Schrickedvr6

I have searched high and low for answers but haven't seen anything that seems to be the identical issue I'm having. The car is a 99 hatch with a b16a2 swap running on the OEM ECU. Car has run flawlessly for the last year and a half. All of a sudden I have a terrible idle. It fluctuates badly up to 3K. It drives perfect as long as your above 3K rpm. vtec works just like it always has.

Its sucking air from lower hole in the TB at idle/off throttle whether its below or above operating temps and its audible inside and outside the car. When I plug the lower hole the idle drops but doesn't act like it wants to stall. Is the lower hole the IACV and the upper is TPS? Car has no FITV. While driving at about 3500 in 5th gear I can slightly roll into the throttle and the audible sucking from the intake goes away immediately with next to zero load on the car (No bucking or surging).

Heres a couple vids to show what its doing. First one is of the car up to temp with the iacv unplugged.
http://s82.photobucket.com/albums/j2...t=73b93b9c.mp4

Here is what it does on a daily basis with IACV plugged in whether its cold or up to temp.

http://s82.photobucket.com/albums/j2...t=c10a7f13.mp4

This is what I have done so far.

Checked for VAC leaks with Carb Cleaner

Seafoamed it

Pulled the plugs and they are great, wires appear fine

Bled coolant

Pulled intake pipe and its sucking air hard from the lower hole in the Throttle body. Plug the hole and the idle is steady where it should be.

First I cleaned the old IACV then I Swapped out the IACV with a new one

Reset ECU (A couple times, after the new IACV as well)

The only other recent work done on the car was a new alternator belt as it was slipping. This problem starter about a week later which also was the point when the weather dropped consistently below 40.

Thank you very much for any help you can offer!

Former User

With the engine hot, test the resistance of the 2-wire ECT sensor located below the distributor. If the sensor is good, you should read 200-400 Ohms.

Schrickedvr6

Will do that tomorrow and report back. Thanks for the lead!

Former User

If the ECT sensor resistance is fine, then you would next test output voltages from the TPS and follow the service manual procedure for adjusting the idle speed (see section 5L in FAQs sticky).

Schrickedvr6

Ok, in the meantime I pulled the codes and got these two. Now I'm confused....

23 Knock sensor
41 Primary oxygen sensor heater

Former User

Are the O2 sensor and KS connected?

Reset the ECU (pull 7.5A hood Back Up fuse for 3 or more minutes) and then see whether either of those codes returns after driving.

Schrickedvr6

I'll have to check it tomorrow as its getting late now. Whats weird is that the car has run flawlessly for the last two years. I'm not sure on the two sensors being hooked up, I'll have to look tomorrow.

Former User

Does your CEL always remain on steady while you are driving?

Schrickedvr6

Not sure as I had to pull the cluster last night because I had a suspicion that the previous owner removed it. Sure enough it was removed. I moved the ebay light over temporarily to get the codes. Still haven't driven it with the light in place so I'll report back on that also.

Schrickedvr6

Readings are between 130-180. It's kinda bouncing around.

Former User

The resistance is out of spec and unsteady so I recommend that you replace it.

Did any codes repeat after resetting the ECU?

Schrickedvr6

Same two codes keep coming back. I'll get it replaced and go from there. Wondering if I should be replacing the o2 sensor also.

Former User

Regarding the codes, the first step is to check whether the O2 sensor and KS are installed and plugged in.

Agreed.

Schrickedvr6

Replaced ect, reset ecu. Same two codes and same issue. Knock sensor and o2 sensor are both plugged in and wiring seems good.

Former User

How did you reset the ECU?

Did you bleed the cooling system after replacing the ECT?

Does the heater element power wire of the primary O2 sensor have battery voltage with the key in ON(II)? What is the resistance of the heater element? If you unplug the O2 sensor, does the idle speed settle down?

Test the KS sensor wire for an open or short. If the wire is fine, replace the KS sensor. If you unplug the KS sensor, does the idle speed settle down?

Schrickedvr6

Just in case anyone is looking in the future. It turned out to be a completely broken off FITV..... Even though it was bypassed it was creating a vacuum. Car runs perfect now.