American Rattlesnake

Hey all,
I drive a 1995 XJ 4.0L, I6, HO and have the infamous "random sputter" problem. I've replaced fuel filter, plugs, wires, distributor cap and rotor and fixed any obvious vacuum leaks, but the problem persists.

I have tested the O2 sensor and observed that it seems to hold a steady voltage at 0.2V, which means to me that either I'm testing it incorrectly or it's not working right.

I don't want to throw parts at the Jeep, but would love to get this fixed, so any ideas are welcome.

Best,
A.R.

Diesel

Anything that controls fuel/air. TPS, IAC, CPS, etc

American Rattlesnake

Thanks, Diesel, can you describe how to test the TPS or IAC? I have unplugged the TPS and put a voltmeter on the wiring harness...get 5V on one side and 0V on the other as it's supposed to. But that's not testing the sensor itself, it's testing the harness, right?

Steph74

Taken from a website for the Rennix engine (not sure if it is the same way for more recent)

Check the voltage at TPS connector pins B (Ground) and A (5.0 volt supply) with the ignition on. If you see about 5 volts, hook up the connector again. and check the voltage at TPS terminals C (positive) and B (Ground) with the ignition on and the throttle plate closed. You should notice approximately 0.8 volts. If you see that voltage, your TPS and wiring should be ok. If not, you'll have to adjust the TPS to get that voltage. If you cannot adjust the TPS to get that voltage, you'll have to replace the TPS and adjust the new one properly. Also, with the voltmeter hooked (terminal C) up and the ignition on, move the TPS arm down and back up slowly and watch the voltage. The change should be increasing and smooth. If there are any dead spots or it is not smooth, it probably needs to be replaced.

American Rattlesnake

Thanks, just tried that. I disconnected the TPS connector and checked voltage at each of the three terminals in the connector: 0V, 5V, 5V. I tried to get a voltage at the pins INSIDE the TPS, but it's pretty cramped in there...is that where I'm supposed to test?

Thanks again, guys...please keep the descriptions and advice coming.

Steph74

not an expert, just learning along.... so take what I say with caution lol

You turn ignition OFF
Plug the TPS (now there are 2 connectors if you have an automatic I figure it is the one with 3 wires you need to look at)
Check between C and B (on mine it is top wire and middle one) so I shoved the multimeter probe in the plug and then went to turn on the ignition... and I got a 0.93V ... keeping everything in place, i losen the screw of the TPS and moved it until it read 0.8V then tighten everything...

I am sure the process is different for an automatic though...

American Rattlesnake

Thanks Steph74, as you were replying, I went back down and figured it out...as you mentioned, you push the probes through the back of the connector while it's plugged into the sensor.

At closed throttle I get 0.56V, WOT I get 4.0V from the TPS. I tried to look for "dead" spots, by opening the throttle slowly, but all I noticed was that it bounced around as I opened the throttle. I don't know if that was just me (unsteady hand?) or not, though...might indicate that I need a new TPS?

Also, I have a manual transmission, if that matters.

Steph74

yes I do too....
actually if I remember properly the 0.8V is just a number...
on my manual they give you a bit of calculation do to ... I am at work now but when i get back I'll see if I can give it to you

OK 17%.... ratio Input (5V or so ) to output (0.8V) or so should be 0.17 (0.85 divided by 5 in the exemple they give)... So I guess you have to adjust your output according to your input...

yours (0.56/4) would be 14% .... have you try to move the sensor slightly to increase the value and see if it works ? with 4V in you should be around 0.63V out with the plate closed I think... try this and see if it works better I guess

kojoff

Honestly, I believe the problem is going to be a bad CPS. My Beep did exactly what you described, and it was the CPS. I figured it out after replacing the coil pack, then the TPS, and a "Old Jeep Guy" told me about the CPS.. .Whiz! Bang!! She cranked right up.

American Rattlesnake

My TPS appears to be non-adjustable...but I've got a '95 H.O. engine, not a Renix, so maybe that makes sense.

0.56V is within normal range for closed throttle, according to Chilton. I'm thinking that the inconsistent voltage as I open the throttle is an important indicator.

More thoughts...?

Also, if I were looking to get a new TPS, what should I be looking for? Appears that there are several brands and pricepoints: MasterPro, BWD, Standard, TruTech, etc.

American Rattlesnake

Hey folks,
Just wanted to check in and let y'all know that she's fixed. Turns out that the variation I was seeing in the voltage on the TPS as I opened the throttle was the culprit...new TPS, no problems!

Main lesson learned....don't throw sensors in there unless you have tested them and know them to be bad.

Thanks for your help!