Will the IAC in a 99 throw a code?

Shernius · #1 (**permalink**) 10-28-2009, 07:40 AM

I read that in a 98 that it would not throw a code if it was bad but would it in a 99?

DarrinBC · #2 (**permalink**) 10-28-2009, 10:26 AM

What is the issue you are having?

Darrin

Shernius · #3 (**permalink**) 10-28-2009, 01:18 PM

Truck would barely idle this morning on the way to work. Low 50s with rain and the trucks idle stayed at 400 RPM the whole 45 minute ride. I was actually surprised the truck did not stall and that the idle was steady.

Went to AutoZone at lunch time and of course the truck ran fine.

Pulled a P1507 code.

1. Engine vacuum leak
2. failed IAC valve
3. open or short electrical condition
4. air inlet plugged

I’ve ruled out 1 and 4 since I don’t believe this would happen intermittently. So as soon as the rain stops I’ll have to check the connections and pick up a new IAC valve.

Toreador_Diesel · #4 (**permalink**) 10-28-2009, 02:40 PM

Sound like the IAC and maybe one of your vacuum hoses got disconnected or is loose.

I wouldn't waste money on a new IAC valve. My girl's truck was exhibiting the same symptoms a few weeks ago and it turned out to be a disconnected vaccum hose and an extremely dirty IAC valve.

When you get off of work tonight, stop by autozone and pick up a can of Berryman's B12 and a can of non-flammable electrical cleaner. Spray your IAC with some B12 until you don't see any black gunk coming out of it. Either that or you can soak it for a few hours with the fuel additive version and get at it with a toothbrush. Either way, follow it by spraying it with the electrical cleaner so you don't have any B12 on the IAC anywhere then let it airdry. Get up a little earlier, put it back on, and you should be good to go unless it's something else, although I doubt it....

eallanboggs · #5 (**permalink**) 10-28-2009, 08:36 PM

You can monitor the IAC counts with a scan tool. You can do a snap throttle to see if the counts go up and down as they should. You can also monitor STFTs while spraying the rubber hoses looking for vacuum leaks(cracked hoses). When you hit a leak the STFTs will jump POS immediately.

blue2golf · #6 (**permalink**) 10-29-2009, 08:38 PM

The IAC in my '99 didn't throw a code when it went bad about 4 years ago. I replaced it with an el cheapo from Advance Auto and it's run fine since.

Shernius · #7 (**permalink**) 10-30-2009, 08:54 AM

My truck was built in August of 1999 and it threw a P1507 code.