Did I adjust the TPS corectly?

Can't freaking search "TPS" because the search minimum is set too low, it should be minimum 3 characters IMO. Anyway...

Measured A with the ignition on and the engine off, A was 4.77 VDC. Measured C and set it to .477.

The one quick howto I found said to set the output at 90% of input but that doesn't make sense so I figured he meant 10%.

Trying to solve an erratic idle, it'll idle super low, then super high, then OK then high then low seemingly randomly. I cleaned the TB with carb cleaner and removed and cleaned the IAC as well, the TPS came up in a few idle threads..

90% is wrong, it whould be something like 80%.

A quick google search netted this.
http://autorepair.about.com/library/faqs/bl232i.htm

87manche said:

90% is wrong, it whould be something like 80%.

A quick google search netted this.
http://autorepair.about.com/library/faqs/bl232i.htm

Click to expand...

You mean 20%?

My TPS range is about .3 volts to about 2 volts, so either my TPS is shot or I'm reading it backwards.

That link was pretty good, to the point. My local library has a subscription to ALLDATA, looked up some confusing info for adjustment, including the method in the link. Some of the crap I read was related to the TCM, which used the same connectors, but had me looking for some nominal voltages that were not present and seemingly un-attainable.
:explosion :explosion :explosion
One interesting note is that they say to measure voltage from the "D" wire to engine ground; any potential over 1/10 volt was un-acceptable, I had one volt. Based on that, I followed ALLDATAs recomendation to splice and extra ground wire to that one. I traced the wire close to the firewall for a tap, and in the process I disconnected and cleaned the MAP and the CPS connectors. I check again for potential and get .01 millivolts, goodnuff.

Then I get to this third set of instructions I printed off, and they don't care what initial input and output voltags are as long as the calculated value is between .825 and .835. Somewhere way in the back of my head, what's left of my math brain is telling me this ratio is a percentage. So if that's what you are thinking, output needs to be 82.5% to 83.5% of input.

I don't think the TPS cares, I don't think the ECU cares: I think what matters is that the value of the ouput divided by the input should be in the range of .825 and .835. I think it matters to have clean dry connections and reliable ground paths.

After all that crap I can't say for sure the TPS was "the problem", but I do expect to not go through this for a looooonnnnnng freakin time. For the record the x runs better than ever, starts easier, does not overspeed at start up, uses less gas pedal to get going, shifts are cleaner and more positive. :kissyou: My sex life might even be getting better! LOL:kissyou:

Thanks 5-90 for getting me skooled, Mike

Right the ECU don't care about the actual voltage, it compares the voltage sent to the TPS to the voltage returned. That why it's given as a percentage not a voltage.

ahh, I see.

Couple things, that connector in the about article has 4 wires, mine has three but that's no big deal. On mine A is in, B grnd, C out from the previous threads I've found.

Mine will go no lower than about 1.0 when it needs to be about .83, I'll assume the TPS is hosed and try to source a new one.

philip_g said:

ahh, I see.

Couple things, that connector in the about article has 4 wires, mine has three but that's no big deal. On mine A is in, B grnd, C out from the previous threads I've found.

Mine will go no lower than about 1.0 when it needs to be about .83, I'll assume the TPS is hosed and try to source a new one.

Click to expand...

the difference is manual and auto trans, the TPS is different. I only have three wires with my man trans, but the procedure is the same.

yeah, you're right. Was just coming to post that after looking for the part online.

Do you suppose I should bother replacing it? It's out of spec but barely, aside from a loopy idle and no power the car seems to run fine.

i'd look at other things.
What year and motor.
If it's a renix rig I'd look at the EGR system with the symptoms you describe.
Might also want to torque down the manifold.
Check for vacuum leaks.
All the standard stuff before you start replacing parts.

philip_g said:

Mine will go no lower than about 1.0 when it needs to be about .83, I'll assume the TPS is hosed and try to source a new one.

Click to expand...

??????????????????
My calculater says that 83% of 4.77 is 3.959. With the TB closed and key on adjust the TBS for 3.959V output. Everything I've read up to this point says the only adjustable is the RENIX? You should have a higher voltage at closed throttle with this system, backwards to the rest of the planet.

Part of the brain damage I went through was looking for a specified voltage at wide open throttle; NEVER HAPPENED! At that point the Mrs. was threatening me with the credit card and diagnostic fee the dealership charges. I turned a blind eye to output at WOT, we don't drive at WOT anyway... :eyes: OK, too often. While I'm still trying to learn this system at mach speed, I'm inclined to think this voltage at WOT has more to do with downshifting the auto. Maybe someone can tell me how close that guess is.

Another part of the frustration was using a digital meter to look for a dead spot in the TPS range. My meter autoranges, three senders failed the test, including the new-in-the-box one; I fault the meter. I couldn't find my analog meter to measure resistance across the TPS. :banghead: This system will have to give me more brain damage some other day.

Hypoid said:

??????????????????
My calculater says that 83% of 4.77 is 3.959. With the TB closed and key on adjust the TBS for 3.959V output. Everything I've read up to this point says the only adjustable is the RENIX? You should have a higher voltage at closed throttle with this system, backwards to the rest of the planet.

.

Click to expand...

you're doing it backwards or thinking about it backwards as I was.
The howto linked above explains that you need to divide the putput by the input so when they say 86% they're really meaning that the output should be 14% of the input voltage.
It threw me for a loop at first too since my output range is about 1.0vdc to about 2.0vdc and no higher.

it should be .81 VDC output in your example as I almost understand it

87manche said:

i'd look at other things.
What year and motor.
If it's a renix rig I'd look at the EGR system with the symptoms you describe.
Might also want to torque down the manifold.
Check for vacuum leaks.
All the standard stuff before you start replacing parts.

Click to expand...

Thanks,
It is an 89 renix, I'll check the EGR, but again EGR is a three letter term and not searcheable the way VB is configured here :confused1

I'll check the mani, and for leaks. Thanks for the tips. All those vac lines are awfully brittle at this age!
I've got a fresh can of carb cleaner I can use to leak check her... or just give up and order a used V8 somewhere

the EGR is a bit of a PITA to check. There's a vacuum operated solenoid on the fender and then it's corresponding valve on the manifold.
This link:
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
has some decent instructions, I won't bother repeating it.

philip_g said:

you're doing it backwards or thinking about it backwards as I was.
The howto linked above explains that you need to divide the putput by the input so when they say 86% they're really meaning that the output should be 14% of the input voltage.
It threw me for a loop at first too since my output range is about 1.0vdc to about 2.0vdc and no higher.

it should be .81 VDC output in your example as I almost understand it

Click to expand...

Divide the output by the input, right! That's what ALLDATA said also. The readings I came up with were very similar to yours with the exception of setting my output voltage at 83% of input. I didn't worry about the 17% change, which would be the voltage drop across the control.

Now, take your highest output of 2.0 V and divide it by your input of 4.77=.4192
That's a 58 % change? Given that one of us may be way off, it's a wonder that both motors still run. If I understand the RENIX correctly: as the throttle opens, the output voltage drops. So if your ECU sees that reduced voltage and thinks the TB is open more than it really is, how would this affect the other controls? My understanding is that this was the basis of 3 recalls on the TPS.

Honestly bud, if the highest output you can get is 2 volts, I think that's the problem. As well as I can remember, I set output around 3.9 volts on the new TPS. Along with changing Plugs, wires, cap & rotor, disassembling and cleaning a multitude of electrical connectors and the IAC. The Jeep has gone form a 15 mpg poor mannered slug to a purrs like a kitten roars like a lion fun to drive machine. If it's wrong, I'm not fixin it! LOL

If you think the TPS for an auto will bolt up, you are welcome to the one I brought home from pull-n-save. I can't verify it's bad with my meter, the Mrs had a cow when she heard "used part". I do know the jeep went from a no start condition to running with this one. Make it to Golden during library hours, we can look up your system also.

Good luck, Mike

Too be honest I don't know enough to tell you if they'll work or not, I'd venture a guess at no since they sell both versions, if the auto version just had a spare plug and worked on the 5 speed they'd only sell auto versions and save on production costs.

I'll hit up pull n save, always seems to be a handful of XJs there anyway and pull one, probably cost me no more than a few gallons of gas and 5 bucks, need a working turn signal switch anyway I think, OH and a windshield.

I agree the voltage seems out of whack but this TPS is no more than a couple years and 15k miles old, I have the receipt from a dealer, but the truck just has NO power. Maybe that's normal, I haven't owned a jeep in 15 years and that was a wrangler with the 4.2.. but it seemed quicker than this thing is... but again this thing runs pretty ok aside from a funky idle and no power, no hesitations or anything that to me could indicate a problematic TPS.
Anyway I can verify the max voltage real quick, but I did set the output to the highest I could make it go by rotating the TPS and it made the car "idle" at 3k RPM LOL

Anyway I'm brand new to XJ's and their quirks if you hadn't noticed, but a V8 swap is sounding better and better.

I must be on crack and mixed up a few measurements.

Right now the way the TPS is set up the input is of course 4.77

the output at closed throttle is .50

the output at full throttle is 4.14

I'm all turned around.
Part of my problem is I tried to use
http://autorepair.about.com/library/faqs/bl232i.htm
on a 5 speed car.
http://autorepair.about.com/library/faqs/bl608e.htm
is for a 5 speed and I'm approaching 16% but I need to be at .38 volts and I can go no lower than .5.

Now I'm just going in circles.

well, maybe I found the culprit.

I tested the MAP sensor, on a cold engine the input voltage was about 4.6, it should be 5 within .5, Ok

On a cold engine, engine off the output read a little low, about 3.6 volts. It should be 4-5, well the input is low so maybe that's Ok.

With the engine running, and still cold the output read 1.2, it should be 1.5-2.1, that's awfully low. I'm letting the engine warm up to check it again.

Cat doesn't rattle and car passes emissions, we'll assume that's OK.
Plug wires and cap are relatively new, plugs are autolite but are colored a perfect white ash color, just where I'd want them.

Alright, at temperature the MAP reads .9, that can't be good.

philip_g said:

well, maybe I found the culprit.

I tested the MAP sensor, on a cold engine the input voltage was about 4.6, it should be 5 within .5, Ok

On a cold engine, engine off the output read a little low, about 3.6 volts. It should be 4-5, well the input is low so maybe that's Ok.

With the engine running, and still cold the output read 1.2, it should be 1.5-2.1, that's awfully low. I'm letting the engine warm up to check it again.

Cat doesn't rattle and car passes emissions, we'll assume that's OK.
Plug wires and cap are relatively new, plugs are autolite but are colored a perfect white ash color, just where I'd want them.

Click to expand...

Don't forget the Vacuum, thats what the MAP is reading.

langer1 said:

Don't forget the Vacuum, thats what the MAP is reading.

Click to expand...

I don't have a vac gauge but can borrow one. The hard plastic line from the TB to the MAP is leak free though.
Maybe I should just go dyno the thing and then know for sure what kind of power it's making and where the AF/R is.

High low high low, borrow a fuel pressure gauge also. Make sure you have a steady 31# at all speeds.