tracing a lean issue and misfires. now the car just misfires on #3 via snapon scan tool with a misfire at startup. I'm presuming its #5 on startup because it doesn't show on the counter but gives a misfire code for #5. strangely #3 is the misfiring cylinder. so my question is what is to low a fuel pressure for proper operation? ive done many things to fix this car swapping sensors bank to bank new fuel filter, inspected air filters, swapped coils, new plugs swapped after since misfire zeroed in on #3.
Could the fuel pump be going and #3 is the weakest injector?
Could the fuel pump be going and junk made it past the filter and be messing with the rt bank as #7 had the issue before #3 after installing new plugs?
also was giving misfires for the whole odd # bank at times with a preference for just 1,5,7 with random. cats passed backpressure test and camera inspection. I've posted elsewhere but this is specific to fuel pressure as i don't want to replace things unnecessary and costly for the customer and frankly this kitty is baffling me.

 

Are there codes for too low , too high fuel pressure?
too rephrase is kitty smart enough to tell me pressure to low.
issues that don't give codes are the most expensive part in the end no?

 

Lean codes can be caused by leaks in the air induction system. Vacuum leaks. Your system has been off a number of times, and the cracks in the plastic could be getting larger, with each removal.

 

Which plastic are you referring to? The big air inlets? Or the pcv lines. They apear good cant feel the right side large libes termination point. And it preemptively siliconed the termination of the push lock line. The inlet tubes appear bulletproof

 

Though misfires can be caused by vacuum leaks, the way to see of you're having leaks is to look at the Long Term Fuel Trims (LTFT). They ideally should be zero %, but it's fine if they vary to +-5% or so. Postiive LTFTs mean the ECU is adding fuel as it tries to reach a Lambda of 1, because there's unmetered air entering the engine vacuum envelope. If you have +10% or more, you have a vacuum leak that needs correction. An example (or test, if you want): I have a good o-ring seal on my dipstick. The other day I was working on the engine and saw both LTFTs up around 7-10%. Mine operates pretty close to 0%, so I looked around until I noticed the dipstick was up a couple of cm, creating a vacuum leak. Pushed it in and the LTFT readjusted to normal in a few minutes. So, I know I have no vacuum leaks.

The best way to correct vacuum leaks is a smoke test. $100 tester from Amazon does the job very well. You'll need an air compressor as well -- the pancake type used for air tools should work fine.

 

You mentioned the fuel pressure can drop to 45psi. Most systems need 55psi. Your problem could be there.

 

companion misfire

unplug ip sensor it will run decent without it

 

Fuel pressure dips while driving. Setting misfires now just normal driving. Previous was just setting misfire when high 4k plus rpms. Smoke machine ordered should show up sat or monday.

 

Fuel pressure dips while driving. Setting misfires now just normal driving. Previous was just setting misfire when high 4k plus rpms. Smoke machine ordered should show up sat or monday.

 

Fuel pressure damper could be the cause and it is a cheap part to switch. Part # AJ83838. Ford has them as well.

 

From page 1894 of 4000 in the XK 4.2l workshop manual, one of two things could be at fault. Fuel Rail Pressure Sensor, or Fuel Pump Control Module.
Probably the first one.

 

I fitted a new Fuel Pressure Sensor/Regulator in my 2006 XK a couple of months ago. A cheap part which took literally 10 minutes to replace as it is so easily accessible at the front of the right-side fuel rail under the bonnet/hood and all misfire/fuel pressure problems are now fixed. I changed the fuel filter as well as I had bought a new one but the sensor replacement had already sorted the problem.

Richard