Need help with my "new" 89 cherokee

Hi, everyone i'm new to these forums but i think i'm gonna be a long time poster here.
I just bought a 1989 cherokee inline 6 4.0 auto trans. , other than some mild rust on the lower panels it ran great when i looked at it and and ran great up untill 4 days after i bought it. I bought this jeep so i could improve it and make a decent 4x4 out of it but right now i'd love it if i could just drive to the grocery store with it.
So heres the problems i've discovered so far with it, and any help is greatly appericated:

1 i'll start with the first thing i noticed, when ever i turn the defrost/heat fan to blow on high i get a a pretty loud "buzz" from somwhere under-infront of the front passenger, it gives a pretty good vibration you can feel even in the centre console.

2. this is most likley related to the next problem, when idling the engine will tend to "chug", also it idles at a pretty low rpm around 100rpm . I've never owned a cherokee before this one and i don't know what a normal idle rpm is. but when it "chugs" the rpms get up to around 1000 and it does this back and forth every second or so.

3. and now why i'm on this forum before even going out and replacing plugs filters and such. i drove it to work today just cuase i wanted to drive my new toy, and it sat for about 6 hours. went to go for lunch and it didn;t start. it would crank but not start.

I looked around a bit on the net before getting here and i read that alot of jeeps around this year have problems with the CPS ( crank position sensor) and that this is the most likley cuase of them not starting but still being able to crank. If anyone could tell me a remedy to this ( i will replace it but first i gotta get it home) , also where exactly is it located and if anyone can direct me to a picture so i know what i'm trying to clean/tighten/jiggle.
Also i'm wondering if this could alse be the cuase of the engine "chugging".

Any and all answers welcome thanks in advance !

A CPS/CKP will cause a "crank - no start" problem. However, the 1989 is "RENIX," and the later CPS/CKP won't work. You'll have to find an earlier one - you can try the dealership, or order it online.

That "buzz" in front of the passenger with the vent fan is is probably something binding up the "squirrel cage" fan blades. The vent fan is accessed from the engine side of the firewall, and it's fairly simple to get to (sorry, no pix handy.) Pull it out, look for something loose - it's either binding up the squirrel cage, or the cage is hitting it (once you have the fan out, you'll see why it's called a "squirrel cage.")

Normal idle for a RENIX (or the 4.0L in general, I think) is about 750RPM or so.

Question - do you have the idle trouble only when cold (and it goes away when warm,) or do you have it at all temperatures?

Before you replace the CPS/CKP, try unplugging it and plugging it in again - the connector is a three-pole Delphi Weatherpack with only two wires, and it's near the rear end of the fuel rail. If the contacts are dirty, that can "wipe" them clean and get you a decent signal again.

Welcome aboard!

ha awesome thanks for the quick reply

yeah i get the abnormal ideling at all temperatures even after driveing for a a few hours. i'll stop at a set of lights and the whole vechile with lug forward eachtime the rpms chug to a 1000 then drop. i've never seen anything like it.

and thanks for the fan answer, i figured something must of got up in there, i was thinking maybe a bad motor on the fan.

well i'll try messing with the CPS if anyone can go more in-depth on it much thanks

after more surfing i found this http://autorepair.about.com/library/a/1i/bl637i.htm

are the pics on this site what i'm looking for ?

StandsOnToes said:

after more surfing i found this http://autorepair.about.com/library/a/1i/bl637i.htm

are the pics on this site what i'm looking for ?

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That is the CPS, follow that pigtail up to the connecter on the drivers side next to the intake. Try unplugging that connecter and then reconnecting it and see if it will start.

The rest of your issues are a cummulation of small things that need addressing. Stay tuned and some of us will walk you through it.

StandsOnToes. Check your PM's(private messages).

well i'm heading out to try and get it running thanks for all the quick responses everyone i'll let you know what happens.

welcome to the wide world of Renix. if you have the fortitude to keep your rig and work out the bugs you will enjoy it immensly. if not, sell it quick.

Bored400 said:

welcome to the wide world of Renix. if you have the fortitude to keep your rig and work out the bugs you will enjoy it immensly. if not, sell it quick.

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He has the RENIX FI manual, so between that and us, he will be OK. We can get him through it!

I like my 90' RENIX 10x better than my other 4 XJ's that are OBD 1-2. It also gets better gas mileage, 24 on the highway, my other XJ's barely squeeze out 21.

And you won't need a high dollar scan tool to diagnose, just a multimeter.

too true!

alright so i went to go see if i could start up the jeep. and bam first try didn;t have to mess with the CPS at all, so thats what others have been telling me happens when theres a problem with the CPS. leave it for a few hours and it will start back up so i'm pretty convinced thats the problem.
i went in to look at it and the cover on the casing was virtually non-existant.The one just under the CPS connection. Is that a big problem?

also the chugging of the engine i mentioned earlier didn't happen when i started it up, it only came back after a half hour of driving. I'm pretty concerned with this, i let it idle for awhile in my driveway and when the rpms drop down it occasionally gets to the point of dieing.

This pisses me off so much it didn;t sound at all liek this when i checked it out, or when i bought it. Oh well i did kinda buy it know it would be a project. I was jsut hoping the project would be minor replacements and lifting etc etc. Oh well.

StandsOnToes said:

alright so i went to go see if i could start up the jeep. and bam first try didn;t have to mess with the CPS at all, so thats what others have been telling me happens when theres a problem with the CPS. leave it for a few hours and it will start back up so i'm pretty convinced thats the problem.
i went in to look at it and the cover on the casing was virtually non-existant.The one just under the CPS connection. Is that a big problem?

also the chugging of the engine i mentioned earlier didn't happen when i started it up, it only came back after a half hour of driving. I'm pretty concerned with this, i let it idle for awhile in my driveway and when the rpms drop down it occasionally gets to the point of dieing.

This pisses me off so much it didn;t sound at all liek this when i checked it out, or when i bought it. Oh well i did kinda buy it know it would be a project. I was jsut hoping the project would be minor replacements and lifting etc etc. Oh well.

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What "cover on the casing" are we talking about, not following you on that!

The chugging idle can be a few things.

I think he means the dust cover over the hole for the CPS..??

Remember that with heat comes resistance-- if the CPS is sending a very weak signal or the connections are barely making contact, the higher resistance may be interfearing with the signal. I know this would be too easy, but I'd change the CPS before I worried about the chugging.

As with all driveability problems on these Renix-mobiles, make sure every ground connection under the hood is clean and tight. The big players are the strap from the rear of the cylinder head to the firewall and the multiple grounds behind the dipstick where the neg battery cable attaches.

Shorty said:

I think he means the dust cover over the hole for the CPS..?

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OK, I get it, thanks Shorty!

X2 on the grounds, after you replace the CPS, clean those grounds!

5-90 has some really nice ground cables that he sells to fix all the evil lack of grounds that the Jeep engineers gave us on the RENIX. Check with him if you want to fix ground issues forever.

Also the chugging could be vacuum leaks JMHO.

About the blower fan motor. I can't remember exactly on my XJs, but he one I pulled out of my Grand Prix had a couple metal clips on the blades of the squirrel cage itself. I am assuming these are to balance it. One of them popped off when I was testing it on the bench, luckily there was a light rust colored mark on the blade where the clip was so I knew where it went. If you don't see anything in the hole for the blower motor, this might be the culprit. A broken/missing blade or two will cause it to vibrate pretty bad at higher speeds too.

AS TO THE VIBRATION FROM YOUR FAN.IT SOUNDS LIKE THERE ARE EITHER LEAVES OR A STICK STUCK NEAR YOUR BLOWER FAN.
YOUR ENGINE "CHUGS" BECAUSE YOU NEED TO REPLACE YOUR IDLE AIR CONTROL VALVE.ITS LOCATED ON YOUR THROTTLE BODY.YOU CAN GET IT AT ANY AUTO PARTS FOR AROUND $90.00

trailtamer said:

AS TO THE VIBRATION FROM YOUR FAN.IT SOUNDS LIKE THERE ARE EITHER LEAVES OR A STICK STUCK NEAR YOUR BLOWER FAN.
YOUR ENGINE "CHUGS" BECAUSE YOU NEED TO REPLACE YOUR IDLE AIR CONTROL VALVE.ITS LOCATED ON YOUR THROTTLE BODY.YOU CAN GET IT AT ANY AUTO PARTS FOR AROUND $90.00

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I'd try cleaning it before I bought a new one, I clean and lube mine yearly and never have any trouble anymore. The IAC can also be voltage sensitive, when the vehicle is idling too low or has battery issues or other charging problems the IAC gets sluggish.
Clean up the IAC and the seat in the TB, let a drop or two of oil run behind the IAC piston, don't try and mess with the piston any, as this can funk up the IAC. Be careful of the "O" ring gasket. It may take a few applications of oil behind the IAC piston to loosen things back up. I use spray oil the first time and then a drop or two of synthetic oil.
There is a bunch of problems that will make the Renix idle low or lug, the IAC is one of the more common.

x2 on trying to clean the Idle Air Control valve.. If you find that the piston is damaged, a replacement from a junker is acceptable. = $5 if that. (they're tiny)

alright so i had a half day today so i was able to squeeze in my hands to look at the CPS, ( and yeah i was talking about the dust cover, i wasn;t too worried about it) but yeah all the connections were nice and clean and i took a rag and wire brush to it them just incase. and its started fine since everytime, its only died that one time...so far. i live out in the boonies so its hard to get parts but i'm gonna replace it first chance i can find one.


So, i believe i may have found the problem with the "chugging" or "loping" as my haynes calls it. heres some pictures cuase i'm not sure what these parts are called, they connect off the metal fuel line near the oil fill.
Any suggestions on how to fix or what i gotta replace are welcome.









heres jsut a pic to show where its located ( circled in red)





while the engine in running fuel leaks out of this at a fairly good rate. it all had evaporated by the time i took this picture.It leaks out of the small opening ( red arrow). i also found fuel in the electrical connection ( red circle) . i know these provide fuel to the cylinders. Is this pretty serious? I'm kicking myself for not seeing this when i bought it ... Oh yeah while the engine is runnign this makes a pretty loud Hisss.



i was going to check the fuel line pressure, but when i went to go release the pressureto check some other stuff , nothing happend. ( doesn't sound like the 50psi thats supposed to be in the line) or is this normal? ( i had the fuel filler cap off) i'm definatly a newbie i just was wondering...