Mr.Fubbs

Hey fellow Honda enthusiasts, I have been working on a JDM first gen b16 that I put in my 89 civic hatch.

Most recently I have swapped my cracked stock manifold for a skunk2 pro-series manifold and now the car will not idle properly. It idles high (about 2000 rpm) when cold and begins to surge when warmed up.

I have bled the coolant and when I cover the TB with my hand the car dies suggesting there are no vacuum leaks.
The IACV is brand new and the new manifold doesn't have a spot for the FITV (which sits on the old manifold) so I simply rerouted the coolant lines and called it a day.

Under further inspection, I noticed when i place my finger over the lower hole inside of the TB there is suction and the idle changes. The lower hole is the port for the FITV (according to my understanding) which no longer exists on my car. In fact the manifold doesn't even have a corresponding hole for this passage way.

Needless to say, I am awfully confused and any thoughts or guidance would be greatly appreciated.

Mr.Fubbs

After I removed the throttle body the problem became quite clear. The port leading to the FITV on the throttle body was overlapping with the skunk2 pro series intake manifold bore.

I decided to fill the hole with some JB weld, hopefully this will solve my issue.

To all first gen b16 owners: although skunk2 claims this manifold will fit your motor, you may have to replace or fab up your stock TB to fit properly.

Mr.Fubbs

My idle has been brought down about 500 rpm, but unfortunately an idle issue persists. Now it surges upon start up for about 1 to 2 seconds, then idles steady but too high.

However when I let of the gas the idle drops down to about 800 for and then surges back up to about 1400.

I checked the voltage on my TPS and it read about .5 at close 4.5 at open as it should. I am now unsure of what to check next.

As usual any thoughts or advice are welcome.

HondaPartsHero

Check and adjust your throttle cable. And perform the idle reset in the FAQ.

Mr.Fubbs

Thanks for the reply, I have set the throttle cable and preformed the idle reset procedure to no avail.
Any other ideas?

Blown90hatcH

Have you tried swapping TBs?

Mr.Fubbs

Thanks for the suggestion! I ended up swapping the TB with a 68mm TB a friend lent me and it would appear my idle is no longer high. The IACV hole on the stock b16 TB overlapped with the over sized bore on my new intake manifold as well.

However, now my idle is too low! I do have a few suspicions as to what the cause may be so I will keep this thread updated when I get the time.

Thanks again everyone for your help thus far.

Blown90hatcH

Turn the idle screw up.

Mr.Fubbs

Unfortunately I am continuing to struggle with my low/lumpy idle problem. While the idle fluctuates slightly when cold, it does it much more severely when warm (between 850 and 300ish rpm).

Also when given gas, the car wont return directly to 850 rpm but will stay around 1500 and slowly work its way down before beginning to yo-yoing again.

The throttle plate is fully closed, I have set the base idle to 500 using the idle screw (with IACV unplugged), I have set the timing to factory and bled the coolant many times with no success. Also my IACV clicks when given 12 volts.

Once again I am at a loss. Thanks in advance for any advice.

Mr.Fubbs

I forgot to mention, I also found a small gap between my headers and exhaust which I sealed with an exhaust sealer, and the ECU has been reset.

Mr.Fubbs

For the sake of closure, I ended up finding a sneaky vacuum leak by the map sensor tube (its the firewall mounted kind), and a tiny coolant leak from the underside of a heater hose leaving the block.
After i fixed those issues and bled the coolant again, she idles fine.