Engine problems - loss of power

[Brissy]

Garage mechanic unable to fix problem with my Yaris.- automatic

Drives fine for a few minutes. Once engine warms up, the car loses power, revs drop, car back-fires and slows to a stop. Worse when driving up hill. If I kick accelerator to floor, the car revs shoot up, drops down a gear and will drive a few metres before losing power again.
Have tried driving in 3rd gear. No better.

Car has had air sensor module replaced, fuel module replaced (mechanic tells me this includes fuel pump, filter, etc). What next? Getting to be v costly.

The car is 12 years old with 170,000km on the clock.

[atomic_hoji]

Ya, no fun when the solution seems to be replacing parts until the problem goes away..
Any MIL/CEL lit on the dash? Maintenance or parts changed on the car? Automatic or manual transmission?

-- Adam

[Brissy]

Car is automatic transmission.
No fault lights coming up on dash
Mechanic says no faults coming up with the computer diagnosis.
Otherwise, all maintenance done by garage when due. Do not remember any major parts replaced recently.

The backfiring is really odd. It seems to be deep inside, not at the exhaust, if that makes sense.

As you can tell, I have no mechanical knowledge.



Asking Dr Google, and one suggestion is an upstream exhaust leak. Anyone have any opinion on this? The description of the 'popping sounds' when the car backfires sounds right. Not sure if my Yaris is burping or farting.

[atomic_hoji]

lol - definitely farting.. it'd be a pretty big problem if it was firing out the intake.

If the car is idling and you pop the hood is there an exhaust smell under the hood or a noticeable 'fog'? When I installed an exhaust recently and didn't have the flanges lined-up and tightened enough there was noticeable haze and smell under the hood.

Sounds silly, but nothing shoved in the exhaust pipe 'eh? The back pressure would cause an exhaust leak and it would definitely rob power... just thinking, occassionally people do stupid s* to folks cars..

Without a code being thrown it's tough to say. Something that substantially impacts power, but isn't serious enough for the ECM to kick a MIL/CEL is odd. What engine is in your car? I notice you're in Australia, probably different choices then the 1NZ we have up here - maybe worth a Google if there's a common power problem with the <insert engine code here> model..?

-- Adam

[Brissy]

Thanks Adam, Will try your suggestions tomorrow and report back

[williew2]

blockage or disintegration in one of the cats maybe, causing exhaust blockage. or check intake for colapsed hoses, vaccum line loose maybe..

[Brissy]

Latest update. Been checking out your suggestions plus trawling google. I could not identify problem. Went back to garage and spoke with mechanic. He thinks it is the coils. Will be replacing the coil packs and the plugs. Will let you know if that fixes the problem. Figure it must be close. Not much else to change. Almost be a new car by the time he has finished with these repairs (as in my Grandfather's axe)
Thaks for all your suggestions

[leturkish2005]

Hello Brissy, i have exactly the same issue than yours
Did you get the solution to get your car done ?

Thanks
KR

[Brissy]

HI KR, I drove the car to work and back today without any issues. It seemed to run smoothly. The mechanic had changed the coils and the spark plugs. I wish he had suggested this before he replaced the fuel module as this repair was half the price. ($750 vs $1500ish).
Reading up on failing coils symptoms, this does sound about right. Although I believe many problems will give these types of symptoms: losing power, mis/back firing, etc.
Good luck with your Yaris.
Lise

[Brissy]

Well, that was short lived.

Drove a few short journeys before the problem started up again. So the car is parked up again until we can come up with another idea.

More back-firing from inside the engine and loss of power.

Completely at a loss of what to do next.

[Fluxtasy]

could it be the O2 sensor? When this part goes faulty, you get lots of weird issues like rough idling, loss of power, etc.

[Brissy]

Fluxtasy: could it be the O2 sensor? When this part goes faulty, you get lots of weird issues like rough idling, loss of power, etc.

Not sure. The entire air module was replaced. Hope that would cover that one.

Latest suggestions have been:
1. Dirty throttle- clean with Nulon cleanser additive and a full tank of 95 octane fuel
2. Problem with the timing chain - when engine is cold the chain is advanced, but not when the engine is warm, hence the symptoms only occurring when the engine is warm
???

Still none the wiser. Will do the fuel additive attempt first. Was told that the timing chain issue is an auto-electrician's job which is why the mechanic would not be able to help.

[CoryM]

Check the catalytic converter. The material inside is probably broken and when you hit a bump just right it plugs the exhaust. If you bump the cat with a rubber hammer or your hand and you hear something loose inside, it needs to be replaced.

[ErniYaris]

Hey Brissy, old thread I know, but did you work out the problem? Mine is doing very similar things and mechanic not sure where to start. No codes.

[ErniYaris]

Ok, so my problem ended up being the O2 sensor before the cat converter in exhaust. Mechanic had to call in his efi diagnostics guy to collect data when car played up (after it has driven for a while). The car now runs WAY better than ever before - since we've owned it.