engine stalls at idle, only after cold start, immediately after spark plug change (2011 v8)

[torontoben]

Hi

I got a cylinder misfire, took my 2011 v8 to a hyundai dealer. they changed all 8 spark plugs. they also found a small leak (P0456) in evap system. they did a smoke test and found leak at filler neck and fuel cap, replaced both parts.

as soon as i got the car back, with in a few minutes, at the first red light at idle, engine stalled. i put the gear to neutral, started the engine. it went fine.
it happened again later. i took the car back to the dealer, who basically said they cannot reproduce. this is the full report they wrote.

"vehicle was scanned prior for any engine DTC - None. Engine operation - Good. Did not misfire or stall out once. Engine misfire graph Cyl. 1-8 no misfires. Could not get vehicle to stall in stop and go traffic at different speeds. unable to duplicate concern"

They actually had my car for more than a week due to someone quitting and not letting me know. I just said give my car back.

Again, immediately my engine stalled at the first red light. once I restart the engine, there's no problem.

summary
1. got new spark plugs, did a smoke test, found a leak at filelr neck and fuel cap, replaced both
2. ever since the dealer did this, engine stalls if i do A) do a cold start, AND B) within a few minutes of a cold start, come to a complete stop.
3. if engine has been running for a while, it does not stall at red light. and engine only stalls when put to idle, never when running.

i really don't want to go back to that dealer again. what can this be?

 

[mikec]

My 2009 V8/Tech was doing the same thing: stalling when coming to a total stop... it would do it once, maybe twice, a 3 to 5 minutes after cold engine start-up. Once past 10 minutes or so it was fine. The dealer had the car for a few weeks and could not reproduce the problem while they had their scanners hooked up... when they tried to move my car one time - and having just disconnected the scanners - it died for them. They eyeballed and re-seated pretty much every electrical connection under the hood and it seemed to help. For a few months. Then the bug returned and got MUCH worse too - stalling and misfiring at random times; later that day it belched smoke out the tailpipes. Towed to the dealer and eventually they decided it was a dying PCM - Powertrain Control Module, what most folks call the ECU. Over two grand later - and roughly a month later as they couldn't locate a replacement part - I got my car back and so far it's been good. See the thread titled "Sudden Engine Cut Off!" for my story and others.

By the way, no OBD-II error codes were generated during the initial stalling issues. The second round, when the PCM was really whacked, would spit out misfire codes and one other odd one that I can't remember now. Another known "just stalls" issue is the crankshaft position sensor crapping out. The PCM only checks it at startup; if it fails later there won't be an OBD-II code. The PCM programming isn't smart enough to say "hey, I got multiple camshaft sensor pulses with no intervening crankshaft pulses. Either the camshaft sensors are generating random noise or the crankshaft sensor is dead. Either way, set an OBD-II code." The crankshaft position sensor is in the bellhousing, directly behind the engine. It is visible from above: open the hood, remove the plastic engine cover, and then stand at the driver fender near the hood hinge and look straight down at the back of the engine. you'll see a small plastic blob with one screw; the wire leading from it heads upward and comes to the top/rear of the engine. Wiggle that while the engine is idling to see if the sensor or its wires are flaky on your car. Tap the sensor with a wooden stick too.

mike c.