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Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > The plugs are bosch platinums with a heat rating of 9 <snipped> 'All' the old Jeep engines 'I' personally have seen (and read about 'many') will 'NOT' run on Bosch platinum plugs. They foul up almost immediately. I would change those before doing anything else and put proper Champion truck plugs back into it. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
Re: CJ5 misfires at high RPM/hard acceleration
Without having experience on your engine / carb /distributor, I can tell you
what is usually the case. I am not familiar with the holley carbs, but most other carbs I have worked on, are designed to idle with the butterfly almost completely closed. The adjusting screw on the butterfly stop, is used just to adjust the buttefly to close almost 99%(enough to not bind on the throttle body) and must not be used for idle speed adjustment. Idle speed is either fixed, or adjusted by other adjusting screws (bypass screw / mixture screw) if available. If you can't have the engine idle this way, the carb idle ciruit and jet need cleaning. At the correct fully closed butterfly position, the vacum port that goes to the distributor's vacum canister, is blocked or above the butterfly. So the engine idles with only the static advance, no vacum advance signal should go to the canister on idle. If you have a canister with two vacum lines, for advance and retard, only the retard vacum signal should be active on idle. When you open the buterfly, the vacum port gets under the butterfly and receives vacum. If your distributor has cetrifugal advance too, check that the centrifugal advance mechanism is working. Remove the cap and twist the rotor. It should be posible to be twisted about 10 degrees, and then spring back to the rest position. If it doesn't spring back, the internal springs are broken and you will need a new distributor. If it doesn't twist at all then you don't have cetrifugal advance. Maybe you should investigate this. At least this and changing to Champion plugs would be the first things I would do. Bill Spiliotopoulos, '96 XJ, 06' TJ. |
Re: CJ5 misfires at high RPM/hard acceleration
Without having experience on your engine / carb /distributor, I can tell you
what is usually the case. I am not familiar with the holley carbs, but most other carbs I have worked on, are designed to idle with the butterfly almost completely closed. The adjusting screw on the butterfly stop, is used just to adjust the buttefly to close almost 99%(enough to not bind on the throttle body) and must not be used for idle speed adjustment. Idle speed is either fixed, or adjusted by other adjusting screws (bypass screw / mixture screw) if available. If you can't have the engine idle this way, the carb idle ciruit and jet need cleaning. At the correct fully closed butterfly position, the vacum port that goes to the distributor's vacum canister, is blocked or above the butterfly. So the engine idles with only the static advance, no vacum advance signal should go to the canister on idle. If you have a canister with two vacum lines, for advance and retard, only the retard vacum signal should be active on idle. When you open the buterfly, the vacum port gets under the butterfly and receives vacum. If your distributor has cetrifugal advance too, check that the centrifugal advance mechanism is working. Remove the cap and twist the rotor. It should be posible to be twisted about 10 degrees, and then spring back to the rest position. If it doesn't spring back, the internal springs are broken and you will need a new distributor. If it doesn't twist at all then you don't have cetrifugal advance. Maybe you should investigate this. At least this and changing to Champion plugs would be the first things I would do. Bill Spiliotopoulos, '96 XJ, 06' TJ. |
Re: CJ5 misfires at high RPM/hard acceleration
Without having experience on your engine / carb /distributor, I can tell you
what is usually the case. I am not familiar with the holley carbs, but most other carbs I have worked on, are designed to idle with the butterfly almost completely closed. The adjusting screw on the butterfly stop, is used just to adjust the buttefly to close almost 99%(enough to not bind on the throttle body) and must not be used for idle speed adjustment. Idle speed is either fixed, or adjusted by other adjusting screws (bypass screw / mixture screw) if available. If you can't have the engine idle this way, the carb idle ciruit and jet need cleaning. At the correct fully closed butterfly position, the vacum port that goes to the distributor's vacum canister, is blocked or above the butterfly. So the engine idles with only the static advance, no vacum advance signal should go to the canister on idle. If you have a canister with two vacum lines, for advance and retard, only the retard vacum signal should be active on idle. When you open the buterfly, the vacum port gets under the butterfly and receives vacum. If your distributor has cetrifugal advance too, check that the centrifugal advance mechanism is working. Remove the cap and twist the rotor. It should be posible to be twisted about 10 degrees, and then spring back to the rest position. If it doesn't spring back, the internal springs are broken and you will need a new distributor. If it doesn't twist at all then you don't have cetrifugal advance. Maybe you should investigate this. At least this and changing to Champion plugs would be the first things I would do. Bill Spiliotopoulos, '96 XJ, 06' TJ. |
Re: CJ5 misfires at high RPM/hard acceleration
Without having experience on your engine / carb /distributor, I can tell you
what is usually the case. I am not familiar with the holley carbs, but most other carbs I have worked on, are designed to idle with the butterfly almost completely closed. The adjusting screw on the butterfly stop, is used just to adjust the buttefly to close almost 99%(enough to not bind on the throttle body) and must not be used for idle speed adjustment. Idle speed is either fixed, or adjusted by other adjusting screws (bypass screw / mixture screw) if available. If you can't have the engine idle this way, the carb idle ciruit and jet need cleaning. At the correct fully closed butterfly position, the vacum port that goes to the distributor's vacum canister, is blocked or above the butterfly. So the engine idles with only the static advance, no vacum advance signal should go to the canister on idle. If you have a canister with two vacum lines, for advance and retard, only the retard vacum signal should be active on idle. When you open the buterfly, the vacum port gets under the butterfly and receives vacum. If your distributor has cetrifugal advance too, check that the centrifugal advance mechanism is working. Remove the cap and twist the rotor. It should be posible to be twisted about 10 degrees, and then spring back to the rest position. If it doesn't spring back, the internal springs are broken and you will need a new distributor. If it doesn't twist at all then you don't have cetrifugal advance. Maybe you should investigate this. At least this and changing to Champion plugs would be the first things I would do. Bill Spiliotopoulos, '96 XJ, 06' TJ. |
Re: CJ5 misfires at high RPM/hard acceleration
Bill Spiliotopoulos wrote:
> Without having experience on your engine / carb /distributor, I can tell you > what is usually the case. A couple comments... You are confusing a throttle body and a carburetor with your directions on closing the butterfly. Carbs adjust that for idle speed once the mix is set, TB's don't. His engine could be set for 'either' a ported vacuum (vacuum only at throttle) or a manifold vacuum. (vacuum highest at idle) Mine came stock with manifold vacuum, I have switched to ported after some modifications. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
Re: CJ5 misfires at high RPM/hard acceleration
Bill Spiliotopoulos wrote:
> Without having experience on your engine / carb /distributor, I can tell you > what is usually the case. A couple comments... You are confusing a throttle body and a carburetor with your directions on closing the butterfly. Carbs adjust that for idle speed once the mix is set, TB's don't. His engine could be set for 'either' a ported vacuum (vacuum only at throttle) or a manifold vacuum. (vacuum highest at idle) Mine came stock with manifold vacuum, I have switched to ported after some modifications. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
Re: CJ5 misfires at high RPM/hard acceleration
Bill Spiliotopoulos wrote:
> Without having experience on your engine / carb /distributor, I can tell you > what is usually the case. A couple comments... You are confusing a throttle body and a carburetor with your directions on closing the butterfly. Carbs adjust that for idle speed once the mix is set, TB's don't. His engine could be set for 'either' a ported vacuum (vacuum only at throttle) or a manifold vacuum. (vacuum highest at idle) Mine came stock with manifold vacuum, I have switched to ported after some modifications. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
Re: CJ5 misfires at high RPM/hard acceleration
Bill Spiliotopoulos wrote:
> Without having experience on your engine / carb /distributor, I can tell you > what is usually the case. A couple comments... You are confusing a throttle body and a carburetor with your directions on closing the butterfly. Carbs adjust that for idle speed once the mix is set, TB's don't. His engine could be set for 'either' a ported vacuum (vacuum only at throttle) or a manifold vacuum. (vacuum highest at idle) Mine came stock with manifold vacuum, I have switched to ported after some modifications. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
Re: Re: CJ5 misfires at high RPM/hard acceleration
On Mon, 16 Jul 2007 10:15:36 -0400, Mike Romain <romainm@sympatico.ca>
wrote: >'All' the old Jeep engines 'I' personally have seen (and read about >'many') will 'NOT' run on Bosch platinum plugs. > >They foul up almost immediately. > >I would change those before doing anything else and put proper Champion >truck plugs back into it. Where do you get this BS at????? It is the wrong heat range that can cause them to foul not the brand if heat range is correct. (some brands to not cross reference properly) You have this guy chasing plugs when this is very likely a fuel issue as I explained above. I guess you just like to hear yourself talk so you can feel good about yourself rather than really help him fix problem. I have been around Jeep much much longer than you and owned AMC/Jeep V8's far longer than you have even owned a Jeep. Just watch and read and you might just learn something. ----------------- TheSnoMan.com |
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