88cherokeepyles

I am trying to solve my emissions problems and come across this odd symptom.

With the hood open I rev my engine with my finger (the lever near the throttle body) and if I open it up fast it will backfire (?.. popping noise sounds like its in the intake, and I can hear the muffler make a noise too) but then it catches up and will rev. If I go slowly it will go all the way with no problem.

I cleaned my throttlebody today and now the idle will not settle down - it's stuck at idling around 1200 rpm (guess - my stupid XJ has no tach) - there was a ton of build up around the throttle but I got it all. I took the TB all the way off and discovered only half the gasket was there- put a new one on when I was done.

What do you think? BTW, the popping noise happened both before and after the cleaning of the TB

Any help appreciated. This rig is making me go insane with all the little problems it has.

brendancfarrell

How do your injectors look? I had something very similar but I would lose throttle while driving and then I would hear a pop and everything was fine from then. I popped my hood and 4 of the 6 injectors had blow back. I took them out and saw that they were not sealed properly. I replaced them with new Volvo ones for better fuel efficiency and now everything is good.

88cherokeepyles

How do you find blow back in an injector?

BTW, fixed the high idle. There is an adjusting screw for the throttle, took some work, etc, but we're back to normal.

It still pops and sputters though, Seriously drives just fine, which is odd.

brendancfarrell

I had black marks on my manifold behind the corresponding injector

cruiser54

Your tPS could be bad or misadjusted.


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 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. 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 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 08-27-2012

88cherokeepyles

Hey Cruiser, thanks for the write up.

I did the first part, testing the resistance. I'm assuming I probe the side that doesn't connect to the sensor, but rather eventually to the power source ; I got 24 OHM and it moves around a bunch if I wiggle the cables.

You say you have a write up for that?

I changed my thermostat back from a 160 (I was in the desert when the original broke, and I had to replace it with the only part they had), to a 195. My CO still failed but the HC dropped back to about 80.

My jeep is definitely running rich right now, getting absolute crap gas mileage compared to normal (I can usually pull off 17 average, now its 14), and the CO of course is a determining factor.

It certainly makes sense that the TPS could be going bad. First I need to fix the wires though, apparently.

cruiser54

Find your Intake Air Temp sensor. It's the sensor just to the rear of the throttle body, has 2 wires, and screws into the intake manifold.
Where it's connector plugs into the harness you will see that one of the wires on the harness side　is brown with a white stripe. Follow the brown with white stripe wire back into the harness. You'll have to open up the split-loom plastic sheathing to follow it. It will come to a splice with 2 other brown with white wires with duct tape over them. They're from the TPS and the CTS. The 3 wires will be　 spliced to a single wire headed toward the C101 connector if you have an 87 or 88. If you have an 89 or 90, you do not have the C101 bulkhead connector.
　
Now go to the MAP sensor. Follow the brown with white wire into the harness from there. You will find a splice with 2 more brown with white wires with duct tape over them. At the splice you will find the 3 wires connected to a single brown with white wire going toward the C101, or just along the firewall towards the engine if you have an 89 or 90. Along with the MAP sensor that you traced, they are the ECU sensor ground port and the diagnostic connector on the passenger inner fender.
　
You now have 2 sets of 3 brown with white wires, one near the firewall and one near the engine.
　
Cut the splices out of each set of wires eliminating not only the crappy factory splices, but also the single wire between them. Bring both sets of 3 wires together. Solder the 2 sets of wires together and insulate them properly with tape or shrink tubing.
　
Zip-tie up your new sensor loom to allow for engine movement.　I prefer to cover it with some new split-loom or wrap it neatly with electrical tape when done.
　
　
Revised 03-09-12

cruiser54

Hope this helps. If you just read and follow the wires as described in the write-up, you'll be fine.

88cherokeepyles

I followed the wires and found that splice - now, apparently if I can get a better connection on that, it should solve the ohm resistance so I can perform the TPS test? Is that connection the only thing that would cause a faulty resistance?

Bear with me, I'm still learning.

I'm going to solder it tonight or as soon as I can get my hands on a solder iron.

BTW, since it seems to not reference the TPS, will making a better connection on the one connected to the MAP sensor affect the other 3 brown wires? I only say this because those are buried in a deep layer of electrical tape from some previous owner, and the write up doesn't reference the TPS on that connection

cruiser54

There is more than one splice. Keep going through the harness as described. You wanna eliminate those crimps and have everyting soldered. It's easy to check your progress with an ohmeter.

88cherokeepyles

Thanks man. I'll keep looking and try to get through that tape and find the other connection. The first one is soldered and now I have 4 ohm resistance from the battery to the connection.

One thing I should point out is that a brand new wire, according to my meter, gave a resistance of 1.5 or 2.... Tried it on 3 different wires with consistent results...So I think thats the number I'm going for here... Correct? The only time it says 1, is when both ends are in the air.

cruiser54

Touch the probes together and that's the lowest number you'll get. Some of the cheaper meters don't zero out when they should.

88cherokeepyles

I found a better meter and finally got 1 ohm on the ground wire after doing the soldering.

Now, I did your test, 4.86v on the reference, and then getting 0 on the output. I replaced the TPS, and still getting 0 output with the brand new plug.

What could that mean? Did I get a bad sensor? I got it from napa.

cruiser54

That's weird. I'd get another tPS from them.