KA24DET won't idle ran fine before

[ZaK687]

Hey guys, so I've been working on my ka24det for quite some time and been working through the problems as they come. Ive been DD'ing my ka24det for at least a month now and one morning on the way home it wouldn't idle any more after i took an exit and came to a light. I can start it and give it gas and it'll drive fine but once i come to a stop the revs drop like a rock and the engine stalls. Ive checked my injectors, sparks, looked for vac leaks (going to go more in-depth on that), sprayed carb cleaner into the aicv and it didn't make a difference, done a compression test and I've recently cleaned my maf (less than a week). I am stumped, car ran PERFECTLY before, tune was spot on, only issue was minor valve stem seal leak.

My setup:
9:1 supertech pistons (150psi across the board)
370cc injectors
t25 hybrid turbo (twisted motion)
n62 maf (grounds combined)
255lph walbro pump

afr's 14.7~ at idle, 11~ in boost

let me know if more info is needed I need to get her ready for a competition in august.



EDIT: the day before this happened i changed the sparks out

EDIT 2: checked codes, only got knock sensor. code showed up before issue and tested a different sensor with no change so i ruled that out. Fuel pump is on a toggle and is producing pressure so thats also been ruled out

[brndck]

make sure your alternator is charging and the battery is in good condition.

[ZaK687]

alternator tested fine and battery is good too, can crank the engine no problem. just no idle.

[DanteTris]

I had a similar issue (with a ka24e-t). Try opening up the iacv all the way (left turn on the screw with the tps unplugged) and see if you can get it to idle that way. If you can get it idling (it will idle high) then try turning it down and down until it idles where you want it. Sometimea after cleaning the aiv the carbon will just build up in the iacv solenoid and cause less air flow.

If that fails you should check the slavk on the trottle cable and if it is too much it can cause the tps to think iys open when it is actually shut. Good luck!

[ZaK687]

ill try that and get back to you with the results. any other suggestions would be greatly appreciated!

[r34sr]

Check to see if your throttle plate set screw has backed out.

[ZaK687]

checked the maf, cleaned it off again, no luck. Tried opening up the aicv and unplugging the tps and only the first time did the idle jump way up then eventually drop back down till it died. checked the set screw and didn't see an issue. I am completely stumped ><

[ZaK687]

Morning bump, tried swapping out ignition coil. No results

[anti tyler]

Air leak after mafs?

Plug the break booster and start it, maybe you've got a good vacuum leak somewhere.

[2.5T_/<ouki]

I see you did a compress test so that required you to remove the spark plugs. Did you happen to examine the ground electrode on the spark plugs to make sure they aren't broken off?

[ZaK687]

Bump Still working on checking for a vac leak and yea the spark plugs were not broken

[ZaK687]

BUMP checked any possible vac leak sources and came up with nothing. also swapped in a spare coolant temp sensor to rule that out. This is beyond me right now.
SO FAR:
MAF is in spec
injectors are in spec
no vac leaks
getting spark
getting fuel
coolant temp sensor is in spec (500 ohms? I test 3 one brand new and they all came to this)
I've redone my timing
sprayed carb cleaner through the iacv (may just pull it and thorougly clean it even tho i don't think this could cause my car to SPONTANEOUSLY not idle yet run fine if i keep giving it gas to keep it alive)

any and all suggestions are welcome!

[kruked]

Suggestion #1. You don't need to bump this. It's not the "For Sale Section". Your problem will still be viewable within the top 10 threads for the next 2 weeks.

Suggestion #2. Re-gap your spark plugs if all you did was change your spark plugs and then this problem came out of left field.

Suggestion #3. If suggestion #2 didn't give you piece of mind, go get new spark plugs.


This does seem like a vacuum leak though. Or you unplugged something stupid and didn't plug it back in. Check your TPS on a DMM.
Do you have an emissions delete? I see that your location is Cali, maybe you're brave enough to ride around w/ no emissions.

[KAT-PWR]

Do you have an air compressor?

[ZaK687]

Force of habit, yes my car is emissions deleted and it's sealed up tight there. I actually just tried gapping them again and swapping them out. No luck. Ended up contacting Martin from rs enthalpy, he thinks it's either my maf or a blown intake manifold gasket. Trying for the maf right now, guess my multi meter is crap.

Yes I do have a compressor

[KAT-PWR]

Well using your air compressor and pressurizing your system would rule out intake gasket. But you did that already?

[ZaK687]

I did not yet, gonna try that ASAP

[KAT-PWR]

This is the issue we usually run into.
You say "no vac leaks"
But you have not truly ruled it out.

[kruked]

Could also use carb cleaner or something of the sort to check for blown intake manifold gasket. If you give it a try, me personally, I'd try it on a cold engine.

As for the MAFS, throw a direct chassis ground onto your ground wires.

[DanteTris]

How do you have your PCV setup? And where did you run the hose from the back of the iacv (not the solenoid vacuum line)?

[ZaK687]

update: compressor belt broke so i decided id just visually check the manifold gaskets. turns out the lower one was missing a huge chunk. gonna fire it up tomorrow and see if that solves it.

[ZaK687]

Final update, problem solved (blown intake manifold gasket). Didn't realize a vac test would be effective in checking the manifold since its behind the throttle body (stupid ><). Thank you for all the help!