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Pacer-258 2V Hesitation on hard accelleration

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ArdsleyTank View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote ArdsleyTank Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2018 at 10:36am
First off, here's a link to a video I made displaying the issue I described. https://youtu.be/Zhl_51FiTCc

I have not checked the timing. I checked the carb, and it squirts plenty of gas. I checked the EGR Valve by sucking/blowing on it's vacuum line. I can hear the flap moving. To verify though, it is the round thing on the side of the intake, below the carb, right?

Does anyone have a pic of the EGR valve, so I can tell if I'm looking/blowing/sucking at the right thing?

Edited by ArdsleyTank - Feb/03/2018 at 10:39am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Feb/04/2018 at 1:55am
These originally uses a positive backpressure EGR valve that only opens if BOTH vacuum and a predetermined exhaust pressure are applied to it. Vacuum alone should not make it open unless the valve has gone bad inside. if that is the case, the valve will slam fully open around 1500 RPM and will either stall the engine or nearly stall it. It'll be one heck of a bog. The engine will just fall on its face. 

Somebody may have replaced it with a standard ported EGR valve. Those do open with vacuum alone, and will still run just fine so long as whoever installed the valve did not use an orifice washer that was too large. 

You can tell a positive backpressure EGR valve from a ported EGR valve by looking at the underside of the diaphragm. It would be impossible for me to describe the difference, so just look at photos online. A POS EGR has a second diaphragm inside. 

Set the timing at 10* BTDC with the distributor vacuum hose disconnected and plugged. Then rev the engine up to 2500 RPM and you should see 20-24* BTDC of timing. Reconnect the distributor vacuum hose at that RPM and you should see a definite increase in timing again on the order of 10-15 degrees. That timing will make your engine run nicely. I've spent many hours tweaking my 1977 232, so I know how to make a 1977 six cylinder sing beautiful music. 
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1972 Wagoneer
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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/04/2018 at 7:36am
Well... That's good to know. I'll have to check that timing.

But with the EGR valve, does the video I posted match the symptoms of a faulty valve?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Feb/04/2018 at 1:01pm
Looks like a textbook lean accelerator pump. The possibility of too much EGR can easily be eliminated by disconnecting and plugging the EGR vacuum line. The EGR will not function at all then.

The accelerator pump must produce two strong streams of liquid fuel (no air bubbles). Your hesitation is severe, like an accelerator pump that practically isn't working at all. Such a condition should be obvious when the throttle is winged open with the engine not running as you look down the carburetor throat. 

May also be a lean fuel mixture caused by something with the main jets and metering rods. The main jets and metering rods must be the proper size, must move freely, and must be adjusted correctly. If the engine produces good power at all throttle openings and loads while driving with no bogs, then the jets and rods are probably fine. Still does not hurt to get an original 1977 AMC Technical Service Manual (they're cheap) and review the metering rod adjustment procedure, their part number, and the part number of the jets. 



Edited by FSJunkie - Feb/04/2018 at 2:18pm
1955 Packard
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tomj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Feb/04/2018 at 10:31pm
spark timing issues and dry accellerator pump issues very often have similar symptoms.

'77 has a lot of smog stuff. ti works fine when it;s all correct and no hoses leak.

for example, depending on how it's plumbed, you could have a decent amount of spark advance at idle/low speed, you crack the throttle open, manifold vacuum drops and spark timing retards.

i would go through all the ignition vacuum signal stuff.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fluffy73 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/04/2018 at 10:40pm
Originally posted by ArdsleyTank ArdsleyTank wrote:

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


Good Job.  That's step #1.  Step #2 would be adjusting the carburetor. Have you done that?

The Carter BBD is much maligned in automotive circles, mostly due to ignorance. They are really a very nice carburetor to work on and when set up correctly, provide years of trouble-free service.

They are however, not a "Performance" carburetor.

Either way;  ensure that your float level is set correctly. If it is set within spec, go outside spec and set it slightly higher to allow an extra little bit of fuel in the bowl.

Depending on which version of BBD you have, you can have anywhere from 6 to 0 settings on your accelerator pump lever.  If it's got adjustments, set it up to have the longest stroke possible but also ensure you are getting "squirt" (that is, the squirters are shooting fuel into the venturi) with even the SLIGHTEST throttle movement. 

This is of course all dependent on your timing being set correctly, idle speed being set correctly and fuel pump is also up to snuff. 
I am genetically incapable of being Politically Correct.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ArdsleyTank Quote  Post ReplyReply Direct Link To This Post Posted: Feb/17/2018 at 8:24am
Okay, so I'm back.  Weather's been nasty here, so I haven't been able to work on it lately.

I have set the timing, replaced the EGR valve, verified that the PCV valve works, and I can see gas being squirted from the jets.

I have also adjusted the air/fuel mixture on the carburetor.  Do dice.  Still does what it was doing.

What have I missed?  Someone here mentioned the float adjustment, how do I adjust the float level? I have a 1976 (I know, I probably need a 1977 edition) Pacer TSM, but it's not very clear...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BeerBuzz Quote  Post ReplyReply Direct Link To This Post Posted: Mar/22/2018 at 3:55am
Is the vacuum advance plumbed to ported or manifold vacuum? Are you 100% on the vacuum routing?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Mar/25/2018 at 11:40am
You just bend the tab holding the needle valve to the float to adjust. The TSM doesn't give what would have been considered "common knowledge" to most mechanics at the time. Carb adjusting is quickly becoming a "lost art".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roguedoug Quote  Post ReplyReply Direct Link To This Post Posted: Mar/25/2018 at 12:18pm
Check for a vacuum leak at/near base of carb.....
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