Nissan Repair: car shaking and check engine light blinking, nissan pathfinder, brake booster

Question
QUESTION: I have a 98 nissan pathfinder.
When I apply the brake, it started shaking and the check engine light is blinking.
What could be the problem?

ANSWER: Hi Justin -

If the car does not shake when the brake is not applied, try checking the brake booster. Are the brakes harder to press than before? Do you have to refill brake fluid on a regular basis? There may be an internal vaccuum leak in the booster.

Please get back to me on my questions so we can go on with the diagnosis -

Thanks!
aloha
calvin

---------- FOLLOW-UP ----------

QUESTION: Thanks, Guys.

The car does not shake when the brake is not applied. The brakes is fine, not harder to press. No, I have not refill brake fluid for a while.
I can hear some kind of noise from muffler.
This happened before without the check engine light blinking. But after I stopped the car, the problem is gone.
This time, when I restart the car, the light keeps solid.
After stop few times at traffic light, it shakes again and the check engine light blinks.

Appreciate for the help!

Answer
Hi Justin -

Please do one more test for me. Remove the vaccuum hose going to the brake booster (should be about a 3/8" line), and plug it.

Then start the car and press the brake (the brakes will be hard to press because there is no power assist).

Please get back to me with the results -

Mahalo
calvin