99 4.6 skip on 4 and 8

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#1
skip came on today for the first time, been running fine, code for skip on 4 and 8

driving showes 20lb boost on acceleration

Any ideas?
 

kev2

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#2
PLEASE whole sentences....
>vehicle year amke model eng trans color
>Codes Pxxxx
> Symptoms - runs rough etc
> work done repairs etc
 
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#3
I wasn't trying to write a book,
it's a 99 Grand Ma, they're all auto OD's
it's skipping
has a code 304 and 308
 

kev2

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#4
the codes are likely P series codes ie P0304 and P0308

simple easy - the PCM sees a misfire on those cylinders- #4 and #8.
BASICS is there spark at those plugs- are the injectors pulsing a 'NOID" light will make quick work of that ck...
a fuel pressure check AND a fuel pressure leak down will help checking fuel injs, finally a compression test.
 

Gus

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#5
Worth are you trying to pull our legs?

Everything you have written is misinformation.....

1999 Grand Ma or Am? With a Grand Am, you either have a 2.4 or a 3.4.....If you have a 1999 Grand Ma, you and your mother must be very young.....

4.6 is a Northstar engine, which would never be in a Grand Am.....

20# boost on acceleration? Now we are talking a supercharger? WTF?
 
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#6
Sorry, grand marque, and I put my bluetooth scanner app on it and for some reason It is showing boost on accelleration. And no it doesn't have a turbo or a SC. Only thing I dould think of is if it is pumping exhaust into the intake if that is possible.

For some reason I've never had these problems on my 65 pickup :)
 
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#7
Oh and I'm gonna wait til tomorrow to check it out, we've been hovering in the low teens the last few days, suppose to be 40ish tomorrow. I was just trying to get some knowledgable insight before I go snooping around.

I do have a noid set so I'll go there if I don't find something else first.

I've never really watched a vacuum gauge while I was driving before unless it was a turbo or SC car, so I'm guessing the only possibility is some type of EGR malfunction if that's possible.
 

billr

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#8
I was guessing it was a Mercury Grand Marauder. See? It is really important to give clear info.
 
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#9
Sorry, I live on Cape Cod, there are more Grande Marques here than the entire state of Florida, it's turned into blue hair city here. You'll have to excuse my slang, by the way did they ever make a Grande Marauder? I thought Marauder was there HIPO sedan?
 

kev2

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#10
your 65 pick up uses the same BASICS...
with the computers things are done electronically, only some new terms with the new technology, a missfire is a missfire - a spark a spark.
 

bp042665

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#11
also i have found on a few ford 4.6L a bad vacuum fitting on the back of intake and it affects the back two cylinders and make them skip easy find with carb cleaner but it could be a coil or a plug or even a plug boot
with 2 cylinders at the same time im leaning to a vacuum leak
 
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#12
that made the most sense to me, I gave it a quick glance yesturday but it was freekin freezin out there and that engine is tucked under the firewall so I couldn't see crap. Unfortunatly I have a run tomorrow to Conn. for a load of stone, so I'll have to look at it Saturday.
 
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#13
OK, couple of things happened, first I didnt' get to it until this morning, and the temp is now 55 degrees out.

When i scanned it this AM it only came up with the #8 cyl misfire. So I swapped out 7 and 8 coils and just for the hell of it I also swapped 3 and 4.

the skip did move to 7 so I replaced that coil and at the moment all is well.

I'm guessing the temp may have something to do with it so I'm expecting # 4 skip to come back,(it's actually in #3 now). But I had to pay 69.00 bux for the coil in town so I just bought the one , and ordered a pair of them from Rockauto for 31.00 each to put on the shelf.

OH and just fyi, when I swapped out the coil and cleared the codes, I had to drive it about 15 miles before it showed up on 7, although it was skipping all the way. I would have thought it would be a lot quicker but I guess not.
 
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#14
"I had to drive it about 15 miles before it showed up on 7, although it was skipping all the way." I hate when the PCM is so reluctant to set a code. Sometimes it is faster to disconnect a coil and run it to see if you can tell the difference between one bad cylinder or two.
 
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#15
No shit, you would think a computer, fast enough to decide it has a skip on a particular cylinder, would be able to find that skip instantly.

After I did the swap to 7, when it wouldn't set a code I drove it to a buddies shop, we put his Modis on it and saw the skip on 7 and it still didn't have a code.

That's either a programing error or intentional misinformation, not sure which.

I still like working on my '65 better.