TPS logging

[455 Buick Regal]

Bought a new TPS because the old one appeared to be "dropping out" intermittently on a 20 frame per second log. It would go from some open % TPs down to zero and back up again, every few seconds. Installed the new one and it does the same. Logged RAW TPS V to see if the signal to the ECM was dropping out and it actually DOES NOT. It goes to 0.43V (=0% for my calibration) each time the TPS shows 0%. So that means there is no signal drop (would read 0.00V). What's up with that?

 

[Nick Micale]

It is not unusual to have TPS issues with a 25+ year old wiring harness as we have found many issues with the 5 volt reference source being low or intermittent?

 

[455 Buick Regal]

Nick - I could understand that, but to drop back to exactly my 0% voltage of 0.43? That makes no sense, but then again, somethings on this evil possessed POS make no sense.
Ramin

 

[Nick Micale]

If you have an issue that makes no sense, then it is probably electronics or wiring?

I am continually seeing GN's with weird issues, and most of them we have never before encountered. We have seen a few issues lately with the reference voltage on the TPS and MAF either low, intermittent or non-exsistant?

 

[Nascar83Fan]

Maybe the contacts on the connector for the tps have some corrosion on them or there's corrosion on the wires going into the connector causing the issue?
On the driver side of the throttle body on intercooled TR's and on TTA's there's an adjustment that you can spin with your finger & thumb which will lower or raise the fast idle, but it also will slightly change what the tps voltage being shown is depending on which direction you were to spin it in. You shouldn't need to mess with that though, as it should be already in the proper setting.
Was the idle and wot setting set properly on the tps when you had put the new tps on?
It's also possible maybe on the tps itself, your tps idle adjustment screw might be turned just enough to cause it to bounce slightly between voltages and not stay steady all the time at idle?

In regards to the tps voltage showing higher than 0.00 volts when it's at it's initial starting position on the car.
Depending on how the screw for the idle setting is set, you would see anywhere from like 0.36 to 0.46 / 0.48 for voltage which is the normal range you should be seeing for the tps idle voltage setting if it was set correctly. It'll should never show anything lower than 0.36 and should never show anything higher than 0.46-0.48 at idle. On the WOT side it should never go over 4.65 ish if the WOT was set properly.

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[455 Buick Regal]

Nascar83Fan - This is a FAST XFI ecm. The idle and WOT voltages can either be auto-calibrated or manually calibrated by graph in the XFI. It's not like the stock ECM where you had to set idle at 0.44'ish (that's just where this one ended up).

The TPS was bought new on Friday to replace the existing one that had this problem; No fix.

I will have to load a pic of a log file for you guys to show you what's going on. At this point, it seems like a circuit in the FAST box is flaking out...

 

[455 Buick Regal]

Here you go. I logged "Raw TPS Volts". Note the X axis (horizontal) is marked in 5 second increments. I did not take my foot on and off the throttle that many times in a 5 sec period. All of the lowest parts of the graph equal 0.45volts, which is equal to 0% TPS. The signal did not "go away" to 0 volts or less. And I had my foot on the throttle at that point. Again, new TPS, same thing. There are only 3 wires: (1) ground - if it was intermittent, TPS voltage signal to ECU would drop to zero, (2) 5v feed - if it was intermittent, TPS voltage signal to ECU would drop to zero, and (3) TPS voltage signal to ECU - would drop to zero if it was intermittent. But the voltage drops to the base voltage of 0.45v. Makes no sense again unless FAST box is screwed.

You'll also note the faulty MPH reading...I was not doing 136 mph! See my other post on help needed on calibrating the speed sensor.

 

[Nascar83Fan]

Ah ok, that makes sense. Can't see sig's from mobile app, didn't realize you were not using the old tr ecm.


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[Lance]

Might want to double check your wiring. The "noise" looks periodic like it might be shorted to some other periodic signal. It's possible it could be some kind of internal short in the ECU but I've never heard of anything like that before just cropping up... Does it clean up if you disconnect the TPS sensor completely? Do any other sensors exhibit anything similar?

 

[455 Buick Regal]

Ah, good idea, hadn't thought of logging without the TPS.

Yes, the MPH read-out seems goofy as well. See my other thread on a request for calibration help (i.e., what are the numbers I need to insert in FAST).

Is it normal for the MAP to go up about 4-5 kPa when the engine compartment is hot (3bar located on the fenderwell)?