Hey all,
I noticed a few weeks ago when I parked my car for a couple hours on a nice sunny day, when I went to start it back up, it idled really rough, sputtered a little. When I'd put it in gear it stalled and when I gave it enough gas it would drive but very hesitently. It would lunge forward when driving and then back off. This went away after a couple hours of driving it the rest of the day. Fast forward to a week or two later, my water temp gauge all of a sudden was reading C even though I'd have been driving for quite a while. It would stay at C and then climb back up to normal temp and then go back to C later. Fast forward to today when I replaced the thermostat thinking it was sticking open. While driving it at first it was fine, then about an hour later the temp went back down to C and (coincidentally or not) the engine starts running rough: attempting to stall at intersections, and "surging" when I'd give it more gas driving away. I think it calms down when it's cruising, but still not great. I installed the 180 thermo corrently and I see it working on the guage. Also, I happened to smell a bit of oil when I'd stop or park in the garage. Any ideas? I'm gonna do some more research but anybody else have these problems? Have a nice day everybody.

 

Are you certain your cooling system is pressurized and has no air in it?

 

I would start by checking all of your major electrical connections.

It almost sounds to me as if a loose connection might be causing your car to experience intermittant low voltage to certain systems within your car. This would explain both the temp guage issue and yourintermitent engine issues.

My theory is that low voltage would cause a poor or weak spark,especially if you are running a high power electronic ignition.

 

I went to a shop I know and they tested my cooling system and found that my radiator cap doesn't hold pressure. I will go replace that with a new one and try to get the air out now that I know there isn't a leak. Good suggestion there, 67mustang302, thanks.

JMD, should I go around and polish all of my engine compartment wire contacts to ensure conductivity? I'll use a multimeter to check the current from the alternator and battery. I've still got points so maybe it's time to take on that mystery beast and check those out.

So far I think I will:
-replace fuel filter (hasn't been done since I got it a few months ago)
-check for vacuum leaks around the carb
-change spark plugs, or maybe I should wait to see if I can fix the problem first

 

I think the items you have proposed make for a good start, and maybe even a good solution to your entireissue.

I am thinking that you may even have a weak battery ground, the ground may be strong enough that high power items (starter, etc.) might "force" the ground to work, but when the car is not using much juice, (like daytime driving) the ground is not capable of carrying a small load effectivly. Next time you have the engine and / or guage issue, switch on your headlights to high beam and observe what effect (if any) that this has with your issue.

If there is a weak ground of the nature I have described, the problem might get better with the bigger current draw.

 

I would check the grounds first - remove the ground connection, wire brush the contact points clean and re-attach. That includes the battery to engine ground cable and the engine to firewall cable. Most connectors need only to be pulled apart and reconnected.
Pull the plugs if only to satisfy your curiosity, and gap them at 0.035 inch. Good practice.
What do you think a meter reading of the battery will tell you - sitting - and running?
Jim

 

Great points all,,,, and the battery part really caught my eye,,,, a cell with an intermitantproblem,(open or short in a cell or two) could cause a lot of issues.......

 

Ok, I bought a new radiator cap. I started teh car this morning and had the same problem so it's not a temperature related issue. I turned on the high beams and I didn't notice any effect. I think I might go to the store and get SeaFoam, it's stuff you spray down the carburetor and it cleans it out. Hopefully this could clean the jets if they're clogged. I will also replace my fuel filter. If these dont' help, I will start inspecting the electrical connections. I'll keep you guys posted. Thanks.

 

Pull your plugs and look at them, if an elec problem is causing it then the very poor spark makes very poor combustion and the fuel won't completely burn(that's why it runs like crap). If the plugs are black/fouled etc then it's an elec problem, so yeah, start with the grounds, and then check the wiring for the ignition system. Also make sure all the plug wires are firmly attached and none of the plugs are broken or have cracked insulators etc

 

Alright, today I replaced the fuel filter and used 2 cans of SeaFoam carb cleaner (about 1/2 can in carb, 1/2 can in fuel tank, 1/2 can in crank oil...and then the other half went back in the carb to repeat the cleaning process). Tons of smoke, felt really bad for the neighbors! Anyway, engine smoothed right up!! It's running just fine right now. So as of this moment, it was either a clogged filter or clogged jets. I will still go through the engine bay electrical to make sure things are clean. Thanks all for the quick and helpful responses. Let's hear it for SeaFoam!


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Forgot to add this last part dealing with the temperature! Anyway, my car used to always run hotter (somewhere between the 'M' and 'P'). But lately it's been running around where the picture shows. Now I know the guage works because it does move around like when it's warming up or during normal driving and I know that the needle can fall even more below where it is now so it's not a case of a dead needle (when turned off, the needle points to the C line exactly). I've always heard people say how hot mustangs run, but is it possible that it's now finally running at a decent temperature compared to before? I'd feel really good to know that my engine is running a bit cooler for the better.