Help with Motor it Starts, Idles Then Dies When I raise Then Lower the RPMS

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Machman

Well-known member
Joined
Dec 25, 2011
Messages
550
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Location
NY
My Car
1971 Mach 1
Hi Guys

I'm having a problem with the car (302 motor w/ auto trans) and need some help as I wanted to get it running so I can drive it to a local car show next Sunday

The car was sitting for years but when I got it I replaced the gas tank, fuel lines, sender , pump , hoses , plugs wires , cap , etc , etc , etc, and got it to start fine but it always wants to stall out after I raise then LOWER the rpms

What I noticed is It takes a little time to start the motor a and when it finally starts it idles but then once I increase the rpms then lower them again (either lowering them fast or slow) the engine stalls and wont start again for a few minutes

The carb was frozen and dirty when I got it but I sprayed the piss out of it w/ carb cleaner & got the float and needle free, put new filter in it , acc pump seems to work ok

The carb is a motocraft 2100D? with electric choke, I noticed when I finally get it to keep an idle (only when I do not increase the rpms) the choke seems to stay closed even after 5 minutes in weather temperatures in the 60s

Earlier I posted about help w/ the vacuum system on my car but as I did not know if any of the vacuum lines were connected properly and did not know if that was the cause of the problem so to be safe I dissconnected and plugged everything except the essentials.

None of this made a real difference and it still does the same thing

Any suggestions or help so I can get this driving by next week would be greatly appriciated

 
Last edited by a moderator:
it sounds like a carb issue. if you were to pour some gas down the carb will it stay alive then?

there are local carb shops so hand them the carb. or if thats too much money, summit racing has inexpensive carbs or even a edelbrock.

let me know and keep us posted.

 
I had a similar issue, turned out to be old gas had plugged up the carburetor. Had to tear down the carb for a re-build. Now I use a gas stabilizer on every fill up (like Lucus Oil). Most fuel these days does NOT have any type of cleaners/stabilizers.

 
I have had the same thing and it took us an eternity to find out what it was.

Changed carb, distributor, fuel pump, spark plugs, everything one could think of, and the problem was still there.

My buddy who works on my car is very stubborn and almost considers it as an affront if a car refuses to work properly ( :) ) and so he eventually tore the motor apart and found that when the motor had been rebuilt 7 years before they had put in one crankshaft bearing the wrong way which caused problems with oil pressure on one cylinder.

It worked for about 7 years before it got too bad.

It idled and accelerated fine, but when I lifted my right foot off the pedal it would die.

Not saying, that this necessarily is what´s causing you trouble, but just wanted to share my experience.

 
Thank you all for the replies, I ordered a rebuilt kit today and will see how it goes, next step will be a different carb

 
If it's been sitting for more then a year, it's for sure the carb. If your rebuild doesn't go well, slap an Holley 0-1850 on it and be done with it. It's a 600cfm, vacuum secondary 4 barrell and they bolt right on.

When the time comes, they are so easy to rebuild it ain't even funny. Not very many parts and they run killer on 302's.

You can pick up a rebuilt one from Clist that needs to be reubuilt for $50-75, then a rebuild kit runs you about $35-50. Just make sure that it doesn't look like it's been sitting at the bottom of the ocean, otherwise it may just be a paper weight. The cleaner the outside, the cleaner the inside, typically.

A rebuilt one for $100-150 is a decent price, but unless you know the builder, you don't know how well it was built. Or you can pick up a new one for $259 from Summit and be done with it.

 
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