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i have 1989 touring wagon with mpfi motor just wondering what the tps does

my car was surging going down the highway so checked fault codes and found that they all lead to the t.p.s (throttle position sensor) now what i have done is disconected the unit (t.p.s) and am now driving the car around the car have been for about 2 months and am now getting bet fuel econmy than before is not lacking in power at all so my my my long winded question is what does this unit do or what is it supposed to do thanku for any reply

Throttle Position Sensor tells the ECU how far open the throttle is. To not have it connected on your car (which is a variable position sensor not just a WOT sensor as the earlier efi subes is) means the ECU will not be giving the engine the correct fuelling, most likely over lean.

the car is not getting hot and i would say that it is the best it has ever ran heaps of power

Probably because a dodgy TPS was overfuelling the car.

If not having a TPS makes the car better, then why did Subaru and everyh other efi engine builder choose to include the item?

that's what i'm trying to work out, like why should the car run at all doe's it mean my econmy will improve with renewing it ???

Its main use is for transient fuel and spark stuff really, like on throttle tip-in or acceleration. Its also used for telling the ECU when to go into idle mode.

I used to run ea82t with microtech.It initially was set up with no TPS at all. So the fuel injector timing based purely on load via MAP sensor.
But either MAP has a bit of lag in, or there are some inconsistencies with the load or whatever.
With fuel injector timing based on a composite of MAP and TPS, you can adjust some points of the map where the TPS setting gets through better giving much better overall response, that and I think it then detects WOT more reliably, when in acceleration.
It also possible to zero all the MAP setting and run purely on TPS, but its very
edgy type of driving then.
I think my best approach to setting the map is to use MAP settings to achieve efficient fuel running,cruise, so not terribly good at acceleration,and then start adding TPS setting to do the acceleration bit.

So with this bit of story I hope you see what the TPS is for IMO.

The TPS is mainly for the Spark map, (85-86 models didnt have ECU controlled spark and thus didnt need a variableTPS) The TPS also improves drivability and economy.

The fuel map is a product of air flow and engine RPM, the other sensors, TPS, o2 sensor, temp sensors ect. simply fine tune it.

and rumour has it that the best power on etrol is gained on the lean side of stoich.

If you have an auto , the TPS is probably pretty useful, helps tell the box when to shift early.

yeah it is an auto but have not noticed any diffrence in gear changing since disconected well i have another on the way so will soon find out what car is supposed to be like i guess thanks for all the replys will repost after testing

It wont have an enrichment while the throttle is in motion like an acell pump on a carby. Basicly as the throttle opens the manifold vacum drops off and air flow speed slows down for the brief moment so the cylinders lean out while throttle (without enrichment) is opened.

steptoe wrote:and rumour has it that the best power on etrol is gained on the lean side of stoich.

Leave the rumours alone, best power is at rich side of stoich, 12.5 - 13:1.
Stoich is 14.7:1, chemically correct to burn all the fuel AND use all the oxygen.