1999 civic EX/Si with D16y8 M/T
codes- P0135: O2 sensor heater circuit B1S1
- P0505: idle control system
recent work: replaced exaust with used OEM, changed timing belt, timing belt tensioner, spark plugs, IACV, TPS sensor
Issues:
1- I have tried pretty much everything aside from replacing the TB including testing and replacing IACV, and TPS sensor. P0505 refuses to go away and stay away. As soon as the code goes from pending to confirmed(when the CEL would usually come on) the car starts to surge by 200 RPM and will buck and jolt whenever letting off/stepping on the gas. This is quickly fixed by either turning the car off and on, or clearing the codes. Planning to install a used TB later this weekend from my old D16y8, hopefully this will finally solve it.

2- when I first purchased the car I had severe acceleration issues. When driving anywhere below 2500 rpm the car has next to no power(even less that an average D series would have) and as soon as it passed 2500 rpm it would just take off. Changed timing belt and made sure timing was dead on (both mechanical and electrical)(still ended up with a fully retarded distributor) and was still sluggish. Was told that having a distributor so retarded could be the cause so I went ahead and advanced it bit by bit (followed full procedure or timing adjustment) until it felt normal and have been driving it like that since.
While it’s nice to have my acceleration back, I would love to have some help figuring out what the heck the issue is so that I can put my car back in time and keep up with the bicycles in stop and go traffic.

2.5- my timing belt in the front end (exhaust side) is a bit loose but doesn’t look loose enough to adjust by another tooth. How would I go about changing this(it does seem to tighten up and loosen as I’m cranking to TDC)

TIA to anyone that can help.
Can provide photos of anything if needed

 

The IACV, was it new or used?

The TPS, did you calibrate it? I am not 100% sure if the 92-95 specifications hold true for the OBD2B 99-00 civics but I do know the TPS needs to be properly calibrated.

Lastly, have you checked the wiring from the TPS to the ECU to be sure there is no breaks or shorts? And also for the CFK sensor at the bottom of the timing belt at the crank and lastly for all the wires from the distributor to the ECU. Any of these if not providing proper signal can give you serious running issues. I would even check the wires from the IACV to the ECU.

Wiring of this age can be a serious challenge and it's a slow painful process to nail down where it's failed.

 

-the IACV was new. Tested it before installing to make double sure.
-Yes I did calibrate the TPS.
- I’ll have to give that a try. Would be nice if it was just a wiring issue.

 

If all that fails it might be an ECU issue. Sometimes it's obvious as in you pop open the ECU to see blown electrolytic capacitors.