Heck if I know. It's just another expensive guess at this point.You've already paid for it, so it can't hurt to try.

I vaguely remember somebody unplugging the MAF sensor for troubleshooting. Does this ring a bell for anybody? IIRC, the theory is the computer is programmed to compensate for a failed sensor. Stored values are used, based on RPM, throttle position, etc. The sensor may have been inaccurate, but not bad enough to set a code. If the engine now behaves (other than a new fault code for the "bad" sensor), the MAF sensor may have been at fault.

Re: Compression issues - I'd put that low on the list of probable causes, but certainly don't just rule it out. You've done most of the easy stuff, and the problem persists. Since your labor is free but parts are expensive, I'd suggest a compression test soon before gambling on additional expensive parts. Maybe not right away, but perhaps next time you have the intake plenum removed for other reasons. It's just part of the normal flow of troubleshooting.

Have you smoke tested or visually inspected the duct between the air filter and throttle body? Check out this resolution for persistent lean codes on a similar vehicle:

https://www.jaguarforums.com/forum/s...solved-198690/

 

when I did the smoke test , I disconnected the air duct from the throttle body plugged the throttle body with a latex glove also I did see some smoke coming out from around button of IMT valves ..a while back I had replaced "O" rings from autozone some crappy ones . I m going to order NEW ones from an online vendor,
Also I tried unplugging the MAF sensor car adjusted to missing sensor kept running - plugged it back in car die.. !!

I will see what happens when I do get the new MAF sensor sometime this week , I m almost sure I will taking the plenum off again -
would like to DO the following :

a) new IMT valve's O rings ( I may try to DO this before removing the plenum off again )
b) compression test on all the cylinders
c) plenum repair bolt 1,2, inserts either heli coils or possibly epoxy the inserts make sure they get fix..
d) maybe even swap the all injectors from driver side to passenger side ???.

 

I can't see how the MAF is much of a suspect unless you check fuel trims and they show it is. I haven't hunted back the whole thread for what the fuel trims show... remind me?

 

sorry the only tool that I m using is I carsot I930 , don't even think I would be able to check those out using this tool??

 

I think this is an excellent plan of attack. I hope you're not getting too frustrated. You've got a persistent problem that is resisting the easy troubleshooting steps. You'll find it, but you have to keep plugging away. Definitely fix the known problems first, such as the leaky IMT seals and the loose inserts. And while you're in there, that would be an excellent time to run a compression test and swap injectors, as you were thinking.

Did you ever check the flex duct between the air cleaner and throttle body? Your answer wasn't very clear on that. Per the thread previously linked, at least two forum members have had that identical problem with the duct.

 

The iCarsoft does read trims. I use a BT to my phone to read my trims, but I have the iCarsoft too. I think I saw LTFT expressed on a 100% meaning that a +20 would read as 120%. Navigate the meter, I believe it's there.

Between your striped threads on your manifold and recent work taking it down to heads onto the block, a vacuum leak is odds on favorite to be sure. Spend time looking exactly for a leak.

My earlier smoking instructions specifically cautioned to include the duct by connecting at the air box . While the duct and bellows certainly could leak in and of itself, you also bypassed the breather tube connecting into it. As another mentioned, any smoke is a vacuum leak.

 

really appreciate the support I m getting from you guys here !
it does make a difference man .. a bit frustrating probably to be expected however is personal NOW ! haha actually I love the car .. few females that I know love it too.. and when I did the smoke test I did removed the duct between the throttle body and air filter , plugged the throttle body with a latex glove while doing the smoke test ..
on another note : if I m able to read the fuel trim using Icarsoft I930 is there a write up on how to do that and what should the numbers be ?

 

Find the points for the left and right LTFT at idle and then with raised revs. The numbers will be moving around, judge it and call our numbers for each of the two engine speeds.

If you want to clean your MAF, wait until afterwards. The dirt is usually visible, only use MAF cleaner. Mass air flow is also a point able to be monitored on your meter. You could experiment with different rpm speeds in part to gauge if the readings track in an appropriate manner.

 

thanks Guys ,

I will look into doing the fuel trims readings using Icarsoft1930 if it is capable of doing that.

 

start with fixing the misfires !
check closely—
spark plugs ,
coils , electrical connections, wires and injectors.
you could start by shifting the no#1&3 plugs and coils
to a different bank and see if the codes shift with them .

 

oh man ! Din't think about swapping the spark plugs .. just assumed they are all in great shape brand new iridium .
I ' ll do that . all coil packs are new from rockauto now so I dont think i have to worry about those

Datsport thanks for bringing that up..

 

in my experience with the dreaded lean bank 1 and lean bank 2 is that if the smoke test shows ANY smoke, it is a leak that MUST BE FIXED BEFORE MOVING ON.

Reason being is that the smoke means a leak. and a leak will look like its lean so the car adds gas making the mixture TOO RICH and runs like crap. but the computer thinks its fine because IT DOESNT EXPECT THE LEAK.

Fix the leak FIRST. then come back

 

there may be no leak . A miss fire can and will cause bad o2 sensor / fuel trim readings and cause Erratic fuel- ing causing rich/ lean codes .
any ways p0174 is isolated to one bank .
opposite to the misfiring bank.,
I would be looking for the misfire first.

 

update ; so I got my new " O" for the IMT valves , replaced them today " notice when I pulled the lower one oil in the inside of it " , replaced new MAF sensor , also fixed coolant leak lower hose to reservuior loose connection .. drove car around neighborhood back and forth to gas station , my observations so far:

car idles MUCH better , good power no hesitation NO CHECK ENGINE LIGHT SO FAR ! I believe I have some improvement ..

 

update : today I drove again it ran pretty bad rough , restricted performance , all codes came back got home let it cool checked oil it was kind of low so added a quart ! started the engine deleted codes sounds pretty good again .. guess I will drive it to work tomorrow I might Do another smoke test before I take it apart again oh yea was able to get fuel trim readings as follow :

short term fuel trim bank 1 -18.0 %
long term fuel trim bank 1 - 20-3 %
short term fuel trim bank 2 - 0.8 %
long term fuel trim bank 2 - 18.0 %

 

It was not too surprising that your codes came back. Resetting the PCM wipes the trims and it is the accumulation of high trim percentages that lights up the lean code notification. I am glad that you’ve found the LTFT points on your meter, you may come to appreciate them in understanding your engine’s state of health. I am still suspecting a vacuum leak being your number one suspect. While your B1 is way too high, B2 is also significantly outside of “normal”. Ideally, you should not exceed 10%. Assuming that these reported readings were at idle, did the LTFTs dip somewhat with an unloaded engine (placed in park) with the revs raised above 2000 RPM? I would also wonder what your MAP reading is when at idle, in park, and with a closed throttle? Both of these examinations are focusing on vacuum. If your leak is large enough, the trims will grow large enough to flag a lean code, but it will also dilute your mixture to a point that it is too lean to ignite. A misfire doesn’t automatically mean a failed ignition component. Yes, I would agree that a failed coil may cause a misfire, I just contend that there are other potential reasons too.



I agree that attempting another smoke test is a good idea and I am sure it is more appealing than pulling that plenum off again, though I would suspect that you are probably getting quite good at it. I understand you did the IMT o-rings, which is a good call and certainly had the potential of being your culprit. Don’t worry about the oil collected in the lower passage. Pay close attention to the quick connect couplings, one on the back, and the one below the throttle body. The one below the throttle body was the one killing my trims, and it was ever so slight. There are o-rings in there and they are prone to leak.



You also need to get realistic on the state of your lower intake. Are the threaded inserts stripped or are they not? If they were stripped before, then I would believe they still are. Did you use a ¼ inch drive torque wrench for assembly? If the manifold is impaired, I don’t think you will ever get this problem solved and if you do find some tentative success avoiding codes, I (personally) would still never be able to be confident with taking the car over long distances. Being 50 miles from home with a car sputtering and unable to accelerate would be absolutely dreadful to me. An epoxy approach to fixing it doesn’t inspire confidence in me, but if I were facing the same circumstances as you, I might give it a try.



When doing the retest, be sure to include the air cleaner duct this time. You missed multiple potential sources of leaks last time. Make sure you give it a real good chance to get deeply throughout the system. The o-ring in my case had barely a trace of smoke and the resulting difference was huge. Consider proving to yourself that you got the smoke throughout the manifold with a bump test such as the easily pulled off and then reattached tube/boot that is also located on the back of the manifold but not the quick connect one. Push and shove on the intake plenum to try and make it leak around the base. It may seem counter to what you would hope to see, but hope is not a strategy and if it is gonna leak, you need to know that it leaks. And lastly, are you working inside a garage? Working outside with a breeze that you can’t even feel will still be enough to obscure a smoke test, no problem.

 

When i did the fuel trims , I just had it idling at parked - I can try raising the RPM above 2000 at idle and look for the MAP readings too..funny you mention the sensor bellow throtle body . the coupling is falling apart I m gonna have to get a new plug ..
when I Do pull the plenum i m planning on using heli coils to replace the inserts both of them , the inserts are bad .. although I did NOT see any smoke coming out of there .
the Smoke test will done outside garage in my driveway , unfortunetkly i have another car inthere unable to move out ! thanks for all teh help!

 

MAP readings at idle.

 

update : another smoke test with air cleaner duct connected (MAF sensor removed tape that off) after replacing O rings on IMT valves no smoke at all.. so I removed the plenum Again noticed oil inside plenum inside lower intake !! should I be worry about that ? removed spark plugs according to pictures online . normal just black carbon build up top part clean white ..
NEXT swapping spark plugs and compression test - i also notice the lower sensor on throtlebody plug broken maybe causing bad connection ? will have to order new plug only has two wires
should i also look at the injectors ? swapping