Leeroy_25

You mean for idle value or overall? either way I am not sure? I assumed they would all be pretty similar as working between 0-5v? I found this online. but not 100% if it is the tps I have.
Part 1 -How to Test the Throttle Position Sensor (3.0L Mitsubishi Montero)
Other ones for other models say idle value is around 0.35-0.75? So I assume this difference in the idle value voltage is what the compensation in the ECU is catering for?

insightful

you're fine as long as you can get it in range while still within that 99% correction factor that microtech gives hardcoded into the unit.

Leeroy_25

Thanks for the feedback. That gives me a bit more confidence to get on a sort out some ind of adapter for the new TPS then! As far as I know it has a built in idle switch but I guess we cannot use that with the microtech? which is basically all I need! the TPS does not seem to do anything when you move it wired up to the idle switch wire which I guess it wouldn't other than some kind of change as it goes in and out of idle position? If I should be able to use that somehow please let me know.

Regards
Lee

insightful

the TPS is basically an idle switch for the microtech, that's about all it is used for in most cases. you can use it for inputs to control various things but i don't, generally because they don't work that well with the narrow input sensor anyways.

Leeroy_25

Okay guys' I need to drag this back up.. Having made an adapter plate an modified my throttle body to run a different TPS as mentioned above I have found the problem has not gone away. So this means the issue does not lie within the TPS unit but presumably the ECU or the wiring too it?
I have checked hot and cold voltage and resistance readings at the TPS plug with no significant change. Earth wire I ran direct from the TPS plug to an earth point on the chassis to make sure that was not a problem.
The only thing I have not checked it voltage on the TPS input at the ECU and if is varies this end with temperature/time?
The new TPS is definitely better and more stable. I just think it is less sensitive. but I still get about 4% variation between hot and cold engine. Has anyone got any more thoughts?
Should a TPS signal wire be shielded? Could it be getting interference?
I wish I could just disable it all together but I don't think you can? if the TPS is adjusted too far to keep it reading zero hot and cold then the indicator states TPS_CAL and i think stops all TPS related functions from working as far as I can see. i.e it does not detect idle which I think effects timing at idle? it prevents pump settings working.. and these from experience seem to work much better in TPS mode. not sure about Decel Fuel cut. I have not been on a long drive and noted that yet as I have been parked up for winter. But as Microtech users you will know the answer and see my issue!
Really want to sort this out. It is such a small detail but playing up so many things.
I have also checked for play in my throttle linkage and shaft and cannot get anything to budge or vary the TSP reading while trying to push or pull it various directions
.

Thank you in advance.

armans

iTrader: (2)

Any correlation between battery voltage (or alternator output) and TPS change?

Leeroy_25

None I have noticed but would need to double check. I know the 5v input to the TPS is steady and solid though?

armans

iTrader: (2)

Definitely worth checking. Also put some electrical load onto the system (brakes pressed, lights on, radio on, etc) and see how it affects the TPS reading.

Leeroy_25

Update.. I did some tinkering today and took various readings to see if I could get to the bottom of this. Noticed a few things. Last time I ran the car I adjusted the TPS when it was warmed up and left it. When I switched on today TPS was say 1% which was less than I expected. The TPS may wonder further after a long drive but I won't be out properly for a couple of weeks. Rather than adjust the TPS I fired the car up and noticed the value dropped to zero right away. It stayed there all the while had the car running. Just warmed it up and switched off. again it may wonder further when used but will have to see. Anyway, I took readings on the Battery display for cold and hot and it was 14.18v cold and dropped to about 14.06v when hot. TPS 5V power is bang on 5V hot and cold.
One thing to query though is I noticed at the ECU you have 5V coming from the +5V pin and the Signal input pin?? Is that right? I expected 0v here? This is with TPS unlplugged as you cannot measure 5v once it is plugged in. you get a drop as measured below. There is not a short across the harness as I completely unplugged it from the ECU too and checked. definitely 5v coming from within the ECU?
The voltage readout varies slightly from hot to cold at the TPS (get the same readings at the ECU end when all plugged in)
at cold idle 5v input = 2.84v, signal output = 2.35v . then
hot idle we have 5v input = 2.80, signal output 2.26
so pretty consistent I think.
This did appear to reveal that my 5v input and signal output are wired back to front? I need to investigate that more.. I have been following the pigtail wires that this connects too assuming they had been wired correctly but it seems the may not have been. Not sure how much difference this would make in the grand scheme of things as I guess it is working like some kind of voltage split.. I could always try and swap the pins and see what happens!?
lastly I measure resistance across the TPS hot and cold.

across ground and signal I got 0.4kohms (cold) and 0.399 kohms (hot) and
across ground and +5v I got 5.19kohms (cold) 5.17kohms (hot)

Let me know if anything sings out or I just need to swap that 5V around and take it for a run and see what happens.

Just an aside.. the TPS correction is set around 72% with this Mitsubishi unit in. was around 25% with the Cosmo one.

armans

iTrader: (2)

I'm 99% sure it is a grounding problem. Ironically, sensors are very sensitive to grounds.
Although I have a different ECU, during last week I've been fixing a very similar (if not identical) problem. Previously, I reset the TPS when engine was cold (it was showing ~ 0.46v), then after engine gets to operating temps, TPS was showing 2-3% open (~ 0.7v). Also note that I have the battery relocated in a rear boot too.
What I did:
First I connected TPS ground directly to the battery negative terminal (I have a 10awg wire from the rear boot of the car to the engine bay). This step helped a liitle bit, but not fully.
Then I made sure my battery is grounded properly. In addition to the existing ground cable, I used a 24" 2awg cable and connected negative terminal to the bolt that holds passenger seat belt release mechanism.
Then with an 8awg wire made connection between chassis (near the driver side tower) directly to the alternator case (one of the four bolts that also have a phillips screw head). Also I cleaned the grounds between engine and the chassis.
After all these mods, today I finally have checked the TPS and it stopped changing at all whether it is cold or hot. Also previouly whenever I put huge load on the battery/alt (e.g. at the same time fans on, blower on, brakes pressed, etc), TPS was being affected too, but now it doesn't do that at all.
So grounding is something you may want to have another look at.

Leeroy_25

armans

iTrader: (2)

I put an extra 2ga cable from battery to chassis because I wasn't sure if existing 4ga cable done by a previous owner was enough.
Here are the pics of my alternator extra grounding with an 8ga wire

https://cimg4.ibsrv.net/gimg/www.rx7...2ad00f1420.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...bcc50a9ec7.jpg

Leeroy_25

That second image link doesn't work.. but mainly I just wanted to be sure I was understanding where you came of the alternator. Maybe I will maybe up a couple decent engine earths and that alternator earth and see what happens. Plus I will check and clean the ECU ground and the TPS ground to chassis. My battery is earthed with At least 2AWG.. I think is it 0AWG in fact. I will check and clean the chassis location though.

Leeroy_25

Well.. Time to report back after a few changes and get this thread finished hopefully!
First of all Armans.. What can I say.. Gab that man a beer! Double thumbs up.. I believe you hit the nail bang on the head!
So recap from above. I had notices that when key in on position but engine off we got a 3-4% error.. once engine started this dropped to zero % and I could just about get adjustment on the TPS for it to work although it would show TPS_Cal every now and then..
So I could not easily run an earth from the TPS switch direct battery -ve and as Armans said that did not totally solve his issue so I thought I would leave that until last.
So in the meantime I got some 16mm˛ earth cables made. One from alternator to a spare M8 hole on the engine block, one from the engine block hole to the earth lead M8 fixing point on the end of the UIM and then a fresh lead from that M8 earth point to the M6 point on the bulkhead where the OEM lead connects. I already had an earth lead from the TPS to the M8 hole on the block as well.
Long and short is TPS appears to hold value perfectly now through the temp range!
To say I am pleased would be an understatement as I have been chasing this issue since I got the car running 18 months or so ago!

Hope this thread helps out some of you other guys.

ARMANS THANK YOU AGAIN!

armans

iTrader: (2)

Awesome! Glad I was helpful.