Why does my motor bog when it hits a constant speed?

[Arthas]

Hey all

1999 Civic DX
1998 D16Y8
1998 EJ8 tranny


The motor pulls fine and it runs decent. I had it with a Y7 TB w/ Z6 rotor and it idled at ~1600 and fluctuated. It was really annoying, but it drove fine. I installed a Y8 TB and ever since then, it idled fine (~1000) but when im driving and say Im going a steady 40MPH, it starts bogging and sputtering. RPM's don't fluctuate, it just sputters and the exhaust sounds like its spitting. It accelerates fine and revs like its supposed to.

Any tips on that?


CELs I have:
-IACV
-Second o2 sensor
-ECU malfunction (ECU works fine btw)

[killakam666]

i reused my Y7 throttle body and i have no idle problems or anything of that nature.... ummm idk, but i think we should race... since we both have beefed up single cams .... also i think your suppose to use the Y7 TB coes it has the IAVC right on it ... hmmm

[95_civic_gsr]

Idle fluctuation is usually caused by an IACV or a FIV. But when the car just bogs randomly it might be your primary oxygen sensor. I had an O2 sensor do that to me. Took me forever to figure that one out. The code was "fuel delivery problem." When your IACV and FIV go out, they also cause a problem trying to maintain idle and maintain a steady highway speed. However its not so much a loss of power (bogging), its just like you let off the accelerator. If you press on the accelerator the engine picks right back up. With a faulty O2 sensor, it will bog down even more when you press on the accelerator.

I'd start by getting rid of the codes first, and then see if that clears up the problem.

[sdlEF]

check your cat too..... it might be clogged.

[Arthas]

Originally Posted by killakam666

i reused my Y7 throttle body and i have no idle problems or anything of that nature.... ummm idk, but i think we should race... since we both have beefed up single cams .... also i think your suppose to use the Y7 TB coes it has the IAVC right on it ... hmmm

I also did the same but I used a Z6 rotor with the Y7 TB.
Yeah I wanna race you soon dude.. haha. Youre not using a Y8 IACV?

Originally Posted by 95_civic_gsr

Idle fluctuation is usually caused by an IACV or a FIV. But when the car just bogs randomly it might be your primary oxygen sensor. I had an O2 sensor do that to me. Took me forever to figure that one out. The code was "fuel delivery problem." When your IACV and FIV go out, they also cause a problem trying to maintain idle and maintain a steady highway speed. However its not so much a loss of power (bogging), its just like you let off the accelerator. If you press on the accelerator the engine picks right back up. With a faulty O2 sensor, it will bog down even more when you press on the accelerator.

I'd start by getting rid of the codes first, and then see if that clears up the problem.

Hmmm pretty helpful post.
I found an IACV for $20 but I need to wait for school to start to pick it up from the guy. Ill try it out and give you any updates.
Primary o2 sensor is brand new though.

Why do you think the idle would change with a new TB though?

Originally Posted by sdlEF

check your cat too..... it might be clogged.

Brand new OBD0 spec cat.

[Arthas]

I took my Y8 TB to get the TPS grinded off and I installed a new Blox TPS and it still feels the same. So that marks off the TPS as a problem.

[C1Civic]

Are all your ignition components in good condition? For replacing things like the wires, it's easiest to go by age.

[sdlEF]

hmm .... are you still using the same map sensor on the TB? also i once had the tps and map sensor backwards and it would start up and idle a bit rough but once i gave it gas it would bog and die on me. that might be helpful to you

[95_civic_gsr]

Originally Posted by Arthas

I found an IACV for $20 but I need to wait for school to start to pick it up from the guy. Ill try it out and give you any updates.
Primary o2 sensor is brand new though.

Why do you think the idle would change with a new TB though?

You said your idle fluctuated before the new TB, and though its not now, it could still be causing your problem, its just not as noticeable at idle.

Anytime your mess with your air intake, you need to reset your IACV. Get your car up to normal operating temperature. Turn it off. Disconnect your negative battery cable or pull your ECU and backup under hood fuses for 10-15 seconds. Re-connect cable or replace your fuses. Make sure all accessories are turned off. (Air conditioning, head lights, dome light, radio, defroster, anything that pulls additional power, even your power steering (just don't turn your steering wheel.)) Start your car and let it idle for 10 minutes. You will hear your IACV working to adjust your idle during this time. When the ten minutes are up, turn off the car. Now your IACV is set. However if you have any check engine lights on, I don't know if your computer will do anything with the IACV. I think it will only run in limp mode, which is why you need to clear out those codes by fixing your car first.

If your car sat for any length of time while your were doing this modification, that would be another indicator of an IACV or a FIV. In my experience, the IACV problems have always shown up after one of my cars sits for a long time. You might check your FIV, its an easy check (link), but it sounds more like you have an IACV problem or an O2 sensor problem. Replace your 2nd O2 sensor especially if you have already replaced your primary O2 sensor, have a new cat and still get the CEL.

[killakam666]

my block is bad though ... yea i used the Y7 IAVC... cuz i had a 2000 manifold and those have the IAVC on the manifold and that was a no no... :O