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Car shakes in idle but only when brake is "partially" depressed

I have a 2000 Nissan Maxima. When I am driving real slow – easing to a stop at a light or easing to accelerate from a stopped position – my car shakes. If the brake is totally depressed and the car is at a full stop, there is no shake. If I am driving – even at a very slow speed, there is no shake. However,if I just ease my foot off the brake a teeny-weeny bit, the car shakes.

It’s the sort of feeling you get when easing a clutch a little too fast on a stick shift (this is an automatic shift).

It’s also a similar phenomenon you get when the engine is sputtering and trying to die.

This is neither of those. The engine doesn’t falter, the tires are 4 or 5 months old (the shaking just started in the last few weeks).

I took it to a mechanic recently to have a new headlight installed and to check out the “Service engine soon” light." He said the light was related to some kind of sensor but he wasn’t sure when it was so he reset it. The light came back on within a few hours after that.

I saw a similar posting that referred to a bad engine mount. Could that be it? Or could it be something with the transmission? I have no problem driving the car any other time.

I’m going to take it back in to the shop but I’d like to have a better idea what to tell them.

Any ideas?

Step 1 find a new mechanic. Step 2 ask them why the service engine soon light is on.

If this car has a brake booster it might have a small leak in the diaphragm that will cause this problem.It will be same as a broken pvc valve tube whan brake is depressed.

Disconnect and plug the brake booster and see what happens…(You will lose power brakes)

+3 for the brake booster.

The extra air, from a leaking brake booster, might be making the engine run SMOOTHER! This would be the case if the engine were, otherwise, running too rich.

ADDED: To clarify, a rich running engine needs to be diagnosed, and repaired. Your vehicle has, at least, two problems.

Thanks all. Based on your feedback and other info I’ve been able to find, the “Brake Booster” seems to be the culprit here. Since I’m not handy around cars, I’ll take it to a local mechanic. If indeed it turns out to be a brake booster, what kind of costs am I looking at? Do I need to replace the booster or a hose or can anything be patched. I’d like to go to the mechanic feeling somewhat educated in the matter?
Also, how dangerous is this? Check one of the following:
A. don’t drive it til you get it fixed
B. you’ll be okay for a while, but don’t ignore it
C. you’ll break something else if you continue driving it
D. drag your feet instead of using your brakes

Brake booster is a fine guess. But before you do anything else you’d be better off finding out what code(s) the engine is throwing. Maybe the mechanic put it on your invoice, or maybe s/he’s remember. Or many auto parts chain stores read them for free. Pull in, ask them to read, write down the exact code(s) - format P0123 - post it.


Good point. The invoice shows the code as PO1356 Undefined code. I can’t seem to find it on the Internet.

I’d double check that code. It should be a P followed by 4 digits. There are no “PO” (pee-oh) codes and as far as I know there are no 5 digit codes either (if it was P-zero-1356). So you have one too many characters. Unless you really had 2 codes - P0135 and P0136. Both of these are about readings from O2 sensors - but someone smarter than me would have to say if or how this could produce a problem connected to braking.

Of course, the codes could be unrelated.

It is the case, however that if your O2 sensors are getting readings out of line for some reason (not necessarily that the sensor is bad) this will mess with the fuel/air mix as would a leaky brake booster.

I’d clarify the codes.