New engine runs weird and tranny wont down shift

I just put a new engine in my jeep(new used) and I heard it from before the guy pulled it so I know it ran good, now that its in my jeep it surges at idle and sounds like it has a massive cam. Also the tranny shifts out of second super quick, almost like it skips it and wont downshift when i stomp on it or go up a hill. I've already adjusted my TV cable a million times. I know my knock sensor had the plastic pulled off it so i pushed it back on and plugged it back in. Could a knock sensor mess with the engine like that?

nope. sounds like a TPS issue. i bet it needs to be adjusted.

i would check all of the vacuum lines as well

Always post year/engine. Your profile shows an 87, so this is the procedure you need to follow for verifying/adjusting your throttle position sensor. It is DIRECTLY involved with the shifting of the AW4 transmission.
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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: Using one 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 other lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance 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 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 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. 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 clearly embossed with the letters
A,B,C, and D.. For the automatic transmission equipped vehicles the four-wire connector
provides data to the TCU.

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. 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.

Check your grounds, head to firewall, TCU and ECU to dipstick brace and negative battery to dipstick brace.

You may have more than one fault going on here. For the motor, check your MAP vacuum line make sure it is plugged into the correct hole on the TB and clean the CPS plug.

For the tranny, the TCU grounds, the TCU adjustment and clean the TCU connectors with a contact spray. Use something to clean the connectors that is oil free. If you don't have contact spray I use brake cleaner or even Ether quick start on occasion.

Easy to get some oil in a connector when swapping a motor out, sensor connectors don't do well with oil, really low voltage.

mine has 2 3 wire connectors

1 is flat and the other Is square right? The square one has 4 holes and one hole is capped iirc
This is the one that goes to the tcu for autos

what setting should my multi meter be on

DC volts.
Make sure your grounds are on the dipstick tube stud, rear headbolt and firewall like 8mud suggested.

they are but my volts on the a and d are 9.8 and the b and d are 0 what am i doing wrong

oh and the engine runs fine, the map sensor vacum line had come out of the TB. now I just cant get it to down shift when i stomp on it or go up hills and it shifts out of second really quick

how fast does it upshift?

it gets into third like within 20 seconds

YOu should have about 5 volts when probing B and D. Are you doing the probing with the TPS plugged in? You're supposed to leave it plugged in and back probe the connectors.

there is a tab on the back of the TPS, it should go under the little lever on the throttle body so that it moves the tab on the TPS. it sounds like it is on wrong and not getting any input as to throttle position.

1990JEEPXJ said:

there is a tab on the back of the TPS, it should go under the little lever on the throttle body so that it moves the tab on the TPS. it sounds like it is on wrong and not getting any input as to throttle position.

Click to expand...

Good point. Seen that happen before.

yeah i have done that after removing my TPS. it upshifted nearly instantly no matter the speed or throttle.

adjusted the tps just like the write up and it runs and shifts amazing now, cleaned my idle air control valve too. everything works great now. thanks

glad you fixed it :thumbup:

Glad to hear of the fix.