idle rpm - The 1947 - Present Chevrolet & GMC Truck Message Board Network

76bonanza · 01-26-2006, 09:51 AM

My truck idles at between 1000 and 1100 rpm in park and about 750 in gear it is an automatic is this about right?

**truckdude239** · 01-26-2006, 09:56 AM

sounds good to me lol

1969 C/K CST · 01-26-2006, 10:19 AM

Sounds within range. Mine is a straight drive. Idles around 900rpm. Usually a bit higher for an automatic.

67ChevyRedneck · 01-26-2006, 10:25 AM

Man, y'alls trucks idle high. Mine idles around 750 in park and 500 in gear (700R4 auto). Motor is a 350. My 00 z71 has some kind of idle speed sensor and it will always idle at 500rpm in park or in gear. Here's a pic of her idlin in park. Are you using a stock dash tack? I've heard they can be off by a couple hundred rpms. Do "built" motors usually idle higher?

76bonanza · 01-26-2006, 11:44 AM

mine is after market tach I think It might be a tad high but 500 in gear I think mine would never run.

Tynee · 01-26-2006, 12:10 PM

A bit off the subject, but still interesting. My '94 350 automatic idled at 400 RPM. I made some adjustment to the Cruise Control cable and raised the idle to 440 RPM. I couldn't even hear the difference, but every time I let it Idle for a few seconds (like at a red light) the check engine light would come on. Took some time to figure that one out.

Longhorn Man · 01-26-2006, 03:42 PM

I think 750 - 800 in neutral is the norm for a small block.
My caddy idles pretty low. My tach is so stupid I can't go by what it says, but it sounds like the 500 -600 in park and 400 - 500 in gear.

76bonanza · 01-26-2006, 04:28 PM

I read some things online and they say around 600-650 for automatic (350)are they talking about in gear or in park they dont say and they only give one number.

Longhorn Man · 01-26-2006, 06:12 PM

I would imagine in park.
I would cringe dropping my tranny into gear at 1100 RPM...

bad68bowtie · 01-26-2006, 08:28 PM

My truck idles between 1000-1250 when it park and about 900 in gear when its cold. Once it warms up its probably around 750 in park and 500 in gear.

Zonaman · 01-26-2006, 08:56 PM

Speak of the devil! I just had to fool around with mine to pass emissions today! Haynes says 900 (in "P" I presume) for an MT; 600 for AT 350. Not to hijack the thread but what, if any (aside from passing emissions), will be the effect of turning the air/fuel screws on an Edelbrok 1406 1.25 turns leaner while turning the idle screw to that rpm?

76bonanza · 01-26-2006, 11:22 PM

got mine down to about 750 in park and about 550 in gear seems ok little rough but it also has a cam. Will see how it is in the morning in the cold.

71-longbed · 01-27-2006, 12:13 AM

mines the same as 67chevyredneck ...... 350/th350 ... park around 750 and 500 in drive at idle ... he also has the same tach as me too .... wierd

Longhorn Man · 01-27-2006, 12:40 AM

gotta love looking at the reflection of the tach light on the windshield at night huh?

67ChevyRedneck · 01-27-2006, 09:19 AM

Quote:

Originally Posted by Longhorn Man

gotta love looking at the reflection of the tach light on the windshield at night huh?

I think you've mentioned that before... I've never even noticed it...

I was an idiot and didn't install the extra ground strap inside the dizzy when I put in the 350. Couldn't get the dang truck to run right. Sometimes it would idle at 900-1000 and wouldn't come down and I'd cringe when I put it in gear cause it would almost slam into gear. Then the gear idle was around 700 and it felt like the truck was "pushing" when I was holding the brakes. I fixed the dizzy problems (wish I woulda know bout this board 2 years ago) and she runs like a top. Is it ok for a truck to idle at higher rpms? Seems like it would wear the tranny when sittin at readlights.

71-longbed · 01-27-2006, 07:59 AM

i usually dont pay much attention to it .. but if i does get on my nerves .. i dim my whole dash down

....

1969 C/K CST · 01-27-2006, 10:48 AM

Mine seems smoother at around 900. When releasing the clutch it bogs and goes with very little throttle. Maybe being a 4x4 makes a difference. I have played with it at lower rpm's but is more comfortable to drive at the current setting. I also have had 4 different carbs on it and all with the same result as far as idle position.

MrC1 · 01-27-2006, 11:12 AM

For a stock-type idle (not a cammed-up engine), normal is about 750-800 in park and 600-650 in drive.

If you've got some lope all bets are off.

Somebody mentioned having a higher idle when cold, then lower when warmed up. Sounds like a fast idle cam not being kicked down before you put it in gear.

If your idle is over about 850-900 in park, you're probably beyond the idle circuit and can't adjust your idle mixture with the screws.

76bonanza · 01-27-2006, 12:56 PM

Would I be right to assume the lower I can get it the better for the engine? As long as it runs?

Tynee · 01-27-2006, 03:01 PM

Quote:

Originally Posted by 76bonanza

Would I be right to assume the lower I can get it the better for the engine? As long as it runs?

For the engine, maybe. For fuel economy, there is such a thing as too low an RPM at take-off. You'd lug the engine badly and use more gas than at a higher RPM.

I don't know that it wouldn't be best to keep a minimum RPM for the Alternator as well.

flatbedchev · 01-27-2006, 02:48 PM

my 350 runs at about 850/900 rpm at idle but it's also a manual tranny

Longhorn Man · 01-28-2006, 07:26 AM

sitting say at a long red light, idleing at 900 or more in gear, does build up some heat in the tranny... not real extreem, but more so than needed. It is also very rough on your tranny and u_joints...and the rear diff, when it slams into gear.

MrC1 · 01-28-2006, 10:23 AM

Agree with the last post. Too high of an idle is hard on the tranny due to excessive heat buildup and the rest of the drivetrain if it's slamming into gear. Too low of a idle is bad for the engine due to poor internal oiiling and coolant flow. It's also not good for the tranny for the same reason - poor oil flow. If the RPM drops low enough, the tranny could actually be somkewhat disengaged.

To tell you the truth, the engine alone would probably be happier at a very high RPM due to the good oiling frm crank throw. Of course, that doesn't happen too much until about 2000 RPM, so that one's out the window.

71-longbed · 01-29-2006, 02:11 PM

would a missing ground strap in the dizzy really cause those problems .... i've never had one in mine .. never noticed any trouble

Longhorn Man · 01-29-2006, 09:53 PM

Are you talking about the one that goes from the coil hold down bolt to the harness plug?
Would one even work without that?

01-26-2006, 09:51 AM	#1
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	idle rpm My truck idles at between 1000 and 1100 rpm in park and about 750 in gear it is an automatic is this about right? __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

01-26-2006, 09:56 AM	#2
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,233	Re: idle rpm sounds good to me lol __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

01-26-2006, 10:19 AM	#3
1969 C/K CST A.K.A- Crummy Join Date: Jun 2005 Location: NC foothills Posts: 3,025	Re: idle rpm Sounds within range. Mine is a straight drive. Idles around 900rpm. Usually a bit higher for an automatic. __________________ 2003 Silverado Z71 Are fishermen all liars?

01-26-2006, 10:25 AM	#4
67ChevyRedneck Hittin E-Z Street on Mud Tires Join Date: Nov 2004 Location: Greenville, SC Posts: 23,090	Re: idle rpm Man, y'alls trucks idle high. Mine idles around 750 in park and 500 in gear (700R4 auto). Motor is a 350. My 00 z71 has some kind of idle speed sensor and it will always idle at 500rpm in park or in gear. Here's a pic of her idlin in park. Are you using a stock dash tack? I've heard they can be off by a couple hundred rpms. Do "built" motors usually idle higher? Attached Images __________________ Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications! Last edited by 67ChevyRedneck; 01-26-2006 at 10:27 AM.

01-26-2006, 11:44 AM	#5
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	Re: idle rpm mine is after market tach I think It might be a tad high but 500 in gear I think mine would never run. __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

01-26-2006, 12:10 PM	#6
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	Re: idle rpm A bit off the subject, but still interesting. My '94 350 automatic idled at 400 RPM. I made some adjustment to the Cruise Control cable and raised the idle to 440 RPM. I couldn't even hear the difference, but every time I let it Idle for a few seconds (like at a red light) the check engine light would come on. Took some time to figure that one out. __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

01-26-2006, 03:42 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: idle rpm I think 750 - 800 in neutral is the norm for a small block. My caddy idles pretty low. My tach is so stupid I can't go by what it says, but it sounds like the 500 -600 in park and 400 - 500 in gear.

01-26-2006, 04:28 PM	#8
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	Re: idle rpm I read some things online and they say around 600-650 for automatic (350)are they talking about in gear or in park they dont say and they only give one number. __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

01-26-2006, 06:12 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: idle rpm I would imagine in park. I would cringe dropping my tranny into gear at 1100 RPM...

01-26-2006, 08:28 PM	#10
bad68bowtie On the college boy budget... Join Date: Oct 2005 Location: Athens, Georgia Posts: 370	Re: idle rpm My truck idles between 1000-1250 when it park and about 900 in gear when its cold. Once it warms up its probably around 750 in park and 500 in gear. __________________ -'68 C10 short/step- 350/350

01-26-2006, 08:56 PM	#11
Zonaman Registered User Join Date: May 2004 Location: Chandler, AZ Posts: 519	Re: idle rpm Speak of the devil! I just had to fool around with mine to pass emissions today! Haynes says 900 (in "P" I presume) for an MT; 600 for AT 350. Not to hijack the thread but what, if any (aside from passing emissions), will be the effect of turning the air/fuel screws on an Edelbrok 1406 1.25 turns leaner while turning the idle screw to that rpm? __________________ 69 C-10 LWB, 350, 700r4, 3.73 posi-traction, front disc brakes. Built for the desert- She can take the heat! Vivat Rex Chevus! Last edited by Zonaman; 02-03-2006 at 12:16 PM.

01-26-2006, 11:22 PM	#12
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	Re: idle rpm got mine down to about 750 in park and about 550 in gear seems ok little rough but it also has a cam. Will see how it is in the morning in the cold. __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

01-27-2006, 12:13 AM	#13
71-longbed Its Magically Delicious Join Date: Jan 2003 Location: oregon Posts: 2,398	Re: idle rpm mines the same as 67chevyredneck ...... 350/th350 ... park around 750 and 500 in drive at idle ... he also has the same tach as me too .... wierd __________________ 71 C10 LWB 350sbc -TH350 12 bolt 3.42 Posi Of all my favorite things to do, The utmost is to have a brew. My love grows for my foamy friend, with each thirst-quenching elbow bend. Beer so frosty, smooth, and cold it's paradise pure liquid gold. Yes beer means many things to me that's all for now cus I gotta pee.

01-27-2006, 12:40 AM	#14
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: idle rpm gotta love looking at the reflection of the tach light on the windshield at night huh?

01-27-2006, 07:59 AM	#16
71-longbed Its Magically Delicious Join Date: Jan 2003 Location: oregon Posts: 2,398	Re: idle rpm i usually dont pay much attention to it .. but if i does get on my nerves .. i dim my whole dash down .... __________________ 71 C10 LWB 350sbc -TH350 12 bolt 3.42 Posi Of all my favorite things to do, The utmost is to have a brew. My love grows for my foamy friend, with each thirst-quenching elbow bend. Beer so frosty, smooth, and cold it's paradise pure liquid gold. Yes beer means many things to me that's all for now cus I gotta pee.



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01-27-2006, 10:48 AM	#17
1969 C/K CST A.K.A- Crummy Join Date: Jun 2005 Location: NC foothills Posts: 3,025	Re: idle rpm Mine seems smoother at around 900. When releasing the clutch it bogs and goes with very little throttle. Maybe being a 4x4 makes a difference. I have played with it at lower rpm's but is more comfortable to drive at the current setting. I also have had 4 different carbs on it and all with the same result as far as idle position. __________________ 2003 Silverado Z71 Are fishermen all liars?

01-27-2006, 11:12 AM	#18
MrC1 Dork For Days Join Date: Aug 2005 Location: Dallas Posts: 407	Re: idle rpm For a stock-type idle (not a cammed-up engine), normal is about 750-800 in park and 600-650 in drive. If you've got some lope all bets are off. Somebody mentioned having a higher idle when cold, then lower when warmed up. Sounds like a fast idle cam not being kicked down before you put it in gear. If your idle is over about 850-900 in park, you're probably beyond the idle circuit and can't adjust your idle mixture with the screws. __________________ 1972 C20, 402/700R4 - My first classic truck, bought in September 2005. 85% transformed from "Farm" to "Cool" status! 1970 Dodge Challenger 440, 4sp (my other toy) 12.67 @ 117 MPH, with a pathetic 2.022 60' 2007 Dodge Charger SRT-8 2008 Cadillac CTS All-American garage, baby! Last edited by MrC1; 01-27-2006 at 11:12 AM.

01-27-2006, 12:56 PM	#19
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	Re: idle rpm Would I be right to assume the lower I can get it the better for the engine? As long as it runs? __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

01-27-2006, 02:48 PM	#21
flatbedchev Registered User Join Date: Dec 2005 Location: Flin Flon Manitoba Posts: 327	Re: idle rpm my 350 runs at about 850/900 rpm at idle but it's also a manual tranny

01-28-2006, 07:26 AM	#22
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: idle rpm sitting say at a long red light, idleing at 900 or more in gear, does build up some heat in the tranny... not real extreem, but more so than needed. It is also very rough on your tranny and u_joints...and the rear diff, when it slams into gear.

01-28-2006, 10:23 AM	#23
MrC1 Dork For Days Join Date: Aug 2005 Location: Dallas Posts: 407	Re: idle rpm Agree with the last post. Too high of an idle is hard on the tranny due to excessive heat buildup and the rest of the drivetrain if it's slamming into gear. Too low of a idle is bad for the engine due to poor internal oiiling and coolant flow. It's also not good for the tranny for the same reason - poor oil flow. If the RPM drops low enough, the tranny could actually be somkewhat disengaged. To tell you the truth, the engine alone would probably be happier at a very high RPM due to the good oiling frm crank throw. Of course, that doesn't happen too much until about 2000 RPM, so that one's out the window. __________________ 1972 C20, 402/700R4 - My first classic truck, bought in September 2005. 85% transformed from "Farm" to "Cool" status! 1970 Dodge Challenger 440, 4sp (my other toy) 12.67 @ 117 MPH, with a pathetic 2.022 60' 2007 Dodge Charger SRT-8 2008 Cadillac CTS All-American garage, baby!

01-29-2006, 02:11 PM	#24
71-longbed Its Magically Delicious Join Date: Jan 2003 Location: oregon Posts: 2,398	Re: idle rpm would a missing ground strap in the dizzy really cause those problems .... i've never had one in mine .. never noticed any trouble __________________ 71 C10 LWB 350sbc -TH350 12 bolt 3.42 Posi Of all my favorite things to do, The utmost is to have a brew. My love grows for my foamy friend, with each thirst-quenching elbow bend. Beer so frosty, smooth, and cold it's paradise pure liquid gold. Yes beer means many things to me that's all for now cus I gotta pee.

01-29-2006, 09:53 PM	#25
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: idle rpm Are you talking about the one that goes from the coil hold down bolt to the harness plug? Would one even work without that?

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