1998 Mark VIII Rough idle/sputters out when I start it after a 20 minute drive.

[32vmeach]

Just purchased a 1998 Mark Viii LSC with 89k for 3000, I’m having problems though the car runs great when cold but when it warms up and you shut it off it doesn’t run smooth it idles real rough and will sputter out. I read one thread and the guy had a 97 with similar issues he changed his crankshaft position sensor and it fixed his issue, I just changed mine and the issue persists though! Can yall please help me out?



1998 Lincoln Mark VIII LSC
32V 4.6

 

[xtriggerman]

The basic things to check are the vacuum lines coming off the intake. Once the rubber gets hot it may let more air suck threw them. also, check the spark plug ports for oil infiltration. Once there is enough oil filling around the spark plug, you can get just what you are saying about rough running and the big fuel filter behind the right side fender pan should be changed out. I have a little over 100K on my 97 and it runs like a jet. Good Luck

 

[32vmeach]

The basic things to check are the vacuum lines coming off the intake. Once the rubber gets hot it may let more air suck threw them. also, check the spark plug ports for oil infiltration. Once there is enough oil filling around the spark plug, you can get just what you are saying about rough running and the big fuel filter behind the right side fender pan should be changed out. I have a little over 100K on my 97 and it runs like a jet. Good Luck

Changed the plugs today and found oil on one of the coil packs what could this mean? A valve gasket leak? Or what would make there be oil on one of my coil packs?

 

[xtriggerman]

A common problem on these 4.6 engines. The Valve covers usually start leaking as you found out. I had 2 leakers 20K ago and haven't looked at them since but know the valve cover gaskets need to be changed. I think the drivers side needs the engine jacked up only on that side to get the cover off. Could be the passenger side, seems I'v read its one side or the other that needs a slight jacking up to get the cover to clear. I'v yet to get a shop price on it. I also have the oil pan seeping slightly when driving. That fix would cost about 700 for a oil pan R&R since the entire K frame has to come down. Also if your oil filter housing plate hasen't been changed, it will sooner or latter. I just did mine last fall. LOTS of small to medium issues with these cars. If your handy enough to stay on top of them, they are great cars that for their age give you about 300hp and up to 25mpg on the interstates. A 6 + second 0-60 is not too hard to pull off on these 3800lb cars. For the 3 grand you have in the purchase, its alot of ride for the buck.

 

[xtriggerman]

Should have said, oil filter housing "gasket" not plate.

 

[32vmeach]

I’ve currently changed crank shaft Position sensor, pcv valve and spark plugs and the rough idle sputter out still persists, is there anything I can do outside of new valve cover gaskets to get this problem to stop?

 

[xtriggerman]

Could be a bad coil pack, give that a try or even a bad fuel pump if the filter is good.

 

[04_Sport_LS]

I’ve currently changed crank shaft Position sensor, pcv valve and spark plugs and the rough idle sputter out still persists, is there anything I can do outside of new valve cover gaskets to get this problem to stop?

Injector "leak down" causing engine "hot soak" ?