TPS noise or wiring trouble?

[cedrics]

Hey guys,

So i've been running MS for a while on a nissan L-series engine. I love it Mates can't beleive how low i can run my idle on a higher-cammed engine

That said, i recently did some port work etc and added a larger throttle body while i was at it. I am now having probems getting a steady signal from the new TPS - 60mm off a toyota prado or some crud like that - the TPS reading is approx ~30 and DEAD dead steady when the engine is off, and moves upwards to 250 when the pedal is depressed with no noise or issues.
However, as soon as i turn my engine on, the TPS reading tends to make quick drops to 23 and back up perhaps once every one or two engine cycles. additionally, a simular observation is made when the throttle is depressed - the TPS reading will rise appropriately but drops intermitantly.

As you can imaging, this wreaks havoc with my tps/accell enrichment and so forth.

I would really appreciate some help with this guys

Thanks, -pete.

[devastator]

Pete,
Did you find a resolution to this issue? I'm having the same trouble.

[Bernard Fife]

Guys,

Have you tried the input smoothing TPS lag factors: http://www.megamanual.com/mt28.htm#sg ? That would be the thing to do after making sure the wiring was either shielded and/or well away from sources of interference (spark plug wires, coils, solenoids, ...).

Lance.

[devastator]

Have you tried the input smoothing TPS lag factors: http://www.megamanual.com/mt28.htm#sg ?

Yes I did this. I have had to set the input smoothing TPS lag factor down to 20% in order to keep the TPS from triggering Accel randomly. Problem now is that the TPS does not send a steady enough signal to be used for Accel. 1 time I'll stomp the pedal as fast as I can and get a different TPSdot value then the next time I do it. I've actually done this without the engine running in order to figure out what is going on. When I look at my logs, I get TPSdot values that are all over the place. I don't have these logs available right now and have a heck of a time making one without trailering my sandrail 300 miles. I had a bouncing MAP signal too, but cured that with a "surge filter" on the line going to the MAP sensor, (like a small fuel filter without the element inside).

I noticed that the Accel is triggering as I climb a hill. I'm assuming that this is a response to the increased MAP pressure from the turbo, (running 50% MAP and 50% TPS for accel). Here's the scenario: I accel up until it backfires due to too much fuel on accel, (I think), then the MAP reads this backfire as a pressure increase and gives me more fuel, which repeats the whole process until I lift my foot from the pedal or the engine dies.

I'm hoping to cure my TPS signal bounce so I can use 100% TPS Accel and eliminate the random Accel events I am seeing. I've been chasing this and a fuel delivery issue for almost 2 years and have finally resolved the fuel delivery issue.

That would be the thing to do after making sure the wiring was either shielded and/or well away from sources of interference (spark plug wires, coils, solenoids, ...).

I separated the TPS wires from the loom and they are nowhere near the plug wires, coil, or anything other than the IAC, (which I currently do not use). All of my ground wires are excellent and attached to the battery for noise suppression.
ANY help would be very welcome.
Thanks,
Dev

[Bernard Fife]

Devastator,

If this was mine, I would do this next:

- Try it on the stim. If all is fine when 'winging' the TPS knob, then the circuit is likely fine. If you get odd results there, I would go over this circuit very, very carefully - it consists of C8, C9, and R9 (plus DB37 pin 22 and processor pin 26) - making sure there is no flux, debris, etc., in the components and that everything is well soldered.
- If the TPS circuit performs correctly above, then I would replace the TPS itself on the assumption that the wiper/track is damaged.

The TPS V3.00 schematic is here: http://www.megamanual.com/ms2/pcb.htm

Lance.

[devastator]

Thanks Lance.

If this was mine, I would do this next:

If it were yours, it would probably be running great!
Anyway.

- Try it on the stim. If all is fine when 'winging' the TPS knob, then the circuit is likely fine.

I will try this, although I tested my MS on the Stim when I first had it built, (by fellow Ms'er Borflink).

- If the TPS circuit performs correctly above, then I would replace the TPS itself on the assumption that the wiper/track is damaged.

I tested the TPS with a meter when I first installed it, but, maybe the meter was not accurate enough to pick it up?

Stay tuned.....

[devastator]

Update:
I have not hooked my MS to the stim to test the TPS, but I did notice that if I unplug the power wire to the WBO2, (LC-1), the TPS signal smooths out tremendously.
Should I add a capacitor to the MS power line or the WBO2 power line, or both?