Rough idle after driving, PLEASE READ!

[[|V|]]

If anyone has any thouhts or conclusions i would greatly appreciate it. I have a 98 civic ex with a 97 lx swap, old engine blew, bought the car with the lx swap. Heres the issue, i would be driving for about 20 miles or so, everything is perfect, then when i come to a red light or a stop and sit at idle without load, my car starts bogging out and has a heavy idle surge, it almost sounds like its camming really hard. Ill try and accelerate in first and my car doesnt want to respond, i can bypass the idle surge if i give the car more gas, and when i shift into second gear and step back on the gas, my car idle down really low, with the gas still being pushed, the car jerks really hard and bypasses the idle surge again untill i go and shift again. When im driving ill turn off my car and restart it, (dump clutch start) after that, everything is perfectly normal. I replaced all my gaskets (tb gasket, iacv gasket, valve cover gasket, intake mani gasket, exhaust gasket, plug seals) , brand new iacv, brand new vac lines, brand new fuel filter, brand new coolant temp switch, brand new thermostat, brand new temp sensor, full lash adjstement, all signal and reference wires are wiin spec, volatage drop on ground is under .2v on iacv and coolant level is perfect. Im so puzzled on why my car idles how it does, and its only sometimes. If anyone can help or has had this same issue please respond to post. Thanks!

 

[00siboy]

Is your mechanical timing good? I have seen different engines act like this, where they drive fine cold but once they warm up they start bogging/stalling. Its almost always the timing belt being off a few teeth.

Any check engine light or codes? I noticed you said it was an EX (d16y8) with an LX (d16y7) swap, which would mean different PCMs. Was the PCM from the y7 swapped over as well or are you still running the one from the y8?

 

[[|V|]]

Im getting a p1509 (Idle Air Control circuit malfunction) . If i turn my car off while the surge is occurring and restart, the problem immediately disappears but engine light stays on. Im almost thinking its a lean misfire due to pcm failure or bad dizzy..

 

[00siboy]

Was the PCM from the y7 swapped over as well or are you still running the one from the y8?

 

[rebirth]

Clean the IACV

If anyone has any thouhts or conclusions i would greatly appreciate it. I have a 98 civic ex with a 97 lx swap, old engine blew, bought the car with the lx swap. Heres the issue, i would be driving for about 20 miles or so, everything is perfect, then when i come to a red light or a stop and sit at idle without load, my car starts bogging out and has a heavy idle surge, it almost sounds like its camming really hard. Ill try and accelerate in first and my car doesnt want to respond, i can bypass the idle surge if i give the car more gas, and when i shift into second gear and step back on the gas, my car idle down really low, with the gas still being pushed, the car jerks really hard and bypasses the idle surge again untill i go and shift again. When im driving ill turn off my car and restart it, (dump clutch start) after that, everything is perfectly normal. I replaced all my gaskets (tb gasket, iacv gasket, valve cover gasket, intake mani gasket, exhaust gasket, plug seals) , brand new iacv, brand new vac lines, brand new fuel filter, brand new coolant temp switch, brand new thermostat, brand new temp sensor, full lash adjstement, all signal and reference wires are wiin spec, volatage drop on ground is under .2v on iacv and coolant level is perfect. Im so puzzled on why my car idles how it does, and its only sometimes. If anyone can help or has had this same issue please respond to post. Thanks!

Before you start replacing stuff, did you try cleaning the IACV. had a similar issue when I got my engine rebuilt. Car was dropping at stops, and then just revving up and down after a while. Mechanic told me I needed a new iacv. I took it apart, and cleaned it with brake cleaner, and then Carburetor Cleaner, and a towel. make sure you let it air dry first. Also clean the throttle body where the iacv connects so that it can open and close freely. Mine was perfect after I did this, and I have not had a problem since. This was over 3 years ago.