MSefi.com read only forum (Jan.15,2018)

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.

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

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.

Lance wrote: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.

Lance wrote: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

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.

Thanks Lance.

Lance wrote:If this was mine, I would do this next:

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

Lance wrote:- 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).

Lance wrote:- 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.....

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?