davidc1

Can a bad IACV(Idle Air Control Valve) (or ours is actually called a RATV (Rotary Air Control Valve) on an 03 with 150,000mi cause a really poor quality idle, especially when cold, dies when hot at a stoplight, and the idle poor enough when cold to cause misfire codes to be thrown?

Here's a history....

Last year, car idle quality was fine but started to die when hot at stoplights. Before I had a chance to check it out, I spun a bearing at the track.

Got a new short block and rebuilt valve train. Head was done by Portflow. Head was upgraded with Supertech everything to provide more protection against over revs.. New plugs as well. Alex at Ballade Sports did all the good work.

Car ran fine for several thousand miles. Brought it to track for first time. On a long left sweeper, twice, at about 6-7000rpm, experienced loss of power and huge plum of oil burning smoke. Thereafter took that turn at higher gear, lower rpm, about 4000rpm and no issues for rest of day. Not sure if this is related to current issues, but thought I'd mention it. Figure the smoke was oil that got into the intake from the PCV. Didn't have to add any oil as no appreciable oil was burned.

No issues for a week after, probably another couple hundred miles or so. BTW, the idle was perfectly fine after new motor, and the IACV never was replaced.

Suddenly, leaving work, after starting, idle was poor, threw codes for misfire, by the time I got to the bank a few miles away, car would barely run. Started a blinking CEL. After idling for a while, couldn't get it started.

Codes were (and these are the same occasionally recurring codes up to today): P0302, P0303, P0304, P0300, P1399. Twice now, it threw a pending code P0410, which is the secondary air pump, but never turned into a real code.

Had car towed to shop. Since then, replaced cat conv with test pipe since cat was starting to break apart again, plugs (correctly gapped), replaced all coil packs with used, but supposedly known good ones (2 were diagnosed as bad by swapping), replaced battery, pcv valve, cleaned pcv tubing, cleaned throttle body with rag and carb cleaner, map whack, sprayed lots of carb cleaner down map sensor port into throttle body, used seafom in tank and down intake,

Key points:

Cleaned IACV twice, and both times, car ran well for a day or two before idle problems returned.

Yesterday cleaned it and no improvement. Cleaned the shaft of the spinning motor thing inside it as well, by unscrewing the electrical/motor part and it seems to spin freely.

Idle is far worse at cold start, and thats when I occasionally will get the aforementioned codes. Idle is much better, but not perfect, when warm. Although has a strong tendency to die at idle when warm. The idle doesn't "hunt" up and down, just stumbles.

Above idle speed, engine runs fine cold or warm, seems like power is fine.

Seems like all vacuum lines are connected properly, but they weren't replaced with new motor. I haven't checked them for leaks specifically. Are there any I should specifically check? In the old days, you could spray something on the vacuum lines and it would temporarily plug any holes...can you still do that? Only mods are exhaust and AEM intake, neither new.

Those codes get thrown every couple of days if when starting up the idle is really poor.

I have the Android app, Torque, so I can use that to check any OBD parameters if you'd like.

I'd just replace the IACV, but at about $150 and no return policy, I'm hesitant to throw more money at it.

Anybody have a known good one I do a trade/test with? It takes about 5 min to remove it.

Thanks all!

LINESUPER

Here is a link to Negcambers Misfire code check list. It sounds like you have already checked into alot of the possible culprits - the one that leaps out at me is the low voltage output from the alternator at idle. Hope it is helpful to you. Besure to post up the results!
Misfire code check list

davidc1

thanks for the suggestion. The alternator sounds like a good thing to check ,next, after all it is pretty damn old.

davidc1

Checked the alternator, it was fine. Well, turns out not the RACV, but instead, I needed a valve adjustment. As soon as that was done, idle is rock solid perfect! Yeah!

LINESUPER

very good!

cadams05nfr

It's funny how sensitive these cars are to a valve adjustment Seems to fix lots of issues!