97 miata tps differant koeo and koer

[nismoautoxr]

Ive been trying to troubleshoot this for a while without a lot of success. I have replaced the tps and also checked the throttle body for shaft play as well as checking my wiring and I just must be missing something. What it will do is I can cal the tps and it will be reading 0 with the koeo but when I start it it goes to -2.3%. If I calibrate it with koer then it will be at 0 idling then I cut the car off and its +2.3. It is also not giving reapeatable readings from one throttle opening and closing to the next . I cant obviously reproduce this on the stim . Anyone shed light on this? I'm attaching a log now and Ill put the tune up when I'm home from work a little later. The false AE triggers have been giving me fits too. Right now having to run 10 lag factor on the TPS and a minimum of 100 trigger on the time based ae and I still sometimes get false triggers. I normally don't have to go higher than a 35 on the trigger threshold or lower than a 80 smoothing factor on past installs but this thing has a gremlin that is illuding me.

[slow_hemi6]

What are the open and closed adc numbers from calibration? Do you see a change in Vref across the sensor (vref to sensor ground) koeo vs koer?

[nismoautoxr]

The closed adc depending on what moment you capture it is anywhere from 125 to 150 closed and.800 to 860 wot. The tps works fine when operated with the engine off or running but not repeatable when closed and opened . The over run fuel cut is also affected. It's almost as if vaccum is acting on the sensor. It will cut fuel then the tps will go from 0 to 4% and it will come out and in of over run each time it does it. It's the strangest thing. Obviously this is also causing CLIDLE and idle advance issues as well. Also having some hot restart issues where the idle valve is inconsistent on startup. Here is the msq

[slow_hemi6]

That 2.3% variation works out to be about 76mV change on the sensor wire. Do the voltage test across the sensor Vcc to gnd. If that is stable you can rule that out at least. Does the TB have an adjustable stop and is there reasonable spring pressure keeping the linkage against the stop? Is there some reasonable slack in the cable between the firewall and the TB to allow for engine movement?

[slow_hemi6]

Bit of a band aid but would the Auto Zero TPS feature help your issue?

[nismoautoxr]

I was hoping it would but it honestly had no affect whatsoever on it. I tried it a couple times but I never affect Ted the negative tps numbers . I don't really understand that feature.

[nismoautoxr]

That 2.3% variation works out to be about 76mV change on the sensor wire. Do the voltage test across the sensor Vcc to gnd. If that is stable you can rule that out at least. Does the TB have an adjustable stop and is there reasonable spring pressure keeping the linkage against the stop? Is there some reasonable slack in the cable between the firewall and the TB to allow for engine movement?

Yes there is a stop, yes there is cable slack, yes there is substantial spring pressure. I can even wiggle the shaft and not get a reaction. It's a stock car that worked fine with the stock ecu. There is something goofy going on probably ly between the ms3 and the tps...could be something about the bob adapter. That I can't test with the stim so I'll investigate that further. That's the only thing I can rationalize.

[jsmcortina]

Check the sensor ground wiring with the ECU unplugged, ensure there's no continuity to chassis ground.

James

[nismoautoxr]

Check the sensor ground wiring with the ECU unplugged, ensure there's no continuity to chassis ground.

James

Thanks James . That is my first mission. I think it's likely that is what the problem is . I'm pretty sure that I have mistakenly done that in my bob adapter to the factory harness.

[nismoautoxr]

I checked the continuity from the SG to the chassis with all sensors connected and the MS3 disconnected and I had 320k ohms. With all except the coolant sensor disconnected I had 4.5m ohms resistance to the chassis. I did however have direct continuity between SG and the crank sensor ground . I corrected that and it seems to have corrected some of the issues I was having . Ill have to drive it a bit to see if this is a fix but it did yield some positive results by moving my crank sensor ground off of the SG.

[nismoautoxr]

well dammit I'm still having trouble . As you can see from the log I'm attaching ...the TPS is at 1.4 % during crank then it goes to 2.9 then it drops after startup but this activity is enough to kill my crank to run taper so it totally dumps the PWM idle duty all at once . This intermittently results in a stall especially when hot. This is driving me nuts . Any more suggestions?

[nismoautoxr]

here is a curious bit of information. I unbolted the tps from the throttle body and left it dangling just to test and make sure it wasn't some weird throttle body issue and the tps percentage still changes between koeo and koer and whats more intriguing is that I can rev the engine without the tps attached to the throttle body and the percentage goes up as if it were moving the tps. not proportionately mind you but it changes. there is some kind of interference causing the tps signal to change . Anybody have any idea what might be going on . This is really in my head at this point. The other thing I am confused about is why I have 330k ohms of resistance to chassis ground when I disconnect the MS3. I shouldn't have any should I ?

[slow_hemi6]

It is a little weird but 330K is still a huge amount of resistance.

[nismoautoxr]

I made a pretty significant discovery today. all of my TPS issues are resolved by disconnecting the wideband input. I am using a SLC Free open source 4.9 LSU from 14point7. If I disconnect the WB wire from the MS3 the TPS reading is rock steady with the engine running or off and I can run the lag at 100 and its is all as it should be. I hook it back up and when the engine is off I got 5% TPS and when I crank it the TPS goes to -1.5% and I get all kinds of false ae triggers. I see no weirdness about the AFR readings I get on both the LCD of the wideband board or the AFR in TS. 12.5 on TS and .87 to .90 lambda on the LCD....yet I got all these TPS issues. This leads me to believe I probably got something wacky going on inside of the MS3. Looks like I'm cracking it open to have a look see. Any thoughts? My thought is that the output of the wideband must be somehow bleeding over into the vref for the TPS somehow. THis is a headscratcher.

[nismoautoxr]

I did some dvom testing . Measuring between the tps signal wire and ground with the tps connected and the wideband output wire disconnected with KOEO with the throttle shut I measure .551 VDC. The same measurement with the wideband hooked up KOEO I measure .841 VDC...not good.

With the TPS disconnected KOEO measuring between TPS signal and ground with the wideband disconnected I measure 2.038 VDC and with the wideband connected I get 3.658 VDC. If I measure voltage at the O2 input wire without the wb hooked to it I get 2.028 VDC.

With the MS3 disconnected measuring from TPS signal to the 02 signal with both disconnected I get infinity on resistance and also infinity to ground and signal ground. I reconnected the MS3 and then checked continuity between 02 signal and the tps signal with both sensors disconnected with the key off and I get 6.51k continuity between them. I do not know what I should read there if anything but that is definitely where my TPS problem lies and probably vice versa with the afr but its just not as noticeable as the TPS issue. I'm not completely sure where to start but obviously this has to be resolved. Anybody got an idea of what it could be ? I feel pretty certain its not flux . I washed the board very well when I was building it with PCB cleaner so its pretty squeaky clean.

[slow_hemi6]

Specifically where and how have you done the wideband supply and grounds? Seems the SLC Free has pin 1. 12v supply (powers everything including heater and units own 5v reg), pin 2. Electronics ground (needs to be at same potential as MS sensor grounds to prevent offset on linear output), pin 3. Heater ground (usually engine ground or batt -ve might be better).

[nismoautoxr]

Luke...up untill yesterday pin1 was hooked to the stock 02 heater 12 volt supply . Pin2 was to sensor ground. Pin3 was to engine ground. Just to rule out an issue with the sensor ground I wired pin 2 to engine ground removing that potential influence on the tps signal so now I think I'm down to a board issue. I feel I have eliminated a harness issue with the testing I've done but I could be wrong I suppose ,but, I can't think of any stones outside the ms3 I've left unturned?

I'm super busy with customer cars right now and the car is well tuned so running without the wideband is a non issue right now but when the turbo gets installed then the problem will need to be gone. I'm going to put it on the stim as soon as I can and compare DVOM results to those on the car. Unfortunately there is no easy way to use the wideband during the stim testing . Ill have to get creative on that one.

[nismoautoxr]

well crap. I got the MS3 on the stim right now and I cannot reproduce the problem on the stim . I would think that if the problem was in the MS3 then the problem would present itself on the stim . What is up with that ?Why can I remove the 02 input in the car and get rid of the issue? This is killing me.

[nismoautoxr]

Well now I'm thoroughly confused. I did not open the ms3. I disconnected it from the car and I took it in the house ....hooked it to the stim and connected to it with the tuning computer. I loaded the tune using the.wideband and.I tried to duplicate the tps issue. No good. The tps worked fine. Tried over and over and it was fine then I took it back to the car and.put it back in the car. I hooked the wideband back up and lo and.behold....everything works fine and there is no problems with the tps. All I did was disconnect the db37 and the vacuum hose and then reconnect the db37 and the vacuum hose and all of a sudden it's fixed. I drove it 5 miles and it's still fine . Could the map sensor be the problem?

[slow_hemi6]

Most likely a poor ground connection through the connector. Was probably causing the voltage offset when circuit current increased due to the load of the wideband controller. Hopefully it's all good now the connections been re made.