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renix..renix...why?

K

kkerem

NAXJA Forum User
Location
Estonia
Hi,

I have 89 4.0 cherokee with renix. So my chero doesn't start well, also, when it idles the rpms are jumping up and down. It runs around 800 rpm, then it goes to 1000 for 30 seconds, then back. Also when I accelerate, it goes well, but it seems to hang for a second or two. On driveing it starts to jerk, then i have to accelerate or take the leg from the pedal. It jerks quite constantly, but sometimes it doesn't do it.

I have checked/changed:
TPS (adjusted)
MAP (new)
O2 sensor (tested)
Fuel pump (new)
Fuel pressure regulator (tested)
Fuel filter (new)
Vacuum lines (tested)
Spark plugs (new)
Wires (new)
Cylinder pressures (tested, equal)

What to suspect next?
Ignition module?
Coil?
Is there any more sensors to test/check?
ECU?

How to read information from test ports?
How the renix system works?
 
The only other thing it looks like you didn't check was the cps.....common problem on xj's.Although it usually causes hard starts and long crank times,and sometimes no start at all,cps could be related to your problem.
Correct me if I'm wrong but,Renix motors are gen 1 obd. they don't actually store codes....it's all live data.B.tw Check all your grounds also.
 
Last edited:
bcguy said:
did you try jumping the fuel pump ballast resistor? If it were going it could cause some jerkiness.

Darren
Click to expand...

Yes I did. With old pump and also with new one. The pressure is ok. I also checked it while driveing.

Distributor cap looks normal. All contacts are fine. How to do "deeper" check?
 
Ok, but is there some way to test the cps? I don't like to change parts just for testing... :wierd:

Why there is camshaft position sensor? Can it be faulty and cause the problem?

How to test injectors? I doubt, that the problem is there, but is there any possibility to check them?

Also can it be ignition control module? There are three connectors on mine, but only two are used.

Thank you!
 
anytime mine does that, its a sure sign that the throttle body needs cleaning-
it does exactly what your saying- idles up and down, with a deadspot right off idle into first gear.

9 times out of 10, the IAC has a chunk of carbon on it, just enough to throw the idle off and allow too much air in when it should be closed.

The CPS, while a pain sometimes, is usually only a good/not good deal-- very,very,very few problems with vehicles running....they usually just give a no-start...*usually*...I use that term loosely.

use a handy ohms meter to check it-- without pulling the manual out, I think I remember it being anything above 75 ohms, but not above 200ohm...but I cant remember which two of the three wires to probe.

same deal with the TPS-- theres two wires to probe that will show you the sweep of the ohms as you press the pedal down and up-or move the throttle linkage...yours is old as mine, so a dead spot will probably be there somewhere....we just work around it.

hollar if no one posts up the wires, and I`ll hit the manual thisafternoon for the specs.
 
200 Ohms +/- 75 ohms between A B.
CPS-plug.jpg

Down on bell housing.
 
I suggest cleaning the throttle body and especially clean the Idle Air Sensor (IAS)
 
Eagle said:
I suggest cleaning the throttle body and especially clean the Idle Air Sensor (IAS)
Click to expand...

x2 I would definitely say that might be your idle problem anyway.
 
Hook up a vacuum gauge and post the results.
 
kkerem said:
Ok, but is there some way to test the cps? I don't like to change parts just for testing... :wierd:

Why there is camshaft position sensor? Can it be faulty and cause the problem?

How to test injectors? I doubt, that the problem is there, but is there any possibility to check them?

Also can it be ignition control module? There are three connectors on mine, but only two are used.

Thank you!
Click to expand...
Leaky injector will cause this also.....do you notice a gas smell under the hood?
 
when I disconnect the vacuum lline, rpms will go up and they are little bit stable. But when I try to drive, then there is no diffrence. So, I tried to smell also the injectors, but nothing. I also found some kind a spray for finding leaks, but it didn't help. Probably no leak.



:rattle:
 
Until you measure the vacuum, you can't say you don't have a leak.
 
I am watching this post intently as my 87 has just started doing something very similar. While diagnosing a poor run and chugging condition I decided with over 250,000 miles to replace some common sensors...TPS, IAC, CPS, also replaced fuel pump, plugs, several vac lines, cleaned ccv system, cleaned TB, installed MSD 6A and blaster coil. My local Napa had to order the CPS so I just installed it today. All of the other sensors and such made improvements so now the XJ runs pretty good. I know I have several leaky injectors and am waiting on an O-ring kit and will install upon arrival. After installing the CPS and starting home from work the engine started to 'act' funny. Only instead of idling up to 1000 rpms...try 3000! Big prollem. So I shut it off, restart, same. I do this several times and it finally idles down. I pulled over and checked the throttle cable and it's free. The 'junk' in the IAC makes sense and I'll check that tomorrow. My question is will the oriface in the IAC flow enough air to run the engine at 3000 rpm?
 
my 88 cherokee used to do that 3000 rpm thing and i have ducuments from the original owner and it happeded to him 6 times and was intermitint and problem was not found.i fixed mine by removing the plug on the t body side facing the drivers side there is an idle air adjustment screw under there it needs to be removed and cleaned and then a minimum idle needs to be set.i can explain on this procedure in more detail.brb
 
Unplug all the connectors in your Jeep and use electronic contact spray on them. That tends to cure 85% of all Jeep electrical troubles.
 
Hi again

Now I have stupid question about CPS... Yesterday I tried to measure resistance of CPS. It should be around 200 ohms or so. Ok, the ohmmeter showed 192 ohms, it is fine, but then the resistance went back to zero. It shows only for a second... The sensor should be a coil and the coil should have constant resistivity. My CPS has a resistivity for a second... Is it bad CPS or should it be so?
 
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