88 renix help
CF Veteran
Joined: Aug 2011
Posts: 10,489
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From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Boy you got me. I'd still check that booster line. That is a crazy lot of brake fluid..almost 1/2 an inch in the reservoir every 3 months? It's leaking somewhere....Anyway let us know how the mod works out!
I figure the 2.6 mm orifice between (I mean "IN") the rear ccv fitting and the intake manifold vacuum really only matters for a new engine. A new engine idling might actually have "positive crankcase ventilation, PCV)" with that. Before long the blow-by will overwhelm that. At least accelerating. Then the crankcase pressure is relieved via the large tube to the airbox. There is some vacuum there, but presumably not much, at least if the air filter is OK. Granted yours is custom, but I really don't think that front vent needs any vacuum from the air cleaner, it just needs a free, unrestricted 1/2 inch tube.
I figure the 2.6 mm orifice between (I mean "IN") the rear ccv fitting and the intake manifold vacuum really only matters for a new engine. A new engine idling might actually have "positive crankcase ventilation, PCV)" with that. Before long the blow-by will overwhelm that. At least accelerating. Then the crankcase pressure is relieved via the large tube to the airbox. There is some vacuum there, but presumably not much, at least if the air filter is OK. Granted yours is custom, but I really don't think that front vent needs any vacuum from the air cleaner, it just needs a free, unrestricted 1/2 inch tube.
Last edited by DFlintstone; Oct 29, 2013 at 01:56 AM.
CF Veteran
Joined: Oct 2009
Posts: 2,867
Likes: 16
From: Fauquier County, Virginia
Year: 1991
Model: Cherokee
Engine: I-6 4.0 HO
ahh i get what your sniffing at. there was a misunderstanding. fluid did not get in the intake manifold once i pulled both breathers. and i figured that's where my oil WAS going because its stayed at the full line for the past 100-200 miles
and why would oil even get sucked into the manifold?(maybe had something to do with the front breather not connected to air cleaner?) (or the valve cover mod needs to be done?)
we will find out tomorrow when the valve cover gets modded and everything get put in the right place. (after i clean the oil out of the lines of course)
CF Veteran
Joined: Dec 2011
Posts: 4,006
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From: Pasadena, MD
Year: 1987
Model: Wagoneer
Engine: Renix 4.0
Answer for this is that the narrow back line going into the manifold has constant vacuum to pull air from the front to ventilate the crankcase. Removing that rear line basically allowed crankcase pressure to build and therefore leave through the path of least resistance (the front elbow because the rear has a restrictor in it).
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Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Oct 2009
Posts: 2,867
Likes: 16
From: Fauquier County, Virginia
Year: 1991
Model: Cherokee
Engine: I-6 4.0 HO
I must disagree with you. It is designed to pull from the hose connected to the filter, through the crankcase, then to the manifold. The narrow manifold line promotes this vacuum pull while keeping oil out with the two baffles under the valve cover. It doesn't change flow direction under normal operation, regardless of throttle. It only backflows when the vacuum is removed (clog, hose removal) and the crankcase pressure takes the path of lease resistance which also happens to be the larger of the hoses allowing oil to blow out and make a mess. A severe blow-by problem will cause this too.
CF Veteran
Joined: Oct 2009
Posts: 2,867
Likes: 16
From: Fauquier County, Virginia
Year: 1991
Model: Cherokee
Engine: I-6 4.0 HO
CF Veteran
Joined: Oct 2009
Posts: 2,867
Likes: 16
From: Fauquier County, Virginia
Year: 1991
Model: Cherokee
Engine: I-6 4.0 HO
Thread Starter
CF Veteran
Joined: Feb 2013
Posts: 1,802
Likes: 2
From: Justin, TEXAS
Year: 1988
Model: Cherokee
Engine: 4.0
alright guys good news and bad news
the new tps from napa fixed my high idle on startup issue
but...my rpms are still high and shifting into overdrive way late
i have to be going over 40 mph for about a quarter mile before it shifts and when it does its still running about 2000 rpms at 45mph...and thats with 31's on stock gears...(they should be stock at least)
what are yalls rpms at 45mph?
the new tps from napa fixed my high idle on startup issue
but...my rpms are still high and shifting into overdrive way late
i have to be going over 40 mph for about a quarter mile before it shifts and when it does its still running about 2000 rpms at 45mph...and thats with 31's on stock gears...(they should be stock at least)
what are yalls rpms at 45mph?
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
alright guys good news and bad news
the new tps from napa fixed my high idle on startup issue
but...my rpms are still high and shifting into overdrive way late
i have to be going over 40 mph for about a quarter mile before it shifts and when it does its still running about 2000 rpms at 45mph...and thats with 31's on stock gears...(they should be stock at least)
what are yalls rpms at 45mph?
the new tps from napa fixed my high idle on startup issue
but...my rpms are still high and shifting into overdrive way late
i have to be going over 40 mph for about a quarter mile before it shifts and when it does its still running about 2000 rpms at 45mph...and thats with 31's on stock gears...(they should be stock at least)
what are yalls rpms at 45mph?
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Has the shifting been late with both TPSs?
Can you feel the trans shift 1,2,3,OD and then feel the torque converter lock?
Have you ever adjusted your TV cable?
Can you feel the trans shift 1,2,3,OD and then feel the torque converter lock?
Have you ever adjusted your TV cable?
Seasoned Member
Joined: Jul 2013
Posts: 432
Likes: 1
From: Spokane Valley, WA
Year: 1989
Model: Cherokee
Engine: 4.0
Definitely adjust the kick down able and take for a drive. If still shifting odd adjust the tps on the tranny side abd try that. Now I've talked to a couple mechanics locally that are jeep wheelers that run larger tires and both have said because you are in essence making your final ratio taller with bigger tires that you can cheat by adjusting the tps to compensate for the bigger tires. I'm running one size up from stock and OD is at 45 mph. Not sure if what they have said works but it's and idea I guess if your shifting seems to be late with bigger rubber.





