DOHC ZC IDLE ISSUE!!!
01-13-2008, 06:25 PM
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DOHC ZC IDLE ISSUE!!!
Yeah This is 
i have a 91 civic hatch with a jdm dohc zc the thing will not idle for **** when its cold, but when it warms up its fine ive tryed changing the map sensor, throttle body gasket, ecu, and IACV an still the problem remains, so long story short im stumped and was hoping someone might have a solution for this problem any ideas or suggestions let me kno thanks....
i have a 91 civic hatch with a jdm dohc zc the thing will not idle for **** when its cold, but when it warms up its fine ive tryed changing the map sensor, throttle body gasket, ecu, and IACV an still the problem remains, so long story short im stumped and was hoping someone might have a solution for this problem any ideas or suggestions let me kno thanks....
01-13-2008, 09:07 PM
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01-13-2008, 10:23 PM
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see i messed with thath screw and it dosent help plus i took the purge solinoids off there not the problem cause i did it on 2 other cars and they are running fine...could it maybe be a cracked intake manifold of broken intake gasket maybe???
01-14-2008, 12:20 AM
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Re: (dubstackz)
dose your car idel high?
even when its worm?
because some honda motor come with the FIT valve. (fast idel thermal)
if it is bad your call will start up like (junk) and when it heats up its cool (perfict)
that sensor/valve is under your throttle body.
if your car is on ideling and put your finger in your throttle body and plug the bottom air vent/hole and if the idel gose down then its your FIT valve.
IF YOUR CAR DONT HAVE A FIT VALVE.
then on your throttle body there is a vacuum valve that also helps you on start up ideling. it right above your throttle cable on the throttel body. it had a vacuum hose going to it.
if it not any of them.
what is it that your car is doing right when you start it???
mybe this will help.
good luck and have fun...
Modified by 424racer at 1:41 AM 1/14/2008
even when its worm?
because some honda motor come with the FIT valve. (fast idel thermal)
if it is bad your call will start up like (junk) and when it heats up its cool (perfict)
that sensor/valve is under your throttle body.
if your car is on ideling and put your finger in your throttle body and plug the bottom air vent/hole and if the idel gose down then its your FIT valve.
IF YOUR CAR DONT HAVE A FIT VALVE.
then on your throttle body there is a vacuum valve that also helps you on start up ideling. it right above your throttle cable on the throttel body. it had a vacuum hose going to it.
if it not any of them.
what is it that your car is doing right when you start it???
mybe this will help.
good luck and have fun...
Modified by 424racer at 1:41 AM 1/14/2008
01-14-2008, 03:37 AM
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Re: DOHC ZC IDLE ISSUE!!! (dubstackz)
First off.
Are you resetting the ecu when you adjust the idle screw on top of the TB?
if not the ecu will readjust and cause an idle issue.
Second:
Are you conmpletely sure that the butterfly valve is closed all the way?
If it is open to far the ecu will read a high air intake.. and the idle air contol valve (IACV) will try and readjust to get the right air/fuel conditions. Normally causes the fluctuating idle.
third:
What are your compression numbers?
Low compression on cold start up will cause a rough or unsteady idle.
fourth (which depends mostly on the third):
Check your valve clearances.
I have had 4 different DOHC ZC's. All of them had idle issues. When I ddid a valve adjustment I have always ran them at the low end of the tolerance spec. This brought up the compression and help with idle at cold temps. I live in NY and have run my ZC in the winter months with no issues after having your same dilema.
For whay its worth.. MY 2 cents.
Are you resetting the ecu when you adjust the idle screw on top of the TB?
if not the ecu will readjust and cause an idle issue.
Second:
Are you conmpletely sure that the butterfly valve is closed all the way?
If it is open to far the ecu will read a high air intake.. and the idle air contol valve (IACV) will try and readjust to get the right air/fuel conditions. Normally causes the fluctuating idle.
third:
What are your compression numbers?
Low compression on cold start up will cause a rough or unsteady idle.
fourth (which depends mostly on the third):
Check your valve clearances.
I have had 4 different DOHC ZC's. All of them had idle issues. When I ddid a valve adjustment I have always ran them at the low end of the tolerance spec. This brought up the compression and help with idle at cold temps. I live in NY and have run my ZC in the winter months with no issues after having your same dilema.
For whay its worth.. MY 2 cents.
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01-14-2008, 03:50 AM
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Re: (424racer)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 424racer »</TD></TR><TR><TD CLASS="quote">
IF YOUR CAR DONT HAVE A FIT VALVE.
then on your throttle body there is a vacuum valve that also helps you on start up ideling. it right above your throttle cable on the throttel body. it had a vacuum hose going to it.
if it not any of them.
what is it that your car is doing right when you start it???
mybe this will help.
good luck and have fun...
Modified by 424racer at 1:41 AM 1/14/2008</TD></TR></TABLE>
In all truth.. you really don't need this to run your engine. As long as you have a good tune with everything else you should have no issues. Even in low outside air temps.
IF YOUR CAR DONT HAVE A FIT VALVE.
then on your throttle body there is a vacuum valve that also helps you on start up ideling. it right above your throttle cable on the throttel body. it had a vacuum hose going to it.
if it not any of them.
what is it that your car is doing right when you start it???
mybe this will help.
good luck and have fun...
Modified by 424racer at 1:41 AM 1/14/2008</TD></TR></TABLE>
In all truth.. you really don't need this to run your engine. As long as you have a good tune with everything else you should have no issues. Even in low outside air temps.
04-10-2017, 11:43 AM
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Re: DOHC ZC IDLE ISSUE!!!
Hey guys i know this thread is old but i cant figure out whats going on with my car. I have a 1997 civic cx hatch that had a d16y7 in it but had blow by so i bought a zc motor from hmo and swapped it in. It starts runs and drives but the idle fluxuates and the thermostat wont open. Im using the stock y7 intake manifold. Only thing i notice a difference is the coolant line on the hard pipe is just a few inches closer to the thermostat housing on the zc than on the y7. My iacv looks fine and gasket is good. Tried adjusting idle screw and did nothing. Any help would be greatly appreciated! Thanks
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