Recent Topics
Moving mobility scooters
by supton. 01/17/19 08:59 AM
Car stumbling in idle
by dan765. 01/17/19 08:58 AM
Fiat 9.55535-GS1 Certification - Ravenol
by RamFan. 01/17/19 08:35 AM
EV Future
by Danno. 01/17/19 08:11 AM
Sayings that people told you...
by Char Baby. 01/17/19 08:04 AM
Certified oils
by waltywalt. 01/17/19 07:55 AM
Favorite Movie Lines And Scenes
by billt460. 01/17/19 07:14 AM
Suzuki Jimny
by ridgerunner. 01/17/19 06:52 AM
Amsoil SSO 5w50
by Vspec. 01/17/19 06:36 AM
Dodge truck question - gear shift
by gfh77665. 01/17/19 06:22 AM
GAC may be coming to America?
by Char Baby. 01/17/19 06:03 AM
Another favorite video
by Char Baby. 01/17/19 04:59 AM
Detail a 2012 Kia Soul
by jerseyguy123. 01/17/19 02:23 AM
Can top end cleaners damage engine?
by avacado11. 01/17/19 01:40 AM
Where are Fram Oil and Air filters made ?
by rubberchicken. 01/17/19 12:42 AM
Based on these specs, which oil is better?
by SlavaB. 01/17/19 12:42 AM
Fram FPS9688 from ebay (Ultra XG9688)
by SlavaB. 01/16/19 11:12 PM
Pick my filter—
by lukejo. 01/16/19 10:41 PM
2007 Camry V6 feedback......
by kenwin30. 01/16/19 10:41 PM
Pioneer SW-8MK2 Subwoofer
by webfors. 01/16/19 10:39 PM
Newest Members
neiltt, Drspel, wwalrus, fedorqwe, Terand_1
66957 Registered Users
Who's Online Now
104 registered members (badtlc, bbslider001, beanoil, Asterix, ABerns, Ag76, 11 invisible), 1,854 guests, and 46 spiders.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums67
Topics296,712
Posts4,957,432
Members66,957
Most Online2,577
Jan 14th, 2019
Donate to BITOG
Previous Thread
Next Thread
Print Thread
Hop To
Page 1 of 2 1 2
Found a fix for 80s to 90s 4.0L Jeeps with CCV #1180182
06/26/08 05:08 PM
06/26/08 05:08 PM
Joined: Sep 2007
Posts: 895
Midwest
buickman50401 Offline OP
buickman50401  Offline OP
Joined: Sep 2007
Posts: 895
Midwest
My old beater Jeep (winter driving and trips to the home improvement stores) suffered from a common problem. Starting around model year 1987 the 4.0L Jeeps used a CCV (crankcase ventilation system) instead of a PCV (positive crankcase ventilation) valve. The difference being that the CCV is a "closed" system on the Jeep 4.0L requiring two ports in the valve cover. One large hose was for intake/return air from the airbox and one tiny (inside diamter of the tube is smaller than #2 pencil lead) tube for the crankcase gases to escape into the intake manifold.

The problem with the system is that the CCV valve (which is inside and built in to the valve cover -a nonserviceable item unless the entire valve cover is replaced) often got clogged up no matter how good the maintainence on the vehicle. This causes gases and oil mist to flow backwards through the system (it has to have some way to escape) through the larger tube and into the airbox fouling the filter with oil.

I replaced all the hoses in the CCV system about 2 years ago (~$115), but it kept fouling the air filter. I was going to break down and buy a new valve cover (at the cost of $200) but ran across a recommendation on a jeep related site buried within the forums there.

The solution is to remove the grommet on the valve cover (for the small line) and replace it with a grommet for a 1985 CJ7 along with the PCV valve for the CJ7. Prior to replacing the grommet, you must bend a metal tang inside the valve cover using a screwdriver. This tang is what forms the "spring" in the built in CCV valve. Bending it up, opens the valve all the way permanently.

Next, take a 3/8 inch quick connect air chuck (the kind you screw into a blow-gun or tire chuck for use on an air compressor equipped with quick connect fittings) and replace the screw in nipple on the manifold (where the original tube attaches) with the air chuck. The chuck is an exact fit (threading and length)but has a much larger internal diameter for the crankcase gases to flow. Finally run a section of 3/8 inch fuel line from the newly installed PCV valve to the new air chuck nipple you screwed into the intake manifold. Attach a hose clap at each end of the fuel line and you're done.

I just completed this permanent fix for the idiotic and horribly designed system Jeep/AMC/Chrysler designed way back in the 80s. It works like a dream. No more blow back into the air box.

Total cost for this fix was $15 and that included a new air filter.

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: buickman50401] #1180224
06/26/08 06:16 PM
06/26/08 06:16 PM
Joined: Sep 2004
Posts: 7,902
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,902
Marshfield , MA
what didja do about the stoopid Carter carb inflicted on this otherwise superb engine?


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: andyd] #1180244
06/26/08 06:46 PM
06/26/08 06:46 PM
Joined: Sep 2007
Posts: 8,598
Florida
artificialist Offline
artificialist  Offline
Joined: Sep 2007
Posts: 8,598
Florida
andyd, this moronic design was continued up until the very last 4.0L. That means many of those engines had multi-port fuel injection.

Anyway, I have dealt with several of those stupid CCV systems, but typically the price to replace that junk was more than the customer was prepared to pay. They just top their oil off more frequently, instead.


2010 Lancer Ralliart Sportback
Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: artificialist] #1180389
06/26/08 11:52 PM
06/26/08 11:52 PM
Joined: Sep 2007
Posts: 895
Midwest
buickman50401 Offline OP
buickman50401  Offline OP
Joined: Sep 2007
Posts: 895
Midwest
 Originally Posted By: artificialist
andyd, this moronic design was continued up until the very last 4.0L. That means many of those engines had multi-port fuel injection.

Anyway, I have dealt with several of those stupid CCV systems, but typically the price to replace that junk was more than the customer was prepared to pay. They just top their oil off more frequently, instead.


You are correct. Up until about 95 this idiotic design was used and then switched over to an equally idiotic replacement.

As far as a carb is concerned, mine is a 1987 Cherokee Pioneer. It was the first time they switched the 4.0L over to MPFI. In this case a Rennix system. The bad thing is, the Rennix MPFI was only used in 1987 and the system is so old, odd, and rare that no scan tools currently available are able to interface with the Rennix engine computer.

Edit: What shocked me the most about this repair job was that the quick connect air chuck is the exact same thread size, pitch and depth compared against the original nipple... and I didn't have to by a quick connect fitting as I had a couple of extras laying around from the last time I bought a new air compressor. Otherwise the repair would have probably cost $20.

Last edited by buickman50401; 06/26/08 11:56 PM.
Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: artificialist] #1180390
06/26/08 11:56 PM
06/26/08 11:56 PM
Joined: Sep 2002
Posts: 39,806
Pottstown, PA
Gary Allan Offline
Gary Allan  Offline
Joined: Sep 2002
Posts: 39,806
Pottstown, PA
I don't care for the CCV (it's Continuous Crankcase Ventilation, btw) over the traditional PCV system ..but I've never had issue with mine. My throttle body is residue free at 140k.

Now have a CJ or Cherokee that's 20 years old with summer camp or plowing ONLY use ..then it's going to be a much more tired engine. The CCV system will reach its limits of coping with too much blow-by. This naturally doesn't take any design flaw (that you mentioned) into account.


My metered orifice is on the intake ..and if I installed a traditional PCV valve, I think I'd have a higher idle. It's too crude a vacuum regulator (it's effectively a filtered manifold leak).

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: Gary Allan] #1180393
06/27/08 12:09 AM
06/27/08 12:09 AM
Joined: Sep 2007
Posts: 895
Midwest
buickman50401 Offline OP
buickman50401  Offline OP
Joined: Sep 2007
Posts: 895
Midwest
I don't think that this repair would work on your setup as you suggested.

The metered orfice on mine is inside the airbox on the return line (which was up until the repair being used as the "outlet" line).

I do now have a bit higher idle (guestimating around 100RPM higher), which isn't a bad thing because the idle has always been too low on this vehicle with absolutley no way to adjust it thanks to the goofy Rennix MPFI. All the repair manuals and even the sticker under the hood specifically states that the idle speed is not adjustable, so I'm happy that this repair helped out in that regard.

Edit: This beast has 220k mi on it.

Last edited by buickman50401; 06/27/08 12:11 AM.
Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: buickman50401] #1180732
06/27/08 12:00 PM
06/27/08 12:00 PM
Joined: Sep 2002
Posts: 4,225
Lakeville, MN
MNgopher Offline
MNgopher  Offline
Joined: Sep 2002
Posts: 4,225
Lakeville, MN
The Renix system was used from 1987 to 1990 on the 4.0l in the Cherokee's. Chrysler's system took over in 1991.

Actually, the Renix system isn't all that bad. Everything is easily diagnosible with a multimeter, but you need to have an idea of what affects what since there are no codes. I actually enjoy working on this setup - but a lot of so called mechanics get a deer in the headlights look when they work on it.


I've heard all the horror stories on the CCV system, but mine has only been replaced once (due to age - the plastic cracked on my nearly 21 year old 1988 Cherokee Pioneer). No significant issues with blowby either, though I've only got 104,000 miles on it now.

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: MNgopher] #1181268
06/28/08 04:35 AM
06/28/08 04:35 AM
Joined: Jun 2003
Posts: 33,771
ME
eljefino Offline
eljefino  Offline
Joined: Jun 2003
Posts: 33,771
ME
wonder how this new vacuum path helps the rear main seal...

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: eljefino] #1181477
06/28/08 12:06 PM
06/28/08 12:06 PM
Joined: Sep 2007
Posts: 895
Midwest
buickman50401 Offline OP
buickman50401  Offline OP
Joined: Sep 2007
Posts: 895
Midwest
 Originally Posted By: eljefino
wonder how this new vacuum path helps the rear main seal...

Probably quite a bit as I've driven the vehicle extensively since the repair and I no longer see any evidence of oil leaking from the rear main.
















Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: buickman50401] #1181578
06/28/08 02:53 PM
06/28/08 02:53 PM
Joined: Apr 2004
Posts: 1,463
CA
gtx510 Offline
gtx510  Offline
Joined: Apr 2004
Posts: 1,463
CA

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: gtx510] #1181606
06/28/08 03:34 PM
06/28/08 03:34 PM
Joined: Sep 2002
Posts: 39,806
Pottstown, PA
Gary Allan Offline
Gary Allan  Offline
Joined: Sep 2002
Posts: 39,806
Pottstown, PA
Ooops. I beg your pardon. The orifice IS on the valve cover on my 4.0 ..just like yours. I just checked the FSM. My 2.5 has it screwed into the side of the valve cover.

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: gtx510] #1181816
06/28/08 09:36 PM
06/28/08 09:36 PM
Joined: Sep 2007
Posts: 895
Midwest
buickman50401 Offline OP
buickman50401  Offline OP
Joined: Sep 2007
Posts: 895
Midwest

Yep, and I replaced all those parts 2 years ago. It didn't fix the problem. And after considering everything I wasn't about to replace the valve cover at the cost of $200.

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: buickman50401] #1181829
06/28/08 09:58 PM
06/28/08 09:58 PM
Joined: Apr 2004
Posts: 1,463
CA
gtx510 Offline
gtx510  Offline
Joined: Apr 2004
Posts: 1,463
CA
Good to know, I might try your fix instead of messing with the Jeep parts.
Do you know if it'll work on a 1991 (non-Renix) engine?
Thanks

Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: gtx510] #1184540
07/02/08 11:32 AM
07/02/08 11:32 AM
Joined: Sep 2007
Posts: 895
Midwest
buickman50401 Offline OP
buickman50401  Offline OP
Joined: Sep 2007
Posts: 895
Midwest
 Originally Posted By: gtx510
Good to know, I might try your fix instead of messing with the Jeep parts.
Do you know if it'll work on a 1991 (non-Renix) engine?
Thanks

It should work so long as the intake manifold has the same threaded nipple that can be replaced with the quick connect air compressor fitting.

In my experience (and others) replacing all the CCV lines will do nothing to repair the problem in most cases as the problem typically lies with the valve cover integrated CCV valve.

And if it dosn't work just save the old parts (including the grommet, line, and nipple) and put the old parts back in if the vehicle doesn't want to run right. At the most you'll be out $10 or so.

Last edited by buickman50401; 07/02/08 11:34 AM.
Re: Found a fix for 80s to 90s 4.0L Jeeps with CCV [Re: buickman50401] #1184602
07/02/08 12:40 PM
07/02/08 12:40 PM
Joined: Dec 2006
Posts: 61
KS
jg1 Offline
jg1  Offline
Joined: Dec 2006
Posts: 61
KS
"The metered orfice on mine is inside the airbox on the return line "

You lost me on that one?

I have 91 yj (4.0). The orignal factory set up was "large" line from airbox to valve cover (no restrictions on this line)and "small" line from manifold to valve cover. The "small" line had a "plastic piece" that mounted to the valve cover(turn and twist lock) had a very samll (metered) hole. No metal spring loaded tab "thingy" on mine.

I have high oil pressure which may play into my problems (75 psi when above idle).

Regardless, interesting idea(s).






Last edited by jg1; 07/02/08 12:42 PM.
Page 1 of 2 1 2

BOB IS THE OIL GUY® Powered by UBB.threads™