Hey everyone,

i have a 04 XJ8. P0171 code that i cant get to go away for months now. i replaced the PCV valve and taken it to a mechanic who said it was possibly o2 sensors which i replaced as well. i fabricated my own smoke test and found smoke coming out of the EGR valve and the oil dipstick tube. from my research it says that the EGR valve doesnt cause that type of code so i havent decided to pay the $400 to replace it and i have no clue about dipstick tube air. mechanic said that its normal to have some air coming out of the oil dipstick tube. any thoughts on what could be my problem? i also get "performance restricted" on the dash for the first 2 minutes of my drive then it goes away. car idles at like 900 rpm whether thats important or not. i found that unplugging the EGR while the car is running seems to not effect the engine at all. also not sure if thats normal or not. any help would be appreciated as yall are great.

 

checked the maf yet?

 

Yes replaced the MAF with a good quality one. not the cheapest. new air filter as well.

 

I'd try to find a new dipstick seal, I had this code in my 2005 Super V8 once and this was one of the things I did to resolve it, I discovered and fixed a few other things at the same time so I can't swear this was the fix but it was the last thing so maybe...

 

- Replace dipstick O ring

- Replace EGR valve

- Replace mechanic

 

"Replace mechanic". nice. good one. seems theres not a competent jag mechanic near me as this is the 3rd mechanic ive taken it to.

The dipstick o ring seems like a pain in the rear to replace. any pointers on that?

ill do what has been advised here. fingers crossed it works.

 

+1

Main issue is the EGR valve exhaust leakage... your valve most likely good, but 1 or both gaskets leaking or the EGR pipe - its throwing your O2 sensors off on bank 1 and thus your persistent P0171.

If you speed up, heavy throttle and shortly thereafter smell the exhaust in the cabin that is your main culprit. You need to remedy sooner than later or you can add a catalyst to your parts list.

 

Dipstick o ring very easy - just match the o ring up best you can. A digital caliper is your friend.

On the downside, the EGR is your pain in the *** to contend with. Rusted, almost inaccessible bolts, etc....

Good luck

 

yea ive already attempted at removing the EGR bolts and failed. i'd be fine cutting them off but that too is a pain with no space to reach.

for the dipstick "o" ring, what parts do you suggest to remove to be able to pull the dipstick tube out? seems the brake oil reserve needs to be moved at least. i've read about leaving the dipstick in the engine to be able to easily slide the tube back into place but how the heck do you leave the dipstick in and remove the tube (red handle top very much in the way)

 

I'm referring to the o ring on top of the dip stick.

 

OOOO really? wow i was thinkin at the bottom of the dipstick tube. ok then ya that would be an easy replace. ill find a new o ring for that

 

anyone have the torque specs of the EGR Valve bolts? ill check to see if they're tightened properly

 

if it’s the o-ring at the bottom it is a PITA

get another dipstick and cut the handle off so you can use it to locate

 

Hyrum,
You're getting some good advice here...lots of experienced folks

- Soak the egr/tube bolts with rust buster daily foe a week, and the bolts will come out. Use six point socket. You may need to remove some of the firewall stuff to get access

- Diagnostic smoke leak at egr valve prob means bad diaphragm, or blown gasket, as noted above. Either way, it needs to come out

- The worst vac leak on my car was vac port adaptor at throttle body elbow. PITA to get to, but if its loose in the elbow, its leakin'

- Your mechanic may have mixed up EGR with vac adaptor - they're right next to each other and v hard to get to. Check to see if adaptor tube is loose before monkeying with the egr valve

- That adaptor tube is sealed in the TB elbow with a tapered sleeve. If the tube is loose, try gently tapping the sleeve in; it may seal up if no too far gone

- There's a molded vac line that runs from adaptor to LH rear of engine compartment. Support it with a couple zip ties so it doesn't work the adaptor tube loose again

 

Passing by from the X150 and saw the headline. I fixed this problem on my '07 NA 4.2 engine.

P0171 is triggered by the Long Term Fuel Trim LTFT passing 20%. Ideal is 0%, typical is +- 5-8%,

Almost always caused by a big or multiple small vacuum leaks. First, clean your MAF. Then monitor your LTFT with an OBD scanner. Until you get Bank 1 & 2 LTFT readings fluctuating near 0, you haven't fixed it.

IMHO, the only way to fix these is a smoke machine. A cheap one from Amazon is fine, but you need to be able to drive high pressure through it. I was only able to find it with a good smoke test -- meaning high pressure one. To get high smoke pressure in the engine, you have to block off the throttle body with a pressure resistant block. Typical rubber glove will leak at too low a pressure, causing you to miss smoke indications of bad seals. I used a Home Depot 3" rubber plumbing stop with a hose clamp.

Got the pressure up and revealed:

Bad EGR gasket
Bad dipstick gasket
Bad oil fill gasket
Several other orings had begun to leak.

And the root cause, one of my injector lower o-rings was ripped, causing a major smoke exit that wasn't visible until the smoke pressure was high enough.

The point is that these engines have a lot of vacuum leaks as the orings and plastics age, and you need to get them all to fix it.

Good news is that a good Oring kit will fix most of them. Of course, the EGR leak is a metal gasket and will need to be replaced. The EGR itself is usually not the problem. The metal gasket is about $15. O-ring kit about $20 (get a vitron one because why not?). Injector rebuild kit (top & bottom oring, pintle cap, intake filter) about $20 on Ebay

Good luck

 

i have a massive exhaust leak at the collectors and my trims are single digits.

the egr flange at the tb is probably what will throw it off. focus on those bolts first

 

his car is not supercharged

 

Thanks everyone for the great advice! i replaced the o ring on top of my dipstick and FINALLY got the dang bolts off the EGR so i can get that removed. i just noticed the new post about a good high pressure smoke test.

With the rubber plumbing stop how did you attach the smoke tester hose into that so it blows into the engine? Also do you remember where you got o rings for the fuel injectors? im gonna look into that as im pretty sure my fuel injectors are quite old.

i may end up replacing the EGR valve just to really cover all my bases.

 

I had a P0171P0174 codes on my 2004 XJ8 (US model).

Long term trims were 19.5 with short term at ~0. Smoke tested everything. Had a leak in the intake hose and bought a used hose and replaced it. The code remained. Pulled the check valve from the brake booster (was looking for anything that could cause the leak). Check valve works (I could blow through it but not suck through it). Kept it disconnected and plugged it. Started the car an long term trims quickly decreased to 12 with short terms at -8.

Changing the booster solved the P0171 and P0174 codes.

 

I'll have to check the fuel trims. Not very knowledgeable on what to look for eith those and what is even normal. I replaced the EGR eith a used but working part and replaced the upper small gasket on the oil dipstick. I'll take it for a spin soon to see how it does.

You said you changed your booster. What part is the booster?