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Pacer-258 2V Hesitation on hard accelleration

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ArdsleyTank View Drop Down
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    Posted: Feb/02/2018 at 1:35pm
So, this is on my brother's 1977 AMC Pacer.  It has the 258 2V engine.

This car has always had this problem since we first bought it--2 years ago--and we've fixed lots of other problems it had but this "gremlin ;)" just won't leave...

So, regardless of engine temp, if I floor it hard too quickly, the engine acts like it wants to stall, and it will sometimes if I don't back off quick enough.  If I feather the gas, it does just fine, punch it, err no.  This can be problematic when you need to jump out in traffic real quick...  I mean, I can give it a lot of gas and it'll be okay, floor it, nah.

Here's what we have replaced:  Plugs, wires, cap, rotor, air filter, we rebuilt the carb.

I have also tried to replace the AMC original, gold finish, oozing Ignition Module, to no avail.  Bought and returned two modules, one from two different companies, and the result was the same:  You can crank all day, but no spark.  Plug in the old one, fires right up.

Perhaps someone here will have some ideas.

Thanks in advance,
Peter
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pacerman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Feb/02/2018 at 2:18pm
Most people know about this but there was a service bulletin eliminating the two prong plug between the module and the distributor (near the distributor).  You cut out the plug and solder the two wires to their respective partners.  Corrosion in that low amperage connection resulted in intermittent (or ceased) signals from the distributor to the module.   Because you report ineffective new modules, have you checked for continuity to and from the distributor while someone jiggles the wires?  You could have an intermittent open in a circuit.

Next, make sure you have a good healthy shot of fuel from the accelerator pump on the carb.  Take off the air cleaner and with the engine off, excercise the throttle while looking down the carburetor bore.  you should see a solid stream of fuel when the pump the accelerator.  

Have you checked timing on the engine both at idle and under acceleration?

Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Feb/02/2018 at 6:41pm
The problem is most likely the accelerator pump in the carburetor. The BBD uses a rubber or leather accelerator pump cup as I recall, and they tend to stick, leak, and generally just get buggered up. A missing inlet or outlet check ball on the accelerator pump can cause this too, as will partially plugged pump jets.

The modern ignition modules tend to be junk. The only ones I have good luck with are the NAPA ones. ALWAYS CARRY A SPARE. The modules will start to misfire and cause the engine to cut out as they go bad, so always carry a spare because it's only a matter of time before you need one on a road trip.

The key to happiness with this ignition is to make sure the connections and wires between the module and the pickup coil in the distributor are intact, unspliced, (do not change their length from factory), routed away from the high voltage secondary wires, and the connections are clean and firm. They don't have to be soldered, but they do need to be good, clean connections. 

And if you don't want your original AMC module, please send it to me. They are the only modules that can be taken apart and repaired. I'm hoarding them.  
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ArdsleyTank View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ArdsleyTank Quote  Post ReplyReply Direct Link To This Post Posted: Feb/02/2018 at 7:36pm
I guess forgot to mention a couple of things.

First off, I rebuilt the carburetor, so it has a new accelerator pump.

The other thing is, it has an exhaust manifold leak. Not sure if it's warped or cracked.

I'm leaning away from the idea that it's the carb since I rebuilt it.
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DaemonForce View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Feb/02/2018 at 9:45pm
Tear off the air cleaner.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mixed up Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2018 at 12:33am
make sure your getting a good squirt of fuel .it could be a flout level problem to low then you might want o look at the accelerator pump setting if it come on to fast you don't have enough throttle opening to except all the fuel it will hesitate   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2018 at 3:28am
Originally posted by DaemonForce DaemonForce wrote:

Tear off the air cleaner.

why?   That won't help. It's there for a reason.Lol
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2018 at 3:33am
How many miles on the engine?   What FS junkie said is good.   Does the engine idle well? Does the EGR work properly? If the valve opens too fast, it'll do what your car is doing. Has the timing chain been replaced? If it's worn, timing will be retarded....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXRWB Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2018 at 9:55am
Something is wrong fix it.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote matty 401 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2018 at 10:15am
check the timing  maybe advance it a bit  i run my 258 in my concord with no vacuum advance and the timing bumped up  made a big difference in it 

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