Author Topic: What should my engine idle at?  (Read 6094 times)

Offline Skunksmash

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What should my engine idle at?
« on: May 19, 2012, 01:04:53 am »
What RPM should my engine idle at? 87 TBI 5.7L/700R4. It seems to idle at about 700 RPM. Is that about right?

Also, what RPM should it shift at? Depending on how much I have the pedal depressed of course. I usually try to drive the truck like a granny would. It seems to shift at about 1600 RPM when I depress the pedal about 1/4 of the way. This seems a little low to me. Most of the engines I've had would shift at anywhere from 1900-2100 RPM. But, then again I've never had a tach in one of these old trucks.

Offline Fairlane514

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Re: What should my engine idle at?
« Reply #1 on: May 19, 2012, 09:29:41 am »
Do you run A/C?  My 84 is has a quadrajet with A/C and 700 rpm is a little too low while its in gear with the A/C on. 850 seems to work better for me.

I just put a new tv cable in my 700R4 and did the adjustment like the experts explain. I then drove it and it shifted a little too soon and somewhat soft, alsmost felt like it was slipping into gear.  I increased the pressure on the throttle valve by pushing the tv cable adjuster towards the firewall a few clicks and it shifter later and slightly firmer.

Online bd

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Re: What should my engine idle at?
« Reply #2 on: May 19, 2012, 02:29:41 pm »
87 TBI generally idles about 600 RPM in drive (as high as 700 in park/neutral).  87 700R4 shifts earlier than 350 or 400 for slight improvement in mileage.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Skunksmash

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Re: What should my engine idle at?
« Reply #3 on: May 19, 2012, 09:16:48 pm »
No my AC doesn't work right now so I don't run it. Just another thing on the long, long list of stuff to fix

Offline Stewart G Griffin

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Re: What should my engine idle at?
« Reply #4 on: May 19, 2012, 10:38:51 pm »
i think 700 is ok.    i thought you couldn't adjust TBI idle?

Offline rickyharp

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Re: What should my engine idle at?
« Reply #5 on: May 21, 2012, 08:39:06 am »
My throttle body unit is sealed off from adjustment,had to use my snap-on scanner to adjust the idle speed.

Offline Skunksmash

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Re: What should my engine idle at?
« Reply #6 on: May 26, 2012, 03:15:32 pm »
Ok where should it shift at? If I'm giving it say, 1/4 throttle, it shifts at about 1600 RPM. But if I really floor it, it will shift at about 2200 RPM. The weird thing is, I couldn't get the RPM gauge to say I was doing any more than 2500 RPM, at any time. I just wanted to give it a test so I floored it for a little, and it would just barely get up to 2500 RPM for a second then go back down to about 2100 RPM. Seems kind of strange. Maybe that's just how an old TBI motor acts?

Offline werewolfx13

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Re: What should my engine idle at?
« Reply #7 on: May 27, 2012, 12:07:47 pm »
Should go higher than that, i'd suspect a faulty tach if it actually sounds like its revving past that.
Chris
'83 Chevy c10 Silverado SWB
'76 Chevy k20 LWB 6.5'x8' Flatbed
“I know that you believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant.”

Offline Skunksmash

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Re: What should my engine idle at?
« Reply #8 on: May 27, 2012, 03:24:25 pm »
Well it sounds like its revving way past that... but then again I've known old motors to sound like they're trying to move the world, and then be doing a relatively low RPM.

Offline Skunksmash

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Re: What should my engine idle at?
« Reply #9 on: May 28, 2012, 04:48:23 pm »
I'll just borrow another RPM gauge from a buddy or something and hook it up real quick under the hood, and verify if mine is working right.