Rough Idle & Hesitation

[Gardd]

Aarrgh, as if that mystery sound in the recently fixed steering system of my Taurus (1999 SE Wagon, Duratec) wasn't enough, a new problem reared its ugly head today when I went out to run some errands.

The car was absolutely fine yesterday. But today the car has a rough, slightly loping / chugging idle, and sometimes hesitates when you step on the gas. Stalled once. Once you're at speed it's absolutely fine though. And it starts okay however if you sit for a couple of minutes, the idle speed decreases to around 800 RPM (is this low?) then the idle goes rough / chugging and it seems just on the verge of stalling.

When I was almost home from my errands (about 10 miles of driving), the Check Engine Light finally came on.

Aargh again.

I've got an appointment to take it into the shop next week to look at the new steering; now I guess they're going to be looking at this new problem too.

Any ideas what this new problem could be? EGR valve? O2 sensor?

[shorod]

Vacuum line broken, cracked, or disconnected, bad spark plug wire or wires, disconnected Mass AirFlow (MAF) sensor wiring, or loose/disconnected air intake tube.

If you stop by a local chain auto parts store while they're open, they should be able to read the codes that lead to the Check Engine Light at no charge. Get the codes and post them back on this forum. The salesperson may make some suggestions on what the cause is, but most of the time they are not trained and their advice may or may not be worth what you pay for it. Did I mention the code reading will be free?

-Rod

[Gardd]

Based on what you said about cracked / broken / disconnected lines under the hood, I thought I'd take a look for myself today before bringing it into the shop this week.

Well...

After poking around under the hood for a minute I found that the large accordioned rubber duct leading from the air filter box had worked itself off from where it connects to the top of the engine. I wrestled with it for a few minutes (and I mean wrestle; with our cold winter temperatures right now the rubber was pretty darn stiff) and finally managed to get it back in place. Gave it a good tightening.

Then I started the car and let it idle for about ten minutes, and gave it a good rev now and then. Seems fine now! But after supper tonight I'll take it out for a good run just to be sure...

[Gardd]

Took it out for a half-hour drive -- it's just running just FINE now. I'm so relieved!

Now... how the heck do I turn off the check engine light?

[shorod]

Great job! Yeah, those intake air tubes can be a bear sometimes to get back on the throttle body.

The quick way to get the check engine light (CEL) turned out would be to stop by one of the local chain parts stores (Autozone, Advance Auto Parts, etc) and explain to them what happened and that you have a check engine light now. Ask them if they can reset the CEL for you. They'll probably read out the codes, and if the code is consistent with what you described, will clear the code for you at no charge.

-Rod

[Gardd]

I didn't have time to bring the car into the shop; it's still running just fine since I reconnected the duct.

But today the check engine light went out all on its own. Huh?

I know it's not burned out, as it still comes on for a couple of seconds as usual, when starting the car.

Like, I'm glad it went out but I'm totally mystified; I didn't think that was possible.