Happy New Year everyone.

The cat has behaved very well until last week. Took a trip into NYC - all good. Got back home, took the cat back out and boom P0171 and RP.

Hooked up my Matco scanner to monitor LTFT's.

What have I done...

Cleaned air filter (K&N) and re-oiled, cleaned MAF, PCV valve seems good. PCV hose (i think there was a split in it. I taped it up.

Now the PVC hose broke in half about 2 years ago. I repaired it. I have a replacement but it's a PITA to get to the TB end.

Checked the vacuum hose near the TB that has that plastic connector. It is still intact but seems to fit the hoses "loose".

Now, I will be getting some brake cleaner to see if I can locate the leak.

Questions? Could the O2 sensor (upstream) be causing the issue? Also, what about those gaskets that connect the SC to the intercoolers/intake? I know they are prone to leaking...

Thoughts and feedback would be appreciated. I reset the PCM but LTFT's are substantially higher on bank 1 (idle about 18 - 20%) but bank 2 is about (15 - 17%) they come down near 0 on acceleration but bank 1 is higher...

Thanks.

 

Wow, no one?

No worries - I'll figure it out myself. I'll keep this in mind when someone else is in need.

Just...wow!

 

As i always mention to those eight pesky intake manifold gaskets.

And i don't have an XJR, but two XJ8's..

Thought i would keep quiet, and let others speak their ideas

 

Thanks - going to check them out tomorrow with some carb cleaner to see of they wave the STFT's - right now after resetting LTFT's are sitting at 12% bank 1 and 10% bank 2 - not near where they should be. Checked the hot spots for vacuum leaks on the SC engine - nothing found. Ugh....

 

Only way i found mine was taking it apart & replacing them.

There was no change spraying chemicals around, car ran fine.

It easily passed tail pipe emissions test, but kept turning the check engine lite on.

 

Do you have access to a smoke tester and inflatable seal? I've been told they make searching for vacuum leaks easier. No experience with the XJR but I'm chasing the same issue with XJ8. I purchased a smoke generator and bladder seal online I'll be trying it out this coming weekend (if it doesn't snow). I plan on disconnecting the air filter inserting the bladder inflating it, wedge the throttle open and connect up the smoke generator. I'll let you know how it works.

https://www.ebay.com/itm/Ammo-Can-M1...MAAOSwzlZaOqcF

https://www.ebay.com/itm/Universal-I...QAAOSwn6RbuVVU

 

Do you have the brake boost connection at the induction elbow like the str. If so i found mine with a crack and the sealing o ring bad. Kind of hard to get to just to check and not replace though. I would get the po171 about every 3 months until i pulled the charger a while back and found the culprit

 

Yes I do. I'm hoping it's not that as I know it's a PITA. Need it to hold out until spring when I'm swapping out the hose under the SC (as a precaution)

I found the vacuum hose backed off the MAP sensor. I was so focused on bank 1 didnt bother to look at the drivers side of the engine.

It wasn't fully off but wasn't seated either. I put a small zip tie after re seating the hose.

Now after a 20 minute drive after clearing the trims LTFT's are at a constant 6% and 5% at idle, which I'm taking are pretty damn good. Previously, they were at 12% - 16% and climbed at idle.

Regardless, since I'm at 105K miles I'm going to swap out the O2 sensors as bank 1 sensor seems out of whack...

 

Great. I found it does not take much to make the trims wonky on the supercharged cars. A smoke test did not show the minute leak i had but the ecm knew it was there. When you get the charger off replace all hoses and vac related stuff you can see

 

Today's drive went well but then the LTFT's started creeping up at idle. Last I checked they were at 18% and 16% so something is still off.

Now, about 2 years ago I cracked the PCV hose in half. I repaired best I can but maybe that fix is not holding anymore. Whatever leak I have must be a large one.

I have a set of O2 sensors coming in and going to swap them out and see if that helps.

Going to dive in again over the weekend...

Might be going all in for that hose under the SC charger sooner than expected and swap everything while I'm at it.

 

I agree only because I have found this to be true in my own testing. I got 0171 with the tiniest of Vacuum leaks that were just barely noticeable after running a smoke test. I’m talking about such a slight whisper of smoke that you almost couldn’t see it. So that being said without further ado replace that broken PVC line because your taped repair will never be sufficient enough to solve that leak. Once you get the new line installed check your trims and report back

 

It was also vital let you make only one change at a time so you can really see the results of that one change. When you make more than one change you might have fixed one problem but created another problem which results in the same symptoms so you think it is something completely unrelated. If you make only one change at a time there is no doubt as to the fact of that one repair.

 

Correct. Going to get the PCV pipe changed out first ( going to attempt to disconnect the TB end from beneath) and inspect the EGR and exhaust while down there and drive a while before attempting to swap out the O2 sensors.

 

its a tight fit but I managed to get either my big cliunky hand down there or some long nosed pliers to squish the retaining ring. Its tough but I manage to do it a few different times accompanied with many cuss words but its doable. Just a pita. I needed new o-rings and some dielectric grease to help seal it

 

The big hose clamp that attaches the air intake tube to the throttle body was recalled because they aren't able to clamp down tight enough, causing vacuum leaks. It usually results in faults to both banks, but it might be worth a look and replacement.

 

I'll check that. I've had it off before and everything looked tip top. Nonetheless, I have a spare...

 

Back at it today and sprayed some carb cleaner at the brake booster vacuum line at the throttle body and the STFT's went full negative tilt (-20 on bank 1 and -16 on bank 2)

Now, I have the replacement piece and o ring that goes into the throttle body and a new throttle body base gasket as I collected everything in anticipation of swapping the hose under the SC.

Questions? How hard is it to remove the throttle body and I'm also aware of a more permanent fix tapping the port and screwing in a 90 degree fitting.

Thoughts and feedback much appreciated.

At least i found it!

I also sprayed the PCV line. Not much STFT movement but nonetheless that hose will get replaced also.

 

The throttle body is not too bad. I have removed mine on an 06 str so it should be similar i think. Remove the windshield cowl and brace if there is one. You can access a lot after this. Remove the big aluminum intake tube and the rubber boot if possible then there is more room. ...if the rubber boot is stubborn leave it because if it rips there are none available to my knowledge as a sepetate item... At this point you might be able to swap out the sealing o ring for the booster tube. If not unplug the connector at the body and take the 4 bolts loose then off. At that point lift the body straight up. It might take a small nudge with something wooden or hard rubber. If you decide to replace the brass bushing find a socket that fits nicely or a bushing driver like i used. Use the new bushing for fitment. Place a rag or towel where the bushing will fall and it drives out easily if the hammer swing space is there. The most crucial step is driving the bushing out easy. When you get the throttle body off you will see what i am talking about. Harbor freight sells a nice cheap driver set. If you decide to just replace the o ring , pick the old one out and replace. The only thing is you cannot see inside the bushing. The bushing is actually driven into the induction elbow. This job is way easier with the charger off and on a bench of course. I forgot to add...when you loosen the seal at the throttle body rubber to intake pipe, use a small screwdriver or plastic body tool. When it is free , pull the tube up and off the boot then slide forward off of the front indexing pin

 

Thanks. I have removed the intake off the throttle body previously so that should come off without issue. I'll keep you apprised of my progress.

Thanks.

 

Here is the replacement part