Your car has to learn how to idle

I don’t miss the old days when you pushed on the accelerator (my grandfather called it the exhilarator, you get a rush from jumping on the gas, I guess) and there was a mechanical connection between how hard you pushed the pedal down with your foot and how far the butterfly valve opened and the slide moved down inside your carburetor to let in more air and fuel to match the fuel pump’s faster pumps to provide more gas to be sucked in using the Venturi effect from the float bowl. Then the points advanced (assuming they were gapped right and locked down a certain number of degrees from top dead center, read with a timing light) and the car ran faster. You set the idle speed through a screw setting and adjusted the air flow through another screw. In 1968 they put a plastic shunt over the idle mixture screw but you could overcome that. You pulled a lever under the dash to close the top of the carburetor when it was cold to “choke” (literally) it until it started. Of course in Model T days you advanced the spark as you advanced the throttle on the steering column, unless, like Mr. Magoo, you had a faulty magneto. You stood there with a screwdriver and adjusted the idle.

Basic, it was... Long term reliable... it wasn’t.

Everything wore. The distributor cap points wore down. The points themselves wore down over time and had to be re-adjusted. Carburetors have a mean hours to failure, like a hard drive. I may miss the simplicity but I don’t miss the result. Older cars aren’t near as reliable as today’s cars. The fact is you don’t need to be a shade tree mechanic to keep a car running in 2018. It just runs. Until it doesn’t.

A thing is a thing until it isn’t any more. When asked, a rich man said, “hey, I had all the money I’d ever need right up to the point I was bankrupt.” 

Recently after a long cold snap the two older cars we let live in our driveway and garage failed to start. The ’99 Jeep, which has been bone reliable since we bought it new, didn’t want to start. Yeah, its battery died but I charged the battery as soon as it got low. I’d done a tune-up recently and I baby it. It only has about 75K miles on it and looks only a couple years old. It’s the one that lives in the garage. I do have a minor problem because I have an Allstate spy device plugged into the diagnostic port so they can watch us drive. I get a rebate check after I pay my premium if we don’t drive like a maniac. The problem is it sucks juice out of the battery. Not a problem in the summer but as it gets colder, the battery don’t like it much and it plays dead. So, charge the battery back up and let modern technology take over again and bang, she starts right up, eh? Well, here’s where logic begins to fail us. The modern car doesn’t need you to do anything to start. You turn the key. No choke. No pumping the gas and flooding it. No flooring it after you pump the gas and flood it. None of that stuff. In fact, there is no mechanical connection between the “exhilarator” pedal and the throttle body carburetor. When you press on the gas you are changing the voltage resistance in a potentiometer located inline leading to an ECM. There is no direct connection. It is all indirect. I knew that? I guess I just never dealt with it much. The reason is cars are so much more reliable now you aren’t out in the driveway with a screwdriver trying to up the idle in the winter time. A computer takes care of that. Until it doesn’t.

Here’s another weird thing. Since you don’t need to do anything to start your modern car, you don’t need to press on the gas pedal to start it, right? In fact you shouldn’t. So when the Jeep and later the Yukon wouldn’t start and I recharged the batteries, they just wouldn’t start. So while I’m cogitating on what’s wrong, Ruth gets in it and gives it more throttle and it starts, runs badly, chokes but then starts to actually run. Won’t idle, but hey, it started. She don’t know not to press on the gas pedal to start it, right? She’s just used to doing it from 1970. I know not to press on the pedal to start it and I’m right. Most of the time. This is after I remove and clean the IAC valve and she still won’t start or idle. This is after I learned that you need a constant 14 volts routed through the battery from the alternator so the ECM can feed enough power to the electric fuel pump in the gas tank to supply an adequate fuel flow to the injector rail. But we had that 14V, measured, and more, after the battery was fully charged and the car was being cranked. If your battery has a bad cell, you’re in trouble but we didn’t.

So?

The car forgot how to idle. Its brain had to relearn it. And no I didn’t change the pentil length when I cleaned the IAC valve. I left it exactly as it had been. Then the same exact thing happened with the Yukon. Its battery got low, got recharged and then wouldn’t start or idle until we manually advanced the throttle (pushing down on the accelerator pedal) then left it run at 2K rpm for a while until the computer relearned how to idle the car at under 1K rpm. Other stuff was happening. Probably also fuel separation between the alcohol and gasoline from sitting for too long? But hey. Your car has to learn how to idle all over again and you have to teach it by applying an adequate amount of throttle for a few minutes. 

The moral: Let it sit idle and your car will forget how to idle.