many problems...what is this?

first off im going to say sorry, because it seems theres been a ton of questions about pretty much the same problem lately...but most have dealt with older xj's with the RENIX system...(mines a 1998) and mines a little more specific. and Ive spent a long time flipping through the other threads trying to find the answer. so anyways the engines been running horribly lately. violent intake backfiring, but only after a few minutes of driving, and once the engine temp has reached about 40-60 degrees. It basically cuts out, stumbles and then backfires...all while low throttle application, (under 2000 rpm). It also occasionally has a very hard time keeping idle and chokes on itself, but the rest of the time is perfect at 750 rpm... so the obvious things I started thinking of O2 sensors, MAP sensor, TPS, CPS, fuel injectors...lots of possibilities i guess. but I started by checking torque on the head bolts for the exhaust/intake manifolds and then took a spray bottle with soapy water and searched for leaks. I came across this thin plastic pipe that looked bent a bit so I sprayed it at the bend and sure enough it bubbled. so I cut the ignition and went to touch it and check it out...completely snapped off and i barely even touched it. very brittle. my question is...what is this pipe and could it also be the problem im having with the engine?

It would help if you cropped those images, and posted them one on top of each other instead of side-by-side, it would help us ALOT.

Anyway, i doubt that a vacuum leak would give you backfire through the intake, that only seems to happen when running lean. Have you checked your feul pressure?

ya I did sorry about that :S when i posted it and saw it I freaked. cropped them down. this should be better and as for the fuel pressure im picking up a guage tomorrow so ill get a reading then..

A large vacuum leak can cause a vehicle to run lean.

Top photo is a MAP sensor, correct me if I am wrong. Just replace that vacuum line all the way back to the sensor.

oh is it? I thought the map sensor was either on the drivers side firewall or throttle body?..maybe im just mixing it up with the older models again...

actually the first pic to the left is an evap solenoid of some kind. on newer models the map is integrated to the intake manifold.

ok so the bottom line of the two connected to that solonoid is the one that is broken over by the intake manifold. is it possible that whatever its purpose is, is the cause of the behavior I posted above?

It's a vacuum line and they get very brittle. I have 2000 and mine crumbled apart in 8 dif. places. I replaced it with tubing from HD that is meant for a hot tub and so far it hasn't been a problem.

ok so temporarily I put in another piece of a small hose connecting the broken section..just to get me to school. but as an update to the situation...what I find strange is that when the backfires and cutting out happens...if I turn of the ignition and turn it back on it runs perfectly fine.... so is my ECU fried? any ideas as to whats going on?

Still running lean .. i bet you didn't check your fuel pressure yet?

not as of yet. picking one up in a couple of hours....so assuming it is running lean, theres still a pretty big number of possibilities that could be causing that. any suggestions as to where I should start with checking/replacing, or common problems that might cause the symptoms listed above? any inupt would help a lot. thanks

Start one step at a time. Check your fuel pressure and make sure its up to par ... im almost willing to bet your pressure is on the low side.

2KXJmakinwaves said:

It's a vacuum line and they get very brittle. I have 2000 and mine crumbled apart in 8 dif. places. I replaced it with tubing from HD that is meant for a hot tub and so far it hasn't been a problem.

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Watch out with that stuff - I'm willing to bet that the line you used is "pressure" line. While not a huge issue, it will eventually soften and collapse under vacuum (which can be a HUGE pain to diagnose!)

"Vacuum" hose is constructed so that, even if it does start going soft (which is will...) it won't collapse under vacuum. That's why there are two types of hydraulic hose - pressure (which is designed to not explode) and suction (which is designed to not collapse - and is usually rigid.) The principles are the same.

Common sizes of vacuum line are fairly cheap at parts houses (in bulk,) but I've yet to see a hardware store that actually carries "vacuum" line in any size at all.

The tube I used is actually really thick, thicker and slightly larger than stock. But, I had never considered it getting soft and collapsing, that's a good point and I'll watch out for that. Thanks

2KXJmakinwaves said:

The tube I used is actually really thick, thicker and slightly larger than stock. But, I had never considered it getting soft and collapsing, that's a good point and I'll watch out for that. Thanks

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So what? The difference between vacuum and pressure hose isn't material thickness, or even material used. It's the structure of the thing that makes the difference... Yes, vacuum tube does have a somewhat thicker wall, but that's not the only difference, normally (especially in sizes over 1/4".)

so I couldnt pick up my pressure guage as my friend who is somewhat lacking in intelligence accidentally took it back with him to university...in nova scotia. lol however I took the cat out as these problems began to arise shortly after i installed it. i also replaced that vac line with some poly-urethane vac line from home hardware. its actually gotten a lot better...still some slight popping, but as a new addition of problems...the RPMS take a really long time to go down when i take my foot off the gas.. its like ive got cruise control. i have to put the clutch in and come to a stop before it really responds...so i guess ill clean out the throttle body and ill need to check the TPS...any other suggestions?

ok. checked it out, says its running really rich now. which makes sense because it doesnt sound like its sucking any air in. noticed both o2 sensors were shot, one had frayed wires and shorted out and the other wasnt working properly and looked pretty bad so i switched those out for new ones...yet now the intake backfires have come back.... it seemed like it was responding a lot better for a few minutes but then just like it had been before it cut out around 40 degrees. so its almost like ive gone from rich to running lean again...any suggestions? the CEL has also come back on by the way.

Whats your fuel pressure? It doesnt help to ask questions on here if you dont try the suggestions. A screwed up fuel pump or fuel pressure reg will cause these problems. Go to autozone or whatever and rent a fuel pressure gage. Dont expect a lot or responses if you dont heed the advice.

hey. sorry, it wasnt my intention to disregard the suggestions I just didnt have a guage at the time and was simply asking if anyone knew of some other temporary things I could check while I was waiting for one, but I guess not. However mine was finally returned to me and I hooked it up and the pressure is dead on 49 psi at the fuel rail test port. I hooked it up so I could watch it while driving and when its acting up and no matter what it is constantly on 49 psi....so any ideas as to where im heading with this? kinda stumped as to what the next step would be. any help would be appreciated. thanks

- as a side note.... I replaced the O2 sensors as one seemed to have stripped wires and shorted out, and the upstream was in pretty bad shape... CEL is back on. going to go by a local shop and get them to read off the codes for me.