Rough idle and stall, but only when hot?

[apostle228]

So, my Satellite is doing something odd... Its always done this as long as I have owned it actually, so for at least 5 or 6 months now, but its just now got me frustrated enough to do something about it.

When cold, my car runs fine, idles great. BUT. After it heats up to operating temp, the idle starts jumping up and down, and gets worse and worse the longer it idles until eventually it just stalls out! Another thing I will add as well, is that it stops doing this if I pop it into neutral. It idles a bit higher at neutral and that seems to fix the problem... so, it only does this while in gear.

Where do I start? I am kind of stumped by this one, I have never had a car do this... Its clearly temperature related whatever it is, because the first 10-15 min of driving around town it doesnt do it, only once she's all warmed up. What should I look at?

As a temporary fix, I may turn my idle up a bit and see what that does... But thats not a solution. Just temporary.

 

[Hemi Rebel]

Sounds like a tuning issue. Have you checked/set timing or adjusted the carb? Sounds more carb related to me.

 

[bigblock]

My 2 cents? You have manifold vacuum ran to the vac advance instead of ported vac.

 

[rebootej]

mine was doing the same thing. what engine is in your car? built up? I had the vacuum hooked up wrong and also added a spacer to my carb. Didn't get to test it to much after the fix cause cars getting body work now.

 

[apostle228]

Its a 318, bone stock except for the distribution system, thats all "beefed up"... Kinda. (orange box, MSD coil, new ballast resistor and rebuilt distributor). My vacuum advance is hooked up correctly, I double checked that... And I just recently tuned her up last month, so the timing is fine... I havnt messed with the carb other that spray it down with carb cleaner inside and out... Should I start with a carb rebuild or buy a whole new carb and see what that does MAYBE?

 

[steve from staten island]

Im sure you checked but is the choke going open all the way after it heats up

 

[snakeoil24]

If your using a Ballast Resistor check the voltage.

 

[apostle228]

Yes the choke is opening all the way when hot... Also, check the ballast resistor voltage, while it's idling rough? I can do that... What should the numbers be?

 

[Texpar]

still sounds like a vacuum leak. as long as the carb is cold and choking with extra gas you are ok. soon as it warms up and the choke pulls off your in a lean condition. extra air pulled in somewhere. bad vacuum line, loose carb to manifold, poorly adjusted vacuum advance.

 

[partmopar]

What carb? May be a Intake leak?

 

[Cranky]

Power brakes? Isolate the booster next time it acts up and see if it makes a difference. Take everything you can out of the equation before digging into the carb or ignition system....

 

[apostle228]

I have considered the possibility of a vacuum leak, but I have been racking my brain and really, what changes with the car being cold or hot though?? In the terms of vacuum that is... I just dont understand how a vacuum leak could not affect anything at all at startup, and only cause problems once the car is hot...

 

[Hemi Rebel]

I have considered the possibility of a vacuum leak, but I have been racking my brain and really, what changes with the car being cold or hot though?? In the terms of vacuum that is... I just dont understand how a vacuum leak could not affect anything at all at startup, and only cause problems once the car is hot...

Air/fuel mixture requirements for a cold engine are different than an engine at operating temp. Hence the choke. It also depends on the size of the leak. Obviously a major leak will cause problems at startup and at temp. But we don't know if you even have a leak, right?

 

[steve from staten island]

You guys may be on to something with the vacuum leak. Just thinking back many many years ago, try replacing the coil with a known good one,i remember i had a very similar problem with a coil that did what your car is doing. Just a thought

 

[artr8]

Anyone remember this problem with the ignition box?

Car starts and runs fine when cold. Idles rough after warmed. Sometimes it may shut down for no reason but starts right up.

Fix: also check the ground on the ignition box. Sometimes when the box is not properly grounded due to corrosion or loose connection, creates a high resistance ground leading to intermittent problems. When cold, the ground is better. Over time, when running, the ground deteriorates.

Just two cents and experience with similar problem.

 

[mopar_71]

Had the same problem. Drove me nuts.
Turns out it was the ignition coil getting too hot.
I moved it from the intake mounting spot and put it on the firewall away from heat.
Never happened again.
Good luck!

 

[apostle228]

Had the same problem. Drove me nuts.
Turns out it was the ignition coil getting too hot.
I moved it from the intake mounting spot and put it on the firewall away from heat.
Never happened again.
Good luck!

This is a very good idea. Do you know how hot it SHOULD be getting? Because I have definitely bumped it while working and had to pull my hand away because it almost burned me... THAT warm... I have also felt my ballast resistor as someone else on another forum said their resistor was getting too hot causing this problem, and my ballast resistor seems to get pretty damn hot too!

 

[mopar_71]

I don't know how hot the coil should be but, I would think the cooler the better for the ignition coil. The aftermarket coil I had in actually boiled the oil inside the coil causing it to leak. That's how I knew it was getting too hot.
Mounting a new one on the firewall fixed that problem you are describing.

As far as the ballast resistor, it should be warm while running because it's lowering the voltage to the coil after it starts. Just make sure the ceramic is not blackened or partially melted.

Hope this help and gets your mopar back on the road.

 

[Europa]

Apostle, did you ever get to the bottom of why this was happening?
My 440 with a Thermoquad is doing exactly the same thing, and only when hot. Many thanks,

So, my Satellite is doing something odd... Its always done this as long as I have owned it actually, so for at least 5 or 6 months now, but its just now got me frustrated enough to do something about it.

When cold, my car runs fine, idles great. BUT. After it heats up to operating temp, the idle starts jumping up and down, and gets worse and worse the longer it idles until eventually it just stalls out! Another thing I will add as well, is that it stops doing this if I pop it into neutral. It idles a bit higher at neutral and that seems to fix the problem... so, it only does this while in gear.

Where do I start? I am kind of stumped by this one, I have never had a car do this... Its clearly temperature related whatever it is, because the first 10-15 min of driving around town it doesnt do it, only once she's all warmed up. What should I look at?

As a temporary fix, I may turn my idle up a bit and see what that does... But thats not a solution. Just temporary.

 

[Dave6T4]

Over time, the phenolic carb body of the Thermoquad tends to warp and gets a vacuum leak. A good way to detect a vacuum leak is to slowly pass over areas where a leak could occur with a slightly opened, but unlit, propane torch. If the idle improves at a certain spot, that is your vacuum leak.