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Yaris '07: Shake, Rattle, and No More Roll

G’day, writing in from Down Under - (we’ve heard about the show down here)!.. Mates, I have a Toyota Yaris '07 … The car has been running pretty rough and ready over the last few weeks… During idle, it started rattling & shaking pretty hard… this progressed with the add-on feature of changing revs during an otherwise steady drive… It chose the (in)opportune time of driving with our 3 year old son, grumpy at that time, down heavily trafficked busy roadways during the holidays and stalled 3 x times… It is in the garage / service center for the 2nd time … They are stumped. They’ve checked air, fuel mix, filters, injectors, spark plugs, etc., basics. Computer diagnostics show nothing (briefly showed fault at Cylider #4 but then that changed and now showing nothing). Toyota Technical is (apparently) stumped. They are talking about needing to order a new computer from Japan (minimum $1200 just for the part).

Any thoughts or experience that I can pass on to the mechanics…?

How many miles? Poor idle could be intake gaskets.

Have they tested it with a vacuum gage? These symptoms have all the characteristics of a classic vacuum leak.

Have they tested the fuel line pressure? A dying fuel pump is a possibility also.

One thing you could try is replacing the vacuum lines one-by-one (to prevent getting the lines crossed up). Vacuum line by the foot is dirt cheap.

Look for other sources of vacuum leaks. Spray possible leak areas with a touch of starter fluid. If you have a vacuum leak, it’ll draw the fluid in and the engine will responds by momentarily speeding up.

Thanks guys, I will forward your thoughts to the mechanics; really appreciated. (They swapped the catalytic converter with another used vehicle but say that it did not rule out anything - both cars worked with either when tested and they’ve put back original parts in each vehicle - now they’re stumped again as they’re having trouble eliciting the symptoms … ?!). Oh - mileage: 60K km or 37K+ miles

The garage service centre had me pick up the car and - no surprise! - same symptoms… rattling at idle, and then stalling when at the lights for an extended period. I called the garage and they suggested changing O2 sensor but they stated they had no confidence that this might work. …

I hope they didn’t charge you.
I also hope you have an alternative garage to try.

This should not be rocket science to fix, but it WILL require some diagnostic skills and equipment. Are you comfortable with “non invasive” tests, like vacuum testing and pressure testing? I’ve never been to a parts store “down under”, but I assume they’re stocked similar to ours, and if so testing equipment and instructions should be readily available. Equipment like a vacuum gage and a fuel pressure tesr kit are inexpensive and simple to use.

@Pizazz has anybody cleaned the throttle body yet?

We just repaired some guy’s 2002 Honda Accord.
He had complained that it would run really rough and stall at stoplights
When we got to the car, it barely started and the idle was very low, about 500rpm
I had never even opened the hood on a 2002 Accord before
I suggested to clean the throttle body, because the check engine light wasn’t illuminated and there were no obvious vacuum leaks
The car’s idling nicely and he was able to drive it home

Maybe you guy’s will think I’m getting sidetracked, but I believe there’s no harm in checking the basics first, especially if it only takes 5 minutes and a can of throttle body cleaner

Thanks, I’ll mention all comments to them - about to take it back, round 3
(Engine light is not illuminated on the Yaris, either)

To “same mountain bike” - completely into the basics and non-invasive around here, whatever works! a mate of mine checks the vacuum hoses by sucking on the ends- checks the seal on his lips before he investigates further! The Aussie way…

That’s pretty low mileage for a 6 year old car. The first thing that comes to mind is bad gas or contamination from ethanol from extended time sitting. Fuel system cleaner ?