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Gary, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1114
Experience:  Senior Technician
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Chevrolet: Replaced ac compressor on my 04 trailblazer trying

Customer Question

Replaced ac compressor on my 04 trailblazer trying to recharge act idles up and down almost to a stall took off intake cover and cleaned throttle body but that did not fix problem error code po303
Submitted: 2 years ago.
Category: Chevy
Expert:  Gary replied 2 years ago.
P0303 is Cylinder 3 misfire.
Is the engine running rough?
Does the DTC come back after you clear it?
Customer: replied 2 years ago.
Yes I cleared code engine will run fine for about 10 minutes than starts to idles rough and whe Africa is on it goes up and down when compressor come on and I get same code
Expert:  Gary replied 2 years ago.
I would be looking at why it starts to idle rough first.
Pull the spark plugs for inspection, swap 2 & 3.
Swap coil 3 with coil 1, now the parts from cylinder 3 are in 2 (spark plug from 3) and 1 (coil from 3).
Make sure the previous DTC is cleared.
Start the engine and when the misfire reoccurs see which cylinder now logs the DTC.
Customer: replied 2 years ago.
I didnt do anything yet just got error code po300 and po526
Customer: replied 2 years ago.
Any thoughts or should i still check the same thing
Expert:  Gary replied 2 years ago.
How old are the spark plugs?
I would give the engine an upper cylinder clean (combustion chamber cleaner).
P0300 is engine misfire but the ECM doesn't which cylinder/s.
P0526 could be related to your A/C as below:
Customer: replied 2 years ago.
Ok that sounds good where do i add the combustion cleaner to the upper cylinder (also dont know when plugs were replaced)
Expert:  Gary replied 2 years ago.
This is the best product that I have used:
And then replace the spark plugs if you don't know how much service they have done.
Customer: replied 2 years ago.
Ok used combbustion cleaner it helped alittle but did clearor code i am going to do it again but they tell to put it in at vacuum a brake booster or fuel pressure regulator but i could not get a vaacuum conidtion at reulator could this be my problem
Expert:  Gary replied 2 years ago.
Hi again,
Good to hear you may be on the right track.
Did you use the product as described and saturate the engine, and leave it sit for a while to do it's job?
Did it blow a lot of smoke for a while after start up?
With the vacuum hose off the regulator, there should be a vacuum leak from that hose with the engine running.
If not you have a blocked vacuum port in the inlet manifold.