Bogging after VTEC crossover

Spork · Post by **Spork** » Fri Sep 14, 2007 3:53 pm

alright, I am about 1/2 way through getting this motor back up to where it needs to be, I am facing 2 problems now:

Knock Sensor CEL (23) comes on after 2-5 minutes of driving... basically, once engine gets warm enough for vtec to work. This happens at teh same time, every time, no matter how hard or soft the car is driven before then. so I believe the sensor is bad, NOT that the engine is knocking. easy fix... new sensor, or a chip that wont read knock(I'm putting cams on in a week or two, so this is the more likely fix)

OK, the real problem: when revving up, the car bogs right after vtec crosses over. At 5200 when vtec kicks in, the car actually pulls less than before 5000, but at about 6000rpms it starts pulling strong again. Without vtec, the car pulls smooth all the way up (vtec didn't work for the first 2 days i had the car, thats how I know this). this also happens after shifting, if it falls in teh 5XXX range, the car just falls on its face until 6000.

we pulled the VC off and lined up the crank pully to TDC and checked cam timing (we thought it might be off a tooth) but it all lined up just fine.

Last night I got a suggestion that it might be an oil pump issue, but if it doesnt have sufficient oil pressure, wouldn't vtec disengage? or would it remain in vtec once it switches over?
or, wouldn't it only do this right after crossover, not after shifts too?

any insight is appreciated, TIA

bildo16 · Post by **bildo16** » Fri Sep 14, 2007 4:05 pm

is your cel on when this occurs? i assume so since you said it only happens when it is warm. i would get that knock sensor issue worked out and i would almost bet your vtec issue will be fixed also. if your cel is on cause of your knock sensor, then your fucked, vtec relies on knock sensor input. even though you arent knocking (running at least 91 i assume) your computer thinks you are because your sensor could be junk, there for it has to compensate for your "knock" by taking away your power aka vtec!

Spork · Post by **Spork** » Fri Sep 14, 2007 4:11 pm

bildo16;67067 wrote:is your cel on when this occurs? i assume so since you said it only happens when it is warm. i would get that knock sensor issue worked out and i would almost bet your vtec issue will be fixed also. if your cel is on cause of your knock sensor, then your fucked, vtec relies on knock sensor input. even though you arent knocking (running at least 91 i assume) your computer thinks you are because your sensor could be junk, there for it has to compensate for your "knock" by taking away your power aka vtec!

sorta what I was thinking... but vtec still engages even with the CEL on, and like i said at 6000, it starts pulling like nothings wrong. thats why i was thinking they are seperate problems.
I guess I'll have to get my 'mother of all sockets' out and go steal the knock sensor off of a DA at pick n pull

... that will be quicker than waiting for a chipping kit me thinks.

SweetEBPSi · Post by **SweetEBPSi** » Fri Sep 14, 2007 10:07 pm

Spork;67069 wrote:sorta what I was thinking... but vtec still engages even with the CEL on, and like i said at 6000, it starts pulling like nothings wrong. thats why i was thinking they are seperate problems.
I guess I'll have to get my 'mother of all sockets' out and go steal the knock sensor off of a DA at pick n pull ... that will be quicker than waiting for a chipping kit me thinks.

I think you should just change that sensor and see if that completely eliminates your problems. The timing and the engine are fine. That leaves the issues with VTEC. I have a feeling that the sensor might be creating all the problems.

Gunmetal Si · Post by **Gunmetal Si** » Fri Sep 14, 2007 10:28 pm

u just need to up ur crossover rpm. mine used to do it and worked the best at 5700 in my case.

90CivicEx · Post by **90CivicEx** » Fri Sep 14, 2007 10:34 pm

Spork;67069 wrote:sorta what I was thinking... but vtec still engages even with the CEL on, and like i said at 6000, it starts pulling like nothings wrong. thats why i was thinking they are seperate problems.
I guess I'll have to get my 'mother of all sockets' out and go steal the knock sensor off of a DA at pick n pull ... that will be quicker than waiting for a chipping kit me thinks.

Sir I have that mother of all sockets btw

LowePerf · Post by **LowePerf** » Fri Sep 14, 2007 11:09 pm

Has it been tuned? Or is it mostly stock? When the high cam comes in it will go seriously lean if you are not commanding enough fuel. When the high cam comes on and more airflow starts moving in there is a sudden need for additional fuel, otherwise you get a big flat spot until it can catch up.
You could compare this to not having any acceleration enrichment off idle. Or a bad TPS that would not tell the computer that you just opened the throttle.
Just as you need less acceleration enrichment as rpm goes up(usually no addition after 4000 rpm) delaying Vtec until reaching a higher rpm can also help correct the situation, although sometimes this leaves a little power on the table.
-John

Spork · Post by **Spork** » Fri Sep 14, 2007 11:32 pm

90CivicEx;67169 wrote:Sir I have that mother of all sockets btw

what size is it btw, I dont want to haul my whole kit around the yard if i dont have to

GUNMETAL SI;67168 wrote:u just need to up ur crossover rpm. mine used to do it and worked the best at 5700 in my case.

this is why I am trying to find a vafc, or chip this damn ecu

LowePerf;67173 wrote:Has it been tuned? Or is it mostly stock? When the high cam comes in it will go seriously lean if you are not commanding enough fuel. When the high cam comes on and more airflow starts moving in there is a sudden need for additional fuel, otherwise you get a big flat spot until it can catch up.
You could compare this to not having any acceleration enrichment off idle. Or a bad TPS that would not tell the computer that you just opened the throttle.
Just as you need less acceleration enrichment as rpm goes up(usually no addition after 4000 rpm) delaying Vtec until reaching a higher rpm can also help correct the situation, although sometimes this leaves a little power on the table.
-John

the motor is basically stock from what I understand... but yeah, it could probably use a tune... after i chip it or get a vafc to hack with, I will probably give you a call

90CivicEx · Post by **90CivicEx** » Fri Sep 14, 2007 11:54 pm

Spork;67180 wrote:what size is it btw, I dont want to haul my whole kit around the yard if i dont have to

I will have to go out and look for you sometime tonight and email you that size, It's a off size I can tell ya that much.

If you need a ecu to tinker with thats chipped you can swap me for the time being to see if we can add some fuel to fix that lean spot.

Also I have turbo edit and a stock PR3 map unless you wanna come down here and me, you and John can try and figure out something with it. Also I will save the map and put it on a chip for you to help you out until you can get enough cash to go see the master of tuneing at Lowe Performance himself.

Spork · Post by **Spork** » Thu Sep 27, 2007 5:44 pm

alright, i swapped out the ECU to my PW0 to see if that changed anything... it did not.
my thoughts now are that it is running either very rich, or very lean. but I am leaning (no pun intended) to it running really rich...
the car has a b&m fuel pressure gauge mounted on the fuel filter and it looks like its reading 39 lbs.
i think the next step is swapping the injectors and seeing if maybe the ones on the car are not obd0 b16 injectors.

any thougths?