TPS response...

[Schrade]

Originally Posted by Franke

Schrade, Something else I just read in the driveability and emissions section states that..." voltage should increase at a STEADY rate as throttle is moved toward WOT about 4.6 volts. The ECM has the ability to auto zero the TPS voltage if it between .46 volt and .62 volt. This means that any voltage between .46 and .62 will be determined by the ECM to be 0% throttle". From that statement I gather that the TPS should be linear. Correct?

I read that STEADY part too, just a while ago.

And the answer is, "Not necessarily does it mean the pot is linear."

It means - that IF my TPS sensor works properly, then what I drew as conclusion before, is correct:

if my TPS IS working, then it is safe to assume that the 5V REFERENCE signal INPUT, FROM the ECM, is inversely exponential, and is calibrated for the non-linear LOGARITHMIC resistance of the internal potentiometer. OR, it is calibrated AFTER the 5V REFERENCE signal RETURNS TO the ECM.

[Schrade]

Seems like many Dodge diesels have problems that are fixed with 'Linear-Taper Potentiometers' installed in the TPS.

Hmm...

[Schrade]

This appears to be the case... , again, IF my TPS is in order:

If my TPS IS working, then it is safe to assume that the 5V REFERENCE signal INPUT, FROM the ECM, is inversely exponential, and is calibrated for the non-linear resistance of the internal potentiometer. OR, it is calibrated in like manner, AFTER the 5V REFERENCE signal RETURNS TO the ECM.

I sure wouldn't mind if someone in the know would post up on this...

Or if someone would take 10 and replicate the measurement.


ed.:
The latter assumption is NOT correct, after observing a STEADY voltage increase, with everything plugged back in .

edit:
Throttle response is in sync with the potentiometer, NOT the voltage reading, which SEEMS linear, after observation.

This is eatin' me up here.

[Schrade]

Just got off the phone with Marc. He was at the bench, and did the impedance test.

First time, he said NON-linear. Baseline 6,740 (units?); pegged 1,000, midway range of motion 4,220.

His cell cut off, he called back post 5 minutes. "It's linear - I did some calculations", he said.



Do my snappics in the other thread look linear? Isn't the 'halfway sweep' reading that I posted AT LEAST HALFWAY???

We gonna' have to rig an arm extension of some sort, and get more reliable readings...


Might be moot however...

The original problem of 'off-idle sag', is attributable to the collapsed MAP sensor hose (yet to check)...

No one mentioned that collapsed MAP vac hose would make for this 'off-idle sag'???

[Franke]

Hi Schrade,
Somewhere in these two posts I thought I mentioned MAP and possibly fuel delivery but I can't find that post. Based on those above readings I can't figure it out. If the pots overall resistance is 6740? and midway is 4220 with WOT at 1000 ohms it would seem to me to be Logarithmic. Oh well. Iffan you do find the sag please post as it will undoubtly help others.

[Schrade]

Originally Posted by Franke

Hi Schrade,
Somewhere in these two posts I thought I mentioned MAP and possibly fuel delivery but I can't find that post. Based on those above readings I can't figure it out. If the pots overall resistance is 6740? and midway is 4220 with WOT at 1000 ohms it would seem to me to be Logarithmic. Oh well. Iffan you do find the sag please post as it will undoubtly help others.

Yessir there Franke...

I missed your MAP issue post , being a possible cause of this sag in TPS response. Thanks!

I sure wish we could get somefeedback on this; everyone knows mods, but when it comes to common issues, or basic tune, either no one posts up, or no one knows ...

[Franke]

By the way I did have a MAP sensor go bad on my Z. The car went nuts until the ECM took over and used a calibrated setting for MAP until I could get her home. I had very little throttle response and stalling. Some idle and then stalling (had to keep the rpms up but even then it was tough) until the ECM learned the issue.

[Schrade]

Originally Posted by Franke

By the way I did have a MAP sensor go bad on my Z. The car went nuts until the ECM took over and used a calibrated setting for MAP until I could get her home. I had very little throttle response and stalling. Some idle and then stalling (had to keep the rpms up but even then it was tough) until the ECM learned the issue.

Marc said the common MAP issue is that the vacuum feed hose TO the MAP sensor collapses when you come off idle. He said this could cause 'off-idle sag'.

Knowledge is good. Sharing it is better yUP!!!

[Schrade]

Originally Posted by Schrade

Marc said the common MAP issue is that the vacuum feed hose TO the MAP sensor collapses when you come off idle. He said this could cause 'off-idle sag'.

Knowledge is good. Sharing it is better yUP!!!

So if I have a MAP response issue, it would show up in DataMaster, in a slow RPM increase, as an erratic change?