Rpm increase when shifting, intermittent.
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Joined: Mar 2018
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From: Chicago
Rpm increase when shifting, intermittent.
Hey guys, have a problem i’m unsure of. So when my car is warmed up properly, whenever i shift or push is clutch relatively quick, rpms will increase. This is more of annoyance and it’s just a quirk i can drive around but sometimes it gets really annoying. I noticed however when the cars cold, it doesn’t do this. I’m running diypnp2 with no tps(adding vtps soon). I’ve checked throttle cable, cleaned throttle body etc but the problem doesn’t seem to go away. Yesterday, it was warm outside. And i completely closed the idle screw in effort to relieve my misery. And the problem didn’t happen at all, but then i drove the car again (same day) at night when it cooled down, and the problem returned. Absent when cold, starts rising upon clutch engagement when warm. Any help? Thanks!
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Thread Starter
Junior Member
Joined: Mar 2018
Posts: 54
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From: Chicago
Also, i’m running open loop right now. The problem doesn’t exist in closed loop but i get pretty large idle droops in closed loop and revs drop like a rock versus rising a little bit.
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Increase in RPM = increase in airflow. There are two things that allow air into the engine, the throttle body and the idle valve. When you dip the clutch and close the throttle to shift, the only way air gets into the engine is through the idle valve. Thus, the idle valve is letting too much air into the engine. This manifests as hanging RPM, or in extreme cases like yours, a rise in RPM. It's caused by improper idle valve settings. This is further shown by a difference in cold vs. hot operation, since the idle valve settings will change with temperature. They sound like they are correct or near-correct when cold, but the initial values are too high when hot.
Thus, "tune your idle"
Thus, "tune your idle"
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Thread Starter
Junior Member
Joined: Mar 2018
Posts: 54
Total Cats: 1
From: Chicago
Increase in RPM = increase in airflow. There are two things that allow air into the engine, the throttle body and the idle valve. When you dip the clutch and close the throttle to shift, the only way air gets into the engine is through the idle valve. Thus, the idle valve is letting too much air into the engine. This manifests as hanging RPM, or in extreme cases like yours, a rise in RPM. It's caused by improper idle valve settings. This is further shown by a difference in cold vs. hot operation, since the idle valve settings will change with temperature. They sound like they are correct or near-correct when cold, but the initial values are too high when hot.
Thus, "tune your idle"
Thus, "tune your idle"
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Thread Starter
Junior Member
Joined: Mar 2018
Posts: 54
Total Cats: 1
From: Chicago
Hmm i’ll give it another shot tonight. Just wasn’t too fond of how quickly revs dropped during shifting.. then again, maybe it’s because i’m used to to the shift *raise 100rpm* *wait* shift.
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