I have a 97 discovery xd pulled the codes it said I had #2,#7 injector miss firing and I had y pipe issues. so the first thing I did was pull the y pipe and did notice it was bad replaced with new one replace both injectors. problem I am having at idle it runs fine once you hit the throttle it miss fires and sputters checked the pressure at the rail it is 38-39psi what do I need to check.

 

Check Crank sensor and wiring, has engine or trans been out? Starter? I ask cause you could have bent tabs on the reluctor

Also check your firing order

You have an ultra gauge or similar to look at what your sensors are doing?

 

What exactly where the codes.....?

 

Sorry for taking so long traveling now for work. I had
P1316
Misfire Excessive Emissions Fault




P03O2
Misfire Cylinder 2
P0307
Misfire Cylinder 7
P0430
Catalyst Efficiency Low Fault Bank B
I have removed and replaced the Y pipe with a new one cause the old one was in pretty bad shape same thing with the plug wires and coil pack they looked pretty beat up so I replaced them after doing this still have the same issues as before idles fine until you step on the throttle then I cuts in and out and will back fire.

 

I don't think either of them have been out I bought it used and don't think they have been out I have put in a new crank senor in the beginning thinking this was the issue I don't have a gauge at home thinking of buying a vacuum gage and going this rout

 

Remove spark plugs on 2 and 7 and see if they're wet or dry. Wet (soaked and clean) can be injector stuck or broken wide open. Dry (bone dry, no soot) would be due to plugged injectors which is very common and is what I think your problem is. Backfiring is just ignition overlap (other cylinders over-fueling to make up for the loss) when your putting the pedal down, it idles ok (no load) hence occluded injectors - engine at idle requires less fuel. Do you smell raw fuel?

 

I came across this thread and think I can relate to the situation with D1 '96. I've got a Cylinder 7 Misfire and after changing the plugs and wires, I still have a rough idle. Engine starts fine and runs, no stalling, but after it runs for a little bit, I can get this strong smell of raw fuel. Why is that?

 

Possibly an injector staying open dumping fuel into a cylinder

 

Did a compression test yesterday and it didn't even hit 30psi on Cylinder 7. Valve stuck, do you think? I ran some seafoam through the system and will retest compression today to see if any improvement.

 

Maybe compression test all eight for comparison, but 30 is way low. Typical for mine is 140 - 160 psi.

More likely than stuck valve, could be head gasket leaking towards the rear coolant passage. Maybe test for exhaust/bubbles in the coolant tank.