I'm at my wits end I have a po171 code and a Missfire that started today after I got gas i highly doubt it's bad gas since my I filled up my other 2 vehicles with the same gas at the same pump today all with in one hour. The XJ is missing sounds like it's running on 5 cylinders. I've replaced the plugs wires cap and rotor. Firing order is correct also. But it still is only firing on 5 any one have any ideas I've tried swapping wires one at a time and no help at all

 

Hmm..a couple of the problems associated with that code are incorrect fuel pressure or faulty fuel injector. Have you check the fuel pressure yet? Might be an injector starting to go maybe?

 

I dumped a can of seafoam in the tank and replaced the plugs but I belive I got some crud on the electrode of #1 the p0171 went away so now I have P301 so #1 Missfire. So I'm gonna try a new plug and wire. If that is of no help my neighbor is parting a XJ so I'll just get an injector from him

 

Well found the issue damn #1 I wish that plug was easier to install

 

Yep that'll sure do it. Glad it was an easy find.