Rep Power: 0

Hey guys I know this has probably come up a million times but I can not find anything that matches my problems exactly. Please bare with me on this topic as I have been chasing this for quite sometime. I also ask that we stay on topic with this issue as I am truly fed up with this thing and ready to give up.


I have a 2001 civic-T with an AEM Fuel Ignition Controller. The turbo kit is that of the one from Turbo Specialties that they made for the 01-05 civics. The car was tuned by Mike in Mobile, AL on only 5.5 lbs of boost. There was an unknown vac leak on one of the injectors that I did not know about before the tune was done. I fixed that vac leak and have not been able to get the car re-tuned since. The boost now holds at 6 and even hits 7 sometimes depending on throttle demand.

First off The car has a surging idle ranging from about 1100-1500 (somewhere in that range) whether warm or cold. At these RPM's the Air/Fuel Ratio is about 10:1 according to my UEGO. There are no vac leaks!! Trust me I have completely ruled that out.

There are 3 codes that are being read by the computer:
P0505-Idle air control Malfunction
P0141-Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor2)
P0135-Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor1)

In boost the A:F ratio is right about 12, but only in boost. Acceleration, no boost, it runs on the leaner side of fuel:air (14 or 15 if my memory serves me correct). After throttle lift, the UEGO reads 18:1, or 3 dashes for those who are familiar with the system.

During cruise (foot on gas no acceleration) no matter the speed or rpm, the A:F ratio is about 15 with spikes of 18 and the feeling of a loss of fuel for a short second then back to normal. Sometimes the car will even "buck" with the spikes of 18:1 A:F ratios. If I Turn the ignition off and then directly back on, the car will "reset" and will drive normal again for a bit.

When I come to a stop sign or red light the car will sit at a 1500 idle until I drive off again. I can even just take my foot off the clutch and the high rpm is good enough to get the car moving.

I believe these are all the problems and I truly appreciate any help that is given on this matter. Understand that I have literally tried everything I can think of and I am at my wit's end on this.

 
Rep Power: 233

I think that may be the problem. The comp thinks there is more fuel because you restricted the air (plugged the vac leak) causing the sensors to report it's running rich causing the comp to make it run lean. Part of the piggy-back system is to interpret different sensor signals as correct, when you change the signal (plug the vac leak) the comp changes the A/F ratio. I think you may just need re-tuning for the new A/F ratio.

Before paying for an expensive re-tune try cleaning the IACV, throttlebody, and intake plenum (P0505).

 
Rep Power: 0

That makes sense. So was there less air during boost, more air before boost?

In other words, if an engine is sucking in air through the intake and also air sneaking past an injector o-ring, the computer would think that it needed more fuel before boost.

During boost the air being forced in through the intake is greater than the air that was leaking in at the injector o-ring and therefore was forced out, equaling less air and making the computer think it needed less fuel.

Does this make sense to anyone else? it does to me...

 
Rep Power: 233

^^ Correct.

 
Rep Power: 0

I hope I am not sounding ignorant here. I just want to make sure that I get this right this time. I would like to have all the answers before I go looking for a tuner again.

How should I go about trouble shooting the o2 sensors? Is there a test procedure? i.e ohms, voltage from the ECU, etc...

I have read that if you have the ignition on, not running, you should get 12v from the ECU to the o2. This came from an unreliable source, youtube. (yes I know, I was desperate). I tried the test, and yet I could not get 12v on any of the wires which lead me to believe grounded wire. So with that said does anyone know which wires are supply and return for the o2? I would like to do an OHMS test.
Does anyone have a wiring diagram online they can point me too? (the auto zone manual sucks)
Should I do this before I take it to be tuned?

Does anyone know a test procedure for the IACV? (besides the one where you have to cover the hole with your finger)

 
Rep Power: 233

https://www.civicforums.com/forums/1...e-updated.html

 
Rep Power: 0

Thanks Laz, that is just what I needed...