es_squared

So this is kind of a toughy, for me at least! A quick rundown of the backstory: I basically havn't hit vtec for 6 months due to the motor being rebuilt, turbo being installed etc.

So today I wen't to get the car dyno tuned, tunings going good with vtec disabled. Next they engage it at 5500rpms or so, once it hits 5500 it misfires like crazy, basically not going higher than 5500. They try to raise it to see if its something else, they raise it to 6000, same thing happens, so we're thinking its something up with the vtec engagement itself.

They suggested it may be a mechanical issue within the head interfering with the lobes, which I will check on with my machinest, but if anyone has ideas of what else would cause this, let me know. Vtec solonoid? I have no idea.

Taracing79

my civic did something like that and it was the added chip in the computer itself had come loose

es_squared

Oh, i've got an s300, and I think its solderd in there, but Ill check on that, anyone else ?

es_squared

?

A Blue Lude

For what it's worth 5500 on a H22 is pretty late, 6000 is wildly late.

But beyond that, no advice, sorry.

es_squared

The exact numbers I couldn't remember so thats what i posted just an example, but thanks for the heads up

boosted k20

is ur car boosted? what cams do you have in the car. i had a similiar problem with a car i tuned. turned out it was the cams. when you have too big of a cam and a really small exhaust system (be it exhuast piping, log manifold, small turbo) you will have this break up issue once vtec engages. You need to swap your cams out bro

es_squared

skunks 2 stage 2 cams these are the older ones, before they came out with the pro line
But I've heard of other people using these cams on boost

boosted k20

i bet u have a log manifold. thats ur problem right there. swap out ur cams for stock ones or either get a topmount or ramhorn manifold with a decent sized turbo/exhaust and ur problems will be solved.

u never want to use a big cam with a restricted turbo/manifold and small exhaust setup. if u do u will have the problems u speak of

Bugermass

i've had customers run retarded big cams on log manifolds, while yes it won't make power and runs like crap, that shouldn't cause it to missfire really bad like that. How much difference is there in your fuel tables between low and high cam?? there may just be too much fuel on the high cam table so once it clicks over it missfires really bad. I've seen this a few times on peoples cars they tried to tune themselves and bring to me to fix. They add too much fuel to the high cam boosted map to try and have a "safe" starting point, but it ends up being to much and it just missfires all crazy when it hits.. if you want send me your calibration and i'll look over it.. just pm me and I'll give you my email..

es_squared

Thanks man, I sent you a pmmmm

es_squared

Anybody else? running outa ideas

swapdohc

I am having a very simular problem, I have exhausted all other possible problems except changing out my stage 1 JUN cams. I do run a restrictive exhaust system (I like it quite) and a log manifold. I will post up the results on Sunday when I change out the cam.

Details can be seen here

https://honda-tech.com/forums/tech-misc-15/vtec-problem-well-researched-2553620/

es_squared

Thanks for the reply, but ya let me know if swapping out your cams solves the issue.. i have a hunch thats not it though.

roni_xxp

i had the same problem before i got my h23vtec tuned, but with stock cams the a/f ratio was too rich i forgot to remove my fmu which is only good for stock computer, car was running fine and vtec engages really good right after i removed it, i have a log style manifold also but that didn't cause any problem..

Musky@RG

I'm the guy who was tuning es-squared's car so I thought I'd chime in here and give some more info. The high and low fuel tables were transitioned smoothly and the AFR's were safe. (mid to high 11's @ 8psi) I tried everything richen and lean the high fuel tables, as well as advance and retard the high timing tables. Also put in new plugs and gapped them to .028 to make sure they weren't blowing out. We were thinking that it could be the large cams and restrictive exhaust as well so I activated the vtec at 4500rpm with no load or boost on the engine and it still misfired badly.
It basically sounds like a 2 step rev limiter or like some injectors aren't firing whenever the vtec is activated.
I tuned the car before when it was NA and the vtec engagement worked fine. Since then the Engine has been torn down and sleeved for boost by another shop, so I'm not sure what was done to the head etc...

ralph11sec

was the afr at vtec fine?
are the fuel numbers at the vtec point an low cam map and high cam map close to each other?
did you change your plugs?
is your vtec solenoid clean?

swapdohc

WOOT!

The Juns are out, type r's back in and voila, VTEC!!!

es_squared

the JUNs are pretty agressive, but thanks for the update!

es_squared

I'm unsure of the other things, but vtec solonoids the next thing on my list to check

Blown90hatcH

And yours are mild with a log manifold? Change manifolds and/or cams and see if it goes away.

es_squared

bump

KWayRacing

very very interesting...bump

trickeng

its not the manifold or the turbo, so don't waste your time replacing them. you said mid to high 11's, but you can't get past vtec switch-over so how do you know???? it sounds like your either way lean or way rich in your high vtec map.

what happens if you engage vtec at a lower engine load and run it up 1/4-1/2 throttle. does it transition better?

stleger184634

hey i am having a similar problem with my car a brief run down of my situation is: I have a 1998 prelude i swapped a f20b it is hooked up currently with the stock h22 obd2 ecu and it runs fine except the throttle isnt very smooth at all and also when i hit vtec the engine light blinks and throw the code to my scanner that i have a misfire in 4 cylinders but i dont feel a misfire. Is this because im using the base maps from the h22 since it is a 2.2 liter and im 2.0 liter the maps might be off causing the uneven throttle and the supposed misfires once vtec engages??? I have a OBD1 conversion but it runs the same and i cant find any f20b maps on pgmfi.org or anywhere if anyone knows way to solve this let me know! thanx