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Honda civic
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Discussion Starter #1
Good Afternoon guys,
So I looked EVERYWHERE, and I can't seem to find any information on anyone having a similar issue as I am... For starters,

I have a D16y8 engine stock ecu, in the neighborhood of 10.5:1- 11:1 compression. stock cam, port matched intake side of head, Polished combustion chambers, new pistons, rings. bearings everything. I run 93 octane, cam is 2 deg advanced, dist is turned all the way retarded (leaves me at 11-12 ign adv. at idle).

Now for my problem.... intermittently I have excessive fuel trim... usually 50% highest has been 59.4. and its only when im cruising. if im WOT the fuel trim is 0.0 and no problems, even when im at idle its fine, only every once in awhile does it act up, and it surges itll drop and if I give it more gas itll smooth out till I go back to 1/8th throttle (to maintain speed). I know I need to tune this just wondering if anyone has ran into this before??? All of my sensors injectors, etc were working before when I had just the mini me. Just want to get it make sure that if its a tuning problem tuning will fix it not spend 450 on ecu and dyno tune for nothing and still have the same problem... Thanks in advance!
 

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Honda civic
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Discussion Starter #2
On my way home from work I was watching my fuel b1s1 oxygen sensor fuel trim and it was corresponding with the regular fuel trim. I also noticed the problem slightly diminished as the vehicle ran longer, so about 15 minutes of driving it almost stopped. Still no check in lights...
 

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ej8
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6,367 Posts
What os the car tune on?
What is it taking for its o2 reading? Wideband o2 ot oem o2 sensor?

What is your cruising AFR tune to? Does it hold this AFR?

WOT switches into open loop, doesnt read fuel trims.
And some tuning software will disable fuel trims for idle correction.
 

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Discussion Starter #4
It's all stock. except for the work ive stated above. Thats why im trying to figure out if its tune related or could be sensor related.
 

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ej8
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you need to wideband gauge to see whats going on.
you up the compression and change the timing of the cam.
It needs to be tune.
The factory ecu is still trying to target X AFR while your car will need Y AFR.
In doing so the fuel trims end up going crazy.
Also the cam timing being different changes the overlap and ecu trys to pull or add timing causing other problems.

So get it tune and it should run better also.
 

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set the distributor BACK TO STOCK

verify base timing is good

reset the ecu via fuse pull, or battery NEG yank for 10-15 minutes


Follow method for idle relearn

go drive.



dont change cam gear timing so much on stock ecu and tuning. it wont work properly
 

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Honda civic
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Discussion Starter #7
I've tried all stock settings when I first put it together, I retarded the cam, andno effect on symptoms just major power loss at low rpm, then went adv, and now it drives perfect except for the random power loss, seems to be more of a problem at or closer to 60mph. ive reset the computer and everything each time I make adjustments, and it doesn't seem to effect the intermittent power loss. it really only changes at what point it does it, im really leaning towards pre-detonation and it trying to correct itself.
 

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you will never see a "major" power difference with a cam adjustment on an otherwise stock setup.

It is possible the timing indicators were mis-interpretted.

what is your timing method? you have 2 things to do.

when cam timing is changed, you MUST retime the distributor and base timing. moving the cam moves the distributor position in accordance with sensors
 

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Honda civic
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Discussion Starter #9
when I did the timing, I lined up the |^| and the V on the white mark and lined up the two white lines on the cam gear to level with the head, just like I always do. I put the distributor back in the middle where its supposed to be, and fired it up.
 

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Classic Man
Civic
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16,355 Posts
60% trim is huge. You have fueling issues, air leak issues, exhaust leak issues, or o2 sensor issues.
 

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Honda civic
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Discussion Starter #11
The more I drive it the more im narrowing out what causes it, its mainly now when im over 60mph and on the highway. It acts all good in the city, but when I hit 60 and try to cruise it starts feeling like its missing, but I can give it more gas and it acts fine, so I think what xile6 said is my problem, I need to fatten it up a bit.
 

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Honda civic
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Discussion Starter #12
im thinking its knock sensor, needing more fuel, so it pre- ignites and then retards it. theres no air leaks, ill swap my injectors with my other ones, its intermittent. like 2 seconds then jumps back up then itll do it again. but only on highway 60+ mph. low rpm for a steady time with load.
 

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Classic Man
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You cant fatten it up with your ecu you need to run a chipped OBD1 ecu or a piggyback to try and trick the OEM ecu.

When do air leaks and exhaust leaks present them selves most? Not at high load and acceleration but at cruise and light throttle. Not saying that is your issue, just saying when the shoe fits fix it.
 

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Discussion Starter #14
I will triple check, and I have to do a manual swap for the chipped ecu , which is my plan this weekend, I have everything except the clutch lines and brake pedal, and starter. I guess ill update you guys once I do another air leak test.
 

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for a good solid 3-4 minutes, and no problems anymore? Something like that just blows my mind lol

***** we do NOT condone street racing around here, take that shit to the track and stop putting other drivers at risk
 

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Honda civic
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Discussion Starter #16
I was talking to a Honda Technician and he said basically the computer has relearned what it needed to do. Sounds about right because now im 3 days without a problem, and before it was every other drive. Thanks for your help guys!
 

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Im certain that is not the case. the stock ecu doesnt adapt under high load and wide open throttle. it has a programmed set of credentials it checks itself against.

being over 100mph puts you in a very high load state, and likely you had the throttle mashed to the floor

the ecu is not taking in hardly any sensor feedback when it detects full throttle. it merely jacks up the fueling, pulls a bunch of timing out, and hopes you dont foolishly blow the motor or kill someone driving like a fucktard going over 100mph on public highway roads

EDIT for the most part, under WoT, its looking at RPMs, TPS position, and possibly coolant temp for an overall attempt to keep the mixture rich enough to keep the motor from splitting
 
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Honda civic
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Discussion Starter #19
I wasn't full throttle, I had it about 75%. And btw the road was empty and it was really late... but sorry. I apologize for "condoning" street racing.
 

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you said 3 or 4 minutes above 100mph

Ive driven a high compression 1.7 stroker. given it had a 94 or 95 DX box behind it, it needed more than 75% throttle and it easily had 20+ more hp and possibly 30tq more than your setup.


you likely finally cleaned a sticky injector or piston ring.


Even so, that poor motor to see 3-4 minutes of abuse like that. Oil temps were probably very high, oil pressure was probably lower than it needed to be.

I wouldnt want to trust that motor much more unless you pop the valve cover off and see if the valvetrain is still in one piece
 
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