High rpms

[SSmooth84]

I got a 1984 monte carlo ss with a 305 v8 . My rpms are running high even when I'm in park . Here are some pics of how high they are running . Any ideas were to start looking?

 

[565bbchevy]

Possible vacuum leak from a cracked hose

 

[SSmooth84]

I forgot to mention I did adjust the idle screw i unscrewed it all the way out very little change . I don't think its a vacuume leak but ill double check that . We're should it be idling normally?

 

[ELCAM]

Without looking it up the idle should be around 800 RPM. Look on the emissions sticker on the fan shroud if it is still there to get the exact specification.

At 2000 RPM it sounds like it is stuck on the fast idle cam, it is under and in front of the choke spring housing. Make sure all the choke linkage and fast idle linkage is free and not bent it is on the passenger side of the carb. You will need to open the throttle linkage first to free the other linkage completely.

 

[Ernest]

With the engine shutdown, tighten the carburetor mounting bolts to the intake, then spray carb cleaner throughout the inside and outside of the carburetor. Start engine, if the problem persists, spray carb cleaner around the base of the carb and around the intake and see if theres a change in rpm to locate a possible vacuum leak.

 

[Built6spdMCSS]

Yup check for leaks, Carb gasket, Vac hoses, make sure they are all good. As mentioned make sure the linkage is moving right also.

 

[spidereyes455]

Are you sure that its actually revving that high? 4,000 rpm at 45mph is excessively high unless you have 5.13 gears or are holding it in first.The factory tachs are notorious for reading incorrectly as they age due to a number of reasons. Such as a loose connection on the jumper at the back of the tach that changes it from the 6 cyl to 8 cylinder calibration.

 

[bracketchev1221]

I agree on check the tach. At speed vacuum leaks have no impact on rpm. So if it’s still high while driving that’s tach not engine.

 

[stew86MCSS396]

Mines seems to idle normal to a little high but cruising at 55 mph lately I've seen the tach approaching 3000 rpms and this would be with 2.41 gears, 26" tall tire and no overdrive. Check out the ECC link... https://gbodyforum.com/threads/tach-reading-too-high-on-el-camino.60406/

 

[Ernest]

i agree as well, it has to be the tachometer reading, its way off.... especially with 2.41 and a 26" tall rear tires, if you cant fix it, get an aftermarket one and install it as soon as you can.