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Gary
Gary, ASE Certified Technician
Category: Chevy
Satisfied Customers: 744
Experience:  Senior Technician
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I throw a po305 misfire code when engine down shifts going

Customer Question

I throw a po305 misfire code when engine down shifts going 75 miles per jour or will throw code when letting off throttle getting off of the freeway
JA: Have you seen the misfire code before? Has the car been stalling?
Customer: No the the suburban does not stall it starts great and even idles good
JA: What is the model/year of your Chevy?
Customer: 1999 5.7l
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Yes , just trying to get ideas qhee to look
JA: Anything else you think the mechanic should know?
Customer: I thought i had a bad air leak between the massairflow and throttle body but i sealed it so that has been cured
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Chevy Mechanic about your situation and then connect you two.
Submitted: 4 months ago.
Category: Chevy
Expert:  Gary replied 4 months ago.

Hi there,

I would swap the spark plug, spark plug lead, coil, and injector to other cylinders.

Plug from 5 to 6, lead from 5 to 7, coil from 5 to 8, injector from 5 to 1 for example.

Clear history code P0305, then roadtest again until the misfire code reappears.

Then hopefully the faulty cylinder now shows up as one of cylinders you have swapped parts to.

Gary

Customer: replied 4 months ago.
I would have to remove the upper plenum to switch injector to a different hole and has the new updated spider
Expert:  Gary replied 4 months ago.

The injector would be the hardest to swap.

If you want just swap all the ignition components first to prove them.

If it then reoccurs as P0305, you know all ignition parts are ok, and need to swap the injector.

I know swapping injectors around is a pain, have done it on many cars many times.

I feel your pain.

Gary

Expert:  Gary replied 4 months ago.

Hi again,

Do you need any further help?

I hope my advice has been of assistance to you.

Kind regards

Gary

Expert:  Gary replied 4 months ago.

Hi again,

Have you had any success at your problem?

I hope my advice has been of assistance to you.

Kind regards

Gary

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