P0171 & Restricted Performance (Solved)
 

I have been getting the occasional restricted performance & check engine from time to time. The check engine light goes off after a few days. The code is P0171.

I have noticed that this only occurs on fairly long runs at about 70 to 80 mph and with the road slightly uphill.

The L shaped intake tube is perfectly OK so are the two load breather tubes on either side are also perfectly fine and the orifice of the part load breather on the left cam cover is also clean.

I have not cleaned the MAFS but I did examine it and it looked OK, I will get a non reside contact cleaner and do that as well but the car otherwise drives fine and idles extremely smoothly.

What have I missed or what else I should attempt.

Hi Aregg,
Fault code p0171. Means bank one running too lean. Two possible reasons 1) Not enought fuel, 2 ) Too much air. Try cleaning or replacing air fillter. Make sure there is nothing stuck in the seat where air fillter cover sits. Make sure air fillter clips are closed tight. hope that will help. On the fuel side you may need fuil fillter changed. But I would have a good look at the air intake first.

Steve

A clogged/ dirty air filter would make the engine rich not lean. Clean the mass air flow by removing the sensor from the tube its screwed into and use a cleaner for mass air flow sensors. If that doesnt work youre probobly gonna need a new sensor if youve eliminated vacuum leaks

Thank you gentlemen.

P0171
 

I also had a similar P0171 issue (which then cause a restricted performance situation). This issue went from once a week, to once a day, to once a trip, to once every 3-10 minutes. Initially, cleaning the MAF may have helped everything clear up for the majority of the month, but then the P0171 started happening again. Cleaning made no difference at this point. Switching out the MAF took care of the problem .
From a logic standpoint, I would have expected a bad MAF to effect both engine banks as opposed to one when dealing with a lean code (P0171 &P0174), but in my case it only set off bank 1 being lean (P0171). I share this so that others don't automatically eliminate the MAF being an issue if they experience ONLY a P0171 or ONLY a P0174.
I would also recommend keeping any old bad MAF with a list of its trouble-causing-codes should you ever replace one. I now have a spare (with only one known problem) that can still be used for troubleshooting a potentially bad MAF should any future issues arise.

A week ago, I pulled the same code, got the lights, and the car's performance dropped, which apparently the ECU does to protect the engine.

I went to my Jag dealer, who actually pulled the P0172 and P0171 codes, meaning both banks were running lean. The service writer and tech are good friends of an ex-technician that I also know. I felt they had my best interests at heart.

There are literally dozens of things that can throw these codes. Their first reaction
was unexpected. They felt that it was likely that I had a tank of bad gasoline, that may have created deposits in sensors and/or injectors, or, that the quality of gas
octane levels was not up to par. Too much alcohol in the fuel can also cause this lean condition. They gave me a small bottle of gasoline treatment (Wynn's). They suggested adding some octane booster, given I had just filled up.

They encouraged me to run the tank to empty and fill up with some "premium" grade gasoline. I had been using mostly RaceTrak here in Dallas. They suggested Shell, Exxon, Chevron. They felt that cheaper gas stations were basically getting the bottom of the barrel as far as gasoline quality.

They said that they had at least six cars in the shop that threw exactly the same codes in recent weeks. They felt that this was happening because gas stations in the area were switching from summer blend to winter blend gasoline as required by the govt. Apparently, storage tanks must be run to nearly empty before the new seasonal blend is poured in. Lots of residue at the bottom of storage tanks that can get stirred up.

So, to save some money, they suggested to look at the fuel quality as the first causality. They also took a peremptory (sp?) look at some of the things that may also have thrown the codes, and found everything to be in order.

I left the shop with the "restricted performance" and engine light on, even though they cleared the codes. I added the additive. Within sixty miles my warning lights went off, and the car's performance is slowly improving. It is still not performing like
a supercharged car should, but, I still have a half a tank of the old gas. It does seem to drive a bit better every time I drive it. I'll give an update when I fill it up with some better quality gas. Good luck.

Ahh, i'm in the camp that uses only name brand gas too, chevron is my fav. If you run out of the wynn's product, buy a 3-pack of BG-44k from ebay and add it to your regular maintenance schedule, maybe every 6-months if you use lots of racetrack gas. I dump a can in every 12 months, to keep the system cleaned and at its best efficiency.

This is so weird, I have the same issues on my 02 XKR. 0171 and or 0174 and or 0172 come and go every few days. I've tried everything, cleaning the TB, checking for leaks, new filters, cleaning spray on MAF...still keeps coming back. Sometimes I get restricted performance just for 10 seconds or so, then it goes back to normal except the engine light stays. I've hooked up my scan tool and O2's and MAF seem normal...but I guess MAF replacement will be next on the list...

As quoted by EdTexas
All gasoline comes in the same pipe lines, any blends will be done at the distribution point as the trucks are being loaded. A very good friend of mine was the foreman for BP Here locally I've seen the operation. You'll have smaller tanks of additives that they will add on the spot. The major brands have set formulas, that's why he recommends buying from a major company. He says the local convenience store owner if he's selling a off brand will determine the formula, so you don't really know what your getting. I always use Shell 93 octane and have had no problems.

You have several hoses you should check and I attached a photo of one that goes under the intake manifold. Your MAFS could be the problem but vacuum leaks seem to be the majority of the problems. A smoke test is best to check for leaks but I use TB cleaner, however, a spray bottle of soapy water will work. Spray vacuum hoses as the engine is running and when you hear changes in the idle you found a leak. This might help http://www.jagrepair.com/images/Auto...otos/P0171.pdf

I've been having this problem for a month or so. I replaced the MAF sensor and the check engine light cycled off. After a week or so the problem came back. Looks like the vacuum leak is my next line of defense.

i had this happen to me and before i could figure it out i was lucky enough to get the dreaded ENGINE FAILSAFE mode. had to have the car towed in to a really nice and professional shop in waxhaw nc. turns out that a bolt that holds the EGR valve on backed out and was gone and the EGR gasket had fallen down and it was sucking air and causing the bank 1 and 2 lean codes. long story short it only cost $300 plus $100 for the towing. i was very pleased and the car runs better than ever.:icon_pimp:

I'm hearing more and more problems with the EGR valve, that could very well be the new part up for discussion on the top of the boards. lol

So maybe I should check that next. Can you point me in the right direction to find that EGR valve? As always, thanks for all the help!

Spoken like a true money-squeezed Jaguar owner... happy to get away with a bill under a grand.

The EGR can also have a broken or loose supply pipe that will set a lean code with rough running as well.

P0171
 

I'm Having a P0171 code as well Happened to me on my way from Toronto to Ky
Last month 1st sigh was after my fillup at a gas station. ( Ohio )
The Bad gass theory would make sense for sure.

Then I got home for 2 weeks it was ok and then this week it coded a P0171 again so i decided to change the mass air unit and once again a few days after
it coded me a P0171 once more.

Fuel Filter is next on my list To do considering it has 170,000 kilometers on odometer.

I will look at the EGR as well thanks for the suggestion.

UpDate on my car

Replaced fuel filter no more restrictive performance problems or P0171 /P0174 error codes.

:icon_beerchug:

I've got an 02 X-type 2.5L that threw the P0171 code for the first time yesterday. As near as I can tell, it was due to the sub-freezing temperatures. My car had sat outside at work all day, and I didn't let it warm up very much. When I first tried driving away, an engine code blinked at me, so I stopped and revved it for a while. I was able to drive at freeway speeds for the next 20 minutes. When I got off the freeway and stopped, a permanent check engine code appeared and the car seemed to stutter a bit when I got it up to speed. After that no problem. I was low on gas and refilled and checked the code ( I keep a code reader in the glove box). It was P0171. I cleared it and haven't seen it since. I'm just saying that sub-freezing temperatures might restrict fuel intake or something and flag the code.

I have an '03 XK8 NA... had those codes when I purchased it. I found (THANKS TO THIS FORUM) a rotted air intake hose, which I repared... all was well for 6 months.
Now its back... Right after my last fuel fill-up? Sounds like oxygenated fuel to me.
Any chance this may come from low bat voltages??? mine does it at start-up.
I'm wondering why its monitoring long term fule trims at start-up?