Idling issue

[Voss]

Lately my Charger has developed an issue when sitting at idle with engine fully warmed. The problem first appeared at a cruise night a few weeks back. The car started to bog out at idle, and eventually stalled. No issues what so ever to start again. It did this 10 times or so in 5 hours so needless to say I got to locate the issue and fix it.

Car is a 68 Charger with a 440, a Carter AVS 4429S carb, and a stock style points distributor. I also have the vapor separator and hard lines to the carb. Tank vent is fine and not clogged. After doing some more investigation I found that when the car starts to act up, I can always save it if I give a little gas. No bogs or issues what so ever when driving, it runs super strong. The issue I have is only at idle. It is especially sensitive if I go from Neutral to Drive and sits at low idle with the foot on the brakes. But it has happened that it acts up even when sitting in neutral. But it is ONLY when the car is fully warmed up (about 190F). Never when cold.

Yesterday I checked the timing, replaced the coil and ballast resistor (since I had these parts on the shelf), but still the same issue. One interesting thing is that I couldn't reproduce the issue when sitting at idle with the hood open. I had the car idling for about one hour (while doing some cleaning of my garage), and it never stalled. But when I closed the hood the issue appeared like after 2 minutes. So SOMEHTING is affected by the heat which builds up in the engine compartment.

I hooked up my dwell meter and it reads stable 31 degrees. It charges good at about 14-13.5V at idle.

I do feel this is ignition related so my next step is to replace the condenser, rotor and cap. They are all fairly new however (2 years). I have more or less ruled out a vapor lock since the car fires right up after it stalls. I am thinking I might have a weak spark, maybe due to a failing condenser, or a crack in the rotor.

Next thing to think about is of course carb and fuel issues, but since it runs super-strong I started in the ignition end. The carb is professionally rebuilt a few years back and has worked perfect. The thing I did replace last season was the distributor, bought a A1 Cardone unit. I have heard both good and bad things about them. But the dwell is stable and it has worked well up until now. Maybe I should mention the ignition is set at about 7.5 deg, and I run ported vacuum to the distributor.

I have to solve this, so the rotor, cap, condenser and points is next in line to replace. If that does not help I am starting to run out of ideas. Or at least I have to start thinking about carb issues.

Any thoughts from someone who has experienced something similar?

 

[5.7 hemi]

Hood open, no problem. Hood closed, problem. Sound like the air the engine is getting is really warm. Just guessing on that.

 

[oldbee]

Cool going bad ? or my 1st choice- fuel boiling over on carb.

 

[mopar 3 B]

Closed hood and only when not moving. Simple heat soak.
So far nothing has been changed that will heat soak. If a tap on the throttle takes care of it for awhile it not likely electrical. Only leaves fuel and air. In fact air has all ready been illuminated. That only leaves fuel. If you are not all ready using it try some non-alcohol fuel and see if the problem takes care of itself.

 

[Voss]

Hood open, no problem. Hood closed, problem. Sound like the air the engine is getting is really warm. Just guessing on that.

Interesting theory. I have run this setup for years with no issues. The only thing I changed this year was the radiator. I got my 2898045 22" stock rad rebuilt by Glen Ray. I now have a 3 row core instead of OEM 2 row. I was running the 22" rad before too but perhaps the new 3 core rad transfers more heat which raises the under hood temp? Would make sense, max temp I see on my gauge is now 190, before it could climb to 210 or even 215-220. I don't think it's fuel boiling in the carb since it fires up directly after stalling. The fuel steel line and carb body is not hot at all and I don't think it would heat up to a level where it boils in 2-3 mins after closing the hood.

I will continue my investigations and rule out all potential ignition issues. But if it is the elevated under hood temp, could this be solved by tuning the carb?

 

[Voss]

Closed hood and only when not moving. Simple heat soak.
So far nothing has been changed that will heat soak. If a tap on the throttle takes care of it for awhile it not likely electrical. Only leaves fuel and air. In fact air has all ready been illuminated. That only leaves fuel. If you are not all ready using it try some non-alcohol fuel and see if the problem takes care of itself.

@mopar 3 B: I think you are right, I have changed the rad to a more effective 3 row core, see my previous post. So the under hood temp is probably higher than what I had last year with the old stock rad. Question then is if I could solve this by tuning the carb a little?

 

[slimt]

fuel line resting up against the block?

 

[mopar 3 B]

@mopar 3 B: I think you are right, I have changed the rad to a more effective 3 row core, see my previous post. So the under hood temp is probably higher than what I had last year with the old stock rad. Question then is if I could solve this by tuning the carb a little?

Most put larger radiators in to lower heat levels. Not understanding the thought larger radiator more engine compartment heat. Could well be the larger radiator is blocking airflow.
You could try leaning the idle circuit or adding more air.

 

[Voss]

Most put larger radiators in to lower heat levels. Not understanding the thought larger radiator more engine compartment heat. Could well be the larger radiator is blocking airflow.
You could try leaning the idle circuit or adding more air.

Yes, I think this can be the case. I will measure the A/F and CO tomorrow with hood open and with hood closed. I figure that would tell me if it runs rich. But I do think you are right.

When I bought this car it was pretty much butchered up in all areas. It had a ton of gremlins, all sorts of issues. And I mean EVERYWHERE. So I decided to restore this car to OEM, or as close as I possibly could get. I have spent the last 4 years chasing used original parts to get it back to original. The list of things is extremly long but the biggest improvement was when I restored a Carter AVS 4429 and placed the Eddy carb on the shelf. No bogs, no hard starts, and the car runs really strong. I also bought a correct 22" 045 rad but it was in so-so shape and I had to repair it twice. Considering that and the fact that I go to shows and cruise nights far out from town I decided to recore the rad. It just felt uncomfortable to have a 50 year old repaired core... So last winter I had it recored by Glen Ray. Not cheap but he does quality jobs, and it is as close to OEM as I could get. Aluminium rads and fans are not an option for me. The tanks were also in perfect shape so those had to be saved of course. But, a 3 core as I now have will restrict air flow and transfer more heat so the under hood temp will be higher compared to the old 2 core. That's obvious. Another area I spent a lot of effort (and money) on was to get the correct WP housing, correct impeller, fan and the right fan spacer, correct size of pulleys and a metal shroud. All in all that solved my overheating issue I had when I bought the car. I didn't even had to use an electric fan. Guess the Chrysler engineers knew what they were doing. So the lesson is that throwing all sorts of mix and match of parts WILL cause trouble, some more severe than others.

I will measure A/F and see if some fine tuning solves the issue. I hope it does. I will post an update later!

Many thanks for the advice!

 

[AR67GTX]

If you are running only 7.5 degrees advance and ported vacuum the motor is probably running a lot warmer at idle than it needs to be and I'm surprised you don't have a big bog upon accelerating from a stop. As an experiment I would put a vacuum T in the choke break vacuum line and tie the distributor to it and see what happens.

There is nothing good about ported vacuum. In simplistic terms it was an early, primitive effort at emissions controls to retard timing on an engine at idle and low speed, to increase it's heat of combustion (and water temp) in hopes of more complete combustion at idle and lower emissions. I can't imagine that any part of that should sound good to someone trying to improve or fix the performance of their engine.

 

[miller]

Maybe I should mention the ignition is set at about 7.5 deg, and I run ported vacuum to the distributor.

No mention of trans type, auto or standard, and I'll toss in, with the lousy gas these days, not even sure it applies. Just meaning the initial timing differences, between the two. Maybe some of the gear-bangers can comment...I'm a 727 guy.
If you do run an auto, do you get much RPM drop, putting it into gear? That's a sure sign of timing off, carb mixture off, or a combination of both.
7.5 deg timing seems low. But, the engine wants what it wants. Your's ain't too happy, right now. I'd look at both ignition, and carb.

 

[Bruzilla]

You might be overlooking another difference. When you're in the car sitting at idle, your foot is on the brake. When you're idling when cleaning the garage, it isn't. My suspicion is you have a vacuum leak that involves either the brake booster or the vac line to it... assuming you have power brakes.

 

[69 GTX]

You might try installing a phenolic spacer under the carb.

 

[furyus]

I'm with the timing guys. Mark where your distributor is now. Bump it up a few degrees. See what you get. Doesn't cost anything.