Misfire cyl 7
 

Ok - so I have a disco II with 107k miles on it, and new magnecor wires and plugs(3 months). and this only happens at highway speeds: when I am driving 70MPH and let the truck coast off the exit(foot off of the gas pedal), the rpms come down, and when I hit the gas to re-enter the next highway, it stumbles a bit and throws a misfire on cyl 7 with no other codes.......this never happens when just driving round town - just at higway deceleration followed by strong acceleration....any ideas?

are you losing any coolant?

no - and headgaskett was replaced 1.2 years ago

have you pulled the plug to see how it looks?

The plugs look good - a nice gray - the code I get is P0307 and the rave says:

P0307 Cylinder 7 misfire detected - Injector 7 excess emissions/catalyst damaging level of misfire


is it a bad injector?

Sticking/leaking injector?

so do I clean it or replace it?

Sometimes you can get it to clean up with a couple of bottles of injector cleaner. The times I've seen them leak it usually ends up a replacement though.

Has anyone replaced a Fuel injector - I.E. is it a DIY or Indy Shop job (easy or tough to do)

I was chasing a random misfire on 6 & 8.
Only happen when I let off the gas at speed on cold days, below 30 or so.

Found that one of the air box lid locating tabs had folded over and was extending across the foam seal of my air filter.
Once I corrected this the problem has gone way?
Don't know why this would effect anything since it is before any sensors like the MAF but my misfires are gone.
I have read posts by others that if the air box is not sealing properly you can get misfires.
Just throwing it out there, something to check.

As far as replacing an injector being DIY, for me yes but I have done my head gaskets myself.
You have to remove the upper plenum to get to the fuel rail.
A few bits to remove to do it but not bad.