B18C1 – Bogging at 2000 RPM (Honda/Acura)

[Sam]

Hello all,

I’ve got a slight bogging or stuttering issue with my car. Its a 1993 Honda Del Sol with a B18c1 engine (from a 2000 or 2001 Integra GSR).

Symptoms: Stutters and feels a bit restricted when accelerating around the 2k-3k RPM band, typically with a heavier foot on the throttle. If I bring the car up very slowly, I can usually avoid it. As well, its usually second gear that I experience it most, but occasionally third too. Lastly, I believe its only evident when the vehicle is up to operating temperature.

Engine Swap: Some info on the swap which may be helpful. The engine is from an OBD2a Integra GSR, I believe 2000/2001. The engine is more or less unmodified, side from an aftermarket intake and headers. Swap was done by myself with the help of a backyard mechanic friend. Original OBD2 engine harness (and distributor, alternator, etc.) were used, and connected up to my OBD1 body harness. I am using a regular OBD1 P72 ECU from an OBD1 Integra GSR. This combination of harness, accessories, and ECU should work without a hitch despite the generation differences – given that I rewire for the GSR intake and knock sensor which my previous engine (D16z6) didn’t have – these changes were done during the swap. The B18c1 engine ran perfectly fine prior to the swap, no bog or stutter, only known issue was some valve ticking. The small rear main seal and oil pan leak were addressed during the swap.

CEL Codes: Initially after the engine swap and first start up, I only had a #41 – Primary Oxygen sensor heating circuit. To my knowledge I dont think this should have much effect on anything except possibly mileage? And may be due to a fouled or dirty sensor… During the break in period when I started to experience the bog, I rechecked and also now have a code #23, Knock Sensor. I’m not sure if this would create the bogging issue. As well, since it appeared during the drive and not the initial start up, I question if its a bad sensor, or if the wiring for it may be at fault.

Known problems: May be unrelated, but there is still a slight oil pan leak, and a very slight coolant leak somewhere around the engine – I’ve yet to get it into the shop and locate the source… The coolant leaks outside, and drips down onto the exhaust causing a burning coolant smell. There is no coolant leaking within the engine to my knowledge. As well, there is valve ticking that will be looked at when it gets into the shop again.

If anyone could chime in with their thoughts that would be much appreciated. My best guess may be something vacuum related? But I’m not sure.

Thanks for any and all help!

Topic

[college man]

Try unplugging the knock sensor to see if it runs better. What on the intake did you rewire?

[Andrew Harris]

If I were you I would chase down and fix the two codes you have first and foremost and then go from there. Fix what you know is wrong first before trying to chase down ghost.

[Sam]

Hm… Reading into it a bit more it seems like the knock sensor is a good culprit – in combination with my loud valve ticking? Anyways, I shall try unplugging it and seeing if it changes.

As for the wiring – or repinning rather, on B18c1 and I believe some other H series intakes, there is an IAB (intake air bypass, or secondary butterfly/runners) that needs to be wired into a GSR ecu for it to function. Typically, people borrow the wire from the EVAP purge solenoid and repin the ECU plug so that the EVAP purge solenoid wire becomes the IAB wire, thus losing the EVAP purge solenoid function. This is what I did. Again, only a knock sensor wire was added from the engine harness to the ECU, and the repinning of the EVAP purge solenoid wire to the IAB.

See pic:
[spoiler]Example of repinning procedure

[Sam]

Welp, after a bit of time I managed to get under the car and take it for a test drive.

I unplugged the knock sensor and reset the ECU. Following this, the engine only had a code 41 – the same primary oxygen sensor heating circuit code. I’ve got a spare o2 sensor that I need to throw on when I can borrow an o2 socket tool.

After driving for a bit and getting it up to operating temp I noticed that it still had that bit of restriction around ~2k rpm when I was heavier on the throttle. Parked it and checked the codes again, this time, the same 2 codes: #41 and #23 – knock sensor.

I think it can be concluded then, that its most likely the wiring between the sensor and ECU causing the code… Reading around, it seems that knock sensors need shielded wiring from to protect it from RF interference (?). Not sure exactly how it all works, but when I wired the knock sensor into the ECU, I used regular ol’ 16ga primary wire.. Any other thoughts on what could be causing this? Thanks in advance..

[Author]

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