2010 XKR 5.0, 75k miles.

So, as some of you may have seen my 75k mile carbon build up thread. What started that endeavor was a cylinder 7 misfire/restricted performance.

I started with plugs. Put new plugs in. No change. Swapped coils around. No change. Got pissed and ripped off the supercharger, cleaned the intake valves, put 8 new injectors in. Start it up today, have cylinder 2 misfire (#7 misfire is fixed) . Swap coils with 1, no change. Swap plugs with 1, 2 looks brand new unfired almost, 1 looks fired.

Does anyone thing that brand new injector is faulty? Or could there be another explanation for this.

 

Not questioning your skill-set, but double-check that you have put everything back together correctly and completely. It may just be a silly over-sight of a wire here, or something else there. It's easy to miss something especially when you are rushed or pissed off.

 

Checked and double checked...the 5.0 is strikingly a very easy engine to work on....but this has me stumped...and the thought of having to pull the fuel rail again has me depressed.

 

Swap the injectors, similar to the coils. PITA but it isolates the replaceable components from another problem. In the Navy we called it half splitting the problem. Pick a point 1/2 way between known good and known bad and check there.

 

The reason i havent done that yet is because it's direct injected...the Teflon seals and retainers need to be replaced anytime an injector is removed...so they say...

anyone have any experience NOT doing this?

 

Yep, and there's a special tool to first stretch the seal then another one to shrink it back down in two stages.

 

Yeah, a special tool and seals I don't have on hand, and hoping to solve this tomorrow before I have to go out of state for work the next few days.

 

Moved #2 coil to #8. Now have misfire code for 2 and 6...wtf is going on here

 

When is the last time you did a Hard Reset? It helped a problem of mine once before.

 

Battery was disconnected over the last 2 weeks while I've been working on it. Otherwise it's just been me clearing the codes with torque pro

 

I feel your pain. While it is possible that brand new injector is faulty, when you heard hoofbeats, think horses and not zebras.

Have you considered that this issue may be fuel pressure related and not injector related? If one of the second stage pumps is marginal it can wreck all kinds of havoc with DI and look like injector's fault.

 

It has crossed my mind, what is nominal pressure supposed to be? I'm getting over 2k when I rev it up, around 900 ish at idle

 

What codes are you getting and are they just moving to different cylinders as you make the swaps or are you getting new ones too?

 

Misfire cyl 2 seems to stay constant, along with misfire detected within first 1000 rpm code. The other cyl misfire codes come and go as I switch. Out of state at the moment but when I get home all new coils will be waiting, so if at the least I hope I can rule out a bad coil. I'll have a new engine before too long!

 

New coils. New injectors. New plugs. Still a cyl #2 misfire. P0302 & P0316 ...No other codes.

I'm about to burn it

 

Do a compression check on all 8 cylinders. Possible a carbon chunk held the valve open and it got bent. It happens and doing the test will help isolate the problem.

 

What is strange is this whole thing started with #7 mis-firing. Then after all of the work it's now at #2. Hard to believe a new injector would be bad but you never know. Did you or can you use a noid tester to see if there is power to the injector. Also when you pull the plug what does it look like. Dry or wet . As I said something strange going on.

 

2 brand new injectors...I pulled the first new injector tonight and put in another brand new one. No change.

 

Plug looks dry, almost un-fired. Going to pick up a noid tomorrow and really start to trace back all my wires.

 

O2 values show low on bank 1. So I'm lean due to the misfire.