Idling, stalling, overheating (electrical?) issue

[CJ007]

I've just started having and an intermittent problem with idle and overheating. It did start and run great, but once warmed up started running rough, stalls and gets hot to the point of almost overheating.

I have experienced some odd things. A couple days ago when it started doing this, I moved wires around near distributor, made sure coil connections were good, cleaned connections to oil sending unit and battery ground (passenger side stuff) and the next time I started (right after it ran bad) it ran great again. Earlier today it did it again and shook wires (to see if there was a short) and ended up pulling wire off top of the oil pressure sending unit and when I restarted it ran great. Later, I then went to the parts store for oil and it is acting up again! I tried all I could think of and nothing yet but crappy idling and temp gauge getting hot and running like it's missing really bad.

I think I have eliminated plug wires (tried spares), plugs (although I put E'3s in just days ago), ECM (plugged in my spare) and a short (pulled off all wire looms and seperated wires as best I could).

So here are my questions; can the E3 plugs be part of the problem? Does a coil overheat or get weak and work intermittently? How about when a distributor sensor (magnetic pick up) is going out? Anything to do with the solenoid?

I am looking for any input that might help me work through or resolve, thanks!

 

[Torxhead]

There are ways to check those electrical componets you mention. I would suggest a repair manual like a Haynes Jeep CJ. There are FSMs online somewhere and Harbor Freight has currently a great deal on a multi-meter to check those componets. A wiring schematic for your vehicle can be invaluable.That dry AZ weather could have dried out some of your wire insulation and the years of moving around can be tough on those copper wires and they can be frayed somewhat. That moving wires around can help find a loose or damaged wire or connection. The coil can be checked with a multi-meter along with the distributor pick-up. Another Item that can go bad is the ignition control module, which if bad can be hot to the touch and can cause havoc with distributor operation. I wish I could find those resistance numbers in my manual for the distributor pick-up and the coil for you, but I am on my way out the door right now but that info you request is out there.

 

[Razorfish]

The one almost independent thing is overheating. I say "almost" because other things can cause some overheating. Like timing but unlikely at idle. If it's overheating, especially at idle, I'd focus on that first.

 

[CJ007]

I pulled the magnetic pick up form the distributor and the ground wires were pretty frayed, so I soldered them up. It didn't help so I figured maybe it was too late for that and went ahead and picked up another and a coil. Didn't help. I took my Ignotion control module down and tested it and it passed.

It is not running good at all now, even cold. I also don't understand what could cause it to heat up. Could the little computer box under the dash be the problem? Isn't that just for idle and the stepper motor or does it have something to with timing and spark? When I unplug it I can't even get it to start so it is working somewhat?

 

[CJim7]

vacuum leak at the manifold maybe? Pulling air in will cause a lean running condition and heat up the engine...it will also cause it to run rough.

 

[Torxhead]

The distributor should only have one ground wire going to it and that comes from the icm. It would be best to just run that ground wire from the icm direct to the battery ground, since the distributor grounds itself out. The other two wires, orange and violet, go to the pick up coil and come from the computer. The pick up coil should have between 400 and 800 ohms, if not, replace it. A bad pick up coil will affect engine operation. The computer does control the timing and fuel mixture. When you turn the key on, you should be able to watch the stepper motor activate, if not, you have a dead computer. If it has been awhile since you have had the cooling system cleaned out, all the that collects in it, like rust, can cause an overheat along with a bad fan clutch.

 

[CJ007]

I did the bypass to check and see if it was the computer. It started and ran good, until warmed up, by the time I got home from about a 5 mile trip it was running rough and getting hot.

I listened an felt for manifold leak but will check again. Could it be the cat is blocked? Something to do with fuel pump or pressure? I pulled fuel line and turned key, it was pumping through pretty good.

I recently rebuilt carb.

 

[jasonmark1993]

Recently rebuilt carb raises suspicion. You can get a little insight on how the engine is running by looking at the plugs. Google "plug color" or something to see different examples of what to look for and identify rich, lean, oil, coolant, etc.

So retarded timing and a lean condition will cause it to run hot. Will it get hot while its idling? Does it start running rough then get hot or vice versa? Important to know. Take a look at the oil and coolant and make sure you dont have one in the other.

Generally, you cant make an engine lean enough at idle to make it get hot just sitting there. The engine will stall first. If you are driving around and its lean, you can definitely make it get hot. You can however retard the timing enough that it will get hot while idling. A nice way to see what the ignition system is doing is hook up your timing light and watch it while its running. Check it at idle and rev it up a little and watch the timing advance. Ensure the timing is set correctly. I've never seen a coil or magnetic pickup failure cause an engine to run hot. The pickup may fail intermittently once it gets hot; but it usually just goes open and your engine dies. Coils can do the same or not put out enough voltage at higher rpm.

The easiest way to know if your exhaust is plugged/restricted is to go from idle to wide open throttle. If the exhaust is restricted, the engine will be trying to suck air in faster than it can get it out. You'll mainly feel the power loss at higher load/rpm. I don't suspect this due to your running rough at idle complaint and the fact that it runs ok initially.

 

[CJim7]

There are only 2 things that will cause an engine to run hot whether at idle or during normal driving:

1> ignition.
Running lean because of fuel mixture. Timing adjustment, vacuum leaks or improper idle mixture. A computer controlled system will lean up an engine if it is getting false readings from sensors.

2> coolant system.
plugged radiator, bad water pump, blocked water jacket, air bubble (AMC 258 i6 / 4.2l are notorious for trapping air in the head, haven't seen it as much with the V8)

Pull your plugs and check for a lean running condition. The plugs will be ashy and white

 

[CJ007]

Thanks guys, the plugs are pretty clean and more white in color like lean/hot on the color chart.

I think jasonmark1993 is right about the carb. I'm going to pull it apart again. It ran so good when I first put back on, I thought it had to be something else. But after cleaning up the wires and going over everything else, it is most likely something to do with that.