Rok_Stok

1994 Civic Si, '97 JDM B18C GSR swap, Y21 LSD tranny

OBD1 to OBD2 jumper harness, OBD2 P72 ECU

When I drive around and put it in neutral to coast it idles at 1500 rpm, I have to come to a complete stop for the idle to go down to 750 rpm. Anybody know what's going on?

EJeff8

Your brakes put strain on the engine.

EJeff8

Also, why do you need the jumper? Both the engine and ECU are OBD2.

Rok_Stok

Yes, but my car has an OBD1 engine harness, I can't use the JDM engine harness because it's made for a RHD vehicle. Normal idle is 750 rpm, so it comes down to normal when I come to a complete stop. I'm wondering why it idles at 1500 rpm while I coast in neutral. It should idle at 750 rpm while in neutral no matter what.

whiteboyGSR98

perhaps take off the idle control valve and clean it out... my single did that and cleaned it worked for a little ended up having to replace it

delsolo95

Any CEL?? Are vaccum lines connected right??

Rok_Stok

Okay I'll try that, I have a spare GSR IACV laying around just in case too.

No CELs, I got rid of them both today lol. They were 17 (speedometer) and 41 (header o2 sensor), which are unrelated. Vacuum lines are all hooked up, I checked them many times because there's a ton since I'm running the stock GSR intake manifold.

I did reset my ECU after I fixed my VSS connector and plugged in my o2 sensor today. This is my first time to run an OBD2 ECU, maybe it needs time to learn? Any ideas?

Rok_Stok

Well I fixed it...

Today I started the engine and it idled at 1500 rpm constantly. I found that the screws were backing out of the TPS, problem fixed.

delsolo95

good to know!

Mad-Mike

iTrader: (1)

My em1 does the same thing.

court76wi

That's normal. I don't know about all Honda's, but most of them have a rolling idle and a standing idle. My 89 CRX and 97 GSR both have a faster idle when the car is moving.

I don't know if it's to help with shifting or prevent the engine from bouncing/surging, but my Integra service manual even mentions the two separate idle speeds...

Rok_Stok

Hmm, never heard of that before. It ended up being my TPS, it was almost off the manifold.

fsp31

That's right. My 97' B18Cr does the same thing. I even drove for a short time without the brake booster connected (blocked the hose to the manifold) due to a malfunction. Idle was not affected at all.