Unusual TPS issue

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LR Max
MS/Extra Newbie
Posts: 32
Joined: Sat Jan 14, 2006 11:03 am

Unusual TPS issue

Post by LR Max »

Hi all,

MS1
Tuner studio
single injector TBI
Fuel only, no spark control
4 cylinder normally aspirated gas engine, running pump gas
Still in the "install and tuning" phase of my MS1

Initially I had an issue with my TPS. For the first 10 minutes of driving it would work fine then all of a sudden jump to 249%. I could pull over, let the truck cool off, then the TPS would work again.

I thought that the TPS was bad. So I installed a new one. Also I re-did some wiring (did it correctly, soldered all connections) during this time as well as installed a LC-2 wide band 02.

I come back, plug everything up. I turn the TPS output on the computer indicates that the TPS is increasing by 1~2% every second...on its own :shock: . It does it with the TPS connected and disconnected. The gauge will literally keep climbing indefinitely. I got tired of watching it after it hit 160%.

Calibration doesn't work. Everytime I try to calibrate, the two numbers are nearly the same.

How did I screw it up this badly? I did try a 2nd TPS sensor (both are brand new) and it did the same thing.

Any input would be very helpful. Thank you.
LR Max
MS/Extra Newbie
Posts: 32
Joined: Sat Jan 14, 2006 11:03 am

Re: Unusual TPS issue

Post by LR Max »

For reference, attached is a quick data log.

Conditions of the data log: Ignition and MS on. Fuel pump disconnected. Engine off.

As you can see, the Throttle Position just steps up...on its own. Also last time I put the MS on the simulator, it worked just fine.

Also I double checked. I am getting 5 volts to the sensor and the ground is solid. Checked with my multi meter. Also checked both TPS, both are good.

Any ideas what could've changed?
kjones6039
Super MS/Extra'er
Posts: 1986
Joined: Sat Jul 22, 2006 8:02 pm
Location: Eureka, NV USA
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Re: Unusual TPS issue

Post by kjones6039 »

Is the TPS wiring routed through the factory harness somehow?

Ken
1979 Corvette - 383 CID SBC w/ Holley Pro-Jection 900 CFM TBI, 4-85 lb lo-z injectors & Walbro 255 pump
MS2 v3 w/extra 3.4.2 Release
36-1, Delphi LS2/7 coils in wasted spark, driven by v2.0 logic board from JBPerformance
Spartan Lambda Sensor from 14point7
TinyIOX from JBPerformance
LR Max
MS/Extra Newbie
Posts: 32
Joined: Sat Jan 14, 2006 11:03 am

Re: Unusual TPS issue

Post by LR Max »

Negative.

Vehicle is a 73 land rover. Was originaly a carb truck.

Also used the megasquirt wiring harness. Except for my connections, its connected properly to the MS1. (well obviously not since its not working...but all the soldering and everything is right)
LR Max
MS/Extra Newbie
Posts: 32
Joined: Sat Jan 14, 2006 11:03 am

Re: Unusual TPS issue

Post by LR Max »

I should also mention that I bought my MS1 pre-assembled. I didn't open it up and go monkeying around inside.
kjones6039
Super MS/Extra'er
Posts: 1986
Joined: Sat Jul 22, 2006 8:02 pm
Location: Eureka, NV USA
Contact:

Re: Unusual TPS issue

Post by kjones6039 »

I would have to submit that we have a floating ground (or something similar) going on here..........

What happens when you calibrate the TPS in TS?

Ken

I would be interested in seeing your msq also.........
1979 Corvette - 383 CID SBC w/ Holley Pro-Jection 900 CFM TBI, 4-85 lb lo-z injectors & Walbro 255 pump
MS2 v3 w/extra 3.4.2 Release
36-1, Delphi LS2/7 coils in wasted spark, driven by v2.0 logic board from JBPerformance
Spartan Lambda Sensor from 14point7
TinyIOX from JBPerformance
LR Max
MS/Extra Newbie
Posts: 32
Joined: Sat Jan 14, 2006 11:03 am

Re: Unusual TPS issue

Post by LR Max »

Nothing happens during calibration.

Also it does this exact same thing with the TPS connected.
ihateforums
Helpful MS/Extra'er
Posts: 35
Joined: Sun Jan 27, 2013 1:38 pm

Re: Unusual TPS issue

Post by ihateforums »

How long ago did you test the ECU on the stimulator? Because it sounds like a bad solder joint on the PCB or something. You may want to test it again to verify the problem is inside or outside the box.
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