Ok what started out as a po171 code every couple of weeks has turned in the last couple of days to a po171,po174 code every 2 mins of running. I clear the code and they pop up almost instantly..

I have checked all the vac. hoses via listening, soapy water, and propane.
I have replaced the gas cap,MAF senor, air filter. I just can fiqure this one out. I ran data on it and jagv8 said it was a large air leak.

I just can't find it

Could it be a throttle body? This is my last guess. I love the car but man it's trying me bad.


I have a elm327 and software though I really don't know anything about the readings.

If anyone can help I appreciate it.

I also do want to thank those that have helped so far.

 

JagV8 is correct... MOST likely cause is an air leak. A secondary cause may be a dirty MAF sensor.

Since you have the 4.2; the air intake goes to the back where the throttle body is. I wouldn't just jump into throttle body replacement.

Has the codes triggered "Limp Mode"? Have they triggered "Restricted Performance"? These two "modes" are different... Restricted Performance means that the code(s) are bad so it will restrict certain aspects of driveability (like full throttle passing). Limp Mode means the code(s) are considered critical and basically all the car will do is idle.

I would start my investigation by pulling off the shroud and intake hoses. Inspect those for any cracks or leaks. Then start tracing back any and all vacuum hoses. Also, pull the MAF sensor and inspect it for any debris (remember a user that had sandy grit in theirs). Clean it with MAF sensor cleaner. Also, check the connector to the Throttle Position Sensor. This is prone to water intrusion and can trigger the codes you listed. Make sure the "cable seals" are good and apply electrical connector grease to the fittings.

See if these help before considering a costly Throttle Body.

Hopefully some other owners of the 4.2 will chime in on some of the tricky vacuum hose locations.

 

Thanks for the reply...I have put a new MAF sensor in. Also it is saying Restricted preformance.

 

Keep us up on the outcome/result, curious about the story.

 

I just went out an sprayed soapy water again,no change in engine. I also broke out the propane tank and sniffed the entire engine bay no change either. I have a new set of fuel injector I have been putting off so I am gonna try installing them now.

I am still leaning toward a throttle body issue I don't know why just a hunch.

 

achy, first off I know nothing about the 4.2's. But after reading another post from Jeff, and learning that the TB is located at the firewall side of the engine, that got me thinking......

What if you pop the hood, then using a garden hose run water from the top of the windshield down, LOOKING for water running behind the plastic wiper cowl (where the seal meets the windshield) and see where it is winding up. If the water is coming in contact with the TB or the TB connections, that may point you in the right direction.

Again forgive my ignorance, it is only a thought.

 

Thanks for the suggestion, but he thrittle body is toward the front of the engine by the radiator... I took duct tape taped the ends of the vac. hoses no change.

I run a scan my long term fuel trims are 19% It throws the codes as soon as I clear them.

I am stuck on this one.........Help!

 

Achy,

Hang in there, dude. I'm chasing the same elusive problem on a 3.0 L, albeit not as prevalent as yours. Mine's about one/week.
Haven't changed any parts yet, going for a fuel cap first, then will proceed from there. Similar result to yours with multiple vacuum line spray-downs. I'll let you know if I sort it. Different mill but could be similar failure mode.

Meanwhile....I'm working and studying in hopes of becoming at least half as "ignorant" as Rick! :-)

 

Rick you got me thinking so I checked the 2 plugin on the throttle body the rear ones clip was broke so it wasn't sealing very well. I blew it out with air and tried duct tape. No avail. However I am gonna run down to autozone and get some contact cleaner and silicone and go to town on it.

Hope this helps

 

Quit clearing codes for a bit. Drive till you get codes and look whether you also have P1000 or P1111.

If P1000, look which monitors are NOT Complete and post them.

But try to get P1111. It may take various driving - see the codes PDF I think for what. Definitely needs some coast downs and overnight soak.

Then check LTFT (long term fuel trim) for each bank at idle and at about 2500rpm (both in park).

If the trims are fairly alike and anything like 19% at idle but reduce a lot at 2500rpm then you have an air leak. I don't think it could be a MAF if like that.

Anything else, post what you got

Especially any other codes.

Anything else relevant? Using jag air filter? Air box OK, not cracked/etc? Air trunking good?

 

I have drove it up to around 25 miles and it only goes to p1000, The LTFT both is at 19% does decrease with rpm at 2500....I have checked air box..K&N Filter ( I codes started before air filter change).

I don't know what a coast down or over night soak is?

I hook it back up to scanner and see if anything else llok out of place.

Thanks

 

More settings

0.60 lbs/min is the MAF sensdor reading

intake manifold pressure is 9.7 inHg

fuel pressure 58.8 psi

o2 sensor 2 bank 1 0.100v @0.0% s.t fuel trim

o2 sensor 2 bank 2 0.480v @ -0.8% s.t fuel trim

o2 sensor 1 bank 1 0.730v @0.0% s.t fuel trim

o2 sensor 1 bank 2 0.775 @ -0.8% s.t fuel trim

 

See the codes PDF(s) in the FAQs. At least about the first 10 pages.

Do both LTFTs reduce similarly? To what?

 

Yes both decrease to around 9%

I have looked over the PDF'S in the F&Q but no info on 4.2 air leaks most all are 3.0 related

 

Read my posts more carefully. You are trying to get P1111 (and also wished to know some terms).

edit: but it sounds almost certainly an air leak.

 

Hmmm... Electrical contact issue will confuse the throttle body and trigger a "lean" condition.

I thought for sure that the throttle body was in the same place on the naturally aspirated 4.2 as the supercharged 4.2 so sorry for the confusion.

Here is a good thread showing the throttle body on the 4.2 supercharged and fixing the throttle position sensor connector...

https://www.jaguarforums.com/forum/s...ics-faq-50741/

So, again, cleaning up the throttle body and TPS sensor would be my first step. See if the codes don't clear then.

The fact that you are getting "restricted performance" and not "limp mode" is actually a good thing since the computer does not think the trouble codes are critical yet.

Also, check for any sign of oily residue on the throttle body or sensors since you are using a k&n filter..

 

Good ideas.

 

Thanks guys

I looked at those pics on the supercharger and the throttle body it totally different in shape and location. I'll snap some engine pics for references.

 

Sorry engine is so dirty winter gook.

 

Just an observation, whys the oil cap removed? Are (were) you checking for vacuum leaks with it removed? Have you checked the underside of the cold air intake for cracks (possible failure) stated in someone elses post.