Hi All,

I just got a check a check engine light with the following codes:
P0087 - Fuel Rail/System Pressure - Too Low
P0088 - Fuel Rail/System Pressure - Too High
P0193 - Fuel Rail Pressure Sensor High
P0411 - Secondary Air Injection Incorrect Upstream Flow Detected
2006 XJ8L 4.2L. I now have about 210k miles, and with the codes it's running without any performance hindrance.
I'm leaning toward starting with replacing the fuel pressure sensor. Before I start buying/replacing parts, I just want to see if anyone had any thoughts on the issue.
Any help and any direction where to buy parts is sincerely appreciated.

 

You can obtain parts from any of the forum sponsors, such as SNG Barratt.

Before you begin condemning and replacing any parts, what is the voltage across the battery terminals with the ignition in the OFF position when tested with a voltmeter?

 

12.58 volts.
By the way, from a cold start last night, it idled at 1500 rpm (which it doesn't go that high) for several seconds, then when it started to come down, it just completely stalled at its regular 6500 rpm. It did this twice. Third time I gave it a little gas to keep it from stalling. That worked, and it idled normally without any further intervention.

 

So all the codes went away on their own today. I'm speculating that the sensor is the culprit, as previously thought. Any input at this point would be really helpful.

 

Check FP sensor wiring for damage or bad connection.

Spigot on sensor can crack leading to vac leak.

 

Have the battery load tested as it's marginal.

 

Yesterday evening, on cold start, CEL returned (I haven't yet checked codes, but assuming same), but no surge and stall when idling. As I was driving home, it was bumper to bumper on the freeway. About 5 miles in, when accelerating from about a 5 MPH crawl, there was serious loss of response/power (to a second or two to get moving when pushing accelerator). When I made it home, the engine had a serious shake at idle, like it was going to stall. This morning it took a look at the FP sensor, no visible cracks or play (it looks solid). However, with the input from @meirion1 , after careful inspection I noticed one of the vacuum tubes connected a short ways away, inward, was partially (half way) off. I reconnected that and checked the rest of the lines. On cold start, still have CEL, but no problems with idle. While driving, I noticed increased performance, no hesitation, no loss of response/power... it felt like there was a slight performance boost. I'll keep my eye on it and report back with the codes, photos, and further progress. Thank you!

 

That's not a test of the sensor and would not reliably detect a bad one.

Any even tiny air leak can be expected to cause trouble. Slightly more than tiny and an engine cutting out is hardly surprising.

It sounds like maintenance needs doing urgently.