TPS values

Regul8r

Registered User
Pulled the codes yesterday.

KOEO test TPS out of value
KOER test TPS again and also an O2 Sensor not switching between lean and rich.

I replaced the Throttle Body a few weeks ago and have been dealing with the check engine light since then.
What is the voltage supposed to be at Idle and at WOT from the TPS and what wire do I measure it on. Apparently I need to do an adjustment on the TPS or throttle stop to bring it in to spec. OR I need to get a new one.

Also the O2 Sensors are Bosch and are BRAND NEW!
So now one of the $50 O2 sensors are bad... BS!
 
Also the O2 Sensors are Bosch and are BRAND NEW!
So now one of the $50 O2 sensors are bad... BS!

Actually, unless you've done a tune for the different curve of the Bosch O2 sensors, I'd say both are bad for that application.

Or at least, that seems to be the concensus of those that tune the EECs on these cars.

If I'm wrong, somebody PLEASE correct me - Bosch sensors are only about $33 at Rockauto for a 1990 SC (Motorcraft are only $37 - worth the extra $4 IMO.)

RwP
 
your thinking of maf transfer curve the o2 sensors do not have a curve they are voltage generators

double check that the hego grounds are good, on the 90 theres a black ground wire that comes from the harness behind the intake manifold.

you want to be 100% sure that its going to a good ground, and it wouldn't be a bad idea to double ground it as well, by double grounding i mean bolt it to the firewall then run another wire from it to the battery

the tps could be throwing the code if its not plugged in all the way, unplug it and be sure its getting a good connection

as long as the voltage at the tps is less than 1.2 you'll be golden

adjusting the idle stop screw to get the tps back into range is not ideal since it will alter the isc duty cycle (idle air control valve)

your best bet would be to drill out the holes on the tps (elongate them with a drill) that way you can twist the tps and have more control of it, but thats only if need be
 
Will check the grounds and the plug ins, thanks.

under 1.2 V at idle and what at WOT?

If I remember right...
wire 1 Ground
wire 2 Power (about 4.5-5 volts?)
wire 3 feedback from TPS

As for the Bosch O2 sensors... those are the ones that came from O'Reilly's for the car, not special ordered. Just in stock off the shelf replacement parts. No need for tune to change O2 sensors?
 
Well, I checked the voltage...

.5 volts at idle/closed throttle
3.4 volts at WOT

What is it supposed to be?


As for the O2 sensor...
well my 90 has a 3 wire connector, driver side, on the car.
The Bosch O2 Sensors I bought are 4 wire.

I did not look at the Passenger side to check that but...
WHAT is going on? The books called for THAT O2 Sensor.
So I pulled the stock one from the Annie manifold and installed it.
I am surprised I could even get that Bosch one connected, with the little nipples that align it in the harness.
 
TPS supplies a reference voltage...you're looking for range, such as:

Idle: 0.97 V
WOT: 4.24 V

Looks like your TPS is low by at least 1/2 volt and shy on range. Typical of worn components.

Suggest you replace it w/new and check the throttle-plate shaft in the body for excess wear, vacuum leaks etc.
 
TPS supplies a reference voltage...you're looking for range, such as:

Idle: 0.97 V
WOT: 4.24 V

Looks like your TPS is low by at least 1/2 volt and shy on range. Typical of worn components.

Suggest you replace it w/new and check the throttle-plate shaft in the body for excess wear, vacuum leaks etc.

this is 100% correct for stock engine tps value's. .9vdc is perfect for idle. its nearly impossible to get exactly that but some people luck out. the max that you want it to be off with a stock tune is .1vdc from .9vdc. much more then that and you'll see some minor problems. some people with mods and a tune will run .5vdc, i do not suggest this for your situation.

your WOT is going to vary from car to car. 4.24vdc is about average. if i right 4.45vdc is the most you want for a stock tune. mine (which is not a stock tune) will idle at .51vdc and WOT at 4.91vdc. thanks to the q-horse i can watch it while running the car. :)

also keep in mind while tuning in the tps you need to make sure your iac and idle are set right aswell. both of those can give you a false tps vdc.
 
As suggested, .5v is low. It needs to be in the .65-1.0 range. Depending on what TB you have, adjusting it may be easy or difficult. Adjust it with the key on, engine not running. Don't fuss about the .9v thing because that doesn't matter.

WOT voltage doesn't matter at all either, but since you are seeing a low voltage, you might want to check and make sure you are getting full throttle.

Good catch on the 02 sensors. Someone's book is wrong! lol
 
The TB is an Edelbrock/BBK 70MM I bought from someone on here.

Had no issues with TPS before I swapped in the new TB.

Have ot spend a little time pulling it off and making sure all the parts are good.
It looks as if the linkage was at oe point pulled off/broke and re-welded to the shaft so looks as thought I need some closer inspection.

Anyone have the tolerance on the throttle plate to TB wall?
I do not want to adjust the throttle stop to get the idle volts and then actually have the throttle plate be too far open.

Well more work to be done.
Have a great day.
 
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