When setting up the TPS..........

[Meaux]

1994 Q45---74K miles, Black/Tan LeatherDriven maybe twice a weekNo other problemsPure *** stockGrocery store car........2nd owner......I've had it 5 years....bought for $10Kw/ 40K from a woman that just had to have an SUV.....She has a can of Sea-Foam in the tank for the heck of it.......

Do you have to reset the computer, jump any plugs, or disconnect the battery?

I checked mine with an ohm meter, set it to work "off idle", but when I start the car, the idle speed is at 1200 or so. Then I left the car running, and moved the TPS slowly till the Idle speed went down. Seems like I'm back to where I started. There is alot of pedal movement to get "off idle" on the TPS. Maybe its gone poo-poo?

What I'm trying to cure is the slow throttle response. My 89 Maxima Service manual says to turn ECU fully contercloockwise, set TPS with ohm meter. I doubt its the same with a Q45.

I checked the full TPS movement (@ the plug next to it) with an ohm meter, and not knowing how to properly read an analog meter, on R1 scale, it is allmost a closed circuit at the idle position, (about 90% of the meter) and goes closed at WOT. (pegging the mater out) Am I making sense? Not alot of movement on the meter. I bought a digital meter the other day, (Sperry DM5300) what range should I set it, and what reading should I get?

Thanks........

[DAEDALUS]

Focus on the TPS first. Pedal released you should get about 400 ohms. WOT you should get around 5000 ohms.The throttle valve switch is tied to the fast idle cam. The car has to be fully warmed up before you can measure it.No batterty disconnects or jumpers involved with this car.

[Meaux]

Thanks, I'll hook-up the digital tomorrow and see what reading I get.

[Q45tech]

The resistance method is very inaccurate [but mostly functional] the ecu translates the output voltage [from the supplied reference [+ 5.000 volts] thru the TPS [voltage divider]] yielding 0.44 volts closed at warmed up idle to greater than 4.000 volts WOT.

The Consult is a much more accurate method to get this critical voltage perfect.

[Q451990]

As DAE mentioned, the TB Is partially opened when the car is not fully warmed up. I once did the ohm test and tried the same trick, except by taking the slack out of the throttle cables. They'll bind without a few MM slack and cause the high idle also.

Your best best is to find a good tech. with Consult to re-set it for you. Oh, and whatever you do, please don't mess with the little screws on the throttle body! Getting those out of wack usually means replacing it.

Heath

[Q45tech]

The TPS resultant voltage is divided into 10 [20] segments by ecu which translates to idle, 5%, 10%, 15%..........WOT.

These voltage segments are backed up by the IDLE switch and WOT switch at extremes.......it is these in between segments [steps] that are at mercy of TPS voltage.

Obviously throttle % [TPS voltage][LOAD] and MAF voltage [air flow] and RPM are the main parameters to the ecu arriving at correct injector open time [2.0 millisecs > 11.0 millisecs]..............at cruise [steady rpm] the ecu is modified by O2 cycling to fine tune into 14.7AF ratio [14.9lean....14.5rich average into 14.7.....unless you use oxygenated fuel then tricked into 14.3-14.1AF] richer than necessary thus up to 3-5% mpg loss at highway cruise.

Consider that on a level road at 60 mph [AC off] the TPS is usually reporting that the throttle is under 20% open as the IAC [80% duty cycle = 1500rpm] is supplying almost enough air to cruise.

[Meaux]

Well Q45tech, since you brought it up, I'm gettin 2000rpm @ 61mph. Does this sound right? I haven't gotten to the TPS test yet because of rain, and Porsches allways take up garage space........

Thanks......

[Q45tech]

The 4th gearing with the correct loaded radius new tires [10/32" >2/32" =1.5% added error = treaded depth] is set to ~~ 2000 rpm at 60 mph [333 rpms per 10 mph].........obviously different brands of 215/65 or 235/60/15 tires will show differences. Plus analog tach and speedo are only 3% accurate AT BEST plus parallax error in eye to needle angle.

1950-2050 depending on tires is average. At 120 mph tires GROW due to forces so the errors increase. Optimistic speedometer calibration always errs on higher than real.

The loaded radius [axle center to road] is a function of sidewall stiffness [ranges from 800 pounds per inch to 1600] and inflation.

http://www.geckermotorsports.c...r.htm

Obviously 35 psi max tires have stiffer sidewalls than 51 psi max tires.