Unstable tps readings

[rcr1978]

I have a problem with my tps reading differently. I will calibrate it then it slowly starts reading off either negative or positive. Recalibrate again same problem it just keeps changing, I notice it the most after restarting. MS2 with 2.890

[Matt Cramer]

Does the reading only get unstable on the car, or does it have this problem on a Stim as well?

[rcr1978]

It seamed fine on the simulator, but I don't remeber calibrating it to the sim, it's been a couple of months. I was thinking about it last night, maybe the connection is dirty on the tps it's used one off of a raptor fourwheeler if thats good I will through the simulator on it. What else could be causing this besides a bad tps?

Thanks

[kjones6039]

Just curious.....

How much variation are you seeing?

Ken

[rcr1978]

Anywhere from -14 to +12, haven't had time to check the stuff I wanted to yet. I just noticed your in Eureka, I'm in Spring Creek

[Matt Cramer]

How exactly is the TPS grounded? It is best to ground it directly to the MS to avoid ground offset issues. If the TPS is grounded to the block or head, it can be affected by voltage drops in the MS ground wires.

[kjones6039]

I share Matt's concern regarding grounding the TPS return. I lean toward returning ALL sensor grounds to the MS when possible.

Beyond that I would be concerned about the mechanical setup, ie. is there enough slack somewhere that the TPS does not return to the exact same position each time.

Feel free to email me: ken <at> kandlservices.com (we could all use some help out here in the middle of the desert, huh?)

Ken

[rcr1978]

All sensor grounds are on the megasquirt, no mechanical interference it's a cable and there is plenty of slack. I will check tonight some of the other things didn't get time last night. Thanks for all replies.

[rcr1978]

Well I got some time tonight, took some logs they don't look very good Looks like things are all over the place, look at the rpm spikes in the log and tps instability. Something weird is goin on, I have R52 the hysteresis pot turned fully clock wise to get a somewhat useable rpm trigger guess I might have to change R45 to a 10k resistor?

[Matt Cramer]

The MAP sensor noise is about the worst. How exactly is the MAP sensor plumbed up?

[rcr1978]

Well it's a single cylinder 4 stroke with a turbo, I am just getting started with it and I am currently running alphaN and speed density. I blend from alpha N to speed density around 3500 rpm, map sensor is on a 3/32" hose that is about 3' long I dont have any filters or restrictions yet but will soon to try and smooth it out some more. I'm running the rpm trigger off of the factory vr sensor it's a fourwheeler with a factory cdi box, Suzuki.

[rcr1978]

This is the best tach signal I can get r56 full counterclockwise, r52 full clockwise. I dont think the dip in the signal is going away must be how the reluctor is setup on the machine

[rcr1978]

Everything works great on the simulator no unstable readings everythings perfect. My tps readings wander all over the place on the vehicle even with all accesories and engine off. Kinda weird

[rcr1978]

well I got it figured out my TPS is toast kinda weird it was off a low mileage unit only a couple of years old. Thanks for everyones replies