90 4.0l 4x4 XJ Running like Crap...HELP!!!

I have a 90 xj 4.0 4x4 with 196k miles that has been having problems. It doesn't idle right, shifts really weirdly, and wants to stall when stopping due to idle dropping when applying the breaks. I can get it not to die when at a stop if I slowly let off the gas after coming to a stop but the moment I step on the gas to take off it acts like it is going to die then it surges forward. Once I do take off sometimes it will act like its misfiring or I like to call it stuttering

I have done a full tune-up, oil change, tested fuel pressure, changed fuel filter. I am not sure what sensors to start testing first. Any ideas, suggestion or anything.

Here is a like to a video of how my idle acts when in park and then in drive when I step on the gas.
http://youtu.be/oS2_P4X-21k

First of all the idle seems awfully low. I'm comfortable with the idle at 500-700 rpm. Have you pulled and cleaned the IAC? That might help a bit with the, IMO, lower than normal idle.

Are all of your vacuum lines in good shape. Seems like it has to take a big breath of air and then comes to life. I'd especially check the MAP to throttle body, EGR lines, fuel pressure regulator.

In the video, why are you accelerating with your foot on the gas, just asking?

...and check this link. It does work and can be done on a RENIX as well as an HO.

http://naxja.org/forum/showthread.php?t=1015963&highlight=throttle+cable

ParadiseXJ said:

In the video, why are you accelerating with your foot on the gas, just asking?

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I wanted to show what happened when I would try to take off from a fully stopped position.

Clean your throttle body ans IAC first.

Then, Check your TPS. TPS sends signals to the engine computer and transmission controller. Since you mention shifting issues along with idling issues, it's a good place to start. They are prone to failure anyway.

Test every sensor and adjust the throttle position sensor properly. Also recheck every ground and connector.

Here is a good site to walk you through all of the RENIX sensor test and adjust procedures;http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Test AND adjust your throttle position sensor. It is directly involved with shifting characteristics (and other throttle characteristics) on the 4.0 engine.
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RENIX TPS
(Thanks to Joe Peters from for this information)

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. Wire "A" is positive. Wire "D" is ground. Remove the three-wire connector from the TPS. Key ON, measure voltage from "A" positive to "D" ground. Note the voltage reading--this is your REFERENCE voltage. Now, reconnect the three-wire connector to the TPS. Key ON, back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. 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 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 four-wire connector. For the automatic transmission equipped vehicles the four-wire connector provides data to the TCU. Disconnect the four-wire connector. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Now, reconnect the four-wire connector to the TPS. 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. 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.

TPS is usual suspect for all those problems at the same time. Test it per the specs. But if it is automatic, test both sides of the TPS sensor!!!

Had kind of that same problem with a 95 xj. TPS was the issue. Be forewarned -- they are a beatch to replace.

luv2offroad said:

Had kind of that same problem with a 95 xj. TPS was the issue. Be forewarned -- they are a beatch to replace.

Click to expand...

????

TPS is easy to replace.

Ecomike said:

????

TPS is easy to replace.

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True story. Remember that the TPS on your 90 is adjustable and must be adjusted. You can't just slap it on.