About 4-6 weeks ago, my son's 04 LR D2 HSE (engine rebuilt about 30K miles ago to put in flanged sleeves after cylinder sleeve 5? slipped, vehicle's made a couple of 2,000-3,000 mile roundtrips over that time, spark plugs have about 12,000 miles on them), started to make an intermittent "chattering" sound under the hood.

It will do it once or twice under acceleration, then doesn't come back for several days.

First thought it was a dropped lifter (my son is not great a checking oil and we've never been able to get the sump pan to seal so it needs a quart top up every 1,000 miles or so), but I got out the mechanics stethoscope and listened to the engine both at idle and up the RPM curve: the valve train and crank block just hum quietly, i.e., no tapping, clicking or other bad metal-on-metal or ready-to-fly-apart sounds.

Usually some time after a chattering event (like 1-2 days), it then throws a bunch of codes, all or some combination of P0332, P0441, P0505, P1171, P1174.

The last few times after a chattering event, a new symptom has shown up: after an engine off and on post a chattering event, on first acceleration attempt the engine stumbles/bogs (gets close but doesn't stall) and otherwise takes a while to get going, like it has a fuel delivery problem (too rich? too lean? failing fuel pump?). However, it only does it once and then once it has its little tantrum, everything is fine until the next chattering event.

I cleaned the purge valve (do this every year or so anyhow, first with brake fluid cleaner, then WD40 to lubricate it) and did the same procedure on the IAC valve.

Right now, I am going with the the P0441, P1171 and P1174 being symptoms and the P0332 (bank 2 knock sensor) and P0505 (IAC valve) being the disease, probably leaning towards the IAC.

So, a couple of questions:

1. What exactly does the knock sensor do and could a bad one cause this kind of noise and then stumbling/hesitation?
2. Do IACs fail gracefully like this or do they just stop working one?
3. Would an IAC butterfly mechanism ever make this kind of noise?
4. Am I totally off the mark here, and the problem is elsewhere.

As always, comments, advice, sharing of similar experiences is greatly appreciated.

 

I’ve had plenty of untouched since nee and completely stuck IACV’s on D2’s I’ve bought or serviced. Some buzz & some are quiet, the main thing is that the internal valve spins freely & doesn’t stick.

On the Purge Control Valve’s I’ve always replaced them with the Hyundai part & never have a problem after that.

 

I would be suspicious that the "chattering" noise you are getting under load is detonation. the knock sensor functions as a way for the ECU to watch for detonation and then alter running condition to stop it and prevent it. Detonation is most often caused by an lean condition, allowing pre-ignition of the fuel charge.

P0441 is a purge flow code, which could cause your Lean codes on both banks. Have you checked the function of your purge control solenoid? It is mounted on the drivers valve cover, rear of the throttle body and lateral to the IAC. I would check all wiring in that area to make sure something isn't wrong there.

The knock sensor code is really only going to set if you have a bad sensor or wiring controlling the sensor. You'll have to inspect and report back. Diagnostic flow for that basically says swap in a good unit and see if it goes away.

If the connector for the IAC is on tight, remove and clean it and reinstall and see if that code comes back

 

OK, to respond:

I'll order a knock sensor as they're cheap and replace that first to see if detonation is the issue (is the as known as pinging?). Before I crawl under the car, online I notice that there are two types: one with a pigtail connector and one without, i.e., the connector is built right into the sensor body. Which version do D2's have? I recall it being the latter, i.e., no pigtail.

Re. the IAC connector, full disclosure: when we reassembled the engine after the rebuild, my son (he's not on this forum so he can't defend himself), lost the metal spring clip on the connector, so it is just pressed on with dielectric grease (no way to tie wrap it on cleanly). That said, it hadn't had a problem in 30K miles, so why now?

The purge valve is 4 years old -- when we reinstalled engine we replaced it with a new Hyundai branded version, so maybe it's time to renew it. Anyone have the the part number handy?

No one thinks the P0505 IAC is an issue otherwise? Used ones are $30, new Bosch $180. Hate to start going too far down the "throwing parts at it" too soon.