Hello,

I am home sick, my wife and son took the Jag to see grams and gramps.

I got a frantic call and it seems the car is having some trouble. It is in "restricted performance" mode with the check engine light on.

I had her go to autozone and get the codes read.
There's p0171 p0174 p1111.

After a little searching it seems like a vacuum leak in one of the various rubber hoses in the vacuum system can cause this problem.

Side note: I had a peek under the hood last night and saw a crack in that top "crank case hose" circled here:


I put a sleeve and clamps on it temporarily - which seemed like a perfectly adequate patch for now. Bad idea?

 

P1111 is normal and should be there. It means all emissions protocol tests have been completed.
171/174 are lean codes left and right bank, or right and left bank, I forget which is which, but the important point is that having both indicates you potentially have a vacuum leak upstream of where the airstream splits to go to the left and right banks of the engine. Plenty written here on it. Search "P0171" "P0174" and/or "Vacuum"

JoycesJag has posted an excellent vacuum line how-to and I believe it is in the stickies.
They should make it home from Gram's just fine, as long as the "check engine" aka MiL is not flashing. Flashing would indicate catalyst-damaging misfires and would be badness. I've had P0171/174 simultaneously and never noticed a performance degradation. I've also had the restricted performance flag and the engine was self-limiting at 3000 rpm....a bit bothersome but still easily driveable.

Edit: Just saw your picture. Not a bad idea, but apparently an unsuccessful mitigation. A leak in the circled hose would certainly explain P0171/174.

 

Great, that is what I was thinking. I told her to drive it as long as it wasn't giving her obvious problems on the road.
Been working on remodeling the house, guess I need to put the circular saw away and get the wrenches back out

 

Hi

The code p1111 just means that the car has not done a complete cycle since the mastered and can be ignored.
The other are showing that the banks are running lean.

code P0171 and p0174 may mean that one or more of the following has happened: The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. There could be a vacuum leak downstream of the MAF sensor Possible cracked vacuum or PCV line/connection Faulty or stuck open PCV valve Failed or faulty oxygen sensor (bank 1, sensor 1) Sticking/plugged or failed fuel injector Low fuel pressure (possible plugged/dirty fuel filter!) Exhaust leak between engine and first oxygen sensor



Read more at: https://www.obd-codes.com/p0171

Copyright OBD-Codes.com

Get your son to clean the MAF first. Then look to see if there is air leak by using a smoke test. I think we can ignore that it may be faulty oxygen sensor as both are reading the fault.

 

He's 8.

 

Never to young to start..

 

The opposite is true, P1111 means that all self tests HAVE completed. Having P1111 is a good thing.

You must be thinking of P1000.

 

This is true.
I had him crawl under with me during an oil change a while back. I pointed out some components and gave him a simple explanation. He was probably 7 at the time. I'm not 100% sure it sunk in.

 

FWIW - It was a very cheap and easy repair.

Before I sent them on the road I had noticed a crack in that top air hose. I temporarily sleeved it with a larger piece of hose thinking that would be adequate temporarily.

So in the process of maneuvering the sleeve and clamps into place I think I ended up making the leak worse instead of better.

A couple weeks ago it got really cold here -- around zero F in the mornings. My wife mentioned it didn't like those start ups in the morning. I didn't think much of it at the time but now I think it was the first sign of that hose starting to leak.

I just replaced it with a <$2 piece of 5/8" heater hose and some SS clamps. Running fine now. Need to clear the mil light. Will it clear on its own eventually?

Even with the cracked hose -- on the highway the "restricted performance" indicator went off.

 

It'll clear only if the fault is fixed, after 3 warm ups.

 

My 2004 S-type jag is in "Restricted Performance" mode. If I sit at idle in park for about 5 min the light goes off and if I get on the highway it goes off. But around town when running in mid-range the light comes on and goes to "Restricted Performance." I've had ALL the gaskets replaced and the smoke test showed NO LEAKS. Any ideas?

 

Not without any codes. Can you read them please and then start a new thread about the problem because I am sure you will get a better response.
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You need to understand this is just the beginning? If you don't go in and fix all the problems they will occur one at a time and it will be much more expensive.

You have the V-6 and as you have read there are a list of known problems that need to be fixed all at once. Your vacuum leak can be from that hose and several others that are waiting to break too. Replace all the rubber vacuum tubing.

Has the vacuum elbow been replaced?
At this late date I would replace all coils and plugs when you go in.
Do you know about the IMT O-rings?
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