Super High Idle and Jerky Throttle - Rochester Monojet - The 1947 - Present Chevrolet & GMC Truck Message Board Network

snowman4839 · 06-07-2010, 09:09 PM

Hey guys, I know I don't have a truck really but this place looked like it had some knowledgeable people about my problem. I have a 69 Buick Special Deluxe with a Chevy 250 in it and a Rochester Monojet MV. I just rebuilt it and put it on and now it runs fine but it idles insanely high. Like 1800rpm on the fast idle cam and 1500rpm after its warmed up. What on earth is wrong with this thing? I didn't have any extra pieces after I did the rebuild and I know I didn't lose any because I had them all in one bucket. I just put a new float, needle & seat, manifold gasket, and the gaskets between the air horn, throttle body and whatever the middle piece is called. What would cause this??

My other problem is that it doesn't want to function normally around the 2300rpm to 2700rpm range. It either runs below that or it stutters then almost dies and then jerks you into high rpms. What would cause that? (I still had this problem before I rebuilt it).

Thanks guys

EDIT: For an exploded diagram, my carb is on page 16 http://www.walkerproducts.com/_pdf/rochester1barrel.pdf
EDIT: I know that this has nothing to do with the idle problem but I haven't replaced the points, cap, and condenser for the distributor.

snowman4839 · 06-08-2010, 01:29 AM

and I'm not sure if it makes a difference it makes an AWFULLY LOUD sucking sound now. It mean it is REALLY bad and it wasn't there before the rebuild. I also just took off the idle compensator and plugged it up with my finger and it dropped like 400rpm. So I think it has something to do with that. but with the throttle completely closed off and when I plug that hole with my finger on it, it still runs at like 1000rpm!? :-(

snowman4839 · 06-08-2010, 03:46 AM

alright guys... fixed it. I put in a little air regulator in the idle circuit... BACKWARDS. I realized it after looking at the exploded view I linked you guys to. And I noticed that the throttle hole seemed to dissipate after I fixed this and the engine was warm. I'm going to replace the dist cap, rotor, points, and condenser so it should run even better and iron out all of the kinks. Thanks

68gmsee · 06-08-2010, 09:19 AM

Glad we could help???

Thanks for the link. I didn't have that one in my monojet folder.

nyncompute · 06-08-2010, 10:05 AM

Yea I was just gonna ask if that doo-hicky air thing was by any chance in backwards.

06-07-2010, 09:09 PM	#1
snowman4839 Registered User Join Date: Mar 2010 Location: Memphis, TN Posts: 6	Super High Idle and Jerky Throttle - Rochester Monojet Hey guys, I know I don't have a truck really but this place looked like it had some knowledgeable people about my problem. I have a 69 Buick Special Deluxe with a Chevy 250 in it and a Rochester Monojet MV. I just rebuilt it and put it on and now it runs fine but it idles insanely high. Like 1800rpm on the fast idle cam and 1500rpm after its warmed up. What on earth is wrong with this thing? I didn't have any extra pieces after I did the rebuild and I know I didn't lose any because I had them all in one bucket. I just put a new float, needle & seat, manifold gasket, and the gaskets between the air horn, throttle body and whatever the middle piece is called. What would cause this?? My other problem is that it doesn't want to function normally around the 2300rpm to 2700rpm range. It either runs below that or it stutters then almost dies and then jerks you into high rpms. What would cause that? (I still had this problem before I rebuilt it). Thanks guys EDIT: For an exploded diagram, my carb is on page 16 http://www.walkerproducts.com/_pdf/rochester1barrel.pdf EDIT: I know that this has nothing to do with the idle problem but I haven't replaced the points, cap, and condenser for the distributor. Last edited by snowman4839; 06-07-2010 at 09:46 PM.

06-08-2010, 01:29 AM	#2
snowman4839 Registered User Join Date: Mar 2010 Location: Memphis, TN Posts: 6	Re: Super High Idle and Jerky Throttle - Rochester Monojet and I'm not sure if it makes a difference it makes an AWFULLY LOUD sucking sound now. It mean it is REALLY bad and it wasn't there before the rebuild. I also just took off the idle compensator and plugged it up with my finger and it dropped like 400rpm. So I think it has something to do with that. but with the throttle completely closed off and when I plug that hole with my finger on it, it still runs at like 1000rpm!? :-(

06-08-2010, 03:46 AM	#3
snowman4839 Registered User Join Date: Mar 2010 Location: Memphis, TN Posts: 6	Re: Super High Idle and Jerky Throttle - Rochester Monojet alright guys... fixed it. I put in a little air regulator in the idle circuit... BACKWARDS. I realized it after looking at the exploded view I linked you guys to. And I noticed that the throttle hole seemed to dissipate after I fixed this and the engine was warm. I'm going to replace the dist cap, rotor, points, and condenser so it should run even better and iron out all of the kinks. Thanks

06-08-2010, 09:19 AM	#4
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Super High Idle and Jerky Throttle - Rochester Monojet Glad we could help??? Thanks for the link. I didn't have that one in my monojet folder.

06-08-2010, 10:05 AM	#5
nyncompute Registered User Join Date: Nov 2004 Location: Southern Nevada Posts: 532	Re: Super High Idle and Jerky Throttle - Rochester Monojet Yea I was just gonna ask if that doo-hicky air thing was by any chance in backwards. __________________ 1972 K-10 SWB Cheyenne



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