extremely fast idle 1985 Chieftain 454

doobiewah · January 11, 2011, 06:25 PM

Hey there members,

When my '85 Chieftain starts up the idle is WAY too fast. Blipping the pedal doesn't do anything. RPM's remain constant with no decrease even after its warmed up. I don't think backing off the idle adjustment screw will help,It doesn't look to be in contact with anything now...but what do I know? If I push the throttle linkage on the carb towards closed position RPM's drop some, but go right back when released.

My guess is the choke is stuck or needs adjustment.. I checked the Chevy Motor Home Chassis Service Guide but didn't find much useful info on carbs. Found nothing at all on chokes. Lots of info on throttle body injectors though. Too bad I don't have one...or do I? lol

If anybody has any info or could point me in the right direction I'd really appreciate it!

DaveVA78Chieftain · January 11, 2011, 08:57 PM

Step 1 - Find carburator number

Step 2 - Download Rochester Quadrajet carburator manual:
http://www.tocmp.com/manuals/Carbs/Rochester/QJet/1973/pdf/1973%20manual%20complete.pdf
While the manual reads 1973 it contains data through 1986.

Step 3 - Look up adjustment specs for the carb number from step 1 above (tables in back of document).

Step 4 - Perform carb adjustments that start on pdf page 36.

Dave

rcaircraftnut · January 12, 2011, 01:32 AM

Sounds like the fast idle cam isnt disengaging. Try cleaning all the linkage with a good carb cleaner spray. If the springs and pivots are all gummed up this can happen.

outsider · January 13, 2011, 09:55 PM

Sounds like a vacuum leak. Check the carb base gasket and the hoses for damage. Use your hand to block air entry into the carb to see if the idle drops

doobiewah · January 17, 2011, 01:15 AM

Thanks for all your responses. I downloaded the manual (thanks Dave) but understanding it and doing the adjustments necessary has proved to be beyond my skill, though I'm still trying.
I've used about 6 cans of Gumout on the thing, the linkage isn't sticking anywhere I can tell. As to a vacuum leak, I've checked all the hoses, base gasket, etc and haven't found anything obvious. Only when air entry is completely blocked do the rpm's drop, and then it stalls (big surprise)
I guess this is going to take some time for me to fix, the only problem is this coach is my home and I live on the street- and I need to move it within 3 days. Would it be okay to drive it a few blocks in the condition its in?

Oz · January 17, 2011, 07:24 AM

When you put it in drive, it's going to really slam the transmission when it engages. I don't know how high the rpm is but, if it's like 1,500 or more... I'd suspect that could cause serious damage? Short of anyone saying it would be ok, I'd suggest that, if you know someone with a pick-up, have them pull you to a different spot.

jimbo16720 · February 21, 2011, 10:18 PM

Try pushing the throttle close farther with your hand and if it slows down there should be a little vacumm module on the front that is stopping it from closing all the way. There is an adjustment on the little rod that is stopping it from closing enough. It's an antistall adjustment. Shorten the plunger and it should be fine.

jjanton · April 03, 2011, 03:29 PM

I had this exact same issue. Gumout and linkage cleaner helped but what really helped was that there was junk left from mice /squirrels left under the autochoke assembly. Once I removed all of the filter housing and unplugged most of the vacuum hoses I was able to get under the carb itself and clean it all out. Once that was done, I was able to truly lube the linkage assemblies and get the idle to go down. Hope this helps!