Ok. Just recently, out of the blue, my car stopped working right. I can still drive it, plenty of power up high and feels normal, but anytime you try to get it to idle (starting, lights, etc) it drops straight through to 0 and dies. The tach doesn't even slow down passing through the idle RPM. At one point, it did idle, but the idle drifted around 450-650 and was extremely rough. I had a code 13 before, but didn't have a chance to get to the O2 sensor yet (it's COLD here) . I threw a code 34 while looking at things, but the MAF is fine (unplugged and it barely ran at all, let alone idle). It was running fine till I tried to start it one day, and it went from a pain to get idling to no idle in 20 hrs.

Hot or cold does not matter, it will not idle at all at either temp, except every once in a while it will try when hot (very very poor).

Any ideas? I'm thinking maybe the IAC is jammed shut...

 

Any time you have an idle RPM issue, the IAC is a suspect. It may not be the IAC motor/valve itself, but the system.

You mentioned a MAF, so I'll presume this is a TPI engine. There are a few possibilities:

1. Dirty or clogged IAC air passages in the throttle body;

2. Sticking/failed IAC stepper motor;

3. Iced throttle body.

The first is fairly common. Try cleaning the throttle body, and especially the IAC air passages. If your car won't idle at all, you may have to remove the IAC to clean the passages thoroughly.

As long as the IAC is removed, you can address the second possibility. It only takes a very little dirt and varnish to make an IAC sluggish and unresponsive:



The top valve was basically "stuck" and unresponsive from only that little bit of varnish.
Only a little more, and it would be completely "dead". Remove the pintle, clean and lightly lubricate it with engine oil, and reassemble it.

Third, and depending on your elevation, temperature, and humidity, the throttle can ice up, including the IAC passages. The factory installed a water heating system to help keep the TB warmed and free of ice, but under extreme conditions, the TB can still ice up. If the TB water heating system was bypassed (a common modification) you have a very good chance of icing.

Cold? What cold? It got way up to 2° last night and I washed and waxed my truck today since it was so nice...

 

This may have nothing to do with your problem, but I once had my EGR valve stick wide open and my truck (S-10) did exactly that same thing. It would idle like absolute dog poop, if it idled at all.

 

Good, that's reasurring Vader, you rock I'll get that pulled asap... Good time to clean the intake runners and TB anyway, too cold to take the tops off.

I've had the icing issue on my Saturn before. It froze at 2/3 throttle in traffic. Real fun... I left the lines hooked up for the winter on the bird, though. I know I've got a dirty TB, I can see it, so I'll get that all cleaned out soon!

P.S. If I pull the TB and the intake runners/manifold, I'm going to have to replace those gaskets too, aren't I?

 

What about loss of vacuum?

 

I thought about that, but it goes fine while driving, and the engine is as smooth as can be, it just refuses to stop at the idle rpm.

I also checked the easy-to-see lines and saw no problems, plus many were replaced 2k mi. ago.

 

Can any of these problems you guys have mentioned be causing a code 45 "rich O2 sensor" or something like that?
Thanks!

 

IAC problems SHOULDN'T cause a rich condition... Doubt vacuum would either... All depends on whether you have a carbed or EFI car. If your ignition is too weak to burn off all the fuel and air being shot into the cylinders, that'll cause you to run rich also. Of course, the problem could always be a faulty O2 sensor..very common. Replace it if ya haven't already..$20, 15 mins, bam done....just make sure to reset the ECM after.

 

I replaced the O2 sensor about 3-4 months ago and the car improved 100%, it used to smoke black before. It's FI (check the signature for details). I had adjusted the TPS and iddle air mixture before, but didn't do it right. I just read Vader's explanation, and that tells me I didn't do it right. The timing is fine, I did that part right. The tps I did right but the part where you disconnect the iac I didn't do. Thanks!

 

Think I got it... A mm of gunk had blocked up all of the passages around the butterfly valves in the TB. I could use the thing as a cup! Put water in, and no flow around the valve at all at idle. So I dismantled it and scrubbed for a good hour. Shiny now I'll put it back together as soon as it warms up outside (snowing now).

 

Never heard of that test before.. Just DON'T LET ANY OF THAT WATER IN THERE!!!

 

I didn't install it with the water IN it. Just with the TB out in my sink.

 

I was trying to be nice with my other comment but I was thinking 'uhm..is he crazy or just incredibly stupid?' I gotcha....didn't think about you taking it off.

 

I'm trying to make one of those James Bond cars, ya know, the ones that turn into submarines? I have to teach it to like water first

 

Ha ha..one step at a time. Turn it into one of those hydrogen powered deals, whose only exhaust byproduct is water!

 

wewt! Plug it all in, and it starts right up! Beautiful...


And the Saturn dies