Sudden RPM drops, sometimes dies on idle when cold

[ryushe]

As some of you may remember, I had the head gasket replaced about a month ago. First week after has been great, no issues whatsoever.
However, somewhere during week two I've been getting odd idling issues where the car will drop RPMs from around 650-700 down to 100 RPM when cold. Sometimes it just judders and comes back, but a few times so far it's simply died on me. Starts right up and drives fine right after for miles and miles.
Today however it died on my again, and after restarting power steering was out. Turned car off and back on, and power steering was back.
And I might be paranoid by now, but it also sounds like there's some ticking noise coming from the engine.

As all of this started happening after the replacement of the head gasket I can't help but wonder if it's related, but I feel I need a bit of a decent idea / argument before heading back to the shop that did the replacement.

Anyways, I pulled codes from the car today, and the below is what I got, which has me plenty worried
Cleared all codes as well, and want to see what I get tomorrow after I clean the MAF, and check for vacuum leaks.

5000km ago: new water pump (Pierburg), new thermostat
1000km ago: new head gasket + all seals and other related gaskets.

Any suggestions what else I could be checking, or should ask the shop to check if it's plausible it's related to the head gasket replacement?

==========
CODE: 2A96 (CRANKSHAFT SENSOR, TOOTH FAULT)
Status: Pending fault present, Validated fault has been present during this drive cycle

CODE: 2E85 (ELECTRICAL COOLANT PUMP, COMMUNICATION)
Status: Test is inhibited by other DTC

CODE: 2C6A (LAMBDA PROBE BEHIND CATALYTIC CONVERTER, MUDDLED)
Status: Test is inhibited by other DTC, Validated fault has been present during this drive cycle

CODE: 29F4 (CATALYST SYSTEM EFFECIENCY BELOW THRESHOLD (BANK 1))
Status: Pending fault present, Validated and stored in non volatile memory

CODE: 29F5 (CATALYST SYSTEM EFFECIENCY BELOW THRESHOLD (BANK 2))
Status: Pending fault present, Validated and stored in non volatile memory

CODE: 2E81 (DME: ELECTRICAL COOLANT PUMP, SPEED DEVIATION)
Status: Pending fault present

CODE: 2EA1 (OIL CONDITION SENSOR, COMMUNICATION)
Status: Test conditions are met, Validated and stored in non volatile memory

CODE: 2E84 (ELECTRICAL COOLANT PUMP, COMMUNICATION)
Status: Test conditions are met, Validated and stored in non volatile memory

CODE: 2F63 (BRAKE LIGHT SWITCH, PLAUSIBILITY)
Status: Test is inhibited by other DTC

CODE: 2E7C (BSD BUS COMMUNICATION FAULT)
Status: Test conditions are met
==========

 

[colb]

Check all the rubber vacuum pipes and intake boots for holes or splits since the head was removed all of those would have been taken off, check the rear underside edge of the intake manifold for lost blanking rubber plugs, they perish and fall off. Not sure why you would get a crankshaft tooth error, they shouldn't have had to touch that with a head job. Clear all after the air leak check and run the car see what comes back.

 

[Mike6]

Just a thought, how old is the battery. If it's say more than 5 years old try a new one in the first instance.

 

[ryushe]

Battery was checked and is fine. Couldn't figure this out, so the shop is now looking at it.
They now suspect one of the 1 1/2 year old lambda sensors, and recommend replacing them all. Something about getting incorrect readings leading to incorrect mixture being set resulting in air/fuel starvation.
Not sure if I buy that, but we'll see what happens.

 

[ivanchen1211]

Clean all codes and run and read code again. Post result.