03 STR - only code so far is p0171 with restricted performance.
obd scanner shows Short term fuel trim bank1 bouncing around ranging from +15 to +25 at idle. If i blip the throttle some, sometimes it will settle back down to around +3. If I tease the throttle some more, it will sometimes go back to +15-+25. Checked the intake hoses and they seem good.

My suspicion is the passenger side crankcase breather hose or the valve it attaches to. The hose runs friggen forever from one side of the pesenger side cam cover to below/beside the throttle body.

While the engine was running, i took the hose off and it almost made the engine shut off. There is some serious vacuum on that hose.... a lot! Stopping the airflow with my thumb leaves a red mark. I expected the pressure to be similar to the driver side hose that runs to the intake tube right after the filter.

Is there supposed to be that much vacuum on that hose?

 

The pcv (pass. cam cover) and hose was just replaced in my 03 STR. It does have a large vaccume. The same code persists, causing me to think the intake manifold is leaking, as we swapped in new hoses and gaskets. Bringing it to Jag for them to figure out via a smoke test, etc.

 

that stinks. My problem is self inflicted... I was messing around replacing the intake tube from the throttle body all the way to the mass air meter with 3" pipe. After I put the stock tubing back on, I got the p0171. At first I thought I just didn't get a good seal on the TB. But after checking and double checking, I don't think that's it.

I removed the the breather hose to the passenger side cam cover. The connection was a little loose where it connects below the TB. Bad news is I could hear the hose cracking all over the place as I was removing it. Whether it is the cause of the leak or not, it needs to be replaced.

Any other vacuum hoses that should be replaced while I'm at it?
Let me know how it goes with the smoke test.

 

Due to your work with the intake plenum hose, your issue may be solved simply with clearing the code, but definitely shore-up the air intake hose to cam cover line (crank case ventilation). A common vaccume leak is the attachment of the brake booster vaccume line to the intake manifold. This was recently performed on my 03 STR and is accessed by removing the intake tube to throttle body, charge coolers, and blower. Did you disturb this line when messing with the intake tube to throttle body? Replace as many vaccume lines as possible. Check the line to the purge valve too (located drivers side, rear of engine, before brake booster). I'll likely schedule the trip to Jaguar 2nd week of May. Good luck.

 

the lovely brake booster vacuum line. yup, broke that one. fortunately i was able to replace it without removal of the intake. this post was very helpful in figuring out how to get it out of the intake. it is a booger to get at.

today i got my replacement hoses and i installed them all-
-breather valve
-hose from breather valve to below TB
-small hose to bypass
-small hose to fuel pressure regulator
-TB gasket

the evap purge valve hose is on back order, so i was not able to replace that. But, after checking the hose, i'm comfortable that it's ok.

it's still firing off the p0171.

I cleaned the gunky TB using sea foam and towels. I checked the TPS and amazingly it looked good and clean.

I did some more looking, and hooked up my laptop and got some captures- I tried pulling each vacuum line to see how it would affect the fuel trim. All of them affected both banks. None were isolated to bank 1.

Here are some captures with it all buttoned up-

short term fuel trim on bank one is all over the place. sometimes it flatlines at zero. sometimes it shows lean, sometimes really lean. It's really erratic like a sensor is failing. Since resolving my catalytic converter issue, I wonder if an O2 sensor got jacked up. Thinking of swapping bank 1 and 2 02 sensors...

Any help is very much appreciated!

 

Do the O2 sensors (*) look alike bank-to-bank?

Your car has linear (wide-band) ones upstream and the older type downstream. The upstreams should not switch in case you've seen that on older cars.

If you just watch them at idle, or rev it at a constant speed or blip the throttle, do both banks' O2s look very alike?

Swapping the actual sensors can be challenging as they can rust in so that you destroy one or more in the attempt....

edit: what are the LONG term trims? If they're not alike then chances are you have an air leak but just haven't found it and blaming the O2s will be expensive and time consuming!

 

Your O2's may be way out of range. I swapped in new O2's at 100k miles. Also check that the steel tube that runs from EGR to the passenger exhaust manifold is not rotted out. This recently happened to my 03 STR, resulting in a new EGR and its tube connecting it to the passenger exhaust manifold.

 

After work, I plan to get some more data. The o2 are easy to get at, no rust or corrosion and once broken loose, they come out pretty easy. Plan is to swap the pre-cat sensors, left to right and see if there is any change. I'll post the long term trims later.

What has me baffled is how bank 1 completely flatlines to 0 in spots for no apparent reason, then creeps back up

The EGR tube and valve seem impossible to get at- looks like all the heater hoses will have to be removed to gain access.

 

You may want to look at the downstreams too. They should switch but not often. If one fails to switch the PCM will try to shock it I think. Either way, the LTFTs before you do anything should be revealing. Both banks, at idle and then at 2500rpm. Both pairs of values should be alike bank-to-bank and if one or both reduces at higher revs you almost for sure have an air leak.

 

You can view the EGR and tube by removing the cabin air filter box (not a biggie).

 

idling fuel trim:
bank1
STFT = +2.2 to +5.5
LTFT = +19.5
bank2
STFT = -1.4 to +1
LTFT = +9

2500 rpm fuel trim:
bank1
STFT = +17.5 to +25
LTFT = +3 to +4
bank2
STFT = -1.4 to +1.4
LTFT = +4 to +6

this is really driving me nuts. wish i would have never messed with replacing the intake

 

Wow look at bank 1 LTFT. You have an air leak on that side, pretty much for sure.

You get a lean code at +25 (it's 25%). A good LTFT:
(a) is up to about 5
(b) does not flatten out at higher revs

The reason an air leak's bad trim flattens out at higher revs is that the leaking air is swamped by the extra air coming in properly at those revs. (Just stands to reason!)

Slight caveat: just could be something else such as a misfire. Misfires leave unburnt fuel & air so the O2 sees extra air. Think what happens next.... Yes, the PCM adds more fuel. It doesn't know not to because it's not psychic. All it sees is more O2 than expected so it adds fuel to fix it. If you're lucky it sees misfires (miniscule jerks in the CKP etc) are absent and flags misfire codes, but it can't always do that. (But this is rare compared to air leaks.)

 

You have an air leak related with bank 1. The only thing different was messing with the intake?

 

ok, so it definitely seems isolated to bank 1 since bank 2 seems unaffected-
if there is a leak, can i assume it is after the supercharger where the intake splits? What vacuum hoses or taps are there into the intake after the supercharger?

But, I didn't mess with anything after the s/c. But anything can happen, something could have been bumped.

Misfire is interesting.

Going down the list of possible causes from the Powertrain DTC Summaries:

Engine misfireAir intake leak between MAF Sensor and cylinder headFuel filter / system restrictionFuel injector restrictionIP Sensor fault (low fuel pressure)Low fuel pump outputHO2 Sensor(s) (1/1, 1/2)harness wiring condition faultEFT Sensor fault (low fuel temperature)MAF Sensor fault (low intake air flow)Exhaust leak (before catalyst)ECM receiving incorrect signal from one or
more of the following components: ECT Sensor, MAF Sensor, IAT Sensor,
IP Sensor, EFT Sensor, TP Sensor

can i assume i can rule out sensors that are pre- s/c or do not have a sensor for each bank?



yes, only messed with the intake. nothing beyond the TB.

 

so were you able to replace the hose that goes from the driver's side cam cover to the stock plastic inlet elbow? I've been trying to track those down but they've been backordered forever!

 

edit: misread your post- I did not replace the driver side hose b/c mine is in good shape. i replaced the passenger side hose.

yup, got it from my local dealer. took them 2 days to get it though. I've spent so much time down there they gave me the link to buy the parts from them online at a reduced cost- check it out if you'd like. it's almost like the EPC with all the parts diagrams.

http://oemdiscountcarparts.com/

 

That's the same side - bank1 - as your fault.

 

thought bank 1 was on right hand side when looking at back of the engine?

 

No. See Vehicle Specs in the FAQs. Jag use the International Standard.

 

page 78, looking at the front of engine bank 1 is on the left?!? same result as what was thinking i said (or what i was thinking, sitting in driver's seat, bank 1 is on the right hand side)

or am i missing something?

i tried plugging both ends for the hose from cam cover to intake pipe right after mas air meter and it was still reading lean bank 1