85 460 engine backfire
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Joined: Jul 2004
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85 460 engine backfire
Hello. Got a question about my 85 F-250 460. I'm having backfire issues.
First problem: it was backfiring EVERY time I decelerated - whether moving or sitting still. I found out that there was a problem with the smog pump. I pulled the vacume line off the front pump, and this problem went away. Question: is there anything wrong with this solution?
Second problem: I pull an 8,000 pound fifth wheel camper. When I'm going down hill and using engine brakes (4 speed standard transmish), I get backfires beginning at around 3,000 rpms. I've been told by a couple of folks that this is normal. Question: is it normal or not? FYI, I recently had the exhuast system evaluated. Had two new Flowmasters installed. Sounds great. They didn't find any other leaks.
Last question: when I'm pulling my 5th wheel up a mountain pass, I drop down into 3rd gear and get up to around 4,000 rpms to make it to 40 mph. Is that engine speed safe for the engine? What is the max rpm I should run at?
Thanks for the help! jerry
First problem: it was backfiring EVERY time I decelerated - whether moving or sitting still. I found out that there was a problem with the smog pump. I pulled the vacume line off the front pump, and this problem went away. Question: is there anything wrong with this solution?
Second problem: I pull an 8,000 pound fifth wheel camper. When I'm going down hill and using engine brakes (4 speed standard transmish), I get backfires beginning at around 3,000 rpms. I've been told by a couple of folks that this is normal. Question: is it normal or not? FYI, I recently had the exhuast system evaluated. Had two new Flowmasters installed. Sounds great. They didn't find any other leaks.
Last question: when I'm pulling my 5th wheel up a mountain pass, I drop down into 3rd gear and get up to around 4,000 rpms to make it to 40 mph. Is that engine speed safe for the engine? What is the max rpm I should run at?
Thanks for the help! jerry
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Joined: May 2004
Posts: 2,223
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From: Billings Montana
As far as the smog pump goes, I just took the belt off of the pulleys and left the hoses connected. If you don't have catalytic converters on your truck, this won't hurt a thing. If you do have cats on your truck, it'll destroy them.
I wouldn't think that 4000 rpm's would be hard if you keep an eye on the oil and water temp and keep the oil topped off and clean, but maybe you should look into an under/overdrive unit or some different gears in the axles if you climb a lot of hills and get into the high rpm's often.
I wouldn't think that 4000 rpm's would be hard if you keep an eye on the oil and water temp and keep the oil topped off and clean, but maybe you should look into an under/overdrive unit or some different gears in the axles if you climb a lot of hills and get into the high rpm's often.
Last edited by big hoss 29; Jul 7, 2004 at 01:14 AM.
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