90-93 idle droop or stall issues
 

If you have a droopy idle, causing stalls when you clutch, especially with A/C on, your problems will be cured by adding a variable TPS.

After installing the vari TPS, my A/C off idle recovery is just like stock, with the A/C on it's not quite stock but is very good and very passable for stock. My idle recovery oscillations are all gone, as well as stalling problems. I drove 15 miles in rush hour stop n go with the a/c on without a single stall.

Now hopefully I can get all the closed loop boost stuff to work. Fingers crossed.

B

Were you using MAPdot accel enrichment before?

-Mike

mind sharing what you adjusted in settings after installing the tps?

Calibrated the TPS and adjusted the closed loop idle settings to work with my car (more settings: idle control closed loop settings). I will take a screen shot if you want to know the exact settings I'm using BUT they really need to be set on a car by car basis.

Have not gotten into playing with accel enrichment, boost control, traction control, or anything else.

B

I suspect doing this will greatly benefit me, as my lightened flywheel plays hell with idle recovery using the MSPNP base map settings

Was the condition you were having problems with when you tip-in to the throttle off idle, like starting from a stop-light or something? Or just having the idle sag when coming to a stop light or something?

For the off-idle response, accel enrichment will help, and if you watch what the MAP does when you just tip into the throttle, the MAP will go into the high load (60+kpa), really low RPM area for a bit before revs climb. If you don't have enough fuel in that part of your map, that can cause it to choke up, too. It can get into that same area when the revs are dropping to (or a bit below) idle, like when you put your foot on the clutch right as you come to a stop. I also found I had too much timing in that area which was causing the car to want to stall when it got into that part of the map.

-Mike

My issue is idle sag coming to a stop light, etc. Maybe that has something to do with it...I need to work on my tuning like crazy, over the whole range.

Yeah the problem is sag when coming to a stop, due to the MS having to recover from the shock of the throttle closing without the benefit of throttle position information. It causes bad droop, sometimes stall. If the ecu is able to recover, it causes oscillations until it settles down. This isn't a problem that you are going to experience as badly, or at all, with any of the 1.8 cars as they all have functional tps sensors from the factory.

Without the tps information, the ecu has to act reactively, where with it, it will react proactively and open the idle valve.

You are right though that too much advance at/around idle causes hiccups. But this is an idle valve issue, not a enrichment, de-enrichment, or time issue.

B

Did a lot more stop n go stuff this morning with the lights and a/c on. It was short, rapid bursts of acceleration followed by complete stops.

Not one stall. Idle recovery is much smoother, as close to stock as can be expected for a "race" ecu. Idle speed is stable. No oscillations. Much much better. I believe I can adjust my fuel underrun settings to work with the TPS as well, I'll look at that once my laptop is charged.

Also, the cold start this morning was also vastly improved. Perhaps it was the TPS, or the tweaked idle valve settings Jerry put in, or a combination of both. But since putting in the big injectors, I've had to wait about 15 seconds before touching the throttle, or else it would stall. This is no longer the case. Start up is basically perfect. And honestly, I never did play with my cold start up enrichments like I was supposed to.

Warm start up is better too. No hunting idle/idle oscillations as before.

IMO, this TPS mod is not optional.

B

Since it keeps coming up, I'm gonna sticky this for a while.

Update: Drove the car in a rainy rush hour yesterday. That means lots of stop n go, most movement in 1st gear with limited time in 2nd. Also because of the rain, a/c, headlamps, and wipers were on. So a pretty good load on the car.

No stalls.

so does the VTPS out of an automatic miata bolt right up to a 92 or willi have to swap out the throttle body and or hack up my harness?

Unfortunately, you'll have to swap the TB, as the shaft is different on the auto TPS. Connector is different as well, so you'll have to either A) cut / splice the wiring, or B) come up with an adapter.

Jeff

fwiw, the shaft of my automatic tps snapped a week ago and I modified a standard throttle shaft to adapt (with a dremmel, a cuttof wheel, a drill n tap, and a steady hand). It is very possible to add the automatic TPS sensor without swapping the whole throttle body, just a bit more work. All 90-93 throttle bodys apparantly have the exact same casting, but you gotta tap the sensor mounting points if using a manual casting for an Auto sensor.

I really hope this makes sense, its based upon my experience with 4 different throttle bodys: 90auto, 90manual, 91manual, 93manual

could you take a picture of the modification to the auto tps?

90-91 tps different from 92-93? (manual)
 

In my quest to source an auto tps for my manual 91 I was told by one vendor that the 90 and 91 had a variable and the 92-93 had just a switch - this based on his review of the schematics.

(he also said the automatic version of the 90-91 had a variable and a switch)

I am out of my depth when it comes to assessing this so I thought I would check here.

You need to tell us what vendor this is so we all know to avoid them.

If you are searching for the BMW TPS part numbers and info (like I was) you can find them here:
https://www.miataturbo.net/megasquirt-18/mspnp-faq-12239/

Hope this helps someone :)

Yes I was looking for just that (thank you). As I understand the post, the Bosch p/n's listed are effectively equivalent, both bolt-ons, same wiring?

The wiring is probably different, but I don't have experience in this yet.

I'm about to make this switch.

I just did it (using the Wells) and it works. The car used to stall every time with the AC on when i took my foot suddenly off the pedal (with my MSPNP9093 on my 91 with light flywheel if that matters to anyone) - No more, I have not been able to make it stall.
The idle still droops a bit more than I would like but I expect that means I have to learn a bit more about how to tweak things (but not stalling is great). I'll be reading here to see what folk suggest for further optimization.

Calibration of the TPS and setting the threshold took all of 15 minutes. I was not sure if the post where Jerry lists all the settings that ought to be changed in addition to the two I did is current but I just copied them over since they do not seem to be vehicle specific. If there are updated settings or further guidance for optimization I would love to see them.

One thing I did note was that the throttle off position seemed to shift after a day of driving (TPSADC from 95 to 90), after that it has been stable (well, I have only had it on for only a few days but so far it is not drifting any more).

Great mod, thanks for the suggestion (and to DIYAutotune for the MSPNP, I really like it).

aside from this window, what else should I change with tps?
http://www.megamanual.com/ms2/MT_accelwiz.GIF
I want to get my car running in its current form before switching to the built motor, then switching to tps idle, enrichment, and boost control.
Thanks

i pulled 2 bmw TPS sensors from the junkyard. but they are both 3 wire units. on looks like the one pictured in the MSPNP FAQ, but it has a plug. the other one looks kinda like the stock miata sensor has 0 208 120 302 on the front. can i use either?

The one I've got is a 6 wire unit, which has "0 280 120 402" printed on it. I've taken a few pics of it for reference:

http://farm3.static.flickr.com/2176/...356be4425b.jpg
http://farm3.static.flickr.com/2330/...aec9ab9aa2.jpg
http://farm3.static.flickr.com/2188/...9242dd6026.jpg
http://farm3.static.flickr.com/2030/...8412e258b6.jpg

This particular one is mentioned in the FAQ (even includes a pin map) so maybe it is just easier to grab one? I haven't installed it in the TB yet but from the comparisons I have done I can't see why it wouldn't work.

Lets say I get my car tuned on a dyno asap, then want to ad the tps...can I just use the tps for enrichments and boost control and not have to jack with other, more complicated stuff / unknown unknowns?

Yes - in fact, you can just add the IAC settings and not even use it for enrichment if you want.

Thats the one I use. Superclean install in my opinion. Use it with the MS1 Extra.

Håkan

Im super confused about the VTPS mod, I got it done to my mspnp because i didnt want to deal with the stalling issues everyone has. But still un aware of what need to be changed. The TB and tps from an automatic?

You can do that. Or you can use one of the TPS shown in this thread, pretty sure they're from a mercedes. Joe Perez is currently trying to retrofit a honda aftermarket TPS to the miata throttlebody so that might end up being an option.
For now the Mercedes unit shown and the factory auto trans miata TPS are the best options.

Where might one get one? Jerry from diyautotune said i needed to get a vtps before i install my pnp.

Read this thread. Then get one on ebay or a junkyard.

What's the going rate for the board mod to accomodate the LTPS?

websales@diyautotune.com Ask them yourself, i'm sure they're willing to give you a price quote.