Ideal idle RPM
 

What's the factory and/or ideal idle RPM for my 4.3 TBI engine? Mine runs at 1.3 - 1.4. Is it normal or too high as I think?

1.3 - 1.4 what?

the truck should idle anywhere from 550 RPM to a max of 750/800 for a manual trans'd vehicle.

of course, the engine will idle slightly higher when it's cold (not warmed up).

Well, when I start mine it goes up to 2000 RPM or something around for like 20 seconds, then goes down to 1300 - 1400 (down to 1500 - 1600 for a minute or less if it's really cold) and keeps that speed even during summer after driving it for hours. It goes down to 1100 when I put it on D with a little kick.

ok, i kinda thought you meant 1300 RPM, but didn't want to assume.


start checking out your IAC (Idle Air Control) it could be dirty or just plain broke.

be careful though, i had one shoot the plunger out completely once (it was off the truck for cleaning) and it never worked after that.

you'll also want to check your throttle body too. make sure nothing is making the throttle plate stick open. even if it's stuck open just a little, it'll affect your base idle speed.


question. you've been a member for quite awhile now, is this something that has just happened recently?

I had this Blazer for 2 years now. It had a bad fuel pump when I bought and hauled it to a servicing garage where it had a lot of parts changed. It was so since I bought it and thought that this was normal. Last summer, I was revving it very high and got the magnet inside the distributor broken into pieces, so I bought a new one from a scrap-yard and changed it myself, and as I tuned the distributor (turning it L & R), when the RPM was going lower than 1200, the engine would start kind of shaking (as I remember). Before I mess with my IAC, is there a way I can tune the idle speed? I thought it's controlled by the computer!

Your idle speed is controlled by the IAC.

So how can I change the idle speed? By using a scanner? (which I don't have :P )

Clean or replace the IAC and its connection. The 'search' function should help out.