I've been getting rich fuel mixture (P0172 and P0175) for 3 days now. Today, I've cleaned the MAF & throttle bore, checked for vacuum leaks, added Lucas FI cleaner, and cleared the codes but haven't driven it yet. I've seen other posts that doing a hard reset is done after throwing and clearing codes or replacing and or "messing" with sensors. Is this "standard procedure" and are there any risks to doing so? Thanks for any input on this.

 

A 'hard reset' will return the ECM to default settings. This is useful to deliberately lose 'learned' settings after clearing codes or suffering some of the 'unusual' electrical manifestations which afflict Jaguars.

The only risk, if you can call it that, is fuel adaptions etc have to be re-learned and a number of settings such as window travel limits stored in volatile memory are lost and have to be reset.

Graham

 

P0172 & P0175 are Rich mixture codes and they show up for several reasons

Link http://www.jagrepair.com/images/Auto..._2001_OBD2.pdf

You should be checking for a clogged air filter, fuel system return blockage, leaking fuel injectors and MAFS among many other things listed on the chart above.

 

Thanks Graham I'll hold off on the reset for now...the issue so far is not effecting anything else, just keeps repeating the two codes. Thanks for useful info...

 

Thanks for the link Gus, I actually ran across it this morning in a different post of yours and got busy using it as guideline for chasing my issue. Printed it to keep in the car. That is a nice site as well, thanks!

 

Gus, Graham. Wanted to let you guys know I'm fairly positive I've stumbled onto the answer to my codes due to a post by princemarko (see below) from earlier this year and piecing together many of the helpful suggestion's given by you. please check out the link. Thanks much to all....

https://www.jaguarforums.com/forum/x...-issues-90125/

 

So it's a set of OE spec NGK plugs and a new set of cam cover seals going on?

I'll not add 'RESOLVED' to your thread title until you confirm the codes are gone.

Graham

 

Hmm!

 

Graham, you had to say it...codes back this morning on cold start which is new..usually happens at normal temp... MAF sensor and cam cover seals on the way.. The iridium plugs I put in (NGK BKR6EIX-11) are supposed to be compatible? I checked around for NGK IFR5N-10 no one had them.

Gus, what are you thinking on your last post? I'm all ears...

 

What is that you are doing when the fault occurs and what things have you checked so far?

Do you have a stethoscope to listen to the injectors? You should hear a chirp and they should all sound the same. It is possible to have one or more injectors affected by the ethanol sludge. It is possible that your MAFS is failing unfortunately the test chart I have is only for a normally aspirated engine.

 

photo 2,6 and 3 are OBD readings at idol just now.
photo 4 and 5 are freeze data readings when the code was logged this morning. Long and short trims way off. While driving home the live data at 50mph for stft on both banks at +3 to 5.5 and ltft at -12 to 13or15ish. At 35mph st. is around +2 to 3, lt is at -5-7 ish or a bit higher.

It seems that it generates the code at or near idol while driving in stop and go, in town situation with the engine at operating temp. Although it produced the codes once upon a morning start up in the garage.

I have checked and cleaned the part and full load breathers(they were not clogged or dirty), cleaned intake breather hose, cleaned MAFs (have a new one coming, and cam seal set), throttle body I sprayed a small amount of throttle body cleaner into...(hesitate to really spray in there even though there is no warning sticker hidden under the mounting bracket as I've seen here in the site), new plugs as identified above (ran for I don't know how long with loose ones) , checked vacuum hoses. I will be able to get my hands on stethoscope later today. Car seems to have plenty of power and runs smoothly other than slight-slight rough idol at norm temp, a little worse at cold idol.

I see the ECT and IAT are also on the list to check... haven't read how to go about doing those as yet. In several threads I see the ECT as a possible related problem. Not sure what the connection is but will price both. I've experienced faulty TPS on other car, it just doesn't seem likely to me? I plan on leaving that one as last resort...read they are touchy as far as cleaning goes, and need dealer set up after replacement.

 

See if this information helps you with the Fuel Trims.

Link JagRepair.com - Jaguar Repair Information Resource

 

ECT and IAT

You can check ECT with a cold engine that's off (ignition II / Run) - should be room temp. IAT, too, I think.

Start engine and ECT should head up much faster than IAT does. ECT gets to nearly water boiling point. IAT better not!

If the values all seem reasonable, both are likely working fine.

 

FirstJag,

Don't pay too much attention to the fuel trims right at a cold start. At that point they are not being used to fuel the engine and the O2 sensors are not in play because they are not at a working temp themselves.

With your data, it's clear you are getting fuel in that shouldn't be there, or the MAF is over reporting air so it's over fueling that way. I think the first thing I'd want to check is the fuel pressure regulator at the rear of the RH bank fuel rail. There is a vacuum hose to it from the induction system. Start the engine cold and let it run for about 30 seconds. Shut it down and immediately pull the vacuum hose off the regulator. See if the hose is by chance wet with fuel. If the diaphragm ruptures it can send a load of raw fuel into the induction system and cause the rich faults. If you can get hold of a hand vacuum pump, you might apply vacuum to the regulator and see if it fails to hold any vacuum. That too is a problem.

If nothing turns up there, you might have to concentrate on the MAF sensor.

Good luck!

 

Thanks Steve, I'll give it try.

I have not been able to test my fuel pressure yet as I cannot find the adapters for my gauge yet... The DTC Summaries suggests the regulator and return fuel line blockage as poss. causes for my problem. If I find the regulator to be okay, I would assume a slow return line will cause a hi pressure reading to the rail as well. Any ideas on how to check on that?

Also if anyone can comment on weather I'm way off on thinking the purge valve could be related to rich fuel or not? I've read that the purge valve can cause a fuel or engine vapor smell in the cabin. I have noticed this smell several times, the smell lasts for only seconds during or just after a really hard tromp on the accelerator and letting her go.

 

You are on the right track, get the adapters you need for the fuel pressure. While a return line blockage is a possibility, historically it is way down the list. I've run into that maybe twice in my entire career. The fuel odor lends itself to the pressure regulator idea though.
The purge valve can show a rich indication, but usually not to the degree you are seeing negative fuel trims. My second paper on using fuel trims, [the link to Gus' website above] shows the result of a stuck open purge valve in the example. Trims are off, but not nearly like yours; and you need to see them at various loads and speeds to be of value.

Good luck!

 

I bought a new MAFS for my 2003 XJ8 for the P0172 P0175 problem - same problem. I finally solved this problem completely by running a bottle of Gumout Xpert series through a full tank of gas, several thousand miles now and no P0172/P0175.