skitter

Specs: 1990 Jeep cherokee I6 Renix


Hello everyone just found your forum! glad i did , i purchased a 1990 cherokee for cheap really cheap threw my work and it had its obvious problems .. purchased about a year ago .. ive done several things to it lift/paint and bodywork .. however it was never really running Right (Yes i lifted it , fixed the body and painted it before fixing the motor ) <dumb

Anyhow my problem is when the jeep is started when dead cold .. it will run at about 1100rpm .. very quickly heads down to 800rpm region then eventually (2min or so) goes down to 400rpm and then eventually dies .. sometimes it trys to idle and will sucessfuly for about 10min but its Running at 400rpm ..

What i've done
Rotor/Cap , Plugs (NGK-R) < im wondering if i need to switch to Champions ?
plug wires
All grounds on jeep (this helped allot with allot of other issues)~The main Ground heading to the Dipstick from the battery is really frayed im going to purchased a new wire tomorrow.
Muffler / donut / TailPipe
Egr valve was clogged .. oil deposits like you wouldn't believe , i took everything off and complete cleaning vacuum lines checked for cracks/holes ..
IAC was clogged Cleaned it really good
Throttle body was horrifying Took it off , replaced gaskets completely tooth brushed / q tiped whatever it took its clean!
Removed Intake/exhaust manifold , clean them both replaced gasket
CPS was replaced
Fuel rail cleaned .. Injectors cleaned (i even replaced one thinking it was damaged .. Replaced All O rings.
Good compression , Spark on all 6 , Fuel pressures good .. im so stumped .. im lucky this is just a after work project and not a DD.

I have one odd question , My Throttle body only ever had 1 vacuum line going to it , The one that runs up to the firewall , obove it ( on the throttle body is an empty hole... It almost looks like there is supposed to be one there.. ? basiclly its a rubber boot going into the TB , 2 holes , 1 vacuum line in the bottome hole .


Any suggestions would be greatly appreciated and thanks for the time.

cruiser54

NGKs are just fine.

Throttle body only has one vac hose to it. The other hole is not open.

Check your TPS on the "engine" side" per the following instructions. Be sure to do the sensor ground test outlined first.

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: With the Key OFF, and 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. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, 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 only a flat three-wire TPS mounted on the throttle bodyand it provides data input to the ECU. It 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. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.
Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.
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, as outlined above—FOR ALL 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. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. 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.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat 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 09-22-2012

skitter

thanks i will try this tonight

ubnormal_ua

try to disconnect o2 sensor and clear ecu to zero( unplug ground battery terminal and few times rotate key to start engine position and get back ground battery terminal)
if after that it stops to dies after 30 sec or so -it was a faulty o2 .

why engine run 20-30 sec and after that start to lower rpm:
you start cold engine and it ignore o2 untill it reach some temp
after that your faulty o2 told that your fuel mixture are too Rich and ecu try to compensate it by lowering fuel injector timing rpm falls to 300-400 rpm and next thus circles start from the beginning until engine stops.

i have self-made renix scanner and i fight with same problem near year or so...

cruiser54

Unfortunately, the Renix ECU is not resettable. It resets every time you turn the key off. The procedure you outline is no accurate.

ubnormal_ua

you wrong)
i saw a collected data that stored in correction tables)
and my reset procedure correct.

if you may see delta alpha (fuel injector long trm data correction) you may see that it is not reset every time, same for some other params.

atteburyc

Popcorn anyone?

cruiser54

Uh yeah. Here we go again. One Hung Low and his off the wall, misleading ideas.

ubnormal_ua

i`m able to prove )

let me few days and i`m create topic with description, analyze software and log examples.

Willys55

szczęśliwa środa


Game on! OK, who has the Popcorn

cruiser54

You do that.

In the meantime, let's the rest of us help the OP with his issue without using algorithms, software, and other distracting rabbit trail ideas.

cruiser54

Keep us informed. I wouldn't be surprised if the tPS is junk. You oughta check both sides of it just in case the trans side is bad.

Check to see if your intake bolts are snug. Start from the center and work out to the ends.

Lower hole on the tB is for vacuum. The upper hole is blind and just holds the connector on. Weird design.

skitter

i tryed the 02 sensor idea had no results other then it just wont die now .. not droping from 500rpm.. My damn ohmeter is fudged! had to buy a new one will get back with my results after work today thanks

Oh i did try unplugging the TPS / in and out , reseting ecu or whatever his idea was .. and it did have a effect once .. it was idling at 1900rpm ! however it was obviously high , i unplug TPS again and back in , and same results i had a video but now its not working on my phone was going to post it today will do it again tonight ..thanks again

cruiser54

Stick with the tried and true methods. All this hocus pocus about resetting, unplugging etc is just bunk.

Multimeter and tutorials is all you need.

Outlaw Star

Lmao
The Renix/AMC ECU is a very simple design so software/logs really aren't nessisary. Test the sensor, if bad replace. Very rarely does the ECU crap out unless it got wet. Im still running the 85'.
Yes. Sounds like the IAC is going out.