Any idea what causes this?

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Mopar Dude

Mopar Dude

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74 Dart 225. Seems like it is idling high but when I drop it into gear it brings the rpms down too low and dies if I don't keep foot on gas and brake. Also having trouble accelerating. When I give it gas it bogs down, I have to keep pumping gas pedal to get her to pick up speed. Car is 17 years older than me so I don't know much about how all that stuff worked back then
 
In no particular order

Improper tune, timing too slow Do NOT necessarily time car "by the sticker" which was for best smog, not best driveability

Generally, condition of ignition components, cap, rotor, wires, plugs

vacuum leaks, including bad brake booster and or hoses and fittings

problems with carb and especially idle circuit or even just incorrect idle mixture

generally poor engine condition, worn rings, valves

worn timing chain/ cam drive

In rare cases, problems with transmission, IE converter
 
choke stickng, vacuum leak, dirty air filter, bad intake gasket?
 
Sounds like a vacuum leak. High idle, no low end power and having to keep it running with the accelerator pump shot says too much air to me.
I'd bet you find your issue by the time you get to #3 on 67Dart273's list ;)
 
So what y'all are telling me is I have a long weekend of diagnosing ahead of me? It ran great before I put a new carburetor on it. The old one leaked air in the middle of the two halves.
 
Yes I did. It back fired the other day and puffed smoke out from under the carb so I tightened the bolts down. Ain't drove it since then. I was hoping the acceleration issue was fixed now. Gonna drive it in a couple hours and find out
 
How EXACTLY did you set idle speed and mixture?

Where is the timing?
 
Distributor advance weights stuck at full advance? Had this happen once on a pickup
Would start and idle but killed the motor every time it was pulled into drive.
 
Check out the carb base gskt,, it's mismatched, and letting air in somewhere.. that's where the puff of smoke came from..
 
67Dart273 said:
How EXACTLY did you set idle speed and mixture?

Where is the timing?
Click to expand...

I couldnt tell you really...I just kinda played with it till I got it running. I turned it down until I got it sounding right and then adjusted it a little...drove around the house...adjusted it a little...drove around the house...so on and so forth lol. Now it doesnt die when I put it in gear and doesnt stutter when I give it gas. Gonna hit the road with it in just a few minutes and see if the acceleration is doing better. The timing was very close to TDC. I cant remember exactly if it was before or after...but its close to TDC.
 
I'd advise you find a local guy, an "old guy" who understands carbs and old cars.

TIMING. TDC is a smog setting. In the days that car was built, TDC was a setting along with Federal smog regulations to cause the engine to "run cleaner." The Feds did not care if you could actually drive the car. I'd start by bumping the timing up to at least 5 BTC

What the poster above was referring to is the timing advance mechanism in the distributor. He's right---the weights could be stuck, but I doubt it would affect this problem directly (at idle)

So far as carb adjustment, get the car completely warmed up, and back the idle mixture screw out until the idle SPEED "peaks" to maximum. Then screw back in CW until the idle "just starts" to drop. This is a very delicate adjustment. Better done with a tach or vacuum gauge.

You may have to adjust idle speed screw if the idle mixture affects idle speed, IE go back / forth between the two

You cannot assume that "there's trouble" if you don't know how to tune it up.
 
You may also have an open fitting on the carb,,, make sure all hose attachment points are plugged.. some carbs have a big hose fitting on the back,, down low,, make sure it's got something attached, or plug it..
 
I just had a similar problem, very rough idle even with a freshly rebuilt carb. (1920 holley) ...We checked the valves and found the exhausts valves were too tight. Adjusted them to spec and it runs like a watch.
 
I had much the same on my dart ,points were not gapped correctly ,I pull the dizzy on my early dart as its a pain to do in the car and also the pcv valve was stuck ,now runs lovely
 
check the idle air bleed. of its a big hole like on most of them the transition circuit is way to lean and you get a bog unless you get the accel pump to cover for it
 
I have a 73 that could be your twin, same problem so
i got a brand new carb it was 40 years old and missing some parts and it did help some but didn't solve problem so valve cover was leaking so went to replace gasket ,and I adjusted the valves and that fixed it!
if the exhaust valve get loose they act like a wiped cam lobe and wont let the exhaust out so when the intake opens it pushes out into the intake runner, and when the intake doesn't open enough it run too lean .if I remember int .010/ext .020
hot!( one of the /6 experts a another sight said this happens because of the long stroke the engine has)
 
If you don't have them a vacum guage and a tachometer would be a good addition to the tool box. Both will help when adjusting the carb.
 
the vids are corny but a wealth of info. search youtube for "MTSC" or "Chrysler LLC. Master Tech series training manuals"

[ame="http://www.youtube.com/watch?v=l2Da60sEgzE"]http://www.youtube.com/watch?v=l2Da60sEgzE[/ame]
 
Got it running. I can shift the transmission throughout the gears and it idles down a good bit but doesnt die. BUT...when I go to take off it dies unless I pat the gas. I can not get it to pull out without pumping the gas pedal, HELP!! lol
 
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