3 days ago car started fine, drove it around and once it warmed up at operating temp, I noticed how rpms stayed high when clutch depressed as in 1100-1200rpms, then it would drop to usual 750-800 in a few seconds, thought it was my IACV which I knew it wasnt good to start with. Got car home and shut it off.

Left ECU unplugged that night to reset it, yesterday tried to start it, wont idle whatsoever, I had to keep my foot slightly on accelator to keep it running. Shut it off and sourced IACV.

Today, replaced IACV (again left ECU disconnected). Now car absolutely wont start whatsoever, it just cranks and cranks. I have spark (checked 3 out of4, should run with 3 regardless), injectors work they put fuel in cylinders while cranking, nothing is clogged, vacuum lines are new, I checked timing on top (DOHC ZC) and its alligned. Doesnt mix water/oil and doesnt leak anything, no codes.

I just lost half of my day figuring this out, and I'm completely lost. I have everything working but when cranking it feels as if its going to fire but it doesnt, I even jumped battery however its new so thats not an issue. Please help. Thank you.

 

Well, It needs 3 things to run

air fuel and spark

So your saying you have all 3


Is the replacement IAVC screen clean? Is the map and IAVC plug swapped?


Just taking a stab in the dark here

 

Exactly I have all 3... Its taken out of a working car and it worked though. I didnt unplug anything except IACV since yesterday and it now absolutely wont start. Thanks for replying btw!

 

Clean the IAVC screen that originally was on the engine.

Let it dry and put it original back on

is there a check engine light on?

 

I've tried that already, wont start even if I keep accelerator down, just keeps cranking and feels like its going to fire but it doesnt .. No CEL whatsoever.

 

Check distributor cap and rotor,

possibly the coil could be bad or cap and rotor

 

Would that cause high idle when warm and then unable to keep idle a day later and then complete unable to start? Symptoms are weird hence why I cant figure it out. Though spark is strong on every plug, plugs are new as well as wires, not even 3 months old.

 

High idle could be a vacuum leak, butterfly open a bit, or psooibly a few other thngs

 

I stop, rpms drop to 1100, stay there for few seconds, then drop to 750-800 and stays there until I come to a stop again. IACV problem right? IACV replaced, car wont start whatsoever. Gets fuel, gets spark, gets air, timing at top is alright.

It cant lose compression all of the sudden cant it? I opened radiator cap and got my GF to crank it, water inside the radiator barely moves (engine shakes while cranking hence very very little movement back and forth, not up), no bubbles either. I dont lose coolant, I dont lose oil, oil cap doesnt have anything on it. Nothing is leaking nowhere though.

 

Try to pull codes.

As it may still be an idle air problem, press the gas pedal very slightly while trying to start. It will not start with the gas floored due to flood control logic.

 

Cant pull codes when theres none, its an obd0 ECU.

Absolutely, I've tried that already and it makes no difference, I know not to floor it, still wont start :/ Thanks for reply!

 

wait a sec..

Now I need the car info, ECU info

Cuz if your using some weird ECU, then thats the problem right there..


List whatever isnt stock on your 96-00 civic

 

Everything worked for 3 years so far. DOHC ZC in 92 del sol, PM7 ECU from Integra I believe? Unsure where I got ECU from however I know its for this engine + it worked. Not like I just did swap though.

 

Well, ECUs do take a ****... Especially ones over 20yrs old..


I dont know what to tell you.. Maybe post this up in the 5th gen forum where it belongs and you may get some better results

 

I know they do but I have fuel, meaning ECU sends signal to injectors, not like I'm missing on anything ... Thanks for your help thus far!

 

Actually I just thought of something, how would I know if spark is strong enough? At some point I had to replace ICM with a used one, could it be an issue?

Btw heres the video of cranking.


I can smell fuel at soark plugs but when I tested them they do spark though.

 

You're looking for a white/blue spark. For what it's worth, I spent a month here and there diagnosing my car, had fuel, spark, and timing was dead on. Turns out while it had spark OUTSIDE the cylinder (testing the plugs grounded to the block) once I put the plugs in, the compression was too much and it blew the spark out. Replaced plugs and it fired right up, it had been running rich and fouled out the plugs. If you have access to a known working distributor I would also try swapping that out.

 

Did you check video above though? Thats how it cranks .. When I pulled plugs they were wet and smelled like fuel however they were slightly black, more of a brown but with a small amount of black on it and they are 2-3 months old ... Tried to dry them and put back in, wouldnt start .. What I'm most confused about, all of the sudden when warm, idle would stick at 1100-1200, then drop to normal after 5 seconds. Tried day later, wont idle whatsoever, changed IACV. Yesterday wont fire at all, like literally nothing else happened or was messed with, symptoms dont tell **** snd no CEL either...

 

Have you checked compression? I would try that. Needs fuel, air, spark, timing, and compression to run.

 

Could I tehnically lose compression instantly? Nothing broke that day I drove it, it just kept idle when warm at around 1100 when I come to a stop and then it would drop it to 800, usual symptoms of bad IACV... It has spark but I cant distungish whether its good spark or a bad one, not sure how strong it is.. It has fuel and timing is set ... I did try opening radiator cap and cranking it, water doesnt move, dont have compression tester but if I try to move crank by hand and a 17mm ratchet, its hard to move (thats good right, meaning it has compression?), if I crank it for 5-10 secs then it moves a bit more easier (I guess oil gets where its supposed to?). I literally showered myself with fuel from injectors, they do get fuel to cylinders hence why sparks are wet/smelly of fuel. Whole engine is sealed, nothing leaks nowhere, water is clean, oil is clean, oil cap is clean, car just doesnt start whatsoever. I find it funny. 4 days ago no issues, 3 days ago warmed up and noticed my idle is at 1100, then it would drop to its usual 800. 2 days ago tried to crank it, wont idle, had to keep gas pedal pressed. Yesterday replaced IACV, no start whatsoever. If anyone could sheed some knowledge I'd appreciate it, this is just getting insane. Fuel pump works, fuel gets to cylinder it just doesnt ignite it apparently?(has spak but I cant tell if its weak or not, it sparks), although whenever I crank it, it feels like starting as you can hear from the video itself but it just refuses to.

 

Unless you had something explode, which I'm assuming you would have noticed, I highly doubt you lost any compression. For the sake of troubleshooting it may not be bad to check, but I highly, highly doubt that's any part of this.

I had a car a few months back that was doing the same thing, plugs were wet and smelled like fuel so I assumed it was getting gas. Turned out I was wrong, once I checked the pressure at the rail I found it was low/nonexistant, ended up dropping the fuel tank and discovering the pickup line for the pump had fallen off.

Have you tried using any starter fluid to get it kicked over?

 

Yeah compression was a long shot, I only suggested it because of how it sounds when it cranks. It's got to be spark, man. The starter fluid idea is worth a shot, only costs $5 or so for a can. If the spark is yellow or orange, it's bad. Try a different coil/ignitor combo out of a known working distributor and clean the plugs.

 

You'd never freaking believe what it was, freaking IACV ... It was blocking air entering the combustion chamber and compression would force air out of intake instead of igniting it with fuel... Had my GF to crank it, air would go out of intake manifold instead of sucking it in, got a new IACV, installed it and cranked it, started like new. I was blown away, at first I thought wtf why is air going out instead of inside through IM, I was already praying to car Gods its not headgasket failure between the cylinders.

 

How exactly was the IACV blocking air to the combustion chambers? That's...like...impossible. What you're describing sounds like the mechanical timing being way off and letting the intake valves open during the compression stroke.

 

It was stuck closed and only way air gets to engine while idleing is through that little hole on TB, right? When I replaced IACV with a brand new (not used) it fired right away and works just fine for the past 3 days. You tell me lol, it was blowing air out of intake. When replaced, worked like a charm, I havent touched a single thing except replaced IACV... Symptoms I explained in previous post were happening with old IACV, since then, no issues whatsoever.