Cold idle problems--'77 280

[bobkat]

I have a stock 77 280 with FI, and it's making me long for the manual choke on 240's. It starts up on cold Washington mornings with no problem, but has a very rough idle until it starts to warm up. Cold idle is only about 1000-1100, so that's part of the problem. I've replaced the air regulator with a new one from MSA but that didn't fix the problem for long. They suggested I clean the electrical contacts, but that didn't help either.

Any solutions out there?

[2ManyZs]

Take a look in this thread and you will find a PDF version of the troubleshooting manual. I haven't looked through it yet, but it should help you with some places to look to find your problem.

http://www.classiczcars.com/forums/showthread.php?s=&postid=73244#post73244

Sounds to me like your problem is probably in the thermotime switch, air or water temperature switch, or the cold start valve. In other words, you're not getting the fuel enrichment you need on cold start up.

[peterc]

Hey bobkat,

Just a couple of thoughts. There is a cold start valve (like a fuel injector) located just behind the Air Flow Meter which spritzes fuel into the intake manifold to assist in cold startups. It has the same electrical connector as the fuel injectors so you should be able to spot it fairly easily. If this isn't working you will definitely experience the symptoms you describe.

Two possibilities for this are a malfunctioning Thermotime switch or bad injector. First see if you have voltage going to the injector. Remove the electrical connector from the injector and have a friend start the car.

****WATCH OUT FOR THE FAN AND FAN BELTS ETC****

Use a voltmeter to see if you have power going to the injector (should be 6 volts). This should be a steady 6v until the car warms up. If there in NO voltage then my best guess would be a wonky thermotime switch which is located above the engine coolant temperature sensor at the front of the engine head just below the valve cover. The thermotime switch remains closed, ie, sends voltage to the cold start switch until the engine reaches a preset temperature. If you have power going INTO the thermotime switch but NOT the injector then there is either a short or the thermotime switch is shot and needs to be replaced.

If you HAVE voltage going into the injector, then you have to pull it and see if it's working. It is pretty easy to remove (2 screws) but be careful not to tear the gasket. Stick the business end of the injector in a clear plastic or glass bottle and have a friend start the engine (engine cold).

If the injector does not squirt a nice, steady, even spray of fuel then it is shot and needs to be replaced.

Hope this helps.

Cheers,

Peter

[bobkat]

Thanks guys, I'll give those suggestions a try.

I did some checking up on this a coupe of months ago and thought the main cause was the air regulator--the car starts up on cold mornings with no problem, just runs rough after that until it warms up, and idles too low. But the gas mileage is bad too--~12 in the city--and I heard one cause of that could be a leaky cold start valve. I'll check it and the Thermotime switch out.

I appreciate your help!