xj_maniac_newb

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 ) of course it didnt blow it off, but it did scare the **** 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 horrible grammer, i just came from outside and cant feel my fingers )

whiteXj2

Back fire through intake = intake valve not closing completely during exhaust stroke. So in turn that means a bent intake valve, or one thats no seating properly.. Had this issue on my renix motor, bent 2 intake valves.
good luck bud.

DFlintstone

Ha! Mine blew the mouse nest in the air cleaner out through the front grille! I drove through the confetti. No sign of the mouse.

First find the source of the noise. Sounds like a vacuum leak. You can listen through a section of hose to help locate it. Also if you hit it with a short little burst of starting fluid the sound of the engine will change.

You can check a couple of easy to reach manifold bolts. If you find some loose, you'll need to pull the air cleaner and tighten them all, working from the middle out.

Hopefully it's just a vacuum line.

xj_maniac_newb

HAHA! thats funny as hell Bet that mouse went for a ride!

Noise is coming from the filter (got a CAI) but not sure where its actually originating from..

Im hoping its a vaccum line, I've been having low idle issues anyways so im probably gonna check the IAC tomorrow while im at it if i can ever figure out how to get those damn tamper proof torx off...

DFlintstone

Yea agreed. Guess the torx DOES work well, I just don't have'm all with the nifty goodies and all. Tj or freedgr mentioned a few times popping back can be from too lean. You might want to check fuel pressure. Also..you gapped your plugs lately, check/clean your cap? Mine was the wire gang going down to the sensors under the manifolds shorting out on the edge of the heat shield, (on my 90). Took me over a year to find it since it was on the bottom. It would be fine for days. Also I could start and run fine all day, but when I'd shut it off heat would migrate to the shield, make it expand, then it would make a little contact, sometimes. Fun one!

Idk which it was grounding, I just wrapped it. It's now rerouted from where it is here.VVV

xj4banger

change ur up stream o2 sensor! good way to check it is to unplug it and drive it around for a while, i bet it gos away

xj_maniac_newb

upstream o2 sensor? hmm i'll do that
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 **** at the moment ) 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.

DFlintstone

Well, I have lots of 12V here as well as cars I can jump from. If you pull the coil wire and ground it, crank it for a count of 10. let the starter cool 20 sec, if it's still cranking about the same on the third 10 count I might call it good.

Hey, I'm thinking you broke the MAP tube. The flimsy thing from your TB up to the MAP on the firewall. The MAP will dump loads of extra fuel if it leaks a little. On mine I hatcheted 2 in. of line from something else and spliced it.

You are joking about "tamper proof?"

xj_maniac_newb

Not at all.. Some jeeps came with them for some reason, they've got a metal piece in the center so you cant fit a normal torx in them. Found out i can buy the right size bit from advance for a few bucks tho.

I think i've broke what is my CCV? valve line running from the valve cover to under the throttle body. I was trying to remove it to replace it and never realized it had a metal end and connected into the throttle body.. I thought it was just the nipple to connect to, apparently it wasnt. I'm thinking on trying to just get a tiny hose clamp and connect on from the piece running out from it.

DFlintstone

Torx. Yea OK. I ran into some of those POS deals on an inverter or something. Tricky to drill off the heads and still leave enough stub to unscrew with pliers.
Not much help. Maybe borrow the driver just 2 minutes to change them?

My 90 CCV is a little different, goes into the intake manifold up front. Anyway don't think tape will do. I'd replace it or splice the break with a tube that fits. I don't usually use clamps on vacuum lines. With a snug fit the vacuum seems to hold well. (even when firing mice!)(he's loaded for cat) Since vacuum is so crucial for the MAP, I'd make sure it nothing leaks. Also, again, if you hit a leak with a short little burst of starting fluid the sound of the engine will change.

Well, all I can say is check that cap & plugs. The IAC & vac leaks. All stuff to do anyway. Maybe check the fuel pressure. Take it from there....

EDIT; Oh and. In my experience, once the thing is running and the alternator is holding the system up around 13 Volts, having a weak battery has not been a issue. That said, I've seen plenty of posts saying a weak battery can cause problems running.

xj_maniac_newb

Fixed the ccv, took a little hillbilly engineering Either way its fixed snug and good, no tape involved at least lmao. Now that i fixed my own mistake, its time to do some work.. Gave the battery a full charger, bought some new champion plugs to try. Hopefully that'll fix it, been about 2 years since they were changed i think probably need to do it anyways.

DFlintstone

Cool. I normally only hire hillbillies for VW work though. Cause I'm cheap, and due to the limited number of moving parts, sometimes I'll clean a dizzy cap (& rotor), in the kitchen sink like anything else. Carbon tracks, hell to see on a black one are the major killer. TWO YEARS! Your gap might be close to 45 thou!

xj_maniac_newb

haha hey they're getting replaced now and to make it worse i never even cleaned or regapped them... ever they're pretty nasty lookin, i've got all but one in and cant figure out how the hell to get around the AC condenser! its RIGHT in my way lmao. And they guy at advanced gave me my gapper for free cause i lost my other one somwhere lmao. I'm almost thinking of just not fixing the backfire if it keeps goin, maybe make it STRONGER! that way i got a Mouse cannon like yours hahah

DFlintstone

Can you fit a 13/16 wrench on the end of the plug socket?
If your old gaps where huge maybe you found your problem.
This optional grader attachment lets you fire "diced mice".

xj_maniac_newb

hahaha ready to serve to the cats!!

Unbolted the AC to get to it, just slid it over. Wasnt hard to get the plug out actually, real problem was the wire... thing wouldnt come off! Finally got it off somehow by pulling at the perfect angle i guess. Jeep actually runs better now, no more low idle and seems to be better.. i think the sound from the intake was coming from the CCV valve being cracked, as the sound is nowhere to be found. Guess i'll just have to see if the back firing is fixed, it only did it every now and again and never when i tried to let someone hear it Gonna replace the wires with a new set i've got when i get time again, they're just at the other house at the moment.