So I have a 2004 XJ8 and a few months ago it started throwing the P0175 code, typically only when the fuel level was low, but then more and more often. It only comes on within a few minutes after any start of the engine (warm or cold, doesn't matter), and when i clear the code, it does not return no matter how i drive. The idle will also go from rock smooth to "lumpy" (throbby - that's the only way i can describe it), then back to smooth again periodically, irrespective of whether the code has been cleared or not. It runs just fine when not at idle. I've done the following things to try to correct after reading these forums:

• Replaced all fuel injectors
• Replaced PCV valve (note that there's always oil at the connection to the air intake past the throttle, even after i changed the PCV valve - I'm thinking this is a likely symptom of what ails the poor car)
• Replaced ECT sensor
• Cleaned MAF sensor
• Tightened up all vacuum connections wherever I could find them
• Checked hose from driver's side valve cover to air intake upstream of throttle (hose and connections are clean, no oil, no leaks)

Any thoughts? I'm kind of at my wit's end with this, every time I think i figure it out, it comes back. To me, the following things are significant:

• oil at the PCV discharge into the air intake
• the fact that once I clear the code after driving for a minute or so, it does NOT come back until I turn the car off, then it will come back when I restart. This is always the case, no matter how I drive after I clear the fault code

Thanks!
Rick

 

your new injectors may be trash. other person on here had a never ending p0175 story because of fake injectors

monitor fuel pressure and make sure sensor is good

 

Oil in the pcv system is normal.

If you do a lot of short journeys oil builds up in the corrugated pipework and if

you give it a blast (kick it down) on a long straight road you will get clouds of white smoke

from the exhaust as the engine sucks in the oil.

Otherwise it does not seem to cause a problem.

 

By law it's a 2-trip code so of course it behaves like that.

I guess if the law allowed it, it would return far sooner.

 

Thanks for the thoughts. I'll watch the fuel pressure. One thing I noticed today when I checked "pending faults" is that P1000 is pending. Don't know if that is always pending, but I'll keep an eye on it. That's an "ECM Fault" code. Any connection?

 

P1000 = system check not complete

P1111 = all clear

if you keep clearing codes you will always have a P1000

 

ah, thank you. That makes sense.

 

It's not a fault code, it's a status code meaning the OBD monitor have not set (aka run happily).

With P1000 many codes cannot flag (& in many places it's a smog fail due to the unset monitor(s)).

Stop clearing!! You're not helping yourself and your car could (but hopefully doesn't) have a serious fault it can't reveal.

It should change to P1111 meaning the monitors are all set. Codes can then be flagged (if any need to be).

 

OK, I'll run for awhile without clearing, see what other codes show up.

Does it matter that it only shows P0175, never P0172? To me that seems like it should indicate an issue on only one side, so common issues like MAF or ECT don't apply. Or does it just hit whichever side P0175 represents first?

Thanks.

 

Ok, just drove about 30 miles on the highway, and did not clear the CEL. After about 3 miles, the Limp Mode announcement went out, and I was able to Rev above 3000 rpm. I also tracked fuel pressure and "Fuel Trim" on Bank 1 and Bank 2. Don't know what that reads, but I figure they should read about the same, which they didn't. See the attached screen shot. Bank 2 always reads positive, and higher than Bank 1.

Thoughts?

Bottom 2 gages are fuel trim sensors bank 1 (left) and Bank 2 (right)

 

Do you have P1111 yet?

If you read the freeze frame data, it may show whether it was close to flagging P0172 as well.

But yes it could well mean an issue on one side (such as a part-blocked/part-failed cat).

 

no, never got p1111. "Pending Codes" just lists the P0175 and P1000...

 

So look at which OBD monitors are unhappy, then try their drive cycles.

If they won't set, report which ones but bear in mind many codes can't be flagged to help you until P1111 occurs. If it doesn't you can be in Catch-22 (which is why clearing codes is a risky thing to do).

 

So it just threw these pending codes. Bank 2 is definitely unhappy. Does this point to anything? It never did move to "verified" faults, but just kept them in pending...

 

clearly bank 2 isn’t working right.

may be just one cylinder causing sympathy misfires. new injectors still highly suspect

 

thanks. Guess I'll try swapping them left to right and see if the faults move to Bank 1.

Could it have anything to do Werth the O2 sensors?

 

Update: I took the car on a short test drive in the neighborhood, after about 5 minutes I did a 3 point turn, and when I shifted from reverse to drive the car took off, I couldn't hold it back with the brakes and when I shifted to neutral it ran up against the Rev limiter. Turned it off and on a few times, each time I turned it back on it revved to the limiter (7000ish rpm). I finally unhooked the battery negative cable, reconnected after 1/2 minute, and the car ran like normal after that. Needless to say I'm pretty shaken and not going to drive it until I get this sorted.

Anyone have issues with runaway engine?

 

Something you did caused it. Try to figure what you've done!