IAC Valve unhooked for a sec, now car won't (rb25det) start

[mmakam2]

hey guys i don't know whats going on, i was testing some catch can setups, and i forgot to hook up my IAC Valve for a couple of seconds, it started up and stalled, then i put everything back the way it was and now it won't start.

I'm definetly getting fuel i can smell it, compression is fine, im assuming its not getting spark, but why would this happen all of a sudden? could i be flooded or is that just a carb thing?

if anyone can tell me some things to try and troubleshoot, it would be awesome

[ultimateirving]

Its a carb thing. You need to take it off

[mmakam2]

take what off? can having the intake hose for my IAC unhooked for a second kill it? and even if it did, i should still be able to start it by giving it partial throttle?

[mmakam2]

so i took the plugs out, they were pretty soaked but they looked fine, so i cleaned them with sand paper and brake clean, put them back in, and im still having the same problem.

im thinking when the vacuum line to the iac valve was open something broke it, and now my car won't start.

Does anyone know if a busted IAC will completely prevent a car from starting?

[2.5T_/<ouki]

If its shut it can. The IACV is what controls the idle when throttle is closed. Take it off and check the spring as well as the screw. Make sure to use a new gasket or silicone gasket when replacing.

[mmakam2]

im picking up a new one if im going through the trouble of taking it off, apparently the 91-94 sentra iac valves are exactly the same, and i can grab one for about 100 bucks. I just have to move the t fitting for the air regulator on to the new one.

[Cease_Super_Hicas]

Check ecu codes first

[Driftwire]

Bro before you go replacing random parts. I would disconnect the battery, allow the ECU to reset. Plug everything how it should be. Dry the plugs and leave em out to let the flooded gas evap. Than fire it up..

[mmakam2]

i tried resetting ecu already, ill try leaving the plugs out with the battery disconnected when i go to school then try to start it when i get back, let u guys know what happens

ill spray some wd40 into my iac too, maybe thatll help

[Chaluska]

i dont think so..

unhooking the IAC for a second or two isnt going to do anything. its a solenoid actuated valve, which will either open or close to allow metered air into the intake manifold, bypassing the throttle body. if you unhook the rubber hose, the only thing it will do is allow un-metered air into the intake, it will make the car run like crap (because you will now have unmetered air coming in the engine) but will not cause it to not run. as soon as you reconnect it, it will work properly

another key, do not hold down the gas when cranking the car, its not a carb'ed car, it doesnt need any extra pump.

I think you have problems elsewhere.. check your spark and check your fuel, if you have both, then check into timing.

[mmakam2]

What's the best way to check for spark?

[Driftwire]

pull a plug out and hold it near something metal and have someone crank the car a second, If you see spark comming from the plug you have spark. Do it for each cylinder. Also pull the fuel pump fuse when doing this to avoid flooding the car.

[racepar1]

ill spray some wd40 into my iac too, maybe thatll help

DO NOT SPRAY WD40 INTO YOUR IAC VALVE!!!!!!!!!!!!!

What you're describing should not cause the engine not to start. Check for spark, check all electrical connections, check for ECU codes, check ANYTHING else that you might have touched.

[mmakam2]

i didn't touch anything, literally, all i touched was a couple of vac lines.

so i didn't spray the wd40. but i unplugged my fuel pump fuse, and the car started up! wtf is going on.

so i plugged the fuse back in, now wont start again.

unplugged the fuse, and it ran like shit for like 15sec

(and yes the fuel pump definetly stopped pumping)


i also noticed a bunch of fuel in the balance tube.. dont know what that means

[mmakam2]

my theory is its still the IAC because when i unplugged the fuel pump it was able to lean out enough to start, when its pumping normally, its not getting enough air to keep the mixture correct


also, does having 800cc injectors have anythign to do with my problems?

[s13chuck]

i didn't touch anything, literally, all i touched was a couple of vac lines.

so i didn't spray the wd40. but i unplugged my fuel pump fuse, and the car started up! wtf is going on.

so i plugged the fuse back in, now wont start again.

unplugged the fuse, and it ran like shit for like 15sec

(and yes the fuel pump definetly stopped pumping)


i also noticed a bunch of fuel in the balance tube.. dont know what that means

to help us out, when you crank it, does it fire and immediatly die, or just crank?

[mmakam2]

with the fuel pump on, it cranks sometimes it makes a noise like it almost fires, but not quite, but pretty much just cranks

fuel pump off, itll run for a few seconds and die.

[shoguner]

my theory is its still the IAC because when i unplugged the fuel pump it was able to lean out enough to start, when its pumping normally, its not getting enough air to keep the mixture correct


also, does having 800cc injectors have anythign to do with my problems?

Uh... Is your ecu tuned for the 800cc injectors?!

[mmakam2]

Of course the car ran perfect before all this I have a 70mm turbo, wiseco pistons 86.5mm, greddy emanate, lots more

[trxrx7]

the IAC has nothing to do with it not running, my IAC is not hooked up and i drive like that just fine, the only problem i have is when rev'd up and the rpm go down again it has a hard time finding its idle, like it almost dies and then jumps back to normal idle, when the IAC is not hooked up it could make it not run properly but it cant make it not run. also when when i start the car it runs normal but lets say i stall the car on a take off getting it to start is very hard i think its from leaky injectors causing it to flood when the motor shuts off i cant start it right away, but when the car is off for a while and the fuel inside the motor has disappeared it starts up no problem. i think your problem is fuel or spark related, but hey thats just my theory, good luck!

[mmakam2]

The problem your describing happens to me too, I've long suspectedmy iac valve was bad , but I think there is difference between not being hooked up and stuck closed

We will see I'm going to take the plugs out again, and the iac tomorrow, and I'llget back to you guys

[silverv35]

it sounds like u just really flooded it out.. just dry the plugs if u have access to an air blower dry out the cylinders if not just unplug the injectors and dry crank it for a while when u stop smelling the fuel from the cylinder your should be ok to reinstall the plugs crank a few more times with out injectors just to be sure its nice and dry then plug them back in and should be ok.

[ultimateirving]

DUDE what you described with the car running with the fuel pump fuse removed happened to me too. It ended up being a huge vacuum leak that i didnt notice.
Do a boost leak test and see if you have a leak.
Then thank me with paypal funds

[mmakam2]

SOLVED: So, my plugs were pretty fouled up, and i was definetly flooded, got the car started with new plugs pretty easily, but now when i go into boost it starts hesitating like crazy.

Going to start a new thread with some other questions, thanks for all your help everyone!