Oil pump? Afm Cylinder 4 misfire

[My07sh*tbox]

Newb here. My 07 Yukon has been in the shop over a week now. (Local mechanic)  Have had the vehicle about a year, changed the oil regularly, replaced oil sensor and sending unit due to the infamous low oil pressure warnings. Thing has driven great until randomly one day she started idle hard and misfired when going into first. I changed all sparks, plugs. No change. Shop is saying my oil pump is completely shot..?  I've had no noise no other signs of it starting to fail. My sensor would routinely go off a month prior to oil change being due. Do these things really just crap out?  Could it be related to my misfire? They are checkin the head on that, otherwise she drove normal and smooth once I go over 15mph. If she survives and my wallet doesn't get drained, I will be disabling the AFM. 

[bg1988]

wht are the codes?

[My07sh*tbox]

 

21 hours ago, bg1988 said:

wht are the codes?

P0400 and P0521, the oil code only came on sporadically. 

[dsr611]

You said they changed the oil pressure sensor and sending unit, but did they check/clean/replace the filter under the sending unit?  If not, I'd replace the filter under the sensor before doing anything else.

 

P0400 indicates a malfuntion with the EGR valve/wiring

P0521 indicates faulty pressure sensor/wiring/etc

[My07sh*tbox]

On 7/5/2019 at 11:48 AM, dsr611 said:

You said they changed the oil pressure sensor and sending unit, but did they check/clean/replace the filter under the sending unit?  If not, I'd replace the filter under the sensor before doing anything else.

 

P0400 indicates a malfuntion with the EGR valve/wiring

P0521 indicates faulty pressure sensor/wiring/etc

Yep,they replaced the screen last time, the heads goin to the machine shop Monday, they don't know if it's cracked or a valve or what. I'm familiar with the oil issues, which I hope I don't regret telling him NOT to put a new oil pump in. Guess I'll find out more Monday, tues. The misfire is something I've never delt with on this vehicle until now. Mechanic mentioned the engine is great. Crossing fingers. 

[swathdiver]

On 7/6/2019 at 4:12 PM, My07sh*tbox said:

Yep,they replaced the screen last time, the heads goin to the machine shop Monday, they don't know if it's cracked or a valve or what. I'm familiar with the oil issues, which I hope I don't regret telling him NOT to put a new oil pump in. Guess I'll find out more Monday, tues. The misfire is something I've never delt with on this vehicle until now. Mechanic mentioned the engine is great. Crossing fingers. 

So those are the only two codes and the shop pulled the motor apart???

[My07sh*tbox]

Lifter and head gasket,  oil pump shot. Just went ahead and fixed it. $1700 all together. Would have been more if it was a shop in my city.