allsierra123

Its usually when Im taking off from a stop and while shifting. Sounds as if its backfiring from the throttle body and from the exhaust its not super loud just a pop and kind of a sputter. Cruises fine and idles fine. Now for what I have done to it.

It has a new set of ford 19# four hole injectors. And a new throttle position sensor. The old sensor was cracked. So I figured that couldnt be good. Also one of the screws for it was missing and up further inspection looked as if it had been broken off. Not sure if that matters a whole lot. But I didnt have this issue before I started fiddling with things.

cruiser54

The TPS requires adjustment on an 88.

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: Set your meter to measure Ohms. 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 runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
If you see more than 1 ohm of resistance, and/or fluctuating 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 flat 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 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.
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.
Revised 03-13-2012

allsierra123

Ok thanks I didnt realize it was needed to adjust them when they were new. Good To know. Lol We have a wedding this weekend. So I dunno If I will get around to it or not.

tjwalker

And if the TPS adjustment doesn't help, two things to verify are fuel pressure and the map sensor.

A backfire is often caused by an imbalance in fuel/air delivery and the above two things are directly involved in that process.

For fuel pressure, you must use a fuel pressure gauge. For an 88, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be sure that vacuum line is pulling good vacuum and is not wet with raw fuel (which indicates a ruptured fuel pressure regulator).

The map sensor can be verified with a meter and a manual. And again, be sure that the vacuum line to the map sensor is pulling good vacuum and that the vacuum line is not deteriorated or cracked, especially around the ends of the line where it connects.

allsierra123

I also noticed what looks like raw fuel around the Throttle body. I istalled a new gasket with it. And I can see the edges of it so I know I didnt forget it when I put it all back together.

cruiser54

There should be NO fuel around the throttle body.

allsierra123

That's kinda what I was thinking.

allsierra123

The tps wasn't working at all. The little arm was above the throttle Arm so when I pushed the throttle it disnte trip the tps at all. Reinstalled it now it works like a.champ.

salad

Nice, glad to hear you got it fixed.

How does it Handel since you fixed the Bachfire?

allsierra123

Like magique lol

cruiser54

How did the lever get on the wrong side?

allsierra123

I installed it wrong. Didnt pay attention to how I took it apart.

cruiser54

Readjust it yet?

Roler

And what about the fuel around the throttle body?

allsierra123

That ended up being oil from something. that's next on my list gotta start plugging the leaks.