I have a p0300 code on my car and i just had work done on it and it wasnt running bad before the work now it is is that the shops fault

we can't tell you what you can do, lacking skills and tools and spares.
I can tell you what a shop does. sure.
P0300 means all cylinders of the engine are missing,
means (physics) weak combusting on all cycl.
bad spark all or bad injections to all (lean) or engine cam out of time?
P1 codes are factory only codes. Jag codes
P1000 means car is not ready for smog tests, the , onboard readiness is not complete, means drive for a day or 2 and is caused by scan tool DTC reset or battery on car went dead or was disconnected.
next P1316 _
Misfire Excess Emission, get the shop to find it.
there are a battery of test to do.
even low fuel pressure can trip p0300.
goes lean ,combustion goes weak and BINGO gross misfire.
or bad spare, but how can all fail and not get one cmp or ckp errors>?
bad fuel> too. put diesel in the gas?
park parked over 1 year or parked less, with 1/8 tank for long long months?
we can not guess history of any car.

What's the fuel pressure? Any vacuum leaks?

What are the OBD2 system fault codes

https://www.obd-codes.com/p0300

P0300 OBD II Trouble Code Random Multiple Cylinder Misfire Detected...


Autolite Challenge Series P0300 Engine Misfire Diagnosis

How To Fix P0300 random misfire codes in your car ...

? 2:56
https://www.youtube.com/watch?v=OyvdWeyDHf4
Feb 5, 2010 - Uploaded by Scotty Kilmer
Scotty Kilmer, mechanic for the last 46 years and counting, shows how to fix your car if the check engine light ...

P0300 - OBD-II Trouble Code - RepairPal

repairpal.com > Encyclopedia > OBD II Codes

OBD II Fault Code. OBD II P0300. Fault Code Definition. Random, Multiple MisfireDetected. Symptoms. Check Engine Light flashing; Rough running, hesitation ...

P0300 - Check Engine Light Diagnostic Trouble Code ...

https://www.engine-light-help.com/P0300-check-engine-light.html

The misfire detection monitor, a software strategy built into the computer, is designed to detect an engine misfire. The computer can also normally identify the ...

Random-Misfire Page

www.random-misfire.com/

code p0300 refers to random/multiple misfires detected===causes --spark plugs-- HT leads --injectors --coils--low compression--- ECM
While it is common to jump on the plugs ht leads band wagon it is also very possible that the injectors are not working properly because of insufficient fuel pressure . Have a fuel manifold pressure test done to check pump/regulator / filter problems first

http://www.permoveo.ltd.uk/tabid/122/OBD-Error-Code/P0300/Diagnostics/Isuzu/Default.aspx My guess would be bad plug, lead or coil. Does it miss reguly if so mechanic will be able to diagnose. trouble is they need it when it is faulting

You will not damage anything, as the system is designed to go into 'Limp Mode' with reduced power if engine managment detects a serious fault that could compromise a emission related component.

You will notice this drop in performance and therefore seek help at your local VW shop or dealer.
If the vehicle is still running normally, then the fault is a 'soft code' or one that may be intermittent.

The lamp ( MIL = Malfunction Indicator Lamp.) can come on for any number of reasons and no drivability problems encountered. The ECU or on board computer will store the fault as a code to be extracted with a scanner plugged into the OBD port under the drivers knee panel ( USA models.)

Have a shop run a scan on the codes stored and let me know what the numbers are. Some shops can only pull power train codes and not body codes. I need to have all the codes stored so I can advise you as to your options.

One of the most common codes will be the P0300 code indicating a random miss fire. This is caused by water in the fuel, bad spark plugs, bad plug coils or engine valve problems.

Awaiting your reply.

P0300 indicated a multiple cylinder misfire. Typical causes are vacuum leaks, bad plugs, wires and/or coils. Could also be a dirty MAF. From what you describe it could also be the seal between the air cleaner housing and the MAF. Make sure the o-ring is not out of place and dry. I put some silicone lube or vasaline on it to help seal things up. That fact that it acts this way when cold points in the direction. That's what I would check first. Let me know how it works out.

For p0300 ,p0240 on chevy tahoe 00- 06 check a wire going along with the battery ground to the engine block thre should be a high resistence on the small wire ,it gets corrode over time ,it should be located on underneath of the driver side engine,