bad MAF and a fouled out plug.

 

[Cujet]

Originally Posted by Nick1994
Sounds like a bad catalytic converter to me.

Sometimes they don't plug up, they'll break a chunk off and restrict flow.



That's my guess too.

 

[SwampSurvivor]

Originally Posted by clinebarger
Ford's are notorious for NOT setting misfire trouble codes, I see them come in all the time with DEAD holes....Missing like mad with no trouble codes!
That's where Mode $06 data becomes your best friend!


A very long time ago, I had to drive mine 2 hours with a dead coil. Was in the absolute middle of nowhere with no cell service and was towing a trailer. Didn't set a misfire code.

 

[OVERKILL]

Originally Posted by Miller88
Originally Posted by clinebarger
Ford's are notorious for NOT setting misfire trouble codes, I see them come in all the time with DEAD holes....Missing like mad with no trouble codes!
That's where Mode $06 data becomes your best friend!


A very long time ago, I had to drive mine 2 hours with a dead coil. Was in the absolute middle of nowhere with no cell service and was towing a trailer. Didn't set a misfire code.


Yup, my Expedition had some pretty high misfire counts in Mode 6 and was breaking down hard under load, absolutely not CEL. Of the three coils I replaced on that truck, I don't recall any of them triggering a CEL.

 

[scurvy]

Y'all are pretty funny, still posting what it could be. The OP already posted the solution!

Originally Posted by spk2000
...Took it to a small shop along with coil pack and said he would change it for $50 but he didn't think it was the problem. It fixed the problem and he was surprised so thanks again everyone.

 

[OVERKILL]

Originally Posted by scurvy
Y'all are pretty funny, still posting what it could be. The OP already posted the solution!

Originally Posted by spk2000
...Took it to a small shop along with coil pack and said he would change it for $50 but he didn't think it was the problem. It fixed the problem and he was surprised so thanks again everyone.



You may want to re-read that post:

Originally Posted by spk2000
My sable had a bad misfire and 3 shops including a dealership could not diagnose the problem or fix it. I was almost ready to give up on it and looked up common issues and the coil pack was a known problem. Took it to a small shop along with coil pack and said he would change it for $50 but he didn't think it was the problem. It fixed the problem and he was surprised so thanks again everyone.

 

[spk2000]

I never did mention car has newer plugs and wires. Used motorcraft plugs but NAPA wires last summer and have put less than 15,000 miles on them.

 

[kstanf150]

Originally Posted by spk2000
I never did mention car has newer plugs and wires. Used motorcraft plugs but NAPA wires last summer and have put less than 15,000 miles on them.


So the coil packs are factory ???

 

[spk2000]

I have never changed them but bought the car with 82,000 miles so not sure before my time.

 

[Black_Thunder]

I don't know how good of quality the Napa wires are as I have never used them.



On my father's 1998 F150 that he had years ago with the same 4.6 engine and coil setup as the cars I had a issue where it would stutter on acceleration, it originally had been misfiring because of a coolant hose leaking into the plug hole and while trying to figure out that issue I had changed the spark plugs and wires and then later found the coolant issue and after that was repaired it no longer misfired but for years it had the stutter/slow acceleration issue.


I had put in autolite plugs and then NGK's but the wires i put on were from Carquest.

after a few years I finally started over and put motorcraft plugs and motorcraft wires back on it and just like that the issue was solved.

 

[Y_K]

I change the coil boots at the same time I change plugs. The boots may look fine, but if you slightly squeeze and twist them, you may see a bunch of cracks

 

[Black_Thunder]

Was the problem solved? Just curious

 

[Black_Thunder]

Originally Posted by Y_K
I change the coil boots at the same time I change plugs. The boots may look fine, but if you slightly squeeze and twist them, you may see a bunch of cracks



While that is good information. The 4.6 in the early to mid 90s still had plug wires. It wasnt until late 90s that they started doing coil over plug and i think that started with the 5.4 as a lot of the f150s with the 4.6 still had wires and the 2 tower coils in the front of the engine