I tried searching the forums for my issue but wasn't able to come up with anything.

When I push the gas pedal down the car shakes (almost like if you were to horsie your car). My car also shakes when I let go of the gas pedal, sort of feeling like you went over several small bumps in the road. I tried pushing/releasing the pedal at different speeds/RPMs, but the issue still occurs. At first, it seemed to have only occurred in 1st and 2nd gear, but I'm starting to feel the car shake when i push/release the pedal while in 3rd gear. Please keep in mind the car only shakes while I am pushing/releasing the gas pedal, not while I already have the gas pedal consistently pushed down. Does anyone know what the cause of this might be?

 

dealership will

 

How many miles are on your car? Maybe a misfire?

 

i think about 26k

 

it doesn't sound good your under warranty take it to the dealer.. get a tech to ride with you

 

I also have a similar thing, but it's very minute. I've always had it and attributed it to the extremely soft OEM engine mounts. I think it's just the engine rocking back and forth from having forward force (from acceleration/holding speed) to deceleration/engine braking.

West way to get it to stop, don't be so herky jerky with the gas pedal; learn to smoothly apply the gas and smoothly release.

And that's assuming what i'm talking about is the same as what you are talking about.

 

I get a shake in 2nd gear, but that's just a combination of engine braking, throttle, and a quirky drive-by-wire throttle that seems to over-react at times.

If the shake is more than a feeling of the throttle suddenly cutting or opening (i.e. a real back and forth motion that makes more than one big jerk and a few minute vibrations at most), then I'd have it checked at the dealer; otherwise I'd say it's normal, kinda like what djct_watt said... just the neoprene rubber mounts doing their soft flexy thing.

I heard that going to a polyurethane (?) or some other plastic type mount helps.

 

it happens even when i push the gas pedal down/release really softly.. the car shudders back and forth about 2-4 times. i'm definitely gonna bring it down to the shop, but was curious if this was gonna cost a lot of money and whether or not it would be covered by warranty. otherwise, i'd go to my own mechanic.

 

It will cost some amount to diagnose it, but that will be covered under warranty if the issue is under warranty. If the issue is found to not be under warranty you will have to pay.

 

This sounds like an engine misfire. Kinda like when an injector doesn't spray or an ignition coil doesn't fire...
Time to take it to the dealership!

 

Wouldn't a misfire typically give a CEL code? Even if not constantly turn on the CEL, at least do it once or twice, just enough to have the error code logged?

Anyways,
If it's misfire, it's probably just a plug or wire. Should be a cheap fix, do it yourself if you know which cylinder is misfiring and save labor costs. Otherwise it's a coil/distributor or some such (don't know what this car uses to build up spark volts yet), in which case it's a hefty replacement cost.

If you have a handheld diagnostic, try plugging it in even without a CEL, when I've had ignition problems there was usually a code logged, even if no consistent warning light.

 

my last car did that...i had an 05 mazda3 and it'd shake violently all the time when id release the gas. it'd stall out of nowhere while i was driving down a highway, at lights, i almost got rearended 5 times. mazda couldnt figure out the problem. i had it in at least 10 times to get fixed. i was about to lemon law it...and it got totaled.

 

Try clutching in as you gas out. Does it still happen?

 

hmm ive been having the same problems recently. just started maybe 2 weeks ago. i havnt installed anything to catalyze this problem, so ive been wondering too. most of the time for me, its at 1st and 2nd gear when it happens. just like nu-nu said, when i let off the gas or push it in, it seems to rock back and forth, and im applying the gas slowly as well.

 

Question: Could this be clutch related?

 

does it do it if you are not moving and just rev the engine? If it is a missfire it should be noticeable. Feel/listen for hesitation on a quick rev of the motor.
Have you noticed any decrease in gas mileage?

 

I don't think it does it when i'm not moving and just rev the engine. I'll have to double-check again when I go to work in the morning.

I don't notice any additional delay, except for the (drive-by-wire?) throttle that the Scion tC has. It happens if I push/release the pedal hard or soft. Sometimes it's really noticeable, other times it's not.

Mileage has been consistent for the most part, I believe.

 

How long have you had the car and is it manual?

Sounds like you are popping the clutch alot. New to driving a manual? Try letting of the clutch really slow and see if the bumps get less.

 

^ agree with nu-nu

if im just sitting there, it revs smooth. its manual and had it since late '06. it happens even if im already in gear, and let off the gas, or push in from not having the gas in. 3rd gear and above it unnoticeable. and same with nu-nu, im getting consistent mileage.

 

I've had the car nearing 3 years. It is manual, and the issue occurs when I'm already clutched out, and I am just pushing/releasing the gas pedal.