TPS voltage dropping

[Toddmc66]

I'm using the Fast XFI 2.0 system and recently I've come up with a tps error. The problem is the voltage is dropping off after the engine is started. I can set the tps at .44v with the engine off and the pin out voltage is the same at the ecu. (BUT) the voltage isn't steady, it jumps or hunts up and down from .44v to as high as .47v or as low as .42v . It won't stay a steady at .44v I checked grounds and for continuity to positive and ground and didn't find any reason for this. Once the engine is running the voltage drops to around .23v to about .28v Something seems to be pulling the voltage down. This is a new problem because I've had the Fast system on if for a while with no problems.Has anyone run into this with or without the Fast system.

 

[Nick Micale]

Just a guess, but I would change the TPS in case it has an issue?

 

[Toddmc66]

Just a guess, but I would change the TPS in case it has an issue?

I did change it and still got the same results. Going to go over the grounds and make sure they're good. Thanks for the input.

 

[Chuck Leeper]

T/b flutter?
What's the MAP reading do, when this happens?

 

[Toddmc66]

T/b flutter?
What's the MAP reading do, when this happens?

I'll get back to it a little bit later today. I'm going to run a dedicated ground for the throttle position sensor and I'll jot down all the other readings, key on engine off and running. I'll post them later today thanks.

 

[Toddmc66]

OK, back at it...... Connected volt meter to TPS and monitored voltage and started unplugging sensors. When I unplugged the the WB02 the voltage went steady. So I adjusted the TPS and reconnected the 02. No difference still have the TPS error. Not sure if this normal to have the voltage fluctuating. Tried both TPS sensors old and new. Even added a dedicated ground for good measure. The MAP was at 40 to 42 at idle. I believed I may have found the problem. The TPS% on the Fast display is 000% at closed throttle. The TPS% won't register until I open the throttle about a half an inch. I think I need to calibrate the tps closed and WOT so the Fast system can see the correct position of the TPS. The TPS voltage and percentage correlation is off. Can't connect to the Fast ECM. I'll have to wait due to my USB to serial port cable is defective. Waiting on a new one in the mail. Once I get it calibrated I'll update the post.

 

[Toddmc66]

Current snap shot. This is with the tps set at .44 at idle.

 

[Toddmc66]

Problem solved. Finally got my new USB to serial port cable. Once I was able to get into the ecu I was able to set the TPS with no problem. Thanks for the assistance.