I have been having p0171 and p0174s for a couple of weeks. I have read through each and every post here related to these codes and I think I am comfortable with possible causes but I still have not got the problem fixed. The first time I had the issue it was quite obvious that the intake tube came loose from the throttle body, I thought this would be an easy fix but even after putting the tube back on and tightening the clamp I still have the codes and the occasional "Restricted Performance". I don't have a smoke machine but I did do the carb cleaner/starting fluid to check for vacuum leaks and have found none. This is a 2005 S-type so the common PCV elbow is not on this gen and I have completely disconnected the PCV and plugged the inlets (one on throttle body and one on intake tube with no change in fuel trim levels. I've also cleaned the MAF with Mass Airflow cleaner (I heeded the warning on not using carb cleaner which would have been my go-to)

I just started driving this car in the last few months (although I purchased and brought it to NY a couple years ago from California as my winter car. One thing I noticed while looking car over is the airbox lid is broken and previous owner (or repair shop) used a screw to hold down the outboard end and that screw (wood screw it appears) had come out. It seems since this is before the MAF, that all air would be properly metered but I'm still seeing Long term trims of 19.5% at idle and 10% at 2500, short term trims are right around zero at idle but sometimes a bit higher at 2500. I have reset the codes multiple times and usually they come back at idle but I have had an occasional light at higher RPMs (1600 once and 1800 once). The restricted performance is very similar to other articles I have read in that it goes away after driving non stop and go a mile or less.

Is it possible that the broken lid could be throwing these codes? I have managed to find what looks like an unbroken airbox on Ebay but I've also ordered a MAF sensor, air filter, and fuel filter (fuel filter will likely wait until spring unless I get a hard fail. I have no service records except what was in CarFax so I have no idea what has been done to the car (other than a front end airbag deployment which might be where the airbox broke.

In the cases I have read that the fuel filter causes these codes, would I expect to see a lower fuel pressure reading (I am getting a pretty consistent 55 psi according the the live data and in the feezeframes.

This car replaced my trusty 2000 Lincoln LS V8 and I will say that even though they are the same platform I do like the Jag better (2000 was gen 1 and this is gen 2 which might be part of it) even performance of the 3.0 seems every bit as good as the 3.9 v8 in the lincoln.

While I'm rambling what readings should I consider normal for Fuel trims (assuming around zero would be perfect) and how about MAP levels at idle?

 

Hello Rick. As you have read up on these codes I am sure you came across the following link below.

The air box lid is a well known problem that throws these codes. Many times people break or do not secure the lids correctly due to not taking the extra 3 minutes to remove the 10 mm bolt and removing the entire airbox when servicing anything related to it. I would remove entire airbox to assess. Make sure the lid is correctly secured, reinstall airbox or replace.

MAF senors on these vehicles are best replaced rather than cleaned. Denso are the are OEM sensors that are found on eBay for about $80.00. Any other makes often cause the codes you are seeing.

Replace the fuel filter now. God only knows if it has ever been changed. Takes less than a half hour. There is a YouTube video by fellow member Vance580 that DIY's.

Another problem that is arising, is on the intake tube the resinator (rectangular box) is disintregrating from underneath or cracked where it attaches to the intake tube. Either way remove completely inspect!!!!

You don't state the mileage of vehicle that I saw.

https://www.jaguarforums.com/forum/s-type-s-type-r-supercharged-v8-x200-15/2005-3-0-v6-color-coded-vacuum-lines-w-pics-faq-52720/


Here is another link you should read. It's a long one but you can skip to post #32 to see what I mean about the resinator box.

https://www.jaguarforums.com/forum/s-type-s-type-r-supercharged-v8-x200-15/still-flummoxed-3-0-lean-0171-0174-resolved-198690/

 

Bear in mind that a tiny tiny leak you can't see or hear will cause codes - so a bodged repair is a nightmare.

 

Thank you to both of you, I have had the intake tube off a bunch and did inspect for damage of the resonator (Although I didn't know that is what it was called). And yes I did realize how sensitive this system was as I pulled the dipstick while watching fuel trims and even though my LTFT's were already 19.5%, the short terms went to 19% with dipstick unsealed, a 1/4 hole. I think I mentioned I completely plugged the vacuum tubes from PCV with no change in trims (in case your wondering, if you unplug the drivers side tube, the car will stall, that would be one massive leak), I've owned an Audi so PCV is always at top of my mind

Still having a hard time wrapping my head around the lid causing the issue since all air should still be going past the sensor (maybe some of the air sneaking past the sensor along bottom of tube maybe? As you have realized, I'm no physicist :-)

Forgot to mention miles, it has 133,000 I bought it with 127,200 (wow almost 6k already in a short 2 years :-) ). This is now my winter daily, I hate to rust it out but I hate the traditional "winter beater" plus I giggle a bit when people realize I'm driving a RWD car in the snow, Lincoln LS was my previous daily. I picked this one up for $1000, I lowballed expecting to be declined and the offer was accepted, paid as much to ship it from California to NY

Last night when wrapping it up, I replaced the wood screw with a nice stainless sheet metal screw, I'll check fuel trims today on the way to work, that should be good for 10hp, same as the cold air intakes that don't take in any cold air at all. in any case my new airbox should be here early next week.

The MAF is a weird looking beast, I really thought something had dripped on it, I have never noticed one with the little glob of amber before, most I have seen are either the old style with screens or just a single wire.

I'll update this when I fix it, I have until June until the next emissions inspection, it just passed this June before the tube fell off triggering all of this

 

Trims at idle, hot engine, parked. Then rev to about 2500 and if you've a leak they'll drop significantly.

 

Yes, I did that and they did drop but not as significantly as I heard they would (Long term 19.5 at idle with short terms hovering around 0 and at 2500 the Long terms dropped to 10 but short terms were up around 3) I had heard that the drop was likely 15 or so if it was an intake leak.

That being said, the 'fixing' of the PO's previous wood screw repair of the airbox dropped my Long tern trims down a couple points, they had been pegged at 19.5 for a week, after the 10 mile drive to work they are both at a bit less than 18. I think I'll not pay much more attention until the new Airbox and filter gets here next week. Thanks for all the replies. Learning about Fuel trims (and buying a reader that will read them) has changed by troubleshooting world, maybe I will start buying more post 1995 cars now

 

Any drop like that pretty much has to be a leak.

Good plan on getting those items. Try the trims again after they're fitted.

 

Just a quick note, since repairing the previous horrible repair a bit less horribly on the airbox, no MIL has appeared. Fuel trims are not where I'd like but not bad enough to throw a code so far.

So here is my theory, original problem was the intake tube popping off the throttle body. When I put it back on, I knocked out the PO woodscrew so even though I have fixed the immediate problem, I caused another. I never looked at fuel trims before this issue so I have no idea what they have been like for the 5000 miles I've driven this in the last few years.

I'm calling this one fixed but will still report back once my new airbox gets here next week.

Thanks again for all the help

 

Sounds a good plan to me.

 

Just a quick update Replaced the airbox (was in wonderful shape, was really happy since it was an ebay one from a wreck). Also replace airfilter obviously, man those fit tight but I didn't break any clips. Replaced fuel filter too (I do think it was original) and even temporarily patched up the inner fender that was broken from a previous wreck I assume.

Still no MIL but trims are still too high at idle so when spring hits I'll pull intake off and replace those O-rings and gaskets and might go ahead and replace pcv's

Also replaced factory original cabin filter (it was really gross), what a pain that is, no wonder people don't replace them, I'll mark this as fixed for now but will revisit if the MIL comes back

 

replace the LOWER intake gaskets Just fixed the same engine and car for the same issue after he went to independent and they replaced catalytic convertors, 02 sensors ??? then upper intake gaskets and a few other things for p0171, p0174. I guess they didn't know that the LOWERS are big leakers of vacuum where the lower fuel injection manifold and engine meet. And they took out the green sealant coated imt orings and put black ones back in too/ His car is all fixed now including taking off the coolant hoses they used for pcv system which are NOT oil resistant and will collapse with time.

 

Thanks Brutal, I was going to do the uppers this year regardless so maybe now I will do lowers too while I have it apart. So far no MIL still but my son took car on a 600 mile trip and I suspect the long distance with limited idle helped clear the code, I think it will be back. Mileage was a bit lower than I've had on highway trips in the past but that might be nothing. So I think my parts list is:

Lower intake gaskets
Upper intake gaskets
Throttle body gasket (?)
IMT o-rings

anything else?

 

I would have on hand valve cover gaskets and spark plug bosses, just in case you find out in the spark plug wells or leaky covers. You can always return if not used.

Also is it close to time to change spark plugs? As long as you have the plenum off, now wuld be a good time to replace.

 

Good question, 134k and I have no service records so I think that means it is time for plugs :-) That cabin filter looked original so I'm guessing anything that didn't break on previous owner is original.

 

Haven't read all the post but thought I'd chime in. My 03 STR was poping those codes up and after chasing my tail.....or 'it's' tail for some time I found that the O ring gasket on my Mass airflow sensor was the problem. I could never find the exact O ring replacement but had success for several thousand miles at a time with O rings that were 'close' and then they too would fail. I was never able to find a spec for the OEM O ring any where and finally just gave in a bought a new unit, which of course, came with a new O ring gasket. Problem solved and still solved some 40K later. WARNING though, pony up the coin and get an OEM unit as none of the other 5 or 6 that I bought and returned in an effort to save the $'s ever worked out. Only the OEM (about $175-250 ish) did the trick. I just got tired of seeing that code pop up and seeing which odd O ring might work.

03 STR, Quartz ex with 'dove' int
00 3.0L S type Mistral Blue with Almond int
first car.....57 XK140 DHC Red with tan int
500K+ in 'P' cars (911's)

 

Thanks, I'll keep this in mind. So far since changing the airbox I very seldom get the code, usually if I let the car idle a long time. I still plan on pulling intake and doing gaskets plus those other o-rings once I have a free weekend this spring as my fuel trims are still too high even if the code is rare now.

 

Good to hear. You can't argue with success!