gregnm369

First off, I have tried a search, but couldn't come up with a similar enough situation to help me.

Today, I upgraded to a SoS 70mm throttle body and did the coolant bypass mod. The inlets on the bottom of the TB are capped off and the coolant line is now connected with no leaks.

At idle, the engine would rev up and then go back down between 2200rpm and 1000rpm. The person who helped me with the install said that it was air bubbles in the coolant because we interfered with the flow. After letting it run for a while, sure enough, the problem was solved.

I left work today and accelerated aggressively (after thorough warm-up). When I put the S2k in neutral at 50mph, the engine started doing it again, but would only do so for about 2-4 "pulses" then would normalize. I can reproduce this effect every time.

Currently, there is no CEL. Although I had one yesterday before the install (because I took off the airbox and didn't put a vacuum line back - I caught that). I have verified that all parts are where they should be before asking this.

My question is this: What is the most likely culprit, and how would I go about fixing this?

RacerXI

Does the car idle normally? Does the car take a sec. to return to a normal idle when slowing for a light? It sounds like an idle issue. It's broken...send it to me

S2oooNvegas

tb opening is too big. this happens with the J's 66mm at times. ask several who have encountered it. they will prob chime in soon. this is the reason i havent gone to a bigger TB yet, i guess ill end up with the J's 64mm. or have my tsocker bored.

gregnm369

Well, the idle has normalized on its own. As I drive and go to neutral, it sort of stays around 2000 and then reduced to 1000 in about a second or less. So I'm ok with that.

The CEL came back on though! UGH! I'm taking it to get the code scanned. I hope its just the vacuum again. The switching valve on the airbox was making a weird noise yesterday. We determined it was the cyl. cap on it making the odd noise, so I'm just hoping that its not performing its function properly and making the light go off.

thetz99

there is a vacuum attachment under the fuel rail cover that you probably dislodged when you were rocking the tb to get the intake pipe on...that's probably your cel and your erratic idle.

Silver9k

It sounds like something was changed with the idle bypass valve. Or something wrong with it. There is no reason for a larger throttle body to do this "because its bigger" On all TB's there are idling motors and bypass valves so that air can get into the engine when the thottle plate is closed.

I'd check and make sure all the connectors are tight and check and make sure there is nothing blocking or in the way of the bypass.

If everything is normal, then maybe they did change something about the bypass. In that case go ahead and reset the ECU, hopefully it will re-learn some new settings for the idle control valve

gregnm369

Problem identified!

I took it to my master Honda tech at work and he pulled the CEL. I pulled code P0411. He said that it was my secondary air pump (smog pump) that was fried because of its relay sticking.

He then gave me the best nudge in the right direction. TSB 06-055. P0411 is a covered code under this TSB and I have already called and set up an appointment at the local Honda dealer to get it done.

The fact that I had put on a new TB was just a coincidence, and we both got a chuckle out of that.

Currently, I have 34k miles in case anyone wanted to know when this could happen.

MikeyCB

He thinks the local dealer will TSB despite your mods to the car? Usually they look for any reason to deny warranty or goodwill coverage.

I hope you're a sweet-talker

gregnm369

Thank god that SoS TB is just an OEM one bored over! They aren't going to touch the TB during the work. In fact, they will only pull the code, look at the part in question. They don't have time to get a car and evaluate EVERYTHING on there before trying to make a decision to TSB something.

chopper-world

we install tbs on a few s2000s. they are very very sensitive, its the sensor on the left side. you must make sure it reads 5.45'OHMS' on a voltage meter .... so try it and u will see your car will be back to normal,