73-87chevytrucks.com

73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: DnStClr on November 02, 2008, 08:24:04 PM

Title: Cleaned IAC and Got A code 42.
Post by: DnStClr on November 02, 2008, 08:24:04 PM

1987 Silverado 350 tbi- My idle stays high after it starts and warms up. I haven't put my tach on it yet. I removed  and cleaned the IAC and it didn't help the idle, but it started throwing a 42 code.(EST) When I disconnected the battery B+ and reconnected it, the code went away so I guess the spark timing is ok. What caused the code? Is it normal after removing the IAC?

Title: Re: Cleaned IAC and Got A code 42.
Post by: Captkaos on November 03, 2008, 01:47:28 PM

I would drive it to see if the code comes back.

Title: Re: Cleaned IAC and Got A code 42.
Post by: VileZambonie on November 03, 2008, 03:34:30 PM

You should remove the B- not the B+. It could very well have caused an eroneous code. Spray some carb clean under the TBI and see if it effects the idle.

Title: Re: Cleaned IAC and Got A code 42.
Post by: DnStClr on November 06, 2008, 10:22:28 AM

It hasn't returned this week so far. No change in idle when carb cleaner sprayed.

Title: Re: Cleaned IAC and Got A code 42.
Post by: Blue 82 on November 09, 2008, 07:14:08 PM

I had a sticking TPS switch cause the same exact malfunction (hi idle)
Cleaned the IAC, checked for vacuum leaks etc, nothing....
it's was acting up for a month or so, on and off
the light finally came on (code 22)
Replaced the TPS and all is fine

Title: Re: Cleaned IAC and Got A code 42.
Post by: VileZambonie on November 10, 2008, 01:32:08 PM

Check the TPS as suggested. If it checks out ok replace the iac motor.