Dwight Schrute

i have a 92 civic dx with a d15b7 with 175k miles.
it has a new cap, rotor, plugs, oem wires, denso 02, pcv, thermo, fuel filter.

it like to have a low idle after it warms up and with surge a little sometimes. usually between 750-950.

the most annoying problem is when i let off the throttle and the engine bucks. it does this when i coast in gear and the rpms drop down to about 2000. or im coasting through the parking lot in 2nd and it starts bucking.

i've read a bunch of archived threads on it, but i haven't found an answer because noone ever comes back and says they fixed it.

petty$rep

It is all about how you drive

The car will not buck once you learn to drive, b/c when i first learned to drive a stick i had the same problem, now i do not even remember what it feels like when the car bucks

Dwight Schrute

it's nothing to do with how i drive. i can eliminate it if i let off the accelerator slowly, but it shouldn't buck how it does. i've read other threads about people having the same problem, so i know it's not normal.

black_EM1

Have you checked your mounts? Loose/worn mounts will cause the engine to wobble, causing the car to buck slightly.

stonedheckler

yeah its more than likey the a mount. had the same problem with mine. check all of them it wont just be one

Syndacate

I agree. It's how you drive.

Honda engines can't operate in parking lots like that in 2nd gear. You can't be running 1.2k RPM's in 2nd gear with light gas and expect the car not to buck. In the case of you with a D15, I know just as good with a D16 - it can't happen. Those engines have low displacement, which means lower torque. It also means lower RPM's don't have **** for the powerband. A regular 4cyl (2.0 - 2.4L) such as my probe for example. Redline is at 6.5k, like on most 4cyl cars. I could blip the RPM's up to 1.2k and let the clutch out no problem. Try doing that on a D15 or D16. It WILL bog, turbo or not (b/c the turbo isn't even spooled at that speed). When driving lower displacement engines it needs to be higher up in a powerband to operate correctly. From my non-caring observations, I've noticed that my Honda doesn't really start to even "catch" and start moving in 2nd until like 2-2.3k RPM's - before that it's useless, too heavy of a car for how low the gear is vs the torque it produces. When you're going <10mph, use 1st gear, it's okay if it's running up in the 3-5k range while you're in a parking lot. I've noticed the same thing in parking lots. You can't use second gear, it's too high vs. the displacement of the engine for such low speeds.

But you probably won't believe me in any way, shape, or form, so that nullifies this post then, doesn't it? Almost. PM me when you fix the "problem" by installing a new anything (I won't get a PM).



Use 1st in parkinglots buddy, and if they're long you can pop it up to second to coast if ur going over say...10mph...but after u get to where the cars are 'n **** and are going like 3mph, ds to first, this isn't a scion tC, it's not a 2.4, it can't hold itself together at such a low speed with it's low *** displacement.

Dwight Schrute

alright, well maybe the parking lot expample wasnt good,but it still does it while im cruising 40mph in 4th. also the low fluctuating idle has something to do with it i believe. im thinking it's some sort of sensor on the intake manifold.

Syndacate

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drewthomas14 &raquo;</TD></TR><TR><TD CLASS="quote">alright, well maybe the parking lot expample wasnt good,but it still does it while im cruising 40mph in 4th. also the low fluctuating idle has something to do with it i believe. im thinking it's some sort of sensor on the intake manifold.</TD></TR></TABLE>

Oh, well you didn't include that part, that was kind of important.

Okay, well there's 3 main things from what I see and hear that cause boucey idles. IACV, FITV, and a vacuum leak. 9 times out of 10 something that makes your idle "bouncy" isn't connected to a driving problem. Are you sure it's "bucking" and not just "slamming" around the engine bay when you let off the throttle b/c your motor mounts are going? Might want to invest in some polyeurathane inserts..that'll stiffen the motor up. Either that or new motor mounts - more than likely your problem. With your engine/setup you can run OEM motor mounts and be fine. That's more than likely your problem, and more than likely it's not connected to the bouncy idle.

Dwight Schrute

i dunno if bucking is exactly the right word. when i let of the throttle, it seems to rock back and forth. i just saw many threads that connected the low idle and the bucking problem. i also cleaned my iacv a month ago and reset the ecu, but it didnt help. what else do d15b7's have? fitv?

Syndacate

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drewthomas14 &raquo;</TD></TR><TR><TD CLASS="quote">i dunno if bucking is exactly the right word. when i let of the throttle, it seems to rock back and forth. i just saw many threads that connected the low idle and the bucking problem. i also cleaned my iacv a month ago and reset the ecu, but it didnt help. what else do d15b7's have? fitv?</TD></TR></TABLE>

'92? Yeah, it has a FITV...under the TB if I'm not mistaken..or under the IM..one of the two :-P - can't remember which :-\

Stilllll think they're not connected...

instrument

yes it's how you drive.
i do this occasionally with kids in the car

not trying to be an ***, but once the car "bucks" once, your foot will keep hitting the gas causing it to keepbucking unless you move it.

i'd occasionally do it after my swap with my new clutch.

wakeboard_dude5

its a motor mount, happened to me in my GSR swapped hatch. Thought it was the rear but it turned out to be the front passenger torque mount. replaced it and the engine hasn't rocked since

Dwight Schrute

i fiddled around with my car for a while checking connections and vacuums. when i unplug the EACV(IACV) while the car is warm the car idle drops dramitically and stays there until i plug it back in. when i took the intake arm off the TB, i felt the lower whole and i could feel air sucking even when the car is warm. the upper hole is for the map sensor i think , so i assume it's normal for it to suck air.

another thing i found is that when i press the brake pedal with the engine running and then let it out. the idle rises a couple hundred rpm. i know if you pump the pedal it should raise the rpm, but when i just have it pressed and then let it out, it shouldn't rise.should it?

Max Kling

Seems to me its an IACV issues. If the IACV is not working 100% correctly, you get ramdom fuel holes, part throttle issues, and tip in and out issues.

Had a big problem with this a while back and just rewired my IACV and it fixed it.

deathplaza

its really easy to tell if your tranny mount is out, just go up to your engine and push it and shake it around, you shouldn't be able to move the engine very much by hand, really i think you should listen to these guys because it really does sound like a mount to me, i got the same problem in my dads car, its either the mount or the tranny, nothing engine related whatsoever.

i was driving with bad mounts and believe me when i switched to innovative motor mounts it was like night and day. i went from my car being extremely hard to drive without making lots of horrible sounds to being a joy to drive through the canyons instantly.

mounts are easier to diagnose than any kind of idling problem you just look inside and if the rubber is cracked or you can move the engine by hand they are toast replace immediately .

Dwight Schrute

anyone else know about the brakes and idle?

Dwight Schrute

up. i cleaned my fitv valve and screwed the plunger all the way in. i cleaned my iacv again which wasn't very dirty either time. I think it's working right because when unplug it , the idle drops and stays there. i also let my car bleed all the air bubbles out by leaving the rad cap off and letting it run for a long time(40+min) fan came on 3-5times. still having problems with fluctuation.

also im still wondering about the brakes. should the idle rise after i let the brake pedal out each time i stop?

Max Kling

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by deathplaza &raquo;</TD></TR><TR><TD CLASS="quote"> its either the mount or the tranny, nothing engine related whatsoever.
</TD></TR></TABLE>

Unplug your IACV and drive around and see what happens, there are a lot of things that could be wrong with the engine that would cause tip in issues .

Dwight Schrute

i'll try driving with it unplugged, but what am i supposed to look for?

also still wondering if my idle should increase a couple hundred rpm's after i let off the brake pedal.

Dwight Schrute

i tried it driving with the iacv unplugged from a cold start. at first it wouldn't even start with it unplugged, but i gave it gas and had to keep giving it gas until my car warmed up why i was driving. the idle sat around 500 which is the bottom line and as i kept driving it eventualy went up to 650-700 and bounced around there.

still dont know what i figured out by doing that. but i would like to know if i should be worried about my idle jumping 150-200rpms after i let off my brakes.

Dwight Schrute

up

Dwight Schrute

bump. i sprayed carb cleaner all over the vacuum hoses and intake manifold gasket and tps gasket to check for leaks and i didn't find anything. i also sprayed some in the TB to see if it was gummed up even though it says not recommended for fuel injected vehicles.

one thing i did notice is that the hole for the FITV still sucks air even after the car warms up.

im am still wondering if my brakes are somehow connected to the idle problem. maybe a faulty master cylinder or maybe the check valve isn't working all the way.

im still wondering if anyone has the answer to my question about my car's idle increasing 200rpm when i let off the brake pedal.

Rcriteser

I had the same problem.My problem turned out to be my ignition module was going bad.I thought it was a vacuum leak or fouled plugs.Nope my 2000 civic DX just shut off one day.It had been bucking for about a month when it died started back up and died again.Try changing the ignition module and let me know if that solved your problem.

Max Kling

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drewthomas14 &raquo;</TD></TR><TR><TD CLASS="quote">i tried it driving with the iacv unplugged from a cold start. at first it wouldn't even start with it unplugged, but i gave it gas and had to keep giving it gas until my car warmed up why i was driving. the idle sat around 500 which is the bottom line and as i kept driving it eventualy went up to 650-700 and bounced around there.

still dont know what i figured out by doing that. but i would like to know if i should be worried about my idle jumping 150-200rpms after i let off my brakes.</TD></TR></TABLE>
I was telling the other dude who is trying to give out misinfomation saying its nothing engine related.

TranspeedMotorsports

It's normal.