Quick, full throttle causes bog, sputter - 1985 AMC150 - JeepForum.com
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Unread 04-25-2013, 10:25 PM   #1
VanHermanator
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1985 CJ7 
 
Join Date: Jul 2012
Location: Vancouver, BC
Posts: 20
Quick, full throttle causes bog, sputter - 1985 AMC150

Hi guys - I'm really banging my head with this one. I purchased my CJ7 last year not running. I replaced the fuel pump and fuel filter, and finally I had the Carter YFA carb professionally rebuilt. I got it running! However, if I floor it quickly, it chokes up and will die if I don't let the gas go. If I apply throttle slowly, the revs go up just fine.

I've recently replaced the distributor, cap, rotor and ignition wires to eliminate anything electrical. Didn't make a difference. (The timing is set to spec)

It idles beautifully, and starts well both hot and cold. I just replaced the O2 sensor too.

The guy who rebuilt the carb is suggesting that it's something to do with the computer control, causing too lean a condition. It's not driveable in this condition, because that little 4-banger needs throttle to get up to speed! I don't have a clue what to check or replace next - help please!

Thanks
Mark

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Unread 04-25-2013, 11:06 PM   #2
wellmax
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1984 CJ7 
 
Join Date: Nov 2008
Location: Hazel, KY
Posts: 1,070
Van,
I feel your pain, I have a 1984 cj-7 with the same little crap motor,
I took the carb off and installed a weber carb, so far it runs much better. still no speed demon.

be sure all wires and plugs are in good shape, check all wired ends, plugin etc: the wiring system on the old jeep was poor at best and now it has nearly 30 years old of abuse.

I would suggest trying this, play around with the timing. not going to cost you anything,
with motor warm, try increasing the timing in 2 degree increments, if after increasing it 6-8-10 degrees, if you are seeing no improvement, then start decreasing it.

be sure you have all the systems set, hoses plugged and rpm's set up to make the timing adjustments per the manual.

I was able to secure a 1984 amc shop manual like the jeep dealer shops had, these books give a lot of detail info, the books you buy at the autopart stores took their pictures from the AMC shop manual.

try this on timing, as I was never able to get my jeep to run right at the factory timing settings.

do you have the correct fuel filter and have it installed properly, proper air filter with pvc hooked up

note to file: these little motors are not barn burners, even when running their best.

the 4 banger that amc bought from general motors up through 1983 was a much stronger engine, but amc wanted their own engine, so we got stuck with a lesser engine,

run some high test gas in the tank, if you can find any, I always used high test, but now use non ethanol as it is still available in my area.
might try some fuel additives such as sea foam, octane booster, etc:

good luck and let us know how it goes.

have you heard of the nutter bypass, if not read up on that, might the answer to your problem if no emission test are required in your area.

the little engine in my jeep will take the fuel fine, but again, its no pavement burner as they do not have over 80 some horsepower. The 6 cylinder was a much better choice of engine for this vehicle.
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Unread 04-26-2013, 12:09 AM   #3
wrongway92407
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1986 CJ7 
 
Join Date: Nov 2009
Location: Devore Ca.
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Some of the time when the carb gets rebuilt they forget to put in the fuel pump check ball or it fall out during the rebuilt and it can happen so fast and its so small you don't know it. I have an 86 and I have no trouble with it accoutering other than the fact it takes a country mile. It will have a 4.0 soon.
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Unread 04-26-2013, 08:48 PM   #4
VanHermanator
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Thanks for the input guys! I appreciate the pointers wellmax. I've since spoken with the shop that rebuilt the carb, and they've agreed to have another look at it. I'm not sure if the accelerator pump is working properly. I hear that I should see a noticeable squirt of fuel when looking down the barrel and applying throttle, but I don't see anything. I do smell gas, but no obvious stream. Hopefully the carb shop will find something!
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Unread 05-18-2013, 02:21 PM   #5
VanHermanator
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1985 CJ7 
 
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A happy ending to my story that was solved by, what else, more money! After replacing the distributor and ignition wires to no avail, the carb was taken off and sent back to the shop. Apparently when I had it rebuilt last summer and installed it, I did not completely drain the tank of many-years-old gas, which was promptly sucked back into the freshly rebuilt carb. I couldn't believe it! It was all gummed up.

Anyways, he cleaned it up and sent it back. I just put it on, made all the adjustments to timing, fast idle, sole-vac idle and curb idle, and it runs like a 4-banger Jeep CJ rocket!

Off to get insurance and put this baby back on the road for the first time in many years :-)
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