Do I need a new tps?
10-13-13, 06:45 PM
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Do I need a new tps?
87 fc n/a s4.
It seems that my tps keeps going out of whack pretty often.
Just got this engine rebuilt from atkins, yielding approximately 8.3-9.1:1 (thats what they told me) compression in both housings although I find it flooding extremely often, and not starting without putting a small amount of oil in the housings., injectors have been serviced as well and used within a week of service. (and i realize that new engines with used components take time to bead in and flood a **** ton so that's fine because it runs and drives just fine).
I set the timing with a timing light (its spot on), cold start works just fine, doesn't leak any fluids (although i suspect there may be an extremely small vacuum leak somewhere in the upper intake maniold due to the starting fluid spray test increasing rpms by about 100, whatever, its pretty negligible for now and only fluctuates about 50-100 rpms at about 750-650rpms, and my idle valve on the dynamic chamber doesnt do anything).
Thing is, I seem to have a HUGE deadspot where it jerks my car back and forth at just like 2100 rpms, especially noticable in 3rd gear. Not to mention, that when I go correct my tps to check if it is sitting at 1k ohms, I keep finding that it drops to about .600-700 (is this normal?), so I readjust it and try again.
My throttle cables are taught as well.
Do I need a new TPS? Why the hell does it keep dropping out of range? I have read in the past that TPS's hardly ever fail, so i just wanna rule this out before I take my throttle body off and take care of that vac leak.
Any feedback would be great, thanks!
It seems that my tps keeps going out of whack pretty often.
Just got this engine rebuilt from atkins, yielding approximately 8.3-9.1:1 (thats what they told me) compression in both housings although I find it flooding extremely often, and not starting without putting a small amount of oil in the housings., injectors have been serviced as well and used within a week of service. (and i realize that new engines with used components take time to bead in and flood a **** ton so that's fine because it runs and drives just fine).
I set the timing with a timing light (its spot on), cold start works just fine, doesn't leak any fluids (although i suspect there may be an extremely small vacuum leak somewhere in the upper intake maniold due to the starting fluid spray test increasing rpms by about 100, whatever, its pretty negligible for now and only fluctuates about 50-100 rpms at about 750-650rpms, and my idle valve on the dynamic chamber doesnt do anything).
Thing is, I seem to have a HUGE deadspot where it jerks my car back and forth at just like 2100 rpms, especially noticable in 3rd gear. Not to mention, that when I go correct my tps to check if it is sitting at 1k ohms, I keep finding that it drops to about .600-700 (is this normal?), so I readjust it and try again.
My throttle cables are taught as well.
Do I need a new TPS? Why the hell does it keep dropping out of range? I have read in the past that TPS's hardly ever fail, so i just wanna rule this out before I take my throttle body off and take care of that vac leak.
Any feedback would be great, thanks!
Last edited by pumpupthejam; 10-13-13 at 06:49 PM.
10-13-13, 07:30 PM
#2
First off the TPS is to be checked and set 'only' when the engine is as hot as it can get and close is not good enough. The only exception is for throttlebodies which have the Fast Idle Cam removed. Usually, it takes upwards of a twenty minute drive to warm up the engine sufficiently and then the TPS reading must occur quickly afterwards before the Fast Idle Cam reverts back to its original position which changes the throttle linkage position which changes the TPS readings.
To better test the TPS for deadspots requires an analog meter (one w/a needle) as opposed to a digital one as it is not quick enough to pick up the variations associated w/deadspots. W/key to on and the Green/Red wire being probed the 'voltage' should rise slowly from one volt to about 4.5 volts in a linear and smooth fashion as the throttle linkage separates from the TPS plunger.
To better test the TPS for deadspots requires an analog meter (one w/a needle) as opposed to a digital one as it is not quick enough to pick up the variations associated w/deadspots. W/key to on and the Green/Red wire being probed the 'voltage' should rise slowly from one volt to about 4.5 volts in a linear and smooth fashion as the throttle linkage separates from the TPS plunger.
Last edited by satch; 10-13-13 at 07:33 PM.
10-13-13, 11:07 PM
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First off the TPS is to be checked and set 'only' when the engine is as hot as it can get and close is not good enough. The only exception is for throttlebodies which have the Fast Idle Cam removed. Usually, it takes upwards of a twenty minute drive to warm up the engine sufficiently and then the TPS reading must occur quickly afterwards before the Fast Idle Cam reverts back to its original position which changes the throttle linkage position which changes the TPS readings.
To better test the TPS for deadspots requires an analog meter (one w/a needle) as opposed to a digital one as it is not quick enough to pick up the variations associated w/deadspots. W/key to on and the Green/Red wire being probed the 'voltage' should rise slowly from one volt to about 4.5 volts in a linear and smooth fashion as the throttle linkage separates from the TPS plunger.
To better test the TPS for deadspots requires an analog meter (one w/a needle) as opposed to a digital one as it is not quick enough to pick up the variations associated w/deadspots. W/key to on and the Green/Red wire being probed the 'voltage' should rise slowly from one volt to about 4.5 volts in a linear and smooth fashion as the throttle linkage separates from the TPS plunger.
And good to know, i'm gonna try to get my hands on one of those. Thanks!
10-14-13, 07:56 PM
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So i compression tested it, and It read about 65-70 psi in each housing HOT. How is this possible? Did atkins not build my engine correctly? When I picked it up, they told me it had very high compression numbers.
I don't understand how this could have happened. Before I dropped it in, I flushed my oil cooler, cleaned everything, soaked throttle body components in carb cleaner. When I put them on they were immaculate, and I set timing immediately using a timing light after it reached operating temperature the first time I fired it up. I used all fabric gaskets. I even primed the engine and poured some oil into the housings to lubricate them for the first start because Dan told me he built it without using Vaseline.
I don't imagine im going to be getting a refund either because I am the one who dropped it into my 7 and set it all up. Ill have to call them I guess.
If that's really the case, im gonna have to sell this thing, with all of the work iv'e put into it. This is a huge, huge dilemma, and I guess iv'e wasted a few grand on paying them to rebuild it, and even more other parts.
Two whole years of work, and it's been hardly driven. What the hell.
I don't understand how this could have happened. Before I dropped it in, I flushed my oil cooler, cleaned everything, soaked throttle body components in carb cleaner. When I put them on they were immaculate, and I set timing immediately using a timing light after it reached operating temperature the first time I fired it up. I used all fabric gaskets. I even primed the engine and poured some oil into the housings to lubricate them for the first start because Dan told me he built it without using Vaseline.
I don't imagine im going to be getting a refund either because I am the one who dropped it into my 7 and set it all up. Ill have to call them I guess.
If that's really the case, im gonna have to sell this thing, with all of the work iv'e put into it. This is a huge, huge dilemma, and I guess iv'e wasted a few grand on paying them to rebuild it, and even more other parts.
Two whole years of work, and it's been hardly driven. What the hell.
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