Renix Idle: Searched

90 aw4 Renix..

New alt/battery & Battery cables,
New TPS, IAC, and yellowtop injectors..
New CCV Vacuum tubes..
Deleted Charcoal canister (recently, but made no difference before/after)

When cold, It takes 10-15 revolutions to fire.. when it does fire, it stumbles until you give it gas..

It then will idle at 800rpm (cold) and slowly drop to 500rpm.. and then progressivly go lower and lower until it Dies.. all in about 45 seconds of run time..


BUT, if you keep it going, feathering the throttle until its at running temp, It will "Catch" and once warm it will High idle at 1100-1400rpm.. And will stay that..


I've put 500 miles on this rig.. and about 500 dollars into under the hood I'd like to start driving it daily

kind of a shot in the dark- but crank angle sensor might be worth a look.

how's your ignition system?

Id check : idle stepper motor. Crank sensor and coolant temp sensor. If all those check out maybe a bad ground? Check those wires between the dipstick tube and harness at firewall

Vacuum line between throttle body and map sensor intact?

bcmaxx said:

Vacuum line between throttle body and map sensor intact?

Click to expand...

Vacuum line seems good.

Grounds are all new and very clean.

Have not check Coolant temp sensor

Check CPS output.

Did you ADJUST your new TPS?

Renix CPS Testing and Adjusting
　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

　
　
Revised 01-26-2013


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 body and 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

Have you checked fuel pressure at the rail?

NW-ZJ-SCOTT said:

90 aw4 Renix..

New alt/battery & Battery cables,
New TPS, IAC, and yellowtop injectors..
New CCV Vacuum tubes..
Deleted Charcoal canister (recently, but made no difference before/after)

When cold, It takes 10-15 revolutions to fire.. when it does fire, it stumbles until you give it gas..

It then will idle at 800rpm (cold) and slowly drop to 500rpm.. and then progressivly go lower and lower until it Dies.. all in about 45 seconds of run time..


BUT, if you keep it going, feathering the throttle until its at running temp, It will "Catch" and once warm it will High idle at 1100-1400rpm.. And will stay that..


I've put 500 miles on this rig.. and about 500 dollars into under the hood I'd like to start driving it daily

Click to expand...

your symptoms at first cry out bad TPS or not properly adjusted TPS.
make sure you have the TPS adjusted properly, if you just slapped one on, it will run like crap until its adjusted and has a good ground.

Also, your symptoms also sound like a few more things are worth checking:
intake leak
vacuum leak
fuel pressure at the rail
bad CPS
Bad IAC (make sure it hasnt fallen apart inside the throttle cavity where it resides)
check fuel pressure
check coolant sensor
also clean all grounds

Get an ohm meter and check the ohms from the TPS ground to the battery negative. Strip/cut the insulation off one side of a short section of the ground wire before the TPS connector. Run the TPS harness over the top of the TB rubber intake. Wiggle/shake the harness a little (especially on/near the friewall while you are doing the ohm test.

If it is an auto, the ground wires are seperate for the tranny and motor half of the TPS and there will be a slight (built in) resistance in the tranny TPS ground (less than an ohm).

Clean out the IAC in the TB. plastic or wooden stick works well. Then spray it down good with a synthetic oil. But keep the connector oil free.

I never replace a sensor before I clean all the connectors. I've changed half a dozen sensors in my Renix since 1987, most times it is in the connectors or cable splices in the harness. The Renix connectors are prone to oxidation and/or resistance from oil that has worked it's way into the connector.

You may also want to check the power into the ECU. The IAC needs every available volt to work well, if you are loosing voltage between the battery and the ECU, it will effect IAC operation.

1100-1400 RPM idle says TPS or vacuum leak. If it leaks vacuum and idles up when hot, I'd check the intake manifold bolts, retorque.

Don't mean to high jack, but I installed an Autometer vacuum gauge in my Jeep back in '92. Only after finding do now know how important vacuum readings are to a Renix:wierd:

GregGA said:

Don't mean to high jack, but I installed an Autometer vacuum gauge in my Jeep back in '92. Only after finding do now know how important vacuum readings are to a Renix:wierd:

Click to expand...

Vacuum readings are important to ALL Jeeps. Just an old thing that the "techies" of these days ignore.

CHECK YOUR EGR VALVE.

Yeah. What Joe said.

TESTING THE EGR VALVE FOR 87-90 4.0 ENGINE
Valve Opening Test
1) With engine at normal operating temperature and at idle,
rapidly open and close throttle. Open throttle sufficiently to obtain
at least 1500 RPM. Movement should be noticed in EGR diaphragm.
2) If diaphragm does not move, probable causes are: faulty
vacuum signal to EGR, defective EGR diaphragm or defective
backpressure sensor diaphragm (if equipped), or leaks in vacuum lines
or connections.
Valve Closing Test
1) With engine at normal operating temperature and at idle,
manually depress EGR valve diaphragm. RPM should immediately drop,
indicating that EGR valve is not leaking and had been properly cutting
off exhaust gas flow at idle.
2) If there is no change in RPM and engine is idling
properly, exhaust gases are not reaching combustion chamber. Check for
plugged passage between EGR valve and intake manifold.
3) If engine idles poorly and RPM is not greatly affected by
manually moving diaphragm up, EGR valve is not closing off exhaust gas
flow. Check for carbon between pintle, leaking EGR valve gasket or bad
EGR valve.
***************

Sounds like none of those to me. The key is the dropping RPMs until warm, and then High RPMs when hot, and hard starting.

Sounds exactly like a bad or very dirty IAT, also known as a MAT, Intake Manifold Air Temp Sensor is bad. It is a variable resistor, resistance changes with air temperature. Remove it, clean it, and test it at various temps and compare to the FSM specs. The data table is in many old posts here.

Alright guys! I have some time tomorrow to start going through this VERY informative list.. I'm going to start with the TPS/IAC, If its not either of those, I will then move on to the EGR..

Start with the air temp sensor. Just check the ohm reading in the morning cold. It should be 3400 ohms at 70 F.

I'd bet money it is WAY off. I wrote a 9 month long 300 post thread on this exact problem 6 years ago when I chased it the hard way, LOL. I called the thread the RenX Files, LOL

Ecomike said:

Start with the air temp sensor. Just check the ohm reading in the morning cold. It should be 3400 ohms at 70 F.

I'd bet money it is WAY off. I wrote a 9 month long 300 post thread on this exact problem 6 years ago when I chased it the hard way, LOL. I called the thread the RenX Files, LOL

Click to expand...

Great.. Found the thread

Now i'm gonna be up all night :tears:

edit: I'll start at the air temp sensor!

Ecomike said:

Sounds like none of those to me. The key is the dropping RPMs until warm, and then High RPMs when hot, and hard starting.

Sounds exactly like a bad or very dirty IAT, also known as a MAT, Intake Manifold Air Temp Sensor is bad. It is a variable resistor, resistance changes with air temperature. Remove it, clean it, and test it at various temps and compare to the FSM specs. The data table is in many old posts here.

Click to expand...

Excellent idea to check/clean the IAT.

Ok. Jeep has NOT been ran in 14 hours. It's approx 60* outside

No change in numbers after a slight cleanup


I also checked the TPS and adjusted it.
IAC is brand new same with TPS

I had a brand new coolant temp sensor on a spare motor. I swapped that on today

I still have not checked true vacuum or Fuel pressure level

Manifold bolts seem snug. I only checked the top ones