Lousy low revs performance. BB4 JDM Si Vtec

mikeholl · Post by **mikeholl** » Tue Jan 26, 2016 11:06 pm

Has anyone any ideas about this one:
Car starts unfailingly every morning, feels crisp, lively, and generally full of go, unlike myself.
As the engine warms up, a hesitating, 'fluffy' kind of flat spot develops,coming and going every few seconds.
By the time the engine is at full operating temperature, the 'flat spots' are so bad that I have to be extra cautious
when pulling out on to a main road, and if I have to tackle a steep hill, from an almost standing start, I crawl up the hill
with my foot almost to the boards, at about 10/15 mph. It simply will not change down unless I force the change.
Bloody embarrassing when a Fiat 500 comes up behind you, and flashes and hoots at you to get the hell out the way.....
This effect is most noticeable at 3000 revs and lower; as the revs slowly rise, things seem to smooth out, and it will
maintain a leisurely cruise at 100mph,with no discernible hesitation, or lack of power.
Seems most likely to be a fuelling problem, or possibly excess air at lower revs, but, as a newcomer to these amazing
little cars, I am hoping someone can save me a lot of messing about trying to identify the problem !!
Any suggestions would be very welcome.
Thanks, everyone!
Mikeholl.

Post by **vanzep** » Tue Jan 26, 2016 11:22 pm

do you think its engine or gearbox related?
your saying its an automatic box...

Post by **Drax** » Tue Jan 26, 2016 11:24 pm

have you checked your valve clearances? sounds very similar to what ludeicrouswill had

Post by **vanzep** » Tue Jan 26, 2016 11:31 pm

butterfly valve in the intake resonator opens at about 3200rpm - could yours be stuck open and drawing more air in than it needs at under 3200rpm.

mind u my BB4 was sluggish at lower speeds and fine once in vtec but that was due to one of the cams having slipped a few teeth and timing was out - noticable at lower revs but ok at higher revs. felt like it was overfuelling

just throwing in a few ideas

Post by **Merlin** » Wed Jan 27, 2016 8:52 am

I experience something similar. I have been told it sounds like a failing O2 sensor.

Post by **RattyMcClelland** » Wed Jan 27, 2016 9:46 am

Merlin wrote:I experience something similar. I have been told it sounds like a failing O2 sensor.

This would be my first go to. Change it and see if that helps.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Wed Jan 27, 2016 6:33 pm

Or knock sensor?
The h22a has one. If it detects knock, it will regard the ignition. If you're not actually in knock, that will kill power.

Post by **RattyMcClelland** » Wed Jan 27, 2016 6:45 pm

wurlycorner wrote:Or knock sensor?
The h22a has one. If it detects knock, it will regard the ignition. If you're not actually in knock, that will kill power.

The knock sensor usually brings up a dash light and safe modes the car almost straight away. But when the knock sensor is working right it will just retard the timing and you wouldnt really tell much difference daily driving on the road but is always a possibility as i did initially think something could be retarding or causing a timing issue.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Wed Jan 27, 2016 6:51 pm

Yeah, it might be worth just checking the timing anyway, to start with?

Post by **4thgenphil** » Wed Jan 27, 2016 10:25 pm

start with the stuff that's free/easy to check, timing, valve lash, plug condition and such then start moving through the car .

also check your fuel pump pick up, i had a similar issue where at lower speeds where the car would cough and splutter, i think i just changed the pump in the end.

when was the car last serviced ?