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Old 06-18-2017, 09:50 PM   #1
Cigar_Maverick
 
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2007 Yaris Loss Of Power Over Bumps

Hello,
I'm beginning to diagnose what I THINK (always dangerous) is an electrical or fuel delivery issue. What I am experiencing is a loss of power if I hit some "sharper" bumps. An example of when this happens is if I turn off of a paved road onto a gravel road and hit some washboards under normal acceleration, I experience a loss of power in the engine. It doesn't die, just seems to loose about 50-70% of the "thrust" it normally has. As soon as I get past them, it picks back up again. SOOOO, my thought was a loose wire of something like that. I brought the car in the shop tonight to see it I could make it happen while sitting here idling. I lightly tapped on things with a rubber mallet and wiggled wires. I also pulled the plugs to see if I could see anything. Nothing stood out.

Now, this MIGHT be related to the "P0420 Catalyst System Efficiency Below Threshold Bank 1" check engine light that seems to indicate a worn out catalytic converter that came on a month ago. Maybe something is loose in there and blocking exhaust flow?

The only other thing I could think of was that it was a fuel delivery problem. About a year ago I replaced the fuel pump. I wriggled the wires at the connector on top of the tank hoping that it was coming lose. Nothing.

I don't know if it matters, but is is a manual transmission.

Maybe it won't fail unless it is under load?

I'm asking for help to find a starting place to figure this out. I'm a little worried that at some point it won't "recover." If there are any clarifying questions that need answered, let me know. I can always hook it back up to the diagnostic computer again at the local parts store to see if any other warnings come up.

Thanks in advance,
Russ
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Old 06-18-2017, 10:53 PM   #2
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Since you have that code, it may be your catalyst. Typically when they come apart you end up with a baseball sized lump of catalyst which is about perfect for plugging the exhaust. When the exhaust is cold, give the cat a thump with a rubber mallet. If it sounds like something is loose in there it's probably step one to fix.
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Old 06-19-2017, 04:41 AM   #3
dogsridewith
 
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Gets on it in the stutter bumps. gravel washboard

Cyclically losing traction, hitting the 6k governor, regaining traction...Hal going "What is this? Outside frequency parameter extremes for the throttle system envelope of my confirmation test program."
(edit: maybe it is doing just what we want? full power comes back as soon as smooth surface is encountered?)
Does the vehicle have traction and/or stability control?
(Gets on it in the stutter bumps. gravel washboard)
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Old 06-19-2017, 08:09 AM   #4
Cigar_Maverick
 
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Quote:
Originally Posted by CoryM View Post
Since you have that code, it may be your catalyst. Typically when they come apart you end up with a baseball sized lump of catalyst which is about perfect for plugging the exhaust. When the exhaust is cold, give the cat a thump with a rubber mallet. If it sounds like something is loose in there it's probably step one to fix.
I will give that a shot hopefully before this weekend and give a report back.


Quote:
Cyclically losing traction, hitting the 6k governor, regaining traction...Hal going "What is this? Outside frequency parameter extremes for the throttle system envelope of my confirmation test program."
(edit: maybe it is doing just what we want? full power comes back as soon as smooth surface is encountered?)
Does the vehicle have traction and/or stability control?
(Gets on it in the stutter bumps. gravel washboard)
That would be a simple explanation! However, no traction control on this unit.
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Old 06-19-2017, 09:17 AM   #5
dogsridewith
 
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Stability control?

Wasn't stability control mandated on all US passenger vehicles produced after some date? I believe this modulates brakes and throttle to achieve trajectories and attitudes Hal thinks the driver wants or are good for his health? (Where Hal may strive to keep the car aimed in the direction it is going...making opposite lock dirt tracking attitudes impossible? And cutting your throttle to prevent wheel spin?)
edit: oops! why did I just notice the thread Yaris is 2007...so no stability control? So what about something to do w/ wheel slip and the rev limiter?
(Very interesting problem.)
Like my 91 Corolla, these have large lifetime fuel filters...maybe they aren't. How many miles on the car?
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Old 04-09-2018, 05:28 PM   #6
Cigar_Maverick
 
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Been a LONG time since I updated this. I replaced the catalytic converter and that got rid of the engine light. I still eventually have problems where the engine seems to "cut out." If the car has traction control of any kind I don't know as I bought it used. However, in other cars with traction control, there is a "light" that tells you it is on. I've never seen this on my car, even when spinning the tires in snow. I kind of gave up trying to figure it out as I was not sure where to start. However, last Friday we had a WINDY day and the "cutting out" was at an all time high for some reason. When I got home I just popped the hood and started wriggling wires to see if I could make it "fail." I got video of this and I don't know if I was bumping the wireless throttle of what, but this video shows what it was doing:

2007 Yaris Cutting out


I checked all the plugs. They are good. Did I inadvertently bump something or did I find an ignition/wiring short?

Thanks,
Russ
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Old 04-09-2018, 05:49 PM   #7
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I can't tell what exactly I am looking at but it looks like the hose in the center of the camera shot is not fully on. It looks like the hose clamp is just laying there. Don't know if that has anything to do with your issue or not, just something that I noticed.
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Old 04-10-2018, 03:54 PM   #8
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Quote:
Originally Posted by NYC-SE View Post
I can't tell what exactly I am looking at but it looks like the hose in the center of the camera shot is not fully on. It looks like the hose clamp is just laying there. Don't know if that has anything to do with your issue or not, just something that I noticed.
In hindsight, I realize that my video was a bit zoomed in. LOL The loom I was wriggling was one that supplies power to the injectors and ignition. Follow the while line. I was wriggling it on the drivers side of the cyl head.



I will also check the hose clamp you mentioned. Would REALLY be nice if that was all it was. But I'll feel dumb for having had missed it.
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Old 04-10-2018, 08:33 PM   #9
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It's not traction control, the Yaris doesn't have it and if it did you always get the indicator light coming on in the dash when it's activated. Stability control wan't made mandatory in all new cars in the US until 2012.

Are you holding a cut wire in the video or is it a small hose? I'd suspect you have some frayed wiring in that harness somewhere that is shorting out for a moment when you hit a bump in the road or pull on the harness. Look for obvious damage first like, get a good light and mirror if you need it. After that take a close look at the connectors on both end of that harness for damage or corrosion.
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Old 04-11-2018, 11:38 AM   #10
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Quote:
Originally Posted by B.B._07 View Post
Are you holding a cut wire in the video or is it a small hose?
Cut wire. From something the previous owner had hooked up. I'll take it lose this weekend and make sure the original wire is OK. I don't know what it was from. Might just be one of those blue wire splicers behind where you can't see. No idea what it was for originally. But been that way for the two years I've owned it.








Quote:
Originally Posted by B.B._07 View Post
I'd suspect you have some frayed wiring in that harness somewhere that is shorting out for a moment when you hit a bump in the road or pull on the harness. Look for obvious damage first like, get a good light and mirror if you need it. After that take a close look at the connectors on both end of that harness for damage or corrosion.
I'll take the split corrugation lose this weekend and give it a gander. Really intermittent. No problems on the 35 mile drive this morning.
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