NewB question: give it gas, RPM's dip before coming up, Normal?
#1
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I've already tried doing a search for this with the keywords I could think of to use. I'm wondering if this is normal for 951's?
I can be sitting at idle and when I give it gas, the RPM's will drop a bit before coming up whether I give it a tap or really tromp on the peddle. It happens even if I'm trying to match RPM's and not at idle, but I don't seem to have the problem in gear. Almost as if there's too much air and not enough gas at that instant.
Vacuum is around 18 or 19 at idle, TPS clicks as soon as I move the throttle, fuel pressure is set at 3 bar, injectors and pump are stock, and FQS is at 0/0.
*edit* Maybe I have it backwards, too much fuel and not enough air.
I can be sitting at idle and when I give it gas, the RPM's will drop a bit before coming up whether I give it a tap or really tromp on the peddle. It happens even if I'm trying to match RPM's and not at idle, but I don't seem to have the problem in gear. Almost as if there's too much air and not enough gas at that instant.
Vacuum is around 18 or 19 at idle, TPS clicks as soon as I move the throttle, fuel pressure is set at 3 bar, injectors and pump are stock, and FQS is at 0/0.
*edit* Maybe I have it backwards, too much fuel and not enough air.
Last edited by TheStock; 08-27-2006 at 07:43 PM.
#2
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I haven't dealt with this kind of problem before, so I can only offer generic advice. But by doing this stuff you might uncover the (or other) problem(s). Just because the TPS clicks doesn't mean it's electrically doing what it's supposed to...
-get a fuel pressure gauge, hook it up to the end of the fuel rail, and check fuel pressure while running, and see how fast it bleeds away after you turn it off
-check the AFM http://www.clarks-garage.com/shop-manual/elect-22.htm
-check the TPS http://www.clarks-garage.com/shop-manual/fuel-06.htm
-check the oxygen sensor http://www.clarks-garage.com/shop-manual/fuel-18.htm
-check the vacuum while opening the throttle, and while the throttle is open.
-check the air filter and fuel filter
Good luck!
-get a fuel pressure gauge, hook it up to the end of the fuel rail, and check fuel pressure while running, and see how fast it bleeds away after you turn it off
-check the AFM http://www.clarks-garage.com/shop-manual/elect-22.htm
-check the TPS http://www.clarks-garage.com/shop-manual/fuel-06.htm
-check the oxygen sensor http://www.clarks-garage.com/shop-manual/fuel-18.htm
-check the vacuum while opening the throttle, and while the throttle is open.
-check the air filter and fuel filter
Good luck!
#4
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Originally Posted by FRporscheman
I haven't dealt with this kind of problem before, so I can only offer generic advice. But by doing this stuff you might uncover the (or other) problem(s). Just because the TPS clicks doesn't mean it's electrically doing what it's supposed to...
-get a fuel pressure gauge, hook it up to the end of the fuel rail, and check fuel pressure while running, and see how fast it bleeds away after you turn it off
-check the AFM http://www.clarks-garage.com/shop-manual/elect-22.htm
-check the TPS http://www.clarks-garage.com/shop-manual/fuel-06.htm
-check the oxygen sensor http://www.clarks-garage.com/shop-manual/fuel-18.htm
-check the vacuum while opening the throttle, and while the throttle is open.
-check the air filter and fuel filter
Good luck!
-get a fuel pressure gauge, hook it up to the end of the fuel rail, and check fuel pressure while running, and see how fast it bleeds away after you turn it off
-check the AFM http://www.clarks-garage.com/shop-manual/elect-22.htm
-check the TPS http://www.clarks-garage.com/shop-manual/fuel-06.htm
-check the oxygen sensor http://www.clarks-garage.com/shop-manual/fuel-18.htm
-check the vacuum while opening the throttle, and while the throttle is open.
-check the air filter and fuel filter
Good luck!
I have a MAP kit and do not have the AFM flapper anymore, so that's out. I replaced a universal O2 sensor with an OEM one and that drastically changed a nasty hesitation problem I had before. Air filter is a K&N and was recently re-oiled but I'm not sure about how old the fuel filter is. I'll check the TPS with the info from clarks-garage when I get a chance. I remember seeing somewhere that I guy had taken his apart and cleaned it out since it is susceptable to oil leaking in from the throttle body, but I can't remember where it was that I saw it. Maybe that would work, but it seems that people change these a lot.
If I'm checking the vacuum with the throttle open, what am I looking for?
As for the fuel pressure, there's already a gauge on the fuel rail and it takes forever for the pressure to dissipate.
Thanks again.
*edit* found the TPS cleaning guide. http://www.arnnworx.com/tps-repair.htm
Last edited by TheStock; 08-28-2006 at 02:57 PM.