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Matt
Matt, Engineer
Category: Chevy
Satisfied Customers: 21622
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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I have a 2008 Chevy Malibu ls and I changed the upstream o2

Customer Question

I have a 2008 Chevy Malibu ls and I changed the upstream o2 sensor cleaned fuel injector and changed the down stream converter and still loses power driving and trouble shifting especially going uphill I have seen the eng power reduced too many times and I don't understand why ...any recommendations????
JA: What happens when you step on the gas? Do you notice a rough idle?
Customer: Definitely a rough idle and little to no power pressing on the gas
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Yes I would like to fix myself and I cleaned fuel injectors changed o2sensor and converter (downstream )
JA: Anything else you think the mechanic should know?
Customer: Has 86000 miles on it
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: 1 year ago.
Category: Chevy
Expert:  Matt replied 1 year ago.

Hello

This sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.

1st thing to try is to remove the fuel filler cap and then flick the ignition on whilst listening for the brief ‘buzz’ of the pump

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,

Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

You can also get this issue with contaminated fuel , if there’s water or dirt in the tank then either the petrol floats on top of the water or the filter sock on the pump is choked up – so if the other things check out then I’d consider pulling out the fuel pump and cleaning the filter sock

Expert:  Matt replied 1 year ago.

Hi

do you still need help?

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