TPS voltage

Took readings from the TPS today. Input voltage is 4.69. Output voltage is 3.98. Multimeter is accurate to +/- 0.3%. Would you replace this unit? I have been having problems with bucking when I have the gas pedal at a certain position ( right at cruising speed on the highway) and she has lost some power.
`88 4.0L 125K miles

Before you consider replacing the TPS..... I would check the C101 connector near the master cylinder/vacuum booster.... The terminals in this connector have been known to get corroded causing problems with the TPS and CPS.

Charles

CharlesS said:

Before you consider replacing the TPS..... I would check the C101 connector near the master cylinder/vacuum booster.... The terminals in this connector have been known to get corroded causing problems with the TPS and CPS.

Charles

Click to expand...

Thank you , now pretend just for a moment your are talking to a complete idiot. How do I find C101 connector and identify it? I can`t locate it in the Haynes manual either.

The C101 connector is a large wiring harness that connects the engines wiring harness to the vehicles wiring harness which is against the firewall on the drivers side near the brake master cylinder and vacuum booster....

Charles

CharlesS said:

The C101 connector is a large wiring harness that connects the engines wiring harness to the vehicles wiring harness which is against the firewall on the drivers side near the brake master cylinder and vacuum booster....

Charles

Click to expand...

Thanks, I have seen that and will check it. Should I unhook it and clean it with contact cleaner then apply dielectric grease and connect it back up??

Your TPS values are almost exactly what I eneded up with after trying (for a few days at a time) numerous settings, sounds good to me.
I went through, adjusting my TPS (found some resistance in the connector), cleaning my grounds, checking for reistance at the 101 connector, cleaning my MAT sensor, checking fuel pressure, plugging vacume leaks, cleaning the throttle body, reindexing my distributor, plugs, wires and a distirbutor cap. Most of what I did, seemed to help some with smoothness and acceration (sucker runs pretty strong). Still hunts at idle just a little.
On a hunch, I changed my O2 sensor, with a known good used spare, I keep around, bucking disappeared.
The book remedy for bucking is re-indexing the distributor, on mine this helped, but wasn´t a total cure. Problem most totaly disappeared, after the O2 sensor change. Every once in a great while, it will have a very slight hesitation, at a round 2000 RPM. Nothing close to what it was doing before, had some serious bucking.
What I´m trying to say is it could be a combination of things, that collectively add up, the worst on mine seemed to be the O2 sensor. Next best improvement was re-indexing the distributor.

Word of caution, the 101 connector is full of gunk, some really nasty looking die electric grease (mine looked like tar). Being kind of anal retentive, I couldn´t bring myself to plug it back together without cleaning out the gunk on my first XJ. Took most of an afternoon, numerous cans of brake cleaner and scrubbing with a toothbrush to get it clean. What a mess. Ended up having to clean most of the engine compartment.
The next time I had a question about the contacts, in the 101 connector, I unplugged both ends of the wire (or downstream and upstream connectors/sensors) and checked for resistance, no resistance = no problem. Saved a lot of aggrivation, in the long run, if it ain´t broke, don´t fix it, is one saying, a person should always keep in mind, saves trouble.

i have a 90 model 4.0 auto and it just strated bucking real bad and just won't really go but idles and starts fine, there is a little bit of smoke when you rev it up but it feels like it is missing. this started the other day after i drove it home in the remnants of ivan that blew through GA. it was real wet and i did go through many puddles that splashed up over the windshield. so far i've repalced plugs, wires, coil, batt cables, rotor button, cap, cleaned the tb and checked the IAC and the tps. nothing has helped i am now at a loss. any ideas would be a ppreciated. could somthing of gotton wet? has someone had these similar experiences before? could this be th 02?
not meaning to hi jack the thread either.
thanks in advance

I didn´t notice you mentioning the air filter. Air filter is pretty fine paper, doesn´t take much moisture to plug it up?
When I´ve gotten my XJ, seriously wet. I pull just about every connector apart and blow them out with air. To many times I went looking for a miss at idle and/or poor perfotmance and found much of it was a wet connector someplace. Try the easy/cheap solutions first.
Word to the wise, if your gonna go in water above the bumper, find someplace else to get your intake air. Not a bad idea to blow out the alternator and starter with air. Do a good grease job and lubricate most anything that moves from the door hindges to the shift linkages. Grease and oil are your friends :roll:
Stay away from spray type electrical connection sprays, that are advertised to dry or displace water. They often contain silicon or wax, that will mess with your sensor values.
Guess I´m lucky, I´ve got an 88 now, that actually runs better, when it´s wet. That´s one oddity, I hope I don´t accidentially fix, looking for another problem.

i wasn't driving trough deep water it was just puddling up on the side and covering the car when i hit it, i mean i have never seen it rain so much so hard. but the air filter if fine.

Bam> Sounds like you have rigged some sort of "breakout harness" to test your TPS? If so, you can check it at is full range of travel. Just supply voltage and the full throttle readings don't really let you know if you are holding a failed part. My 93 FSM gives specs as follows:
output at idle (center wire) greater than .2 volts.
At wide open, voltage must be less than 4.8 volts.
Between idle and full, look for any deviations in the voltage as it increases. An analog multimeter works great for this. The TPS works like a rheostat, and can have a bad "spot" in it without the entire thing failing. Move throttle from idle to full several times, very slowely, and look closely for a jump in voltage, or a momentary "fall off" in voltage.
Someone mentioned the O2 sensor. Very good idea to check it. It is an easy fix, easy check. The O2 sensor should have a resistance of 5-7 ohms.
scottiebobbie> same for you, I might think...
Best of luck with your respective repairs.
TheRasper.

Rasper> Thanks, I didn`t check the O2 sensor. I did watch the multimeter while slowly moving the throttle and didn`t see any erratic fluctuations (sp?). I have ordered an O2 sensor , MAP sensor and CPS. If this doesn`t help I will just order a TPS and be done with what seems to be the more troublesome sensors in an XJ.