ZC swap idle surging when warm

[moosebrew]

Hello, so I did a ZC DOHC swap on my 90 civic DX with a 1.5. I did the DPFI to MPFI conversion and am using a PG7 ECM. I made sure the TPS outside wires were swapped over as per the instructions and everything seems to be wired correctly.

Now for the problem, the motor starts, runs and idles fine when cold but when it warms up the idle starts surging from about 700RPM's to about 2000 RPM's. You can rev it fine but seems to be running somewhat rich.

Noticed that the idle smooths out when the vacume line is disconected from the MAP sensor and plugged. The MAP sensor is the factory one from the DX and is mounted on the firewall.

We have cleaned the throttle body and IAC sensor as well. Did have some O-rings leaking on the injectors, could a bad lower injector O-ring be the cause of this?

ECM s/n: 37820-PG7-L031 684-112059 8Y

Any ideas to what might be the cause would be appreciated!

Thanks
Mark

 

[D16SiHatch]

You could try getting a new iacv seal. i had a leak between the iacv and the intake manifold that i couldnt hear, and i couldnt pinpoint by spraying sudsy water in the area. but once i popped in the new seal it started up and idled perfectly. not sayin this is definately your problem, but its somethin you can look into, as it sounds like you may be running low on ideas at this point lol. to rule out possible vaccum leaks and possibly narrow it down to the iacv. just unplug the iacv while the engine is running and the engine rpm should drop to damn close what its supposed to be at idle. if it does then you know its either a faulty iacv, or the seal. If it continues with the hunting idle or doesn't come down to around 700rpm or so, then its safe to assume its somethin other then the iacv. then to clear the cel just disconnect the battery for a few mins, or pull the respective fuse which powers the ecu.

 

[jlicrx]

i would try a different MAP sensor if the idle is steady with the MAP vacuum disconnected - also make sure that it is completely full of coolant and that there are no air pockets in the cooling system

 

[moosebrew]

Thanks for the suggestions, I'll order up a iacv seal when I order the upper and lower injector o-rings. It was a bit of a suprise to see the spray of fuel when we tried starting it up the first time.

We did bleed the coolant system via the bleed valve but now that I'm thinking of it I am not sure if the heater valve was opened when we did it. I suppose it is possible the coolant flowed around the valve after we bled the system to cause the problem.

I am also going to see how much the coolant temp sensor is and if its not too much I may just replace that as well. I think I have read through just about every "idle" problem thread on here and there are tons of this type of problem occurring, but not to many answers I am finding.

Keep coming with the sugestions PLEASE!

Thanks
Mark

 

[moosebrew]

Surging idle fixed.

Well its been a while but I ended up taking the car to a shop. The guy said he cleaned the throttle body really good and adjusted the air flow (not sure what that means) but the surging idle is gone.

It sat for around 2 years so i have been working on cleaning the car up and running fresh gas through it. Today it started leaking coolant from the back of the motor but I couldn't figure out where from. Seems to be from around the oil filter, is there coolant in that area?

Mark

 

[D16SiHatch]

there are many lines with coolant back there so it's hard to say where exactly it might be coming from. nearest thing to the oil filter anyway would be the coolant pipe that runs along the back of the block.

 

[moosebrew]

thanks I'll have to check that again,
I could see there were a ton of lines on the upper part of the motor but the leak seemed to be coming from below the intake manifold. This is a DOHC ZC motor and it has what lookes like coolant lines running to the oil filter houseing. Is that something these things had?

Mark

 

[ZCpowerdSI]

the closest thing to the oil filter are the coolent lines to the oil cooler. maybe the lines are cracked or something.