Okay so I have a 91 civic hatch std with the z6 swap using a p28 ecu. When I have all of the vacuum lines hooked up it idles really rough and has really bad throttle response and when you release the throttle it sometimes dies. When I unplug one of the lines it runs perfectly, no rough idle or throttle response issues. It also runs fine when all lines are plugged in if the cooling fan is on. Also I have a cel code 9 incase that makes any difference. Where should I start?

 

Start with the ECU error.

What distributor are you using?
Assuming you used the correct P08 TD-42U
If you don't have that distributor, then stop and go get one.

Code 9 (cyp sesnor error) -
Check your wiring for the distributor.
If wiring is good, then get a new distributor.

 

I am pretty sure its a bad distributor because I had a code 41aswell, but I fixed that and the code 9 went away with it but only for 6 hours or so and the next morning it was back, ill check my wiring before I replace it though.

 

Okay so I fixed the check engine light, it was a loose wire at b12 on the ecu plug. Now Im stumped as to what is wrong with the idle. When I unplug a vacuum line from anywhere it runs fine the idle isn't even high, but as soon as I plug the vacuum lines in it idles terrible probably around 400 rpm. I've already cleaned the IACV and the FITV twice and it hasn't helped much if at all.

 

Throttle position sensor? Similar issue I had and this resolved it. Does it fluctuate when it tries to idle?

 

I'm having the same issue I've cleaned and replaced the tps, FITV, IACV, fuel pressure regulator and still having the issue. I can hear the idle fluctuate sometime when its idling really low no cel I'm really irritated I've been trying to figure this out for two weeks now and i have to drive 10 hrs to school this weekend if anyone has a solution please let us know. Thanks

-92 civic lx
-d16z6
-p28 ecu
-5speed tranny