View Full Version : TPS Voltage range

07-05-2005, 02:26 PM
Could low TPS voltage affect WOT Performance?

I ask because I have been trying to figure out why my car has been down on power for a long long time (can only chirp the tires from a stop). I measured the voltage last night and at idle it is at .956V and at WOT it is only at 4.13V.....now I was reading over on TCCOA that the range for WOT should be 4.3-4.8V but that was for a 5.0. Of course my service manual and EVTM do not give the specified range, thanks in advance for any help.

BTW I do have a BBK 75MM TB and I do have the holes elongated already, should I get another TPS?

07-05-2005, 02:55 PM
Hi Doug,

Your TPS is right in the perfect range, as long as it varies voltage smootly from idle to wot then I would say thats not your problem.

Does you car run rich and gas mileage worse than before?

Tune up recently?

A little more info on to of it just chirps the tires off the line will help us help you :D

Did the power just go down since it has gotten hotter outside, being the m90 generates alot of heat power does go down quite a bit when hot outside.


07-05-2005, 04:52 PM
Well I was just hoping that would be it.

Actually it does eat gas with higher than normal boost about 16 PSI.

It does it either on hot or cold days and has been for over the last 4 years/6,000 miles. I guess I am just used to being able to nail it at 20 mph and fry the tires. The whole story is as follows: I replaced the engine with a 94 longblock about 5 years/6500 miles ago with the 36lb injectors, As far as engine mods:
73mm C&L with 36lb sample tube and 9" cone filter
75mm BBK TB/with ported inlet plenum
Ported "s" model
Raised top
Intercooler Fan
Ported exh. manifolds
190 LPH Fuel pump
2 1/2" high flow cats into single 3 1/2" back into 2 1/2" mufflers

Also I am running new plug wires and Autolite Double Plat's

I have agonized over this for as long as I have had the problem and I know a Tune by Dave D. would help but there is something else that is wrong that I will find eventually.

I have done to it, I have replaced almost all the sensors as they went bad

XR7 Dave
07-05-2005, 05:08 PM
What's your fuel pressure?

07-05-2005, 05:46 PM
Fuel pressure is 38 at idle and climbs to 52 and holds steady at WOT.

XR7 Dave
07-05-2005, 07:31 PM
38 with the vacuum line on or off? OE setting of 39 with the line off should generate 55psi at WOT with 16psi boost. I would set base fuel pressure (vac line off) at 40-41 and try again. You should see a lb for lb rise with boost.

When idling with the vaccum line connected expect approx .3psi drop for every inch of idle vacuum. Most cars idle at about 32-34psi with the line on.

And then let me tune that beast. :D :p

07-05-2005, 08:01 PM
39 With vac line on, I will adjust it down a bit to see if that does anything.

07-06-2005, 09:25 AM
Well last night I tried to adjust the AFPR and it just is not working right (pressure is all over the place, it must be no good). So I put the factory FPR back on and now at idle/line on is at 34psi and WOT/line on about 50 psi. Still no change in performance.

Yes I know you need to tune it Dave but I just can't afford it at this point,(if I could only sell my steel valve covers for $450.00 I would be set)when I do you are the only person that will do it. :)

Joisey Jim
07-06-2005, 01:28 PM
Have you changed your fuel filter lately? You should be getting 55-60 psi at WOT. Also, how are you checking the WOT pressure - I used an extension hose on my fuel pressure gauge (off the fuel rail schraeder valve) and tied it to one of the wiper blades; so I could monitor it on the highway. My problems went away by changing the filter every 15,000m

07-06-2005, 01:48 PM
I rigged the guage up in a similar fashion, the filter has only about 2,000 miles on it.