I finally scanned my blazer, and got DTC-35, Idle Air Control

It's a 93 S10 Blazer

It has been starting fine, and for a while now, when I am in park, or stopped at a light for a while, the check engine light comes on. I have holes in the exhaust and no cat from previous owner, so it's noisy and does smell like exhaust at times in the cab, so I didn't think much of it.

Now (past week or two) it's been revving quite high when it's in park. I start it up to warm it up since it's winter, and it will idle high until I get in and shift into Drive or Reverse, then the idle drops. When I shift back into park before shutting it off, it revs up then too.

Where should I start?

 

Just like the code says, it sounds like the IAC valve. You can clean it or replace it. Plus, get that exhaust leak fixed. You do know that is dangerous to you, right?

 

I tried cleaning it, didn't do anything, still idles extremely high at start up.

Any good cheap place to get a new one? Or any other ideas.


I'd like to fix the exhaust, but it isn't worth the money right now, this is just my winter beater, and it's been two years so far without any problems. If I could find a use full exhaust for super cheap I'd do it.

 

Checked the wiring, doesn't look like any damage, breaks, burning, or anything near the unit, and the plastic wire loom is still around it and in good condition

I put a new idle air control unit on today, and it didn't really change.

Idle was high at start up til I shifted into drive. I took it for a spin, and when I stopped at a light, the CEL would still come on after sitting for like 30 seconds. When I got home I put it in park and left it for a bit. The idle went up like usual, probably around double normal idle (no tac), and it had a sputter to it while idling. I shifted back into reverse, and the idle dropped to normal, then back to park and it did the same thing.

not sure where to go from here.

 

How about the EGR valve? Have you cleaned it? Checked over all of the vacuum lines to ensure that you do not have a vacuum leak?

 

I picked up a filter for the EGR valve, and when it warms up a little outside, I'm going to pull that off and clean it and see what happens. The EGR valve has been replaced at some point (before I bought it), because it looks fairly new, so maybe this issue has happened before, i've heard its a common problem with old blazers.

I'm gonna check around a little for damaged vacuum lines too. Does anyone have a vacuum diagram or anything showing the location of all the vacuum lines?