seems as tho every tps forum is on 86-89 tpi motors. so i have a 90 firebird formula 350 5.7 tpi alldata says tps voltage should be .96v at closed throttle this is the NON-ajustable tps of coruse. so i Metered mine out. and im at .54 closed throttle and 4.27 WOT now these are fairly good specs for the ajustable tps but mines not ajustable and alldata says .96v is spec for closed throttle. SO if anyone can enlighten me on some info on 90-92 tps specs thanks

I believe that it is supposed to be anywhere between 0.7 volts and 1 volt. Mine is at about 0.84 volts and is around 6 volts at WOT. I have not had any problems with it. I guess what you should check is if when you move the throttle lever the change in voltage is linear and progressive, it does not stick or jump. Sometimes even though the tps is not adjustable, loosening it up a bit and re - tightening it will cause the voltage to go up. However, I don't think that your voltage is bad.

The TPS on SD cars is self zeroing making adjustments unnecessary. Just make sure it has a smooth voltage change when moving the throttle. 5v should be max. Any higher and I would think there's a problem.

ok yea it moved up really smooth and without jumping or cutting out.

just trying to get to the bottom ofy slightly rough idle. The actuall idle speed seems right on its just rought at about 600 in gear and 700 in P or N

shes not as fast as she should be either. 14.90 and she has headers and the factory dual cat setup with an 80 series.

literly ive checked everything as ive owned a tpi before that had similar problems.

Injectors, Fuel pressure, egr is new, ports arnt clocked., TB and IAC is clean and operational.

ran several good tanks of gas though her. new CTS, map sensor. new plugs with proper gap, new dist. with cap rotor and wires.

Scoped her. spark is good. all cylanders are close to even on RPM drop.(so compression is good.

any more ideas?

What'd you check in regards to your injectors?
A couple of unlikely but possibles would be ignition module and distributor shaft.

i ohmed them. 17.-- all 8

they looked new when i go it they were cleaner then the rest or the area then when i ohmed them 17.-- they are probably new.

yea the only thing with anything spark related is like i said i hooked it up to a Scope and it reads spark and also the sparks intensity and they are all even and spark stong. so that would rule out ign modual. and dist shaft as those would have affected spark correct?

Have you checked out your exhaust? Sometimes the stock cats would get clogged, causing your car to run rough. I had a similar problem with mine.

i havent actually check them but i have strong flow comming out of the tail pipes. but im planning on straight pipeing both of them anyways so i will eliminate that possibility soon.

the one thing that is throwing a red flag is I cant get any scan tools to connect with me ecm. it keeps saying no data.

ive verified 5v serial and ecm ground. and ses light indicator.

i can jumper A and B and my check engine light flashed 12 and fans kick on.

but i cant get any scan tool to actually read it.

so the ecm might be shot too.

I like to know if SD car should also have 4.0v @ WOT. I currently have .77 @ idle and 1.79v max at WOT. not sticking everything runs fine. I also check volts to the switch is 5.0-5.1 is this normal???

Shouldnt I have 4.0v or better @WOT with SD??


ETA I'm using a autoXray for my readings

Yes. SD should also be up towards 5v at WOT.
My 92 SD runs .57 through 4.56v.

Last time my WOT voltage was less than 4.0V I had to replace the ECM to fix it.

The TPS settings for 90-92 thirdgens are the exact same as for 85-89 thirdgens. Between .50V and .60V at idle and more than 4.0V at wide open throttle, with the key on but engine off.

Kevin did you experience any other problems?? how does one know when the ecm goes bad? any warning or codes it throws, or does it just go to crap and die.

this is exactly what the problem was, Thanks Kevin

also had problem with the fans kicking on and off at startup, then running all the time.

sounds like your car was going into Limp Home Mode

when I scanned the temp, it was reading 240 plus so I think the ecm thought it was overheating. It was also very hard to start when cold, Im sure the fuel was on the lean side thus hard to start when cold.

I have a 1992 camaro service manual and this is what it says.... "at closed throttle position the voltage output of the TPS is low (approximately .5 volt). As the throttle valve opens, the output increases so that, at wide open throttle (WOT), the output voltage should be approximately 5 volts. That is for the 5.0 and 5.7 TPI motors. I hope it helps

my speed density setup is at .54 most people say it should be at .70
i tired to set mine there but get a code for tps lol as im sure you noticed the non adjustible ones are still adjustible just not as much as the older ones

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What sort of scan tool do you have? I don't think you will find one at your local auto parts store that will read an OBDI system. You can get one from Snap-On or Mac that will read it, but the last time I checked with them on price they quoted me $2500.00.

I never would have known it was a problem until I hooked up my scan tool while on the dyno. So, no warning or problems or errors at all.

I've never encounterd your problem on an L98, but I did encounter something similar to this on an 87 Buick Grand National.

It sounds to me like you are running off the cal-pak in the ECM as opposed to the PROM. The cal-pak is a rudimentary tune burned into a separate chip on the board and is used if the computer loses connection with the PROM. Normally, when this happens, it throws a check engine light; but it didn't in my case with the Buick. I discovered the problem because I would make changes to the chip via tuning software and nothing would happen.

I don't have any idea if that is what is going on with you, but it sounded familiar so I thought I would comment.

Definitive answer: .54 V at idle, 4 V WOT.

Anything higher at idle given ALL stock circumstances will richen the fuel, anything over 4 volts at WOT in unnecessary because the ECM at that point allready thinks the thottle is wide open.

Nuh-uh. The 90-92 7730 speed density ECM doesnt really care what the value is at idle, as long as its within its acceptable range*. (As Viprklr said on 05/03/08) It will use that for the zero point when you turn the key on. If you set it to .54V, that's its zero point. If you set it to .64V, that's its zero point, etc. I've never noticed richer fuel when setting the TPS higher than that on a 90-92 f-body.

*I'm not sure what the acceptable range is without getting an SES light, but anywhere from .50V to .70V seems to be ok.

While a motor is running, have you ever moved the TPS only, just a little while looking at a scanner with wide-band o2??

Well, I have and the fuel enriched slightly.......

I locked the TPS down at .7 - .8 and restarted the car. A/F r's were slightly higher than when set to .54

Just an observation.

after 20 - 25 min of driveing with it higher then .60 causes my computer to throw a code.
then it idles very high once the code has set around 1200 rpm .
the whole tuneing with the tps sensor is worthless atlest for me .

it dosnt work the same way as changing fuel pressure but even going to far with that can cause injectors to stop working or set a o2 code.


any where from .50 -.60 works fine and should be the correct setting
but most sites say this like this example from iroczone "Once you get the proper setting (0.540VDC for MAF or 0.710 for SD), the better your throttle response will be.

ive tried setting mine to many differant settings .54 seems best
but throttle responce is best around .70 but mine throws a code

Well of course. Moving the TPS while the engine is running makes the computer think you are opening the throttle. So its going to add a little fuel.

I knew it would do that while running, because that is the purpose of the TPS.

It's the last part of my last post that needs an explanation. If the ECM would have accepted the higher setting as the zero TPS % when car the restarted, the fuel shouldn't have changed, but when I restarted it, the A/F ratio was higher.

That tells me that it didn't accept .7 - .8 as zero.....
When reset to .54, A/F leaned back out to 14.7.

Also keep in mind, I did this test back when we had REAL gas, not this E10 garbage......

That's really interesting, and I've never noticed that before. I've always set mine to around .60 to .65 and didnt worry about it.

Could it be that when you set the throttle blades to .70 or .80 that the IAC could not close all the way to keep the engine idle down? So you were seeing a higher air fuel ratio (leaner) because the engine was getting extra air from the open throttle blades?

no Kevin it idles normaly till it sets the code for tps like 20 min or so then once the code has set it idles high so its not an iac problem .

the ecm seems to think im giveing it gas at stop lights when i set it below .60 every thing is fine above that and i have issues the code .
also sets a code if im driving on the freeway right after adjustment it seems like the ecm really wants to see below .60
so ive just started assumeing its really supposed to be .54

what are you referring to ,when uy say higher afr? you mean numerically higher than 14.7 or rich like 11.2?

My 92 seems to like .54 volts at closed throttle. Runs great!