306 asi Air box

[Jimy]

Hi iv got a 306 xsi. When i floor it past 4grand it stays flat and stops picking up power any advice on what this could be thanks.

[Mighty306]

Could be a lot of things tbh. Since you mentioned the air box in the title you might as well check the condition of the air filter first.

After that I'd say you'd need to do some diagnostics to narrow it down. Any other symptoms?  Does it seem down on power with hard acceleration below 4k, esp up a hill? Are you getting a check engine light?

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The other v quick check you can make btw is whether the adjustment on the throttle cable (by throttle body) is correctly set. If not the throttle body butterfly won't fully open. It should be set so there's no slack n butterfly will open with slightest depression of accelerator.