Idle Misfire/Stumble
 

Apologies for creating a new thread, but I'm not certain what the actual issue falls under. On cold startup the car idle surges between 400-1800 RPM, with audible misfires especially in the lower rev ranges. In the video I'm holding 30% throttle to keep it running. If left to it's own devices, it will either completely die or keep tach-bouncing and popping becomes horrific.

It sounds very similar to the DI seal issue, however once it's warmed up the car drives as normal and I believe DI seals would be a constant.

My only theory at this point is a cam gear issue---when the oil is cold it doesn't actuate properly, and then resolves itself once the oil warms up.

This initially presented ONLY on the Visconti pumpgas map several months back, but is now happening on ALL maps including stock. Only modification is catless 2.75" J2 frontpipe, catback and K&N drop-in. I realize the danger in letting it run this way, but as it hasn't popped any CEL's yet after a clear (even when it dies), Toyota will not commence diagnostics. Only made the video for the sake of getting it documented.

Open to any suggestions or ideas you guys may have.

https://plus.google.com/u/0/10312936...45/posts/p/pub

Let me know if the video doesn't work.

Exact same scenario. At least our cars didn't catch fire.

I remember reading about this but don't remember the end result. Were you able to solve it? A friend's car had a cam gear fail and it acted just like this. Once it's up to temp it drives fine, but even on pumpgas, I can barely get the car to stay running now. :\ Don't know why it'd present on John's tune two months ago, and only show up NOW on my other tunes. Something must've exacerbated the underlying issue. I'm just at a loss here.

I've got some logs of the startup if anyone's clever enough to assist. I'm a newbie at best. Only thing I can identify is that it's running really lean now once it starts trimming. Previously I'd get 20-25% positive LTFT on John's tune, but now i'm seeing 32-40%. :\

I'd say it just needs to be retuned with more fuel thrown into the cold start maps, but I've seen other folks get away with header+full catless exhaust and start just fine on the stock map, so I can only assume I've now got a mechanical problem to contend with.

Video does not work. The page is blank for me. You sure you are not hearing the cat warm up ect?

Interesting that today was my first cool morning with the new FR-S and the car stumbled at first then idled very high for a bit.
Was fine when I came out at lunch though.
No mods yet except to get rid of that stupid cabin noise assembly.

Yeah this is not the usual catalyst warmup pinging. This is a loud bang/misfire through the exhaust every other second. Sounds like the "fireworks" description for DI seal failure. I've always had a light idle stumble on cold mornings (I drove it in winter, so I'm used to it high-idling), especially on E85, but it always pops to high rev and smooths out. This just continuously fluctuates, and bangs constantly. The car WILL stall, every time, without immediate throttle input after firing.

I'll try to find an alternative host for the video and the data logs.

Hmm... I dont think its the di seals. You have a automatic. we have yet to see a case with the auto and di problems.

It appears that it may be a fueling issue. I sent John a log and he responded within an hour with ideas and explanations. Looks like I may have joined the disintegrated filter club and it's restricting fuel flow.

Oh man.
How long have you been on e85?

I have been on and off all summer on the corn. about two weeks ago I threw a high circuit code and I went back to pump gas and have not looked back.

I would drain it out and go back to a stock tune for a bit and see if that helps.

I don't believe it's E85. Plenty of people with tens of thousands of miles on their E85 setups. It's just a postulated fuel problem at this point, I haven't investigated the filter housing or lines to see if there's debris. Just the only thing I could think of as I haven't heard of pump failures (crickets don't count).

Let me know if you find an issue.

That would also explain the lean conditions you are also experiencing..

Yep. Fuel trims steadily climb. It makes sense, I'm just praying that debris hasn't made it's way into all the fuel lines, all eight injectors, etc. That would be a bad day.

Is your a/c on during cold start up? If so, turn it off.

AC is not on and I prime the pump for 5 seconds before turning it over, etc. This isn't the usual idle stumble everyone complains about. I had that previously. This is MUCH more drastic. LTFT's on stock map are now +40% across the board. ;)

What does the short term trims look like?

They max out when the LTFT's reset of course, otherwise if the LTFT's are staying at 40%, the STFT's range from -5 to +5, so normal. Trying to see if I've got injector duty cycle in these logs...

I have been seeing -14 to +14 sometimes other times -10 to +10 I need to get that looked at. Short trims my long trims are disabled currently.

Honestly that doesn't sound all that bad to me. I'm a novice, so mad_sb or one of the other pros would have to give further thought, but if that's the total variance... if you had LTFT's enabled that'd be like a +10 constant LTFT, and +/- 4 for STFT. Not perfect but that seems pretty decent compared to some of the crap I've seen. LTFT's turned off to narrow in maf scaling or something?

boosted FRS here on e85

Short trims are -3 to 3
and
Long are 13.3

No tony has them off to keep the ltfts from stacking up and from giving the stock ecu issues when going wot and adding extra fuel. I autocross all year long and this year I was switching from 93 to e85 every few weeks.