What makes the RPM drop at low idle?
Check the timing both in and out of gear. If the timing is falling way back in gear, that’s most of your problem. Usual culprit is a centrifugal and/or vacuum advance kicking in at idle. As soon as you throw it in gear it drops back, making the RPM drop worse than it would ordinarily be. Also check for vacuum leaks.
How does idle speed work on a GMC Truck?
Scan it for codes. The control module controls idle speed with an idle air control (IAC) valve. The desired RPM is based on sensor inputs and the actual engine RPM. Four circuits are used in order to control the IAC valve, allowing a precise amount of air into the intake manifold.
What should the idle speed be in neutral?
In Park or Neutral it idles up at 1500. But when I drop it into drive it goes all the way down to around 600. This seems like an excessive drop to me. I had to set the curb idle high so that when it went into gear it wouldn’t stall out.
What’s the idle RPM on my Chevy Suburban?
My 1997 Chevy Suburban (5.7) is acting up on me. When I start it up the RPM and idle seem fine. As I let it sit for a couple of seconds the RPM’s slowly begin to drop until they finally bottom out at about 1K. As soon as I put it into Reverse/Drive etc. the RPM’s drop below that mark and it struggles to stay running.
Scan it for codes. The control module controls idle speed with an idle air control (IAC) valve. The desired RPM is based on sensor inputs and the actual engine RPM. Four circuits are used in order to control the IAC valve, allowing a precise amount of air into the intake manifold.
Check the timing both in and out of gear. If the timing is falling way back in gear, that’s most of your problem. Usual culprit is a centrifugal and/or vacuum advance kicking in at idle. As soon as you throw it in gear it drops back, making the RPM drop worse than it would ordinarily be. Also check for vacuum leaks.
My 1997 Chevy Suburban (5.7) is acting up on me. When I start it up the RPM and idle seem fine. As I let it sit for a couple of seconds the RPM’s slowly begin to drop until they finally bottom out at about 1K. As soon as I put it into Reverse/Drive etc. the RPM’s drop below that mark and it struggles to stay running.
In Park or Neutral it idles up at 1500. But when I drop it into drive it goes all the way down to around 600. This seems like an excessive drop to me. I had to set the curb idle high so that when it went into gear it wouldn’t stall out.
What should the idle be on a car?
Timing is set at 13 degrees. Thanks in advance for any advice!! Adjust your mixture screws and lower the fast idle for the choke. Check the timing both in and out of gear. If the timing is falling way back in gear, that’s most of your problem.
What should the vacuum gauge be at idle?
It gets around 11 in/Hg at idle, vacuum gauge doesnt seem to jump around much, just slight twitches around the 11 mark. Timing is set at 13 degrees. Thanks in advance for any advice!! Adjust your mixture screws and lower the fast idle for the choke.
Why does my car idle at a higher RPM than normal?
Updated January 19, 2019. If your car seems to be revved up to a higher-than-normal RPM while idling, it’s not necessarily a problem. If this problem happens while the engine is cold, it may be part of the engine’s design.
When to idle high on the idle cam?
There is adjustments on the idle cam on the carb and mentioned, on warm days after you already started it, it should not idle high. But on cold days it should always idle high unless you drove it already and it has not cooled back off. You said you hit the pedal and it idles fine.
What to do if your car is idling too fast?
A throttle body cleaning is likely to cure the high idle speed as well. There are many possibilities when your engine is idling too fast. Here are some common ones to help guide you towards the root of the problem.