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Unread 02-28-2013, 03:07 PM   #1
aldersonfilm
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Strange Start up and Idle Issue

Jeep started up fine today, drove it around a lot, but when I started it up for about the 5 time today, with the engine warm, it struggled to start and when it finally did fire up, it died immediately. I tried it again and held the throttle open for about 30 seconds. THEN it would stay running, but with a slightly higher idle than normal. Once I started driving it around, the automatic tranny started acting up. It wouldn't go into gear properly and the engine surged every time I feathered the gas. The tranny has acted up before, but not this badly and the engine has always had a rough idle.

Changed wires, plugs, all filters, oil, cap and rotor, cleaned throttle plate and cleaned up the grounds at the dipstick and battery ground, though they might need some re-crimping. Could the MAP sensor cause all of this? Or the TPS sensor?

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Unread 02-28-2013, 03:35 PM   #2
cruiser54
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TPS is for sure suspect.


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
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My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 02-28-2013, 05:35 PM   #3
CJ7-Tim
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Quote:
Originally Posted by aldersonfilm View Post
.... struggled to start and when it finally did fire up, it died immediately. I tried it again and held the throttle open for about 30 seconds. THEN it would stay running, but with a slightly higher idle than normal.
I would check the battery, alternator, and wires. See symptoms 1 and 2 below. Low voltage may possibly have an effect on the transmission computer also.


For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging. Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem.

Your symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will relearn the idle settings after a short period of driving and the engine will start and idle normally.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace them as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body.

If the symptoms reoccur, you need to have your battery and/or the alternator load tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.
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Unread 02-28-2013, 06:50 PM   #4
aldersonfilm
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Tried testing the TPS, but I've run into a problem and a possible cause: The possible cause is that the large circular fitting on the air box were the rubber duct attaches is collapsed inward around one section of the edge, allowing air to pass by. Not sure that this would really make a difference though. There is quite a lot of grease build up in the rubber duct as well.

Upon trying to test the TPS, I discovered that the plastic connectors are very brittle and the tiny latch is broken off of all of them. That's not the issue though. The problem is that one the 4 way connector, there are no letters embossed on it. There are on the the 3 way, but not on the 4 way, so I have no reference. This thing probably needs to be replaced anyway, so I'm probably just gonna bite the bullet and get a new one and adjust that one. Anything I need to know for doing so?
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Unread 02-28-2013, 06:53 PM   #5
aldersonfilm
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One more thing. My throttle plate does not lie completely flat. It is at a slight angle. I see that there is an adjusting bolt. Should it lie totally flat or is it normal to be angled a bit?
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Unread 02-28-2013, 07:22 PM   #6
cruiser54
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Quote:
Originally Posted by aldersonfilm View Post
Tried testing the TPS, but I've run into a problem and a possible cause: The possible cause is that the large circular fitting on the air box were the rubber duct attaches is collapsed inward around one section of the edge, allowing air to pass by. Not sure that this would really make a difference though. There is quite a lot of grease build up in the rubber duct as well.

Upon trying to test the TPS, I discovered that the plastic connectors are very brittle and the tiny latch is broken off of all of them. That's not the issue though. The problem is that one the 4 way connector, there are no letters embossed on it. There are on the the 3 way, but not on the 4 way, so I have no reference. This thing probably needs to be replaced anyway, so I'm probably just gonna bite the bullet and get a new one and adjust that one. Anything I need to know for doing so?
Use the flat connector:

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
__________________
Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 02-28-2013, 07:23 PM   #7
cruiser54
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Quote:
Originally Posted by aldersonfilm View Post
Tried testing the TPS, but I've run into a problem and a possible cause: The possible cause is that the large circular fitting on the air box were the rubber duct attaches is collapsed inward around one section of the edge, allowing air to pass by. Not sure that this would really make a difference though. There is quite a lot of grease build up in the rubber duct as well.

Upon trying to test the TPS, I discovered that the plastic connectors are very brittle and the tiny latch is broken off of all of them. That's not the issue though. The problem is that one the 4 way connector, there are no letters embossed on it. There are on the the 3 way, but not on the 4 way, so I have no reference. This thing probably needs to be replaced anyway, so I'm probably just gonna bite the bullet and get a new one and adjust that one. Anything I need to know for doing so?
Cruiser’s Renix Throttle Body Butterfly Adjustment

Okay. Let's start from scratch. First off, that's not an idle adjustment screw. It's a throttle butterfly stop screw. It's purpose is to allow the butterfly to be as close to completely closed as it can be without binding or wearing into the throttle body. It was never intended to be adjusted in the field. But, Uncle Bob didn’t know that, did he?

Engine off. Back off the butterfly stop screw with a 3/32” allen wrench until the butterfly is completely closed. Now. turn the screw in until the FAINTEST movement of the butterfly opening is detected. This can be done more easily with the throttle body removed. If you remove the throttle body, be sure to replace the gasket underneath it after thoroughly cleaning the old one off.

Revised 07/07/2012
__________________
Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 03-02-2013, 08:29 PM   #8
aldersonfilm
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Replaced the throttle position sensor today and calibrated it. It may have helped with the tranny surges, but I tried starting it today and at first it started fine, but just as before, when the engine was hot and I tried to start it up, it tried to die unless I held the gas for about 30 seconds. Then it idled fine.
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Unread 03-02-2013, 08:33 PM   #9
cruiser54
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Quote:
Originally Posted by aldersonfilm View Post
Replaced the throttle position sensor today and calibrated it. It may have helped with the tranny surges, but I tried starting it today and at first it started fine, but just as before, when the engine was hot and I tried to start it up, it tried to die unless I held the gas for about 30 seconds. Then it idled fine.
Did you do the test in my instructions under IMPORTANT NOTE?

Which connector did you use to do the TPS adjustment? The flat one or square one?
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 03-02-2013, 10:54 PM   #10
aldersonfilm
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Not yet. Wanted to replace it first and see if that helped. I adjusted it using the square connector.

Let's say there is a fault in the harness somewhere. Would it be possible to cut the ground wire, stick a terminal on it and ground it closer?

Also, why would the TPS cause a very rough start like this, that gets better after 30 seconds of keeping the revs up?
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Unread 03-03-2013, 04:30 AM   #11
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2 things. For driveability issues, always use the flat connector, not the square one. That's for the trans.

Secondly, do the sensor ground test. It' easy to fix if there's alot of resistance in the circuit. That circuit is the ground for a bunch of sensors that COULD cause your problem. Don't spend money unnecessarily when about 5 minutes of testing will give you good info to make a good decision.

Make sure your intake manifold bolts aren't loose while you've got your noggin under the hood poking around.
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 03-03-2013, 11:37 AM   #12
aldersonfilm
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I used the square one cause I am having a lot of transmission issues. I'll definitely check the manifold bolts, but I do I have to remove anything to tighten them up?

And let's say the sensor ground test fails. What's the fix?

Thanks for the help cruiser!
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Unread 03-03-2013, 11:46 AM   #13
cruiser54
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Quote:
Originally Posted by aldersonfilm View Post
I used the square one cause I am having a lot of transmission issues. I'll definitely check the manifold bolts, but I do I have to remove anything to tighten them up?

And let's say the sensor ground test fails. What's the fix?

Thanks for the help cruiser!
Removing the air filter box helps on the intake bolts.

Test the sensor ground first before I give you the fix. Be sure to wiggle the harness!!

Did you do the COMPLETE ground refreshing?

Connector refreshing?
__________________
Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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