Replaced TPS - Idle now WORSE!

[peuglow]

Some years have the 'tamper proof' Torx screws, some don't. I did my '96 a year ago, and was amazed at what was in there. Especially considering that it's only air, not an air/fuel mixture that passes through there, as in a carb. I got a set of 'tamper' bits at Harbor Freight for a few bucks.

I'll dig around and see what I have. I may have some of them, but I'm not sure. If I don't, I'll just slap the TB on there and take her for a spin, see what has been fixed (or what hasn't :flamemad: )

 

[peuglow]

Ok tossed the cleaned TB and IAC valve in. She was still hunting for an idle. It was a bit better with the AC running.

Took the XJ for a cruise, and the bog down was the worst it has been. Sputtered the whole way, even stalled coming back up my driveway. With even throttle pressure the engine almost cuts out and surges back.

No CEL and to recap what we have done:

New plugs wires rotor and dist cap
New TPS did not help
Cleaned TB and IAC valve
New cat and muffler

Any help would be great!

 

[heyhar]

Throughout this thread, the subject of TPS has come up numerous times. I recall you saying that you've got a new one in there now. But, as has been my experience, the brand new one I bought was the worst of about half a dozen I'd tried. How many others, if any, have you been able to get hold of? Some trial and error is probably what's needed. I know it's a pain in the arse, but now that you've got the rest of the ignition pretty much squared away, I think sensors are the key. Your problems still sound suspiciously like what my TPS was doing to me. I know it's getting frustrating, and throwing cash at it might now be the wisest thing, so that's why I think some from the bone yard is probably the best thing. Maybe half a dozen for the cost of one new one. That's if it isn't the IAC, O2 sensor, MAP, CTS, bad grounds, etc. Keep us up on what you do and what you find.

 

[Ecomike]

Change the CPS before you go any further.

You can test the TPS and the O2 sensor with a high impedance (20,000 ohm per volt) analog volt-ohm meter to see if either is the problem.

 

[peuglow]

Because the new TPS seemed worse, I put the old one back on. I don't have a probe to test it, but I may pick one up.

I am going to get a JY IAC and TPS in the next few days. I will seeing I can get a CPS too, although starting it hasn't been a problem, and this is the first time it's stalled.

Any chance it's the fuel filter? I don't know what symptoms that would throw.

 

[Peteyg]

That is one I have never heard of, very interesting.

I thought I was going crazy. The Jeep was eating coils like candy. I replaced practically everything, and was about to part out the Jeep. Finally, we had the scanner plugged in watching it at idle after I put the 5th (!) coil in in 3 weeks. It idled fine for about half an hour, then started sputtering. i watched the scanner in disbelief as, all at once, it threw EVERY code in the computer, then started throwing "Unrecognized Code" errors, and the engine quit. It HAD to be the computer.

I had found a small post buried in a sudden death thread on Jeepforum (under dozens of worthless "Change your CPS" posts) saying that the guy had found the same problem, put in shorter screws and never had a problem since. So, I figured I had nothing to lose and pulled all the case screws out. It has run perfectly ever since. In fact, it's running better than it ever has, and I've put over 1000 miles and 3 wheeling trips on it since then without even a hiccup.

 

[heyhar]

Wow, There needs to be a thread titled 'Y'all ain't gonna believe this s**t, but...', because that's about the only way to explain it! Or, Unexplained Mysteries of the Universe. Thanks for the heads up.

 

[Ecomike]

Because the new TPS seemed worse, I put the old one back on. I don't have a probe to test it, but I may pick one up.

I am going to get a JY IAC and TPS in the next few days. I will seeing I can get a CPS too, although starting it hasn't been a problem, and this is the first time it's stalled.

Any chance it's the fuel filter? I don't know what symptoms that would throw.

I see a lot of posts where they changed the fuel filter and it did nothing. I see many posts where the hose on the pump in the tank came loose!!!

Get a good high impedance analog volt/ohm meter before you go to the junk yard!!!! Test your sensors (using the guides here, learn how to test them), and then use the meter to do selective shopping at the JY!!!!

 

[90XJay]

It's been a pain trying to figure this out (poster's friend). I mostly deal with renix jeeps. I know these 96's can be odd with 1/2 new 1/2 odd style parts. I'm gonna stop by eventually with my meter to test the sensors. Finally learned how to use a meter this year, might as well learn how to test sensors. Also after some searching any thoughts about it possibly being the upstream o2 sensor? read a few naxja posts where people did that for the heck of it and it fixed their issue.

 

[heyhar]

There's instructions somewhere on this site about how to test the O2 sensor. I've done it, don't remember offhand. Here's where the wires are on my '96. There's four, two for the heater and two for the sensor. I carefully stripped each wire, to read the voltage to the heater, and watch the alternating signal from the sensor. I found that the four year old sensor had become lazy, and I replaced it. MPGs went back up. Blk/wht and blk/blu are grounds, with grn/org the heater+ and blk being the O2 signal. Your wires may be the same, or not. Find the grounds first, and the other two will be hot, one reading, I think, 12v, and the other with a variable signal.

 

[peuglow]

Ok. I bought an analog meter, but I'm not sure if I'm using it right. I'll try again tomorrow and let you know the results.

Should I disconnect the battery before doing any of these tests?

 

[heyhar]

If you're going to test the O2 sensor, the car needs to be running. So, no. You need to look for voltages to the O2 heater, and read the O2 sensor, looking for the needle to be sweeping back and forth while the O2 sensor reads the exhaust gas and adjusts the mixture, as the engine runs.

 

[peuglow]

In going to throw a scanner on there. I'm having issues testing with the multi meter. I think I'm a bit over my head until I learn how to really use the multimeter.

I'll keep you updated.

 

[bimmerjeeper]

found the same problem, put in shorter screws and never had a problem since. So, I figured I had nothing to lose and pulled all the case screws out. It has run perfectly ever since. In fact, it's running better than it ever has, and I've put over 1000 miles and 3 wheeling trips on it since then without even a hiccup.

Can you be more specific? You replaced the screws that hold the ECU to the fender well? How did you know what screws to get? Just shorter ones? How much shorter? Why would mounting screws cause such a problem? Were they shorting something out?

Are you looking to sell one of the other 4 coils that are probably good? I have 125k and might as well replace my coil at some point, unless it's NOT a 100k type of maintenance item.

 

[Ecomike]

Note that your picture (thanks for posting it) shows where you tapped into the O2 sensor wires on yours, and the sensor in the photo is the CTS temp sensor in the T-stat housing, and not an O2 sensor (posting this for hard core newbies, LOL).

My Oxygen sensor test how to thread is here:

http://www.naxja.org/forum/showthread.php?t=1012701&highlight=sensor+test&page=6

It could use the info you posted on wire colors for your year!!! HINT!!!

Note that one finds the ground wires using ohms scale (Jeep power OFF, and looking less than 1 ohm from the ground wire to the battery negative post.

There's instructions somewhere on this site about how to test the O2 sensor. I've done it, don't remember offhand. Here's where the wires are on my '96. There's four, two for the heater and two for the sensor. I carefully stripped each wire, to read the voltage to the heater, and watch the alternating signal from the sensor. I found that the four year old sensor had become lazy, and I replaced it. MPGs went back up. Blk/wht and blk/blu are grounds, with grn/org the heater+ and blk being the O2 signal. Your wires may be the same, or not. Find the grounds first, and the other two will be hot, one reading, I think, 12v, and the other with a variable signal.

 

[Ecomike]

Ok. I bought an analog meter, but I'm not sure if I'm using it right. I'll try again tomorrow and let you know the results.

Should I disconnect the battery before doing any of these tests?

I hope you paid attention to getting one with at least 20,000 ohms per volt impedance in the specs, lest it will not work well on the 0-1 volt test of the O2 sensor for live data. That is the one test that needs the high impedance meter!!!

 

[Ecomike]

If you're going to test the O2 sensor, the car needs to be running. So, no. You need to look for voltages to the O2 heater, and read the O2 sensor, looking for the needle to be sweeping back and forth while the O2 sensor reads the exhaust gas and adjusts the mixture, as the engine runs.

Note: Many O2 tests can be run with power off (but keep the battery connected!!!!), simple ohms test for good grounds on the two O2 sensor ground wires. Also the heater inside the O2 sensor (disconnected from the harness) should be about 8 ohms (IIRC), not zero and 1000000 ohms. Then engine off, power on, power test for the 12 volt heater voltage at the O2 sensor (it is fused and has a relay, that can go bad on late year models!!!).

Then if that is all good, then test the O2 sensor 0-1 Volt signal as described in the link I just posted, with a high impedance analog volt meter.

 

[Ecomike]

Ok. I bought an analog meter, but I'm not sure if I'm using it right. I'll try again tomorrow and let you know the results.

Should I disconnect the battery before doing any of these tests?

NO, absolutely not!!!

 

[Ecomike]

In going to throw a scanner on there. I'm having issues testing with the multi meter. I think I'm a bit over my head until I learn how to really use the multimeter.

I'll keep you updated.

Google a few Youtube videos on how to use multi meter. Great short cut!!

 

[peuglow]

Thanks Mike good tips!! I'm just getting to the point where the learning curve is killing me. I really just need to get this running again. Faulty tests due to my own mistakes will only prolong this process

I absolutely want to learn this stuff, I just need to get this repair done ASAP it's been 8 weeks with no dd!