Hi everyone,

We have here a 2005 XJ8 with 124k miles on it.
I've been chasing lean codes on bank 1 and 2 and random missfire codes on this car since the cold weather is starting to come in the morning.

Symptoms: it does not like cold mornings at all. It usually takes about 3 tries to get the car started withing 4-5 seconds of cranking. I have tried priming the fuel pump as suggested in previous posts and I manage to get 44 psi of fuel preasure when I do this. Once it runs it does two things; it revs on its own to about 2.4k rpms and slowly goes down jittering to about 800k rmps. Then when I put in on drive, take it out and reach a stop sign, the whole car wiggles like a car straight out of a 60's cartoon. These issues go away as soon as the car reaches a good temp, but I don't daily drive it enough for it to reach said temp. At times it struggles to switch gears it seems, specially down to 1st when cold.

So far, we have changed the fuel filter (which was pretty much sending brown fuel); done a smoke test that revealed few vacuum leaks that were mostly O rings and the valve cover gaskets. The one vacuum we have yet to fix is a throttle body leak. And, I am running Techron Chevron fuel cleaner through it which has improved acceleration, but not the iddle.

In the past, it had coolant leaks so it probably has overheated a few times, I assume, and the previous owners probably had it sitting for a while.The starter sounds good and health!y. What is the move here? I wouldn't think the throttle leak would cause it to be so shaky in the morning.

Feel free to ask more questions and give suggestions.

Thanks in advance!

 

Sounds like one or more air leaks.

 

That will cause it.

Additionally, you should continue to smoke test after you fix any leak. In chasing the same issues I've found that smoke testing will reveal the leaks from the paths of least resistance, and as you fix those you may discover new leaks that didn't appear before. So you may have other leaks besides the throttle body one.

Good luck!

 

Coldest morning so far (32F, 0°C) it took quite a bit to start it. Soon after starting I heard about 4 or 5 knocks that slowed down for the next 7 seconds or so. Had a fairly big cloud coming from the back once I put it in reverse, but it went away after driving it for a bit. I will do another smoke test as suggested. I don't know if it matters but ai park the car outside on a low incline. What are the odds its more than an air leak?

 

It sounds like a massive air leak(s). Check the short term fuel trims and let us know the values. You can do the butane/starter-fluid/WD40/etc.. test or smoke test to locate the source. I am guessing you have multiple leaks. Have you checked to make sure the intake tube is securely attached and sealed? That resonator likes to become disconnected with time and mechanics resting their weight on them, especially if it isn't attached to the mounting bracket.

-j

 

When I get the lean codes its said LTFT +25% STFT+15% approximately on both banks. They come down to about LTFT +8% STFT +3% on both banks once warmed. When reving to 2.5k rmps, LTFT goes up with STFT to about +18% when warmed. Suddenly letting go of the pedal puts LTFT and STFT at 0% for a second or two.

I tried spraying break cleaner around that intake tube but I didn't think about the resonator, I'll check it again. Weirdly, spraying the break cleaner at the leak from the throttle body didn't change the rpms, at least not that I could tell.

 

So there might be two issues occurring at the same time.
1) a big vacuum leak when cold that seals up at running temp, indicated by your LTFT and STFT at idle
2) The values at higher RPM are not indicative of standard vacuum leaks. Usually simple leaks disappear at higher RPM due to the increase in air pressure with the throttle open. The likely culprits in your case are faulty sensors or restricted fuel flow/pressure. What is your fuel pressure at higher RPM? what are the readings of your MAF sensor at different RPM?

 

J,

Here's some pictures I got earlier of the OBD II live data.

Fuel primed 3 times, lowest reading showing the first "on" cycle to connect to the computer.

Fuel pressure plus reving to 2.5k (that bit of wiggle in the middle right)

MAF readings also reved to 2.5k at idle.

Is it normal for the fuel pressure to spike to 65 psi when priming?

 

Did a smoke test and found a few leaks:
One of the valve cover gaskets that we thought we fixed is still leaking, the EGR, the throttle body from the spring unit; and the tube into the throttle, right where it connects to it, seems like its not clamping enough.

Any tips on getting that hose fit better in the throttle?

 

Sorry for the slow replies, I am super busy at the moment. Is there an o-ring on the connector for plastic pipe you are referring to? If so replace that. I went through and replaced all the o-rings on my vacuum hoses, if i recall correctly.

 

Sorry, maybe I didn't explain that well. It's that big tube that goes into the throttle that has the resonnator and comes after the MAF. If that is what you also referred to, then no, no O-ring on sight, but that would be a pretty big one I would imagine. Also, no worries in the slow replies, you are already helping a lot J.

 

I got a few pictures to show a little better the condition of the leaks:


Inside of the intake tube into throttle

EGR leaking from the very top, where the solenoid sits.

Leaks basically "turning on" when commecting that hose

No smoke when stoping airflow into bank 2 valve cover

As seen in the description of the pictures, we tried troubleshooting the leak right after the mass airflow. In doing so, we covered the hose into the valve cover in bank 2 with our fingers to find that no smoke was coming out of the leaks at all. It was only when connecting that hose that the smoke will start to show from the leaks. I don't really know if thay is a problem but I thought it was interesting at the very least.

It's hard to tell from the pictures, but seems like that elbow intake tube is leaking at the very end of both the air filter and the throttle body. I couldn't see any O ring or seal on either end.

For the throttle body, is that spring serviceable? Will there be a gasket or seal that can be replaced in there? Or is my only option to spend some clams on a new one?

 

Any leak at all is a problem. Even a tiny one is big to the car.

 

Absolutely,

is it possible the "weird" results on the smoke test could be cause by the PCV? I feel like I am going on one too many rabbit holes for an obvious solution: replace what's leaking. However, if there is a better cheaper solution I would love to hear it or if its even possible. For example, the leaking spring on the throttle or the potential O ring in the intake tube.

 

Bit of a development on the situation here,

We tried servicing the throttle body with no avail, but we at least gave it a good clean. We did noticed that inside the intake manifold, right after the throttle body there was a whole that seemed like connects from the EGR. This whole in question was basically blocked by a black smudge that was somewhat soft. We weren't sure if that was just a factory seal or not so we didn't touch it much. Question is, is that smudge there normal?

I also double checked the LTFT on idle reving to 2.5k rmps and there was no drop on them but STFT was pushing negatives making the total closer to 0%

EDIT:
didn't take a picture of it, but the circles area is where the black smudge was:

 

Exhaust gas recycled into your intake manifold, left its calling card there.

 

When you did the smoke test where was the smoke entering the system and did you open the throttle butterfly? If not, it will leak smoke at the spring and you won't get smoke where it might reveal where your real leak(s) might be.

 

Mac,

The butterfly was in, what I thought to be, a neutral position slightly closed with the car completely turned off. The throttle did have a bit of a palpable bump of dirt on the inside side which has since been cleaned. So from your question it sounds like there are parts that will give a false positive on the smoke test with too much pressure. Is that the case here?

 

The throttle butterfly has to be opened slightly to let smoke pass. PLEASE do this gently so you don't damage the stepper motor. I used one of those nylon flat tools for removing interior panels/fasteners to hold the butterfly open slightly without damaging the throttle body interior or the butterfly.

 

UPDATE:

And a bit of a confession too. We did a valley hose replacement without changing the intake manifold gaskets so we went ahead and replaced those now (they did look pretty flat and dirty in that area). In doing so, a few "weird" things happened. When I disconnected the fuel line and released the pressure fully, I took the socket fully out and two seconds later it shot fuel at me. Could that be a sign of a clogged or obstructed fuel delivery? Also, we found the knock sensor cracked, which I can't imagine how it would influence the lean condition, but I though it is worth mentioning.

For now, the intake manifold gasket replacement seems to have helped a bit. It seems like I don't get missfires as far as I could tell from the OBDII. However it still throws lean codes on both banks and restricted performance. Also, worth mentioning, the oil pan gasket is leaking quite a bit as well as the front engine cover on a corner but not as bad. But, I don't see how those would create a lean conditions.

We have yet to run another smoke test through different intake holes. But my question is: where should I have to smoke come in through to check for leaks fully? I was thinking the top hole of the throttle elbow from the PCV, are there any other entries that would help diagnose the leak?

I did take a video of the start in the morning at 31F (~0°C) which has a few knocks along with the start. I will post that soon but I figured I will throw these observations out first.