P0456 P0455 P0442 P1294 Code Bananza!

So finished up overhauling my brakes, adding new shocks, changing all the tie rods, and doing a number of completely unrelated things and took her for a test drive. She immediately threw a P0456 (small EVAP leak) :flamemad:

After looking through the hoses and not seeing any clear hose issues (cracks..etc) I ordered a new Mopar gas cap and installed it. I unplugged the battery to rewire all my speakers (don't ask). After taking driving for a few miles the engine light came back on, except this time it was P0455 and P0442 (a big leak).

A few miles more it throws a P1294 code.... it sounds like a vacuum issue but I've checked just about every hose and connector on this thing and nothing seems too out of the ordinary (cracks...etc).

I'm not smelling any fuel on a regular basis (I had smelled fuel under the hood when I removed the vacuum tubes to the intake manifold so assumed that was normal). The car seems to run just fine and the idle seems ok despite the P1294 code.

I hate to start throwing parts at it considering the amount I've already put into the other areas... any bright ideas or do I just start with the purge valve and hope that works... then move to the charcoal canister... then move to the fuel tank... filler hose... :bawl:?

Instead of shotgunning random new parts at an undiagnosed problem, you should follow the trouble codes, and find the root cause of the trouble codes.

Always suspect the most recent repairs or modifications may have caused the problem, or that while doing the work, you dislodged or damaged a hose or hose fitting.

Starting with a comprehensive visual inspection and a smoke test is recommended.

What year? Considering the location, i'd have a good look at the evap canister, as it would have been easy to snag it dropping out the rear shocks.

Thanks Tim and RCP!

It's a 2001 XJ Automatic 4x4 with 138k miles

What complicates things is that I had to run all new stainless brake lines so I could have dislodged just about about any part of the EVAP lines considering they run next to each other.

I did a pretty thorough inspection of the hoses yesterday and nothing seem too bad with the exception of a super rusty line that goes from the tank to the charcoal canister. I'm not clear on how to replace that one as it's a hard line and not plastic but I also didn't see an obvious break in the metal.

I pulled the large short hoses at the leak detection pump and they were perfect. I'm curious if pulling those caused further deterioration of a hose down the line as my P0456 went to a P0455, P0442 soon after... the only connection near that spot I couldn't really look at as it was directly behind the engine next to the firewall. I may just have to pull that entire hose to get a better take on that connector.

The short larger diameter soft connector next to the left lower control arm seemed a little worn and cracked so I went ahead and replaced it. I also had a purge valve sitting around from a poorly diagnosed EVAP issue on my previous Cherokee; I knew it worked so I threw that in their also. I reset the code but suspect it will be back since I haven't found a smoking gun. If so I will have to get my halloween decoration out to blow some smoke.

I'm curious, how does one know if the charcoal canister is bad? Is it obvious external damage (cracks..etc) or just testing to see if the input/output flows freely?

Thanks again!

you can install that purge valve upside down pretty easily, it is labeled top or bottom iirc, is easy to identify though.

just another thing to check.

A smoke machine is ideal for chasing EVAP leaks. However, where the brake lines run down out of the engine bay, near the drivers side rocker, there is a rubber joint on the EVAP line. This rubber joint can crack even on the top side where it can't readily be seen. You might want to check it. I had a mechanic smoke mine about 10 years ago and he found that rubber joint was shot.

md21722 said:

A smoke machine is ideal for chasing EVAP leaks. However, where the brake lines run down out of the engine bay, near the drivers side rocker, there is a rubber joint on the EVAP line. This rubber joint can crack even on the top side where it can't readily be seen. You might want to check it. I had a mechanic smoke mine about 10 years ago and he found that rubber joint was shot.

Click to expand...

My 2001 had a small crack in the rubber fitting described, it could not be seen and was only found when pressurizing the Evap system with 5-psi compressed air, not having a smoke machine.
The leak could be heard, when the compressed air was applied.
The pressure was limited, using an air brush regulator in series with the compressor's regulator, to prevent damaging the fuel tank and another sensitive parts .

Thanks everyone for the help here. After about 40 miles after replacing a couple of rubber hoses and the purge valve the light came back on (P0455).

I had a couple of free hours today so I just pulled all the lines, pressure tested them, and replaced all the rubber (got tons of extra new hose laying around). The one with the clamps next to the exhaust manifold was a total PITA. Some rubber connections looked better than other but none of them seemed terrible.

I pulled the charcoal canister and tested it. It seemed to flow OK between the small inlet/outlet tubes when blown into. I didn't' see any noticeable cracks either. I did have the old charcoal canister from my previous XJ sitting around. I did notice that one sounds like it has sand inside when I shake it and the one I took out of this XJ made no noise when I shook it. Not sure if that has any bearing on it being good or bad.

What does seem suspect to me is the connection between the gas tank and the charcoal canister. The metal is really rusted and it seems like it might be loose at the top of the gas tank.. but I don't know if it feeling loose is normal. I took a really good look at the metal line and didn't see any obvious holes or cracks. I assume the only way to know for sure is to drop the tank and check the connections? Really don't want to do that.

I'll go ahead and reset the code and see if it pops back on... I assume it will as I really haven't found anything that looks like the culprit. I'm just hoping it doesn't end up being a fill hose or something on top of the tank.. :bawl:

Thanks again!

Well... P0455 came back after 40 miles of driving. I'm giving up and taking it to mechanic as I'm completely stumped on this one and I've wasted too much time trying to fix it without proper diagnostic equipment. I suspect it's either that rusty line from the gas tank or something to do with the gas tank itself.. maybe the leak detection pump... hopefully someone with a smoke machine and pressure testing equipment can figure it out.

Let us know what you find

FIXED:

Got my local shop to smoke test it ($49) a couple weeks ago and found that the metal line (the really rusted one) that appears to have been added before my time did in fact have a leak in it but would have been difficult to detect without getting it smoked.

I went down to autozone and bought 3' of 1/4" evap hose and clamped it on in place of the rusted line. I've put a couple hundred miles on it since then and it appears to be fixed!

Lesson: Get it smoked tested if nothing is obvious and go from there.

Thanks everyone for your help!