Backfiring through intake, loud sucking sound from intake

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xj_maniac_newb

NAXJA Forum User
Location
Summerville, Ga
Alright guys i've been having this problem for around 2 weeks or so ( i think, who knows days have been running together lately). Jeeps been backfiring through the intake every now and again. Used to just do it every now and again but i never thought anything of it because i didnt know that was what the noise was until now lmao. Heard a loud pow (thought it blew my filter off :D) of course it didnt blow it off, but it did scare the shit out of me. Well that was yesterday, today (well about 15 min ago actually) i came out and cranked my jeep and I heard a loud sucking sound coming from the intake. I could literally hear it inside the jeep over the engine at idle. Any ideas whats going on? I'd go out there and tinker with it myself but its 15 degrees outside with 40mph winds, so its kinda not happening lol. Any help would be appreciated, thanks guys.

And sorry for my shitty grammer, i just came in and its cold as hell outside so i cant exactly feel my fingers all that well.
 
popped a vacuum line off? Just about anything on the intake can cause a sucking sound-- You're probably gonna have to brave the weather and look for the source.
 
I dont think its a vaccum line, did a quick look over yesterday and didnt see any out of place guess i could have overlooked it. The sucking sound is coming from the filter (ive got a CAI) but of course its not the filter itself making the noise, but more the sound is just exiting from the intake tube. Im gonna check it out early in the morning tomorrow, winds blowing too hard tonight to do much. Forgot to mention The jeeps been having a low idle issue as well, not sure if it would be a related issue or not. And i've also got a small blow by issue (nothing that really alarms me, just a tad bit of oil in the intake tube) And on top of that now the jeeps making another noise.. Didnt even bother to really check it out, just went ahead and drove home. Things really pissing me off lately to say the least.
 
Checked again this morning, all the vacuum lines were connected... on the ends. Seems i broke one in half when i was fiddling with it the other day, taped it back up (hate away, im poor as shit at the moment :D) Seemed to get rid of the sound pretty much. But the jeep still runs a little rough, my battery is about horrible and the jeep will just barely turn over in the morning. Could that have anything to do with it? Maybe its not getting the proper amps... who knows. Gonna check the cap, wires, probably replace the plugs, check the IAC if i can get the damn tamper proof torx out somehow..., Im probably gonna go over every vacuum line i can think of. And is there any way you can check to see if the battery is bad without just getting a new one? I'm pretty tight on money right now and really cant afford to replace it if i dont have to. Thanks for the help
 
pull the battery and take it to your local AAP,Auto Zone, Oreilly, etc. They all have the ability to check/charge it for you. While you are there, get a foot of bulk vacuum hose with the same inner diameter as the outter diameter of the vacuum line you broke-- probably about a dollar for the bulk hose.
 
Took the battery, their tester said it just needed to be charged. And the vacuum line i broke is not holding.. I then noticed it doesnt just "come out" of its holder, its got a bolted end under the throttle body other end connects into the valve cover. I've searched for a bit and found its the CCV line i think. I broke it off before it taps into the intake below the throttle body, but i think i have enough plastic line left from breaking it to maybe clamp a new piece onto it and continue it to the valve cover. Think that'll work?
 
I've had similar issues with a carburated 258 cu. in. 6cyl. Jeep engine. Seems, after checking twice, and thrice time all vacuum, electrical, brain box, distributors, and carb., exchanges, the correct timing@top dead center degrees advance, etc., and everything just fine.., wires/plugs, and on, and on.., would still, when 'rapping-up' the fuel/engine rpm, would give a backfire through and out of the carb. (at idle.., it just purrs away). Hmmm.., so at this point I 'believe' I have a restricted exhaust problem in a crossover pipe with it's share of repairs, and or the other probablilty of either a restricted CAT, or collapsed muffler to look into. (best figured out by my next proceedure of dropping the exhaust pipe down from the exhaust manifold by by-passing any further restrictive guess work to better remove suspicious varibles). Sort of like considering a thought experiment of sticking a potato in the tailpipe. Rap on the gas, and what happens? Not enough proper exhaust, leaves the next new fresh gas explosions in the cylinders to perhaps accumulate extra unspent raw gas that builds up to the point that the only clear outlet for the massive over-rich condition must go out the only way remaining to it, i.e., out the intake, and up and out of the carb. Well, on these throttle bodies, there is not too much difference in the flow mechanics as for the aforementioned condition to leave the engine. Hmmm. It's the only thing I can think of if all else is proper.

If your engine idles ok, then spark plugs are down there somewhere on the list.., but I'd replace 'em anyways, along with wires, cap/rotor, etc., just because it can't hurt. Don't know what XJ you have, nor the year.., but there are some good experts that can shed light on the subject of your ECM, and other related fuel/timing sensors, and which to target for specification/values checks, and stuff. Let us know!
 
hmm exhaust... the cat was replaced about 2 years ago because the original was clogged, however the rest is all stock as far as i know.

I've got 1995 w/2.5 4 banger.

Im thinking the CCV line being partially cracked was the issue with the noise from the intake, seems to be gone now that the line is repaired. The backfiring occurs EXACTLY the way you have described yours, when spooling up the engine or when the RPM's are dropping afterwards. And it seems the plugs and/or repair to CCV have fixed my low idle issue, seems to purr like a kitten now. I may try removing my muffler and seeing if that helps, even tho i hate sounding like a ricer :D Muffler is pretty beat up, i'll take it off and see if anything improves however the engine only backfires when it wants to...
 
Well, stock type mufflers aren't too pricey, and running without one will wake the neighbors, and possibly get you a fix-it-ticket should Johnny Law hear it, lol, just put it in neutral, and idle on by, lol! Could be someone here will have had a similar experience working on one, or owning one with same problem.., Anyways, let us know.
 
Haha johnny law dont care much around here. You hear trucks with straight pipe exhaust running down the road all day, and if they pull me over i guess i can always say "You think it's loud too?? I thought it was just me but i could of swore it sounded louder" :D

Hopefully doing the plugs and CCV stopped it, but first time it pops... Im getting ahold of that muffler :D Right now my main concern is 2 new sounds coming from the jeep. Have had no time to listen and see where they're coming from (or if its just 1 sound and im crazy) but from hearing it out the window one sounds like its coming from the tranny :facepalm: And the other slightly sounds like a pulley or something. I'm thinking maybe its the A/C pulley because it didnt make the sound before i fiddled with it (had to unbolt and slide over A/C to change the front plug). Hopefully its just the pulley, but the second sound kind of sounds like a squealing/metal on metal sound that seems to change should the clutch be pushed in... Looking like im bout to find out if i have an external or internal slave.. Lmao
 
Even on a 4cyl? I know nothing of the 4cyls, especially late models, so I'm just curious.

Do you hear a kind of a rhythmic hissing/spraying noise near the motor? If you do, check your compression... my first sign of my impending head gasket explosion was a crummy idle, then backfiring through the intake if I goosed the throttle, then a few cylinders missing regularly at idle and backfiring through the intake under load, then a rhythmic hissing noise and two cylinders dropping, then a severe lack of power. It still runs, so now I have a 6 cylinder / 4 cylinder 2.7L Jeep motor :anon: though it's going to need swapping really soon now.
 
The CCV line at the bottom side of the throttle body runs to the MAP sensor on the fire wall. When it leaks (breaks or comes loose), it makes the engine back fire during heavy acc or dec. Usually it gets knocked loose doing other service work under the hood. The backfiring and sucking sound are the clues!!!!
 
Backfired again today, seems i didnt fix the problem. Relocated the IAT to the intake tube to see if it would help any, seems i've got blowby with oil and what smells like gas? What in the hell is going on with my jeep?

And yeah, i actually do hear some kind of noise.. But after a little inspection i found that the new noises i hear are coming from the tranny.. Looks like i need to hurry up and find that new 4wd tranny, guess my search for parts for my 4wd swap needs to be put on maximum overdrive.
 
After the sucking noise

xj_maniac_newb said:
But after a little inspection i found that the new noises i hear are coming from the tranny.. QUOTE]

Are you sure you are not talking about a party gone wrong up in San Francisco:roflmao:
Click to expand...
 
If you're sure you've repaired all the vacume leaks and are still experiencing back firing through the intake. It can be caused a a lean air/fuel mixture, I'd check your fuel pressure. But definately make sure you have all the vacume leaks fixed first cause that would cause both symptoms.
 
SC Rednek said:
My girl had a "loud sucking sound from the intake" the other night. I don't think that's a problem. Can't give you any advice on the backfiring.



sick man, just sick
Click to expand...

hawkeye 1 said:
After the sucking noise
Click to expand...

xj_maniac_newb said:
But after a little inspection i found that the new noises i hear are coming from the tranny.. QUOTE]

Are you sure you are not talking about a party gone wrong up in San Francisco:roflmao:
Click to expand...


Lmao, old girl's been making some weird noises.. Was talking about trading her in for a newer model the other day and she got all heated and started smoking :D
 
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