Got a 91 jdm zc sohc motor & 91 si tranny...Everything was swapped in for a d15b2 and converted to mpfi with a pm6 ecu and d16a6 intake manifold...All wiring was depinned professionally and has been gone over many times along with the vacumn hoses.

It has 1/4 tank of gas and does NOT throw any CEL or ECU codes while it idles normal or rough...Spark plugs,spark plug wires,oil,radiator,cap and rotor are all brand new...The car is still obd-0 with d16a6 injectors and resistor box.

Main relay and pm6 ecu are both working and so are the back ups...Car does not overheat but the radiator fan switch does need to be replaced...TD-02U dizzy being used is the one that came on the zc sohc from the jdm importer...Full compression in all cylinders and spark plugs are not fouled and don't smell like gas

Problems:
1)Starts when it wants to after cranking a couple of times and sometimes it doesn't start at all after trying for a while...Battery is charged and I got spark,fuel,air and the timing is spot on.

2)When it does start sometimes it idles normal at 1000 rpm and when I turn it off and restart it it idles at about 200 rpm and feels like it wants to die but doesn't.

 

I have almost that exact setup in my 91 std hatch and I sometimes have problems like this.
Does it ever idle perfectly fine and then suddenly drop? Its a nerve racking problem.

So far ive tried cleaning the IACV but that did nothing. Does your IM have the FITV on the back? If so, is it wired and functioning? I am beginning to suspect that.

 

yes sometimes it cranks up and idles perfect and then it suddenly drops when i give it some gas at times...im also using the d16a6 intake manifold with the fitv wired up but aint sure how to test if its working...i do have a extra fitv laying around but aint sure if that one works or not since it was given to me with the complete a6 manifold as a back up

 

Video 1:
This is what happens after I turn it back on after idiling normal for about 20 minutes...As you can see it idles really low like if it wants to shut off but doesn't...It also doesn't throw any CEL or ECU codes
http://www.youtube.com/watch?v=p0f3Xed5Huc


Video 2:
This is the video from when I first started it up today from a cold start...As you can see it revs and idles perfect...As soon as I shut it off and start it again the idle is like crap and it bogs and shakes like crazy
http://www.youtube.com/watch?v=JmndcaTPuBc

 

find out what your fuel pressure looks like. I have a similiar issue once in a blue moon where my car fires up and idles low, but after gassing it, it comes right back. I know my issue is related to my horrid basemap that have yet to finish tuning. It could also be a bad sensor, either coolant/air temp/or o2 sensor. Those are the only sensors i know of that change with temperature that could be adversely affecting things. I still am leaning strong on a fuel pressure issue. DPFI is more forgiving with stuff like that.

 

might be that your idle just needs to be adjusted. I know when I start my car up from a cold start it idles a little high, around 1800rpms, then after it warms up the idle drops to around 700-800 rpms. don't know if this is your problem but just throwing it out there. it seems that your idle is adjusted low, so on cold starts it idles "normally" then when the engine warms up it drops too low.

 

idle has been adjusted but still no se puede...i know the idle screw is kind of messed up on the throttle body but as stated there is times when it idles perfect but then after it heats up the idle just sucks...it doesn't idle up and down irractically either

 

for a resolution...!!!

 

 

 

still need some help

 

ive heard of a bad map sensor making it idle low. maybe trying switching that out?

 

this is a strange one alright.. have you tried another distributor to see if anything changes?

also, above you mentioned something about being unsure about wiring for the fitv. the fitv does not have any wiring lol. you're thinking of the ficsv. if you had one the fitv would be beneath the tb and is controlled by the expansion/contraction of a thermowax plunger that reacts to the coolant flowing near it. the ficsv (fast idle control solenoid valve) however, which is on the driverside corner of the intake manifold, raises idle by adding a small amount of air when ambient air temps are like super duper cold lol. so what i'm getting at is your idle/way your car is running is not likely related to the ficsv. if you want to hook it up though. one side of the switch is ground i believe, and the other goes to b3 at the ecu.

 

map sensor is plugged in fine and never gave me a problem with the old d15b2 motor.

the ficsv is hooked up already and was brought up as a fitv by garageef above as a potential problem...i haven't tried out another dizzy yet because clipse hasn't given it to me...its weird because it starts up fine when its both cold and hot when it wants to.

sometimes after i turn it off and back on again it idles fine or it just bogs and shakes with a very low idle to the point of dying...i let it idle for 30 minutes and it would idle normal then all of a sudden it will do the low idle then go back to the normal idle after about a minute.

this is the final problem im having to getting my car back on the road...still no CEL or ECU codes with the crappy idle ether...btw the idle doesnt fluctuate since that was just me giving it some gas in the video...it has a steady idle whether being normal or very low.

 

awhh.... man this problem sounds very familiar to what happen to me when i swapped my ZC into my hatch.. and did mpfi
problem is that was a couple years ago.
;/ sorry man... From what I can recolect is changing out the map sensor... I remember mine wasnt throwing codes either.... and I haven't had a problem with the idle since then, until i over heated my car and it burnt up the eacv. ( recently )
good luck with your problem Hope this junkyard pocket trick helps :D

 

but from reading this... sounds like your idle screw needs to be turned in... and when its cold the choke vaccumm on the side of ur Throttle body is keeping it at normal idle... then as soon as it warms up it goes down.
flat head right above the opening of the throttle body, by the red fuel canister hose on TB
if i remember right... IN is up RPM idle and OUT is down, just have it running when you do it... you'll find out real quick

 

it has already been adjusted correctly when the timing was done last week...!!!

 

worth a shot to turn it in... all it is, is a big flat head.
good luck... looking forward to seeing the resuloution

 

ok i think i might of found the problem but need confirmation...when i first start it up from a cold start all the way to when its at operating temp the little suction hole inside the throttle body sucks air at all times while the car idles at 1000 rpm...when i plug it with my finger it then wants to shut off but goes back to normal when i remove my finger...when i unplug the iacv the car doesn't die out.

when i shut the car off and turn it back on the crappy low idle comes back and when i put my finger inside the throttle body to block the hole there is no suction at all...it doesn't even shut off and when i give it gas it still doesn't have any suction to it.

im still running a d16a6 intake manifold and there is no fitv mounted on it either just the tps,iacv and the ficsv...i have a new iacv laying around from the old zc sohc intake manifold if this is the problem

 

tps

 

well i changed out the iacv with a newer one and there is no change...!!!

 

i believe the there is a tps on the zc also, check grounds, take intake hose of and drench it with TB cleaner, sometimes residue build on the butterly, also check compression in cylinders, where did you get motor from?

 

tps is fine,no code 7 or jerking,all grounds checked,tb is clean,compression in all cylinders and motor was purchased from a legit jdm importer with a 6 month warranty...!!!

 

damn that's odd. im confused - is it temp activated or not? cold engine, 1st start rpms are always good, 2nd always low right? warm engine, 1st sometimes good? 2nd sometimes good?

given your intake vacuum note -
sounds like IACV to me. ruled out defective IACV, this leaves defective ECU closing it for no reason - or bad ground leading to ECU receiving false RPM readings, and sending bad signals to the IACV. As far as I know the IACV should be sucking in air anytime the idle is anywhere near 800, even at 1,000 rpm. for whatever reason its not, so that could be ur issue.

 

it does it when i start the car back up after it reaches normal operating temp...its starts to do the crappy low idle but when i rev it off and on then the idle drops to about 800 rpm.

iacv was replaced yesterday and it actually increased my idle to about 1200 rpm steady...primary pm6 ecu and my extra pm6 ecu are working fine...wiring and grounds were checked again and cleaned.

i did notice that the new dizzy rotor i bought from kragen has a odd shape from the manufacture and spins at an angle instead of straight.