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Old 05-19-2003, 06:48 AM
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Post 3800 RPM miss

I have a '77 T-bird that misses at 3800 RPM. If I back off of the throttle, it clears up. If I keep my foot in it, it will drop 1000 RPM. I have checked the fuel supply and it's good to go. I don't want to just start replacing parts to trouble shoot this.

Thanks...

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Old 05-19-2003, 03:55 PM
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You have provided very little information to go by, but here goes. You said that you checked the fuel supply. If you are talking about checking pressure with it sitting, that may not help. Many years ago, I had a similar problem. We ended up changing the fuel pump, carb, and who knows what else. The problem, we found out, was a piece of rubber fuel line. The line had degraded with age. There was a piece inside that was working like a flapper valve. When driving, never when sitting still, it would close off the fuel. We had checked the fuel pressure several times, even at WOT while sitting. It never showed up that way. We had to put a fuel gauge in line and watch the pressure while driving to find the problem. Another possibility is the vacuum advance in the distributor. GOOD LUCK.
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Old 05-19-2003, 04:00 PM
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Check your EGR Valve, remove and plug the vacuum hose and road test.
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Old 05-20-2003, 06:35 AM
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Sorry for the vague post. Thanks to both of you. I have constant fuel supply at all times. There is no EGR valve on this vehicle and it has a brand new Holly 2BBL Carb and a rebuilt Distributor.
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Old 05-20-2003, 04:42 PM
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CJ you might want to try posting this question to the ENGINE board. Maybe someone there can help you. You need to make sure that you provide enough information for someone to consider. Things like the ignition system, any engine modifications, ENGINE SIZE, and such helps. All engines and parts act differently.
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Old 05-21-2003, 09:12 AM
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how old are your plug wires
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Old 05-21-2003, 11:23 AM
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First, thanks to all of you who have tried to help me even though I failed to provide accurate information. Let me regress. This '77 T-bird has a rebuilt stock 351M (less than 800 miles), C-6 Trans, 3.89:1 rear gears, new Holey 2BBL carb, new plugs, new plug wires, rebuilt distributor, no emission controls and stock Ford electronic ignition. When it misses at 3800 RPM, there is no backfire through the exhaust or carb. There is constant fuel supply at all RPM ranges and the "tell-tail" hissing through the carb indicating that there is no fuel going into the intake is not there.

P.S. If the person who has the power to move this post to the "ENIGINE Board" is reading this, please move it for me.

Thanks...
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Old 05-27-2003, 07:07 AM
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Thanks again to those of you who tried to help me with this. I just thought I would share with everyone what the source of the problem was. The control unit for the electronic ignition was bad. I replaced it and now I'm good to go.

Thanks again...
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Old 05-27-2003, 06:15 PM
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CJ... For the record. The reason that I suggested posting to the Engine Board is this. Many people only read the posts on the boards that they are experienced or interested in. As I have little interest in Engine performance, I generally don't go to that board. On the other hand, there are likely people that go there instead of the Electrical board, because they have no interest here. That is why there are several different boards. If people post to the right boards with their questions, they get answered quicker and are more likely to get the right answer.
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