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2004 Toyota Echo, rough idle, LTFT at 25-30% #5377258 03/15/20 07:12 PM
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davlac89 Offline OP
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Hi,

I’ve been working on my girlfriend car lately, it’s an 2004 Toyota Echo with a manual trans. Car started to have a weird uneven idle, and small and subtle misfire while driving. There is no CEL on. The car start fine, no issue with that, and it will idle fine while cold and with the IAC open. When it gets to normal temperature and idle speed (650 +/- 50rpm) the LTFT start to grow in the positive up to 25-30%. The LTFT will go down to around 0% when you rev it up to 2000-3000rpm. It runs fine at this speed.

Here’s what I’ve done:

- Sprayed everything vacuum related (hoses, injectors, gaskets, etc) with brake cleaner and tested with propane too.
- Built a homemade smoke machine and tested it. Only smoke came out of the oil cap, under the valve cover. Obviously 2 hoses get directly there. The PCV, which to Toyota spec should let a small bit of air form this side, looks ok, I did take it off and tested it. There’s another hose which gets in front of the throttle plate, this one is not under vacuum and serves to let air into the block to then vent out the PCV. When the car is idling and under the said issue, if I clamp the particular hose, the car dies, I still have not figured that yet……
- Replaced the intake gasket, throttle body gasket and IAC gasket.
- I cleaned the IAC, it’s super smooth, tested it the way the manual says to do and it’s behaves normally.
- All MAF readings under different rpm looked good, nothing jumped around or looked out of place. I cleaned it with MAF cleaner.
- Replace the rear o2 in december after the CEL light came on. The idle issue came just a bit after this, I suspected it because it was a Denso and not a Toyota so got a Toyota one at the scrapyard, installed it and the problem persist. The front o2 reading looked normal, jumping from 0.05v to 0.9v.
- Fuel pressure is 47psi at idle. Spec is 44-50psi
- Tested the injector with a pulse generator. Tested them at 40psi with 30 7 millisecond pulses. 1-2-3 came out at 31 psi, 4 came out at 30.5 psi.
- IAT and ECT sensors reading are normal.
- I put injector cleaner into a 1/4 tank of gas.
- The car have a leaky exhaust gasket, it’s always been this way, I don’t really suspect this but I want to mention it anyway. It’s a small leak, no gaping holes in the runners.
- I clamped the brake booster and the evap line while the issue was happening, nothing changed.
- The intake is not cracked.
- I took a compression test, engine was cold, throttle was held open. The 4 cylinders scored into the 205-210 psi bracket.

What’s left to do:

- I did not record a vacuum reading yet.
- I did not test the Oil Control Valve related to vvt-i, which could affect timing.

Lucky for me my girlfriend don’t use the car to go to work so it’s not a pressing issue to get it on the road again. I am starting to pull my hair on this, and I really am running out of ideas….. If any of you think about something else, please feel free to get involved.

Thank you!

Last edited by davlac89; 03/15/20 07:17 PM.
Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377287 03/15/20 07:33 PM
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14Accent Offline
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If it's only at idle, it's almost got to be a vacuum leak, or a MAF that's just under-reporting at idle. Sounds like you're on the right path, though.


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Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377302 03/15/20 07:42 PM
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painfx Online Content
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Smoke machine is your best bet to find vacuum leaks.

Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377334 03/15/20 08:07 PM
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PimTac Offline
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Denso is Toyota.


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Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377403 03/15/20 09:05 PM
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madeej11 Offline
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You've been pretty thorough. Maybe egr valve needs cleaning or replacing?

Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377408 03/15/20 09:11 PM
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eljefino Offline
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If you can get techstream ($15 with cable on ebay for a knockoff) it has options to manually add and subtract fuel for diagnostics. Maybe you can lean it some more and nail down a particular cylinder or not.

To me it sounds like an intake manifold gasket, but you should have found it with your checks.

Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377418 03/15/20 09:22 PM
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rob1715 Offline
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For what it's worth, I have a 1.8L 2003 Matrix. In November it threw a P0505 code which was the idle control valve. Same exact issue you're describing. It's located under the throttle body.

Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377645 03/16/20 08:00 AM
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Trav Offline
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Quote
The car have a leaky exhaust gasket


This can definitely effect fuel trims, if the leak got worse that could be a problem. I learned a long time ago start with repairing what you know is broken that could effect the problem you are chasing, in other words don't repair the rear door latch because the battery isn't charging.
An exhaust leak after the upstream O2 but before the down stream O2 will 100% cause fuel trim issues, also look for cracks where brackets are mounted.


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Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5377714 03/16/20 10:03 AM
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The_Eric Offline
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What is the maf reporting for airflow at hot idle?


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Re: 2004 Toyota Echo, rough idle, LTFT at 25-30% [Re: davlac89] #5383967 03/23/20 06:07 PM
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davlac89 Offline OP
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Well people, I just wanted to keep you updated, I found the culprit! God [censored] exhaust manifold leak...I patched the little holes where the runners begin with high temp epoxy and voilà. Went for a ride and the car has stable LTFT at 0.8% and STFT jump around the +/- 5%. Don't underestimate the exhaust side looking for high positive LTFT, it had all the symptoms of a vacuum leak but it was not.

Thanks!

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