Honda civic lx 2009 (R18 1.8L) turbo’s and 350cc injectors with hondata tune.
During cold starts while idling I’ll get a couple sputtering sounds. The air fuel gauge goes from 15.4 to 17.3 where it becomes rich
If I drive under 2500 rpm’s it won’t really missfire to much after little bit of heat, but if I try boosting while not hot, it’ll missfire like crazy and in all cylinders when we put a scanner on it.
Once it’s completely hot/running temps I get 0 missfires. The tuner wasn’t sure why it’s only misfiring cold, my guess is the Honda needs a valve adjustment after I put one step colder plugs and tune on it. But anything else that may cause a non-isolated misfires?
15.4 AF to 17.3 is lean to very lean. Both would cause misfires. With E10 gasoline your idle AF should be in the area of 14.2 or so or a Lambda of right at 0.97 to 1.0.
Have you taken a look at the coolant temp readings from the computer? When you first start it from cold, coolant temp should read around ambient air temps. And it can be off/wrong, but if not in an “implausible” range wouldn’t set a code. But it’s important to the AF mix. Not likely the issue, but easy enough to check.
Not typical… E10 91 octane fuel has an optimum AF ratio of about 14.3 as I posted previously.
Your tune should try to maintain that 14.3 for idle and normal operation. When it is cold, 14.3, when it is hot, 14.3.
Under full throttle it should go richer to make maximum power and to protect the engine. That is true for factory tunes and aftermarket tunes. 12.5 AF generally provides the highest HP but a little richer for turbo engines prevents detonation.
If your tune is not giving you that it should be revised. A tune is not only about max power full throttle blasts. A good tune is also driveable. Yours clearly is not properly tuned for driveability. This assumes all your sensors and fuel system are operating properly.
Interesting, and asking largely for my own info. I always thought a cold start required a richer mixture, and the ideal “stoichiometric” of 14-ish:1 was with an engine up to full temps. (And the colder the weather, the richer the cold start mix). But I’m also not a tuner and haven’t ever dabbled in it.
Well, it does… and it doesn’t! Cold air is more dense and has more oxygen per volume. Carburetors meter air volume, the cold air is more dense so it need more fuel.
Fuel generally injection measures air mass so even if the air is cold the mixture is close to correct. An air inlet temp sensor helps a bit more. All this happens before the O2 sensor gets hot enough to work properly. The engine may run a bit richer than 14.3 when cold to light off the catalytic converter.
For straight gas, the optimum AF would be 14.7. Add some ethanol and it shifts closer to 14.3 or a little less.
One of the issues is cold air and metal doesn’t vaporize the fuel as efficiently so an EFI enrichment scheme usually accounts for this- as well as a host of other contributing factors like increased friction from cold oil, getting the cat up to temp faster, idle adjustment- a bunch of design parameters that may influence A/F ratio on a cold engine; injector spray pattern, port design, injector location etc GDI is another beast but some of the above still applies in a cold cylinder…
The stuff written by OP appears backward to me- it is lean when cold and gets richer as it warms up. Plus this:
The air fuel gauge goes from 15.4 to 17.3 where it becomes rich
As pointed out by Mustangman, that is getting leaner not richer. Maybe I interpret it wrong?
I’m still wondering about the ECT sensor readings…It’s a basic parameter for setting AF ratio, and especially important on cold start. But IDK. Maybe I’m just loopy. Or maybe if you have tuning add-on stuff going it’s not relevant. But if you’re already in there looking at the AF ratio, the it takes 2 seconds to look.
Okay perfect, so between both of you there’s a cold mode and run temp mod. Obviously it’s running perfect while hot, so I need to recall the tuner and say your A/F during cold mode is off and causing missfires can you please retune the cold starts?
Or do I need dyno time and to start from square 1?
I’ll have to wait for coolant temps, I just got a basic code reader, and my mechanic friend has nice tablet for that live data so I’ll swing by him later this week.
He did recommend since tunners put 1 step colder plugs in to redo the valve adjustments at the dealership as spec might be off. But I felt that the car would missfire 24/7 if valves were off not just while cold.
He said hey man I got it all tuned up, then only hiccup we had was during cold stars it was misfiring a lot. After we got it warmed and tuned we were unable to see the problem.
So just make sure your car is warm and you won’t misfire. But on hondata everything’s looking right so we’re not sure why it’s doing that.
I was like oh…. Alright?
But month later I rather not sit in parking lot for 6-8 minutes just to drive.
My 20 yr old $50 code reader does not do live data or ect. My newer $50 reader does. If you say yours does not then it is what it is.
My old one would not erase codes. Bit annoying.
Yeah, let it cool overnight and the coolant temp reading should be right around air temps - or possibly between that and whatever the overnight low was if there’s a big difference there. Like I said, I’m not guessing that it is a problem, but it’s a simple thing to cross off the list.
Well ECU temps seem to warm up and read right. I did notice on cold start that the S trim L trim and air fuel are messed up until the car gets adjusting.
Was the temp sensor right straight from cold start? (Don’t worry about whether it warms up right. If it was like 70F on cold start, did the ECT read around 70F?)
S Trim is short term fuel trim (STFT). It’s the moment by moment adjustments of A/F ratio (largely about injector pulse). It should constantly bounce up and down with a range of, say +/-5%, though +/- 10% is fine. Negative is rich (pulling back on fuel) and positive is lean (adding fuel). The rapid bouncing is just part of the normal game.
L Trim is long term fuel trim (LTFT). It’s more of a long term running average. STFT is all over the place because it’s moment by moment. Lay on the throttle fast and hard, the STFT will go temporarily lean. Lay off the throttle, it will go temporarily rich. The LTFT basically smooths the calculations out to give more of an overall picture.
Your LTFT is flat. I can’t comment on that. Seems abnormal to me. The STFT, in my experience (which is somewhat limited compared to others here) is also looks weird. I can’t tell where the zero point is on that graph, but it should be raggedy/zig zaggety like the AF ratio is. That also looks weird to me. But others might be able to enlighten me / us on that one.
See that big spike early on in the AF ratio (went really lean)? It’s echoed by the STFT. And the AF ratio hangs lean in that early part of the graph. As it has seemed since the beginning, you’re too lean on cold start.
If it were me, I’d actually be thinking about something like a very minor intake manifold leak. Contracted cold metal that expands with some heat. It’s like how some tiny exhaust manifold leaks can, more of less, seal themselves up once the metal expands with heat.
I’m thinking on other things that would only be an issue right at cold start. Like maybe sticky injectors, but IDK. Others will have more thoughts, I think.
I did find one interesting thing tho. So I start the civic it’ll run for 30 seconds then make a putter sound from exhaust for the missfire. It’ll be warming up another 45 seconds then putter once, it’ll do that 4-6 times before it’s warm enough not too.
If I start my car, and put it into drive or reverse like within 10 seconds the car will not misfire if I let it sit in a gear. If it’s cold and I try to boost it’ll misfire like crazy in all cylinders. If it’s hot operating temp and i boost no misfire.
But otherwise looking to do boost leak test to make sure manifold is good. Then bring it to dealership to check the valves and maybe get an adjustment. Otherwise have no clue
Also this 2009 lx after market turbo is an automatic as well tho no sure if transmission will give any information.
Cold air is more dense and has more oxygen per volume. Carburetors meter air volume, the cold air is more dense so it need more fuel.