Slant Six Won't Hardly Idle

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/6 Matt

/6 Matt

30 Degrees Crooked
Joined
Jan 19, 2010
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Location
Lincolnton, NC
Ok so here's what happened. One day, I drove home from work and the car was fine. I got home and went inside for about 20 minutes and then got back in the car to go visit my girlfriend. I already have hard starting issues when the car sits warm, I haven't done the fuel line mod to combat fuel percolating. The car was harder to start than usual and it started, ran terribly slow for a whole two revolutions and died on me. As I hit the starter again I noticed a plume of white smoke rising from under the hood, the engine caught and started and ran rough like it usual does when the fuel percolates, so I thought nothing of it and went on my way. Going down the road, I noticed when I was cruising with the throttle shut, and then I pressed the gas it would stumble like it's about to run out of gas. The car drove fine otherwise, until I got to my girlfriends house. I had to roll down her driveway in neutral and feather the throttle to keep it running, then it died finally.

So here's the specs.

1970 Dart, 225 Stock with factory electronic ignition conversion and NGK ZF5RN plugs, auto trans.



Here's what I've done and found.
  • I replaced the spark plugs which seemed to have ash deposits. #5 was very nasty
  • Replaced the wires after one of the crimps on the wire came off on the plug tip during removal
  • Replaced the cap and rotor, signs of arcing was present in the old cap as well as engine oil residue
  • I have verified that the timing is at 10BTDC, the mechanical advance is working as well as the vaccum advance.
  • The carb was loose on the intake, new gasket and proper torque.
  • Checked for vaccum leaks and leaky vaccum lines, none were found
  • Found the positive wire on the ign. coil was loose, just to insure no corrosion happened from the loose connection, I took sandpaper to the ring terminal and nut before putting the wire on and tightening it.
  • The fuel pump has been checked, it seems to be a little weak but there is clearly defined spurts just like the manual says there should be. Oil doesn't smell like gas.
  • No oil in coolant or coolant in oil, no white smoke out the exhaust.
  • The valves were adjusted ~2-3 months ago .010" intake, .020" exhaust.
  • I found the spring in the PCV to be broken causing the valve to rattle. Blocked off PCV vaccum hose with a bolt and test drove the car, no change. Will replace PCV tommorrow.
  • The fuel filter was replaced ~5 weeks prior after running out of gas
The most confusing symptom so far has been the fact that any changes I make or any adjustments made make the card idle better... Untill I test drive it and then we are back to square one. When I found and fixed the loose carb, I had the car Idling great save for a slight skip, I test drove it and only .1 mile up the road it was idling like **** again. I have observed the engine idles worse when it reaches operating temperature.

I bought a GP Sorrenson carb kit and I'm gonna pull the carb and redbuild it this weekend. Anyone got ANY other ideas? I'm :banghead: on this one.
 
Oh and tonight, when I found and blocked the PCV line, it idled better but still skipped, I test drove it and .2 mile down the road, it was idling bad. Came back home and it died in my driveway.

I noticed during the testdrive though, a new symptom, a slight loss of power. I'm also noticing the exhaust seems kind of.... Noisy.
 
I second the motion for crap in the gas tank.
 
Check the fuel mixture screw on the carb as well as the idle adjustment screw. I'm guessing you have a 1920?

Also, if you have a stock exhaust manifold, make sure the heat riser is free to operate. I use a good penetrating oil to loosen up the heat riser every now and then.

Best regards
 
Yes, 3x on the fule delivery being plugged; the sitting could allow some of the crap to fall off of the sock and you are OK idling and then plugs up as it starts to pull more strongly.

Also, see if the rubber line from the tank to the metal line under the car is collapsed/soft or cracked and letting air in.

Any fuel return system on the car? Try running it with the gas cap off or loose to see if the return vapor/vent line from the egnine compartment to the tank is plugged. The evap canisters have been known to get plugged up in rare cases.

Do you have a coil and ballast to swap in just in case? Have you measured the IGN1 voltage to the ballast cold and hot after the issues start?
 
I haven't checked the crap in the gas tank idea yet, my plan is to buy a section of fuel hose and connect it to the suction side of the pump and throw it over the fender into a gas can to see if the car will at least idle for me.

GEO said:
See it the chokes opening up and that the choke pull off is working
Click to expand...
The choke is operating properly
1970Dart198 said:
Check the fuel mixture screw on the carb as well as the idle adjustment screw. I'm guessing you have a 1920?

Also, if you have a stock exhaust manifold, make sure the heat riser is free to operate. I use a good penetrating oil to loosen up the heat riser every now and then.

Best regards
Click to expand...
I've already tuning the carb through both these screws, the mixture screw in particular seems to take alot of input to make a change. I have already checked the heat riser, it is moving freely and operating as it should.

nm9stheham said:
Yes, 3x on the fule delivery being plugged; the sitting could allow some of the crap to fall off of the sock and you are OK idling and then plugs up as it starts to pull more strongly.

Also, see if the rubber line from the tank to the metal line under the car is collapsed/soft or cracked and letting air in.

Any fuel return system on the car? Try running it with the gas cap off or loose to see if the return vapor/vent line from the egnine compartment to the tank is plugged. The evap canisters have been known to get plugged up in rare cases.

Do you have a coil and ballast to swap in just in case? Have you measured the IGN1 voltage to the ballast cold and hot after the issues start?
Click to expand...
The car drives decently fine, it won't idle for **** though. I will check the rubber line asap. There is no return system on the car, this is a non-california 70' Dart. I don't have a coil and a ballast, I haven't checked IGN1 voltage, what should the spec be? 12 volts?
 
I'd take out the idle mixture screw & blast the hole with a 2 second shot of starting fluid then replace the screw. Take the top off of the carb & see what the bowl looks like for crud/water globules. If any doubt of the gas condition you could plumb a 2 gallon can of good non ethanol gas to the pump inlet & set the can in the eng bay & take it out for a spin which'll tell you something pretty quickly. If ign it might be the ECU/pickup or coil acting up. Holler how it turns out!
 
/6 Matt said:
The car drives decently fine, it won't idle for **** though. I will check the rubber line asap. There is no return system on the car, this is a non-california 70' Dart. I don't have a coil and a ballast, I haven't checked IGN1 voltage, what should the spec be? 12 volts?
Click to expand...
IGN 1 ought to be in the 11.5v range +/- if the circuitry is all good when in Run but engine not running, and battery decently charged.

When you say that car drives 'decently fine', does that mean that is accelerates fine and cruises fine? If so, then the most likley cause is not fuel delivery or a plugged line or cracked line; fuel delivery is at its minimum at idle and increases as you go off of idle to cruise and so forth.

Likely casues are: vacuum leak, idle circuit in carb gummed/plugged, or fuel pump weak. Since you report the idle improving a bit when you plugged the PVC line, then I would be exploring the vaccum leak first. You can find plenty of references in this subforum about spraying a bit of gas or other combustible fluid around the manifold flanges and seeing if the idle improves when this is sprayed at some location; there is the leak. Also, temporarily remove/plug all vaccum line frothe carb and intake manifold.

I also note that you 'found and fixed a loose carb'....did you just tighten down the carb base bolts? It may be time to put a new carb base gasket in; that would be a great source of vacuum leaks.
 
You stated #5 spark plug looked bad. I'd do a compression test on all cylinders just to be sure. Taking the carb apart and cleaning it couldn't hurt either. I'd also pull the pickup tube out of the tank and check to see if the sock screen is still attached.
 
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