What in the world is this thing on the airbox?

[dick.breakey]

89 cherokee(sport i believe) 2 door 4.0 w/ aw4. 155k

here it is. i think its vacuum actuated if im not mistaken. im having trouble with the jeep running correctly. i bought it for 350 bucks from a guy who couldnt get it to run right. from the symptoms i figured it was just a grounds issue and wanted to capitalize on his inability to properly diagnose it. before it would only run with the gas pedal pressed in and it would run very rough. would barely idle if it did idle. after a full tune up and cleaning the iac and tps, and replacing the o2 and cps sensor it now will start on its own, and idle perfectly, for a minute. then it will randomly kill its self. sometimes it just bogs down where the rpm's barely register so it shakes like crazy and then i just shut it off. if i open the throttle too fast, and i mean any faster than a CH at a time, it will instantly die, yet when i do it slowly it will rev perfectly. but most times it will die if i just let off the throttle all the way. if i step it back down it will go back to idling. so ive been troubleshooting this thing on and off, and the haynes manual has helped some but nothing this specific. so ive gone from hardly starting and no idle to starts, idles great(before it shuts its self off) and kills its self when the throttle is opened. i also have not been able to check the fuel pressure cause i dont have a gauge and cant find one for an affordable price. i might just go to harbor freight in a little bit though. anyways. so after everything, i think ive got it narrowed down to either the fuel pressure issue or this thing i have no idea what it is. the pics show where it is on the air box and this flex tube that goes under the intake manifold. what is it and what does it do? i couldnt find it in the haynes either and i have never seen one of these on the h.o. motor, so i assume its renix specific. lastly, while its running, instead of opening the throttle a little at a time, if i go WOT immediately, sometimes it will stay running, but cough real bad for few seconds and then rev up and when the revs come back down and i try again, it will pop as if its coming from the intake, but also kinda sounds like its coming from this mystery part. any help would be appreciated. i dont know the 4.0 real well, only from what ive researched and all my 4.0 buddies say.

 

[DoctorK]

I had the same question last week.

http://www.naxja.org/forum/showthread.php?t=1040033

Unfortunately, I don't think it's the cause of your problem.

 

[5-90]

That would be the intake preheater door, and it's vacuum actuated. It's supposed to switch to draw air through that corrugated metal tube, which is attached to a "choke stove" - a sheetmetal housing that surrounds the exhaust manifold.

The gate is switched by a thermal air cleaner valve on the back end of the airbox, it's in the top half. You'll see two vacuum lines going to nipples about a half-inch apart on the airbox lid - that's the thermal switch.

Utility? Almost none - fuel injection automatically compensates for ambient temperature, and port fuel injection uses a "dry" manifold and isn't really subject to icing like carburettors and throttle body injection (the original intent of the intake preheater was to bring warm air into the intake - this helped with fuel vapourisation on cold starts and helped to prevent carburettor icing. We don't really need it; it's a remnant and a holdover, and about as useful as the vermiform appendix.)

 

[dick.breakey]

thanks. i tried searching, but when i had no clue as to what it was, i didnt know how to search for it. so i plan on making a home made snorkel for this from one of the writeups on here(the $74 one haha) can i just eliminate it or do i need it for the computer to run correctly?

 

[dick.breakey]

nvm. i see where someone else in that thread said to throw it away. thats good news. ill go do that in a minute. now ill start a thread about the rig not running right. thanks yall

 

[5-90]

thanks. i tried searching, but when i had no clue as to what it was, i didnt know how to search for it. so i plan on making a home made snorkel for this from one of the writeups on here(the $74 one haha) can i just eliminate it or do i need it for the computer to run correctly?

Piffle. Ashcan the thing - I lost my corrugated hose years ago, and still pass CA smog without the thing! (I got a short section of replacement hose and just faked it into place. Emissions show no negative effect from not having it in workin' order - as I said, it's not necessary with PFI.)

Now, if they'd just let me get rid of that wretched EGR valve that craps everything up with carbon, I could be almost happy...

 

[dick.breakey]

id hate to deal with cali emissions. i miss back home in Texas where if it looked like it was safe, they passed you. here in pittsburgh, if they even think somethings modified, your up a creek. you really have to "know" someone who will pass shite if theres anything wrong or not in stock form

 

[old_man]

That little part can be quite important if you live in a area that routinely has rainy days right around 32f. If it is not there, you can get what in the old days was called carb icing. Around here, that is almost never a problem.

 

[joe_peters]

I wouldn't worry about that thermostatic system as far as inspections. All of the cold air intake systems do away with it completely, even the CARB approved kits.

CARB--California Air Resource Board, or emissions NAZIs if you prefer.