PoorMansWrangler

Hey guys, running into issues with my jeep again. Its a 2000 Cherokee sport, 135k miles and I'm just beginning to work on it. I am not mechanically inclined what so ever, but I'm trying to make it work. I recently replaced my motor mounts with brown dogs, and almost immediately after that I have noticed at idle it wants to run. I can hear the engine struggling, almost like it is almost out of gas/air. I have replaced the o2 sensors, the spark plugs, TPS sensor, oil pressure sending unit, and also a new air filter and I have cleaned the IAC valve and throttle body, along with a new throttle body gasket. My jeep does not have a distributor, or spark plug wires, just the coil pack. The jeep runs perfectly long along the highway, but if I stop for more than a minute, it starts acting like it is going to die. I was going to replace the fuel filter, but it is in the gas tank. I seafoamed the throttle body, and added royal purple fuel additive cleaner, with no real change. I am lost as to what it could be, any ideas? Thanks!

CurrySoSpicy

Go to your FLAS (friendly local auto store) and rent or buy a fuel pressure gauge. We need to confirm your getting good pressure at the rail. I can't remember exactly what the pressure specs are. You can look them up using the search function. Diag before firing the parts cannon again.

CurrySoSpicy

It's 49 PSI at idle, plus or minus 5 PSI. Anything out of the specs. Look into replacing the fuel sending unit.

PoorMansWrangler

Thank you! If I swing it by, will they be able to check the pressure? Is it a plug in or some sort of other situation?

CurrySoSpicy

There is a sort of Schrader valve (like a bicycle tire) on the fuel rail where the gauge connects to. They won't check the pressure for you. You will have to "rent" the gauge. They make you pay a security deposit, when you return the gauge they give you your money back.


The fuel rail valve


The gauge attached

PoorMansWrangler

Got it thank you! Will check back in tomorrow. Was doing some research, and I don't think it's a clogged cat, if it helps at all. It started acting up right after I changed my mounts, so I am wondering if I bumped a sensor or a wire?

CurrySoSpicy

Could be. Could also be a bad IAC (sometimes cleaning isn't enough, the physical unit needs replacing), maybe issue with TPS. Report back after fuel pressure test. There will be plenty of people here to help. Seems like your problem is happening at idle only. That gives us clues. Good luck.

PoorMansWrangler

Yesterday I ran to autozone, and I checked the fuel pressure which was 33, so that's normal. On the way to the store, my check engine light came on, for the auto shutdown relay, so I went ahead and replaced that. I had no clue about this , but it seems like this could be the issue. I haven't been able to drive the jeep yet, but I am going to take it for a spin tonight, and plan on driving it into work the next couple of days and I'll report back later

CurrySoSpicy

dude, your fuel pressure is supposed to be 49 PSI at idle. 33 PSI is out of spec. Too low.

MtnGoat

Hiccups. Low fuel pressure. Fuel filter?

tjwalker

Yup, if your 2000 XJ is truly at 33 psi of fuel pressure, you should replace the entire fuel pump assembly (inside the gas tank). That is the only way to resolve and get you back to 49 psi.

Do not install an Airtex or anything rebranded by them IMHO. Bosch is my favorite, Carter is okay.

PoorMansWrangler

Sorry, looks like I fat fingered it, typing on my phone my fuel pressure was 43ish. I replaced the ASD relay, as the check engine light code came on for #P0135 O2 B1S1 heater circuit, and P0141 O2 B1 S2 heater circuit. This morning on start up, check engine light came back on, and I will have them run the code again. It's tough for me to pin point/describe, because it won't idle rough all the time. This is why I don't think it is my fuel pump, however I could be wrong.

tjwalker

The codes you mention may be related to a blown "fuse" for the oxygen sensor heater circuit. Yes, it is fused. The fuse is in the PDC (black box under the hood) and I believe it's a 15 amp mini-fuse, although I can't recall off hand the exact location, maybe somebody will chime in. Start by checking all of the 15 amp fuses.

When you have multiple codes and they all have the word "heater" in the code definition, you MUST check this fuse before moving onto anything else! I have seen these exact codes before in combination and it was a blown fuse. Here is a related thread that you should read.

https://www.cherokeeforum.com/f2/o2-...circuit-33042/

Good luck and let us know what you find!

PoorMansWrangler

Ok I will do that this evening! Driving home yesterday, jeep started hiccuping again, and I lost all power to the engine. Luckily I made it to the median and turned it off and it cranked right back on first spin, and I got it home. Could this be another issue? And would you recommend just pulling all of the mini fuses and replacing them, or just pulling them and looking at them and replacing them? Would I need to re set the computer after replacing the fuses also?

tjwalker

The fuse you are concentrating is a mini-fuse (there are 2 sizes of fuses in the power distribution system). I'm pretty sure it's a 15 amp, but pulling and inspecting the mini-fuses is very easy. The fuse casing is designed so that you can look at them and see if the filament is blown or not. This is a 5 minute job, so don't delay.

No computer reset necessary if you find a blown fuse. Replace the fuse and see if that resolves the issue.

Yes, there could be another root cause....but you must eliminate this simple possibility first. Otherwise, you could be chasing your tail......