I might have done so today. I finally found (for the 20th time) the vacuum leak and believe I fxed it. I ran the drive cycle today but didnt get back into SDD to check it out.

 

Reading through this thread... does the "R" S-type have an idle air bypass system? If so have you cleaned it and/or replaced the actuator? Back in the day I saw Ford have similar problems like this.

My other thought is a dynamic leak. For example with the engine & exhaust cold no leak is found. But after fully warmed up maybe a crack is opened and causing a leak.

 

No, it doesn't.

 

I replaced my upstream 02 sensors with OEM's and after was still getting the lean codes P0171 and P0174. Everything on the forums said it might be a leak somewhere in the system. After we did my 02 sensors, we did an old school seafoam treatment to the engine and a fuel return line (I believe that's what it's called,I work at a small dealership and the mechanic works on the Jag) was disconnected. The Jag ran like **** until we reconnected the line, cleared the codes and it's been running great ever since.

Check the workshop manual for those codes as well, it will help you pinpoint areas to check. Dirty/clogged fuel injectors can cause lean codes as well. I ran some fuel injector cleaner through about 2 tanks of fuel and it seems to be running much smoother. I have 145k on my STR.

Best of luck

 

Can't be right - there is no fuel return line.

Wonder what it was...

 

I’m gonna say it again you need to go and find the vacuum leak.you have one. It’s small. But it’s there. I’ve been struggling with these lean codes for a year now and I keep finding vacuum leaks and I repair them and then I get another lean code and I repair it and I find a different leak and repair it and then I find a different leak. I just recently started getting the cat efficiency code which is also due to a vacuum leak at my injector O-rings

I found leaks at my O-rings for my vacuum lines I found leaks at the throttle elbow base vacuum connection. I found vacuum leaks at the exhaust pipe to exhaust manifold. I found vacuum leaks at my injector O-rings. I found vacuum leaks at my intake manifold gaskets. All of these leaks were valid leaks that needed to be repaired

You need to monitor your O2 sensor outlets and get busy with some carburetor cleaner and spray every location that can possibly week and look for a wiggle in the signal.

 

Hey everyone. I jumped back into this problem and want to see if this is normal or not. Looking at the obd2, the upstream sensors seem to be showing 0 volts. Is this normal? Could there be a wiring issue or ground issue causing that? Thanks.




 

Those are pass or fail montor test results....the green check marks mean pass...the numbers are actually the counts...to pass, the recorded value has to fall between 0 and the high limit...the monitors do not record values, only counts and pass or fail...those monitors have passed the obd2 protocols

 

But doesn’t the Sensor 1 saying “failed or incomplete” relate to why the O2 emissions test is still stuck on incomplete?

 

Glad to hear you haven't given up.

Long thread, a thousand pardons if this has already been discussed: Have you tried a different OBD scanner? I'm wondering if the problem may be related to the interface, not the vehicle itself.

 

I have been using a generic bluetooth scanner. I thought about grabbing something more advanced like the icarsoft scanners to see if I can get more information on the engine.

 

They're not voltage-based (they're current sensed) so it's probably a misleading value. It should probably display NOT APPLICABLE but a lot of software is quite poor.

 

yes, sorry i did not mention those...you are correct, those 2 monitors being in a fail or incomplete phase will be a fail for emissions testing....again you need to see the real time values of those two aspects of the o2 monitors...a little more specific scanner could help...although your numbers posted already may not change much

 

heres what my O2 sensor outputs look like when its running right with no


leaks.

 

So update here. Aarcuda was correct about looking again for a vacuum leak. After doing another smoke test. I have found a vacuum leak on the common brake booster hose elbow in the rear and have now replaced it. But after doing that, I seem to still have a vacuum leak as both LTFTs are now at 10.94 idle and even out at 2500 rpm. I have done another smoke test with no signs and have done the traditional spraying brake parts cleaner/ carb cleaner. With no luck. Are there any other common spots that create this vacuum leak? Supercharger inlet gasket? PCV valve? I'm assuming it's before the air breaks up into separate banks as they are both the same number. Any advice is appreciated. Thanks.

 

If they stay high even at 2500rpm that sounds like some other problem (bad MAF, blocked cat, misreading IAT, ...)

 

Drive the car for a week and then check it again. Are they at +10 or -10?
If you had a leak before your long-term fuel trims would have been really rich. So after you remove the leak it would go normal but because the long term fuel trims were rich you’d want to try to start subtracting gas. And if that’s the case just let it keep adjusting until it meters it down to zero as it makes long-term adjustments

When I was using the carburetor spray I also had the O2 sensor current and voltage output on the screen so I could watch them wiggle when I hit the right spot so you might want to try that. Also make sure all your hose clamps on your intake tube a tight and on the throttlebody but not too tight that you put a hole in the rubber like I did

 

Yeah you might be onto something. When I first started the car after the fix, the LTFTs was at +19 each and after idling for 10 minutes or so they came down to +10.94. Maybe it needs to idle longer and be driven. I'm going to do the carb cleaner trick again and keep an eye for negatives in the STFTs while doing it.

 

YES! Thats what I would expect! Jusr keep driving it and then come back and look/ As ;ong as the LTFTs stay below 20 I think, it wont throw a code

 

Right now your car is adjusting all the blocks for trim over the rpm and load ranges. Its trying to get them as close to 0 as possible