97 Lincoln Mark VIII LSC intermittent bucking/jerking under load


New LVC Member
Dec 14, 2022
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Hey guys, I'm a new member here who just bought his first Lincoln, a 97 LSC with 64k original miles. It ran quite nicely at first, but then it started bucking/jerking under light acceleration, usually just following upshifts (i.e. low in the rev range). At full throttle it seems fine, if a tad slow. I'm also getting abysmal fuel economy (the car says 15 MPGs), but then again I'm usually just thundering around town with OD off. Hard to keep my foot out of it, with this car.

I have replaced the spark plugs and boots--there was a some oil on the boot of the cylinder closest to the firewall on the passenger side, but none on the plug itself. I have also replaced the trans fluid with Mercon V, cleaned the MAF sensor, and replaced the air filter. The strange thing is this problem is very intermittent. The car will go days and days running amazing, and then suddenly it'll start bucking and sort of missing at idle.

Also, I should mention that the car ran fine all last week, and then I put a can of seafoam in the gas tank when it had ~1/4 tank of gas. Shortly after it started acting up again. I wonder if this could this be responsible?

I don't really know what to do next, especially since it's hard to tell if I'm dealing with an engine problem or a trans problem. Thanks guys. I hope people still come on this forum...
Thanks tom. I believe I also have clogged cats due to the infamous "rotten egg" smell I get when flooring it, so when I get the exhaust shop to address that I will probably get them to replace the o2 sensors also. Do you happen to know if deleting the 3rd cat is okay legally in NC? I'd like to delete it, then have a 2.5" catback setup. Any muffler preferences are welcome.
I know nothing about NC 3d cat delete law, but I'd be very surprised if it's legal - it's an alteration of the OEM emissions system. I used a Borla center mounted (2 x 2.5" in and 2 x 2.5" out with internal x-pipe) XL 400286 with Kooks headers. Be warned: the Trubendz 2.5" pipes fit around the gas tank is terrible. Review the Linc vs. Cad posts of complaints and the mods to make them fit. The Borla sound is deep bass and growling, but not too loud. Good luck...
Another thing to try is replace your fuel filter behind the passenger side inner fender pan and the sensor that sits in the top middle of the intake manifold. I think its called the IAT Intake Air Temp sensor. Its like a 1.5" round metal can with a wire plug out of it. Those are typically replaced where rough idle happens. I wrote up my pipes mod here. If your not going to do much in the way of engine power mods, I would go with a pair of 2.25" duals. They would be WAY easier to heat shield the tank and have them tucked in high n tight with a little working space to boot. I have an air intake mod in Article section also.
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Thanks triggerman. The fuel filter was one of the next things on my list. Would it being clogged cause poor fuel economy? I would think that if it was clogged, the engine would be getting/consuming less fuel, translating into at least okay fuel economy...but I could be quite mistaken. I've also heard you need special tools to change it, which is partly why I've been avoiding it. Also, which brand should I get? The only one I see available on Autozone's website is a unnervingly cheap Duralast one.
Its very simple to replace. I didnt have any special tools. I think its just Ford style pull off to the side clips. Its very much like a universal fuel filter. Pretty good size. Also you want to check the vacuum lines coming off the manifold. Any vacuum leak will mess with the AIT numbers going to the ECM. One of the most common is the vacuum to the EATC (AC control). Give those rubber lines a good look, You can see the cracks in then pretty easy. One kind of Vac leak will give you a default Air blowing only threw the windshield defroster vent regardless of what vent button you push.
I would also say you have a vac leak, as for the fuel economy. At the same time though, it sounds like you have what we have always referred to as torque converter shudder. Someone on here back in the day always swore by some stuff called (Dr. Tranny). LubeGuard 19610 Dr. Tranny. Comes in a 2oz tube I believe.

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