4wheeldrivenewbie

Ive had this cherokee The guy i got it from was the second owner he had told me something about a vaccum line he would leave halfway off so the car would idle smoother and wouldent die.

Here's what it will do fairly hard start. During idle tranny in park the thing will rev drop rev drop every few seconds from say 900 rpm to 400.

When i put it into drive and goto accelerate if i dont step on it just right i get a hesitation and the car tac drops and it almost dies if you press the pedal too lightly. Dies more so in reverse when u touch the gas.

I have to let it idle backwards if i touch the gas it wil stall out.

Cold or hot tac will bounce and go up and down randomly

Ill take off from a stop light and ill get hesitation.

If i come to a intersection and i let of the gas to try and roll threw it slowly then step on the petal i get the hesitation.

Ive tryed and tryed to find out what is going on hundreds of dollars later nothing.


Ive tryed cleaning sensors like the tps the iac vaccum lines air cleaner took out the trottle body cleaned it spotless changed the fuel filter checked grounds new plugs cap wires.

Id say about 90% of the stuff i replaced was prolly still good new vaccum harness new tps new iac tryed seafoam.

The only thing i noticed is after replacing the iac it seemed like the tac wasnt as bouncy i seemed to get more of a steady idle but i think that was mostly after the seafoam treatment i poored some in the brake booster and most of it down the throttle body slowly till it barly wants to run like people said.

Still im getting a hesitation today and 20 years later the car still runs almost the same a couple mechanics looked at it over the years couldent figure out whats wrong.

Whats funny is the car recently seems to idle low when cold then idle higher when hot go from about 700 rpm to about an idle of 1200 after running for 5 mins.

The only thing ive seemed to notice idk if this makes sense.
Is that if you give it gas from under the hood if you grab the top of the throttle rod near the tb linkage and you rev it.

But when u press the petal from inside the jeep it seems to hesitate more so

The throttle seems right there almost like it would take off no problem.

Ive always noticed the throttle plate being loose like some sort of play.

But i dont wanna throw money away replacing the throttle body ive been holding off.

Ive also replaced the master cylinder and redone the brakes so the booster checks out as good ive taken the hose off to pour the seafoam in and it was sucking in plenty of air to the intake


If its cold the jeep seems to go when u press the petal as you warm it up starts running crappy.

89Renix

X2 on this??? im curious too?!?

i cant be much of a help, but it seems like youve done almost everything

88TwoDoor

I had problems that sound just like yours when I first got mine. Almost went insane trying to figure it out. After trying everything i could think of I took it to a mechanic friend of mine and it ended up being my fuel pump. It was working but was cutting out intermittently. If I had checked the fuel pressure a few more times I would have figured that out. Check your fuel pressure if you have not. Also there is a screen type filter in your gas tank on the bottom of the fuel pump. The screen can get extremely clogged in a dirty gas tank( mine was horrible ). Good luck

UJSLOST

Just gonna throw this out there since you said the previous owner leaves a hose off to idle better. I have the same problem on mine. I leave my EGR vac hose off the EGR valve. If I plug it in it barely idle and idles rough. I need a new EGR valve.

Might not be your problem but seemed similar so figured Id throw it out there.

cruiser54

Try this test on our TPS:

RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.
Wire "A" is positive.
Wire "B" is ground.
Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.
Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION:
RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector clearly embossed with the letters
A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module.
Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.
Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.
So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 11-28-2001

4wheeldrivenewbie

Thanks ill look into that stuff and let everyone know if i find ne thing

4wheeldrivenewbie

Btw the vaccum line that u would pull half way goes to the pcv valve not the egr. If you look to the back of the motor passed the oil fill cap theres a line coming off of a gromitt just above the oil fill cap thats the line you would take halfway off at the other end near the Harness.

It goes into a rubber elbow. You would pull it halfway out of the rubber elbow and the idle would improve.

4wheeldrivenewbie

If it was the fuel pump say??? why would the car hesitate if you touch the gas in the right spot all the time if u touch it just so car sputters and hesitates.

So ill goto take off from a light and it will hesitate till i give it more throttle.

But if i were to keep the pedal lightly pressed from a stop light to where it would hesitate i could keep the pedal right there hold it and the car will run like its hesitating and sputtrering the whole time . Which obviously at that speed is 5-7 mph you wouldent drive that slow behind a bunch of cars.

But When u take off theres always that hesitation point once u get passed it it will take off.

if it was the fuel pump as someone stated??? wouldent the cars acceleration be right there sometimes and sometimes not????

During takeoff the throttle is not right there ever.

I get hesitation then your off. Just to clarify things and when u let off the pedal too fast the tac needle will shoot down low then come back to normal.

If im going along at say 25 mpg and tromp the pedal down the thing does seem to pick right up i can go from 25 to 40 and the gas is right there

I will be using this for a rd test hopefully i dont get failed ill have to have the idle turned back down.

But once i do that the tac will drop even lower when i goto take off and the jeep will be more likely to stall. Ill goto backup and the thing will die.

Atleast now rpms dont drop enough for it to die it dont shoot down low enough. however once the cars warmed up you get 1200-1500 rpm idle

cruiser54

Sounds like a TPS to me.

4wheeldrivenewbie

Ive replaced that with a brand new one idk if the part number makes a difference if theres a certain one everyone buy's 60 or 70 bucks i think i paided

cruiser54

Did you adjust it after installation?

akita8

Does it run rich (black smoke from tailpipe)?

4wheeldrivenewbie

No i dont seem to be getting black smoke. See at one point the tach was bouncing up and down at idle and she would stall very easy.

After restart sometimes she would race right up to like 2500 rpm and be stuck there for a couple mins and maybe come back down.

I replaced the iac and the tps after i did that i used alil seafoam in the brake booster hose poured some in my tank and poured some in the throttlebody. I cleaned up a couple grounds.

After all that that she now seem to idle steady the tach dont bounce up and down

When it is cold out i notice the idle seems steady the tach dont bounce around. As she warms up its more likely to bounce up and down at idle.

When I take off from my driveway you get a hesitation then it goes. at a stop light ill slow down if it turns green before im fully stopped ill go to step on the pedal and ill get the hesitation then it will take off like normal.

If im going to back out of a parking spot if i dont step on the pedal enough it will hesitate and stall out.

Once in a great while ill goto take off from a light and the accel will be right there the jeep will actually go.

At idle sometimes ill go out and hit the pedal and the tach will go up then drop way down when u let off to like 100 rpm sound like its gonna die then level off.

Ive still got bosh platinum plugs in it i plan to go with original champion copper.

I dont know what exactly im chasing. Ive got a buddy that has the same jeep has 200 thou miles on it and runs like a top.


Any more clues would be helpfull this thing is a brain buster

cruiser54

How about this clue? Did you adjust the TPS?

mocrawlin

O.P. please answer cruiser54's question. lol he knows what he is talkin about! a couple pm's and whatnot back and forth to him and mine runs 10 times better then when i got it using cruisers info and adjustments. again, thank you cruiser54!