pignose.007

Hey guys, I just finished building my KA and dropping it back into my car, and it will start and fire, but idle like absolute crap. When it idles, the engine will drop RPM's and eventually die over a period of about 45 seconds to a minute. When it is idling, the entire engine shakes quite a bit, and it also sounds like it is misfiring somewhere. I have a few variables on what it might be but any advice from you guys would be great.

1) I have a tiny crack in one of the vacuum lines that snakes through the intake, but I wouldn't really think it would cause the engine to run THAT badly.

2) I checked all the resistances for the fuel injectors and #'s 1,3 and 4 checked out with a 11.2 ohm resistance which from my understanding is within OEM specifacations. (11-14 ohms) #2, however put out a reading of 3.8 ohms, which leads me to believe that the fuel injector is bad. I back-probed all of the connectors, so I know that it is not a faulty wire or ground.

3) Could it just also be that will all the new parts on the engine, they just have not had time to break in yet? List of new parts:
-Connecting Rod Bearings, Wrist Pins, and Pistons
-Timing Chain and Cam Sprockets
-Machined Crank
-Cap and Rotor for the dizzy
-Plug Wires and Plugs
-O2 Sensor (Upper)

I know I have the timing set correctly, and followed FSM procedure to do so with the engine brought to TDC on cyl.1 (the yellow mark on the crank pulley), and the dizzy set with the rotor facing where the #1 plug wire goes, I unplugged the TPS sensor to begin setting the timing and set it at 20* BTDC and the mark will line up perfectly when the idle is at about 1500 RPM's.

I've pretty much run out of ideas, so any help would be greatly appreciated. Thanks in advance!

GreinTime

Pull the number 2 fuel injector plug off after you start and see if it will stay running. Or do it before and see if it starts easier. Mine ran on 2 cylinders and idled fine when I accidentally swapped wires 1 & 3 I think. It ran, just not sure if those were the ones I had flipped.

In regards to item #3 the answer would be no.

In regards to #1, you should replace it just to eliminate the variable, even if you just loop it around the intake for now.

signal240sx

hi there.my engine ran the same exact way a few years back and it was for sure a injector.i replaced it and all was well.id say that was your problem but since its a fresh build who knows lol.just thought id share my experience I had.i think I pulled the injector wire connector off one by one.if it died that was a good injector.if it stays running the same you know that injector was bad and not making a difference.

signal240sx

ok greintime put that up as I was typing didn't mean to piggyback your answer dude ha

GreinTime

You're good man, I laughed and said the same thing to myself about you typing it

pignose.007

I have a new injector on the way soon. Should be here in a couple of days. Thanks for you help. And Signal240sx, it is a fresh build, but I didn't replace the injectors, thinking that they were okay. Weird though, because they ran fine before the motor spun a bearing. XP

pignose.007

And GreinTime, thank you for answering with responses to my other questions as well.

signal240sx

no prob let us know if it works after that. and damn wish I woulda thought to put 007 in my name somehow ha

andisan

Yeah bad injector will make it run bad and shake, when mine does that I know it's an injector and I unplug one at a time to see which one it is.

Good luck

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pignose.007

Alright. So I threw a new injector on and it runs a ton better. I also got a new fuel filter as well. It still idles kind of rough and when I pump the brake pedal it wants do die. I believe it may be a vacuum leak somewhere, but I'm not totally sure.