Hesitation? Holds RPM? Stumbleing at idle?

[Ninjabread]

OK, well, I got done putting in another KA to replace my old one with the messed head. So far it seems to be running good except for this small problem. At Idle, sometimes the rpm will stumble a bit, and also when I'm in gear, it seems that If i give too much throttle, it will stay at whatever RPM I'm currently at, sort of like a launch control would do.

Now, I did check my timing, I tried 15* and 20* with no obvious difference. Spark plugs are brand new, new-er igniter and spark plug wires. The only thing different from my old KA is that I removed all the emissions stuff (ie: EGR system and AIV system), also deleted the carbon canister. I'm thinking my problem could be vacuum related. Right now, since I delete egr and such, I have 1 line comming off the intake manifold on that nipple. It goes to my FPR edit:( I used to have one goes to the actuator for the secondary butterflies, but removed it for now.)

I researched this, but came to no conclusion about what it might be.

Here is a video that better describes my problem.

[Ninjabread]

OK, so my buddy came over, we checked the timing, and it was off by a bit. We set it to 20*, car will still sometimes stumble a bit at idle, and when driving, it will randomly hesitate, moreso when I apply 100% throttle.

Right now, trying to see if it's vacuum, eletronical or fuel related.

*edit: In my eyes, could be clogged fuel filter (although it wasn't before), failing fuel pump, bad ground or maybe a vacuum leak.

[pr0ject TRUENO]

Did you eliminate the idle system too? Check all the vacuum lines going from the intake to the back of the intake manifold to the IAC/IAV

[Ninjabread]

Eliminated:

-EGR (block off plate, sealed with silicone)
-Pretty much the whole vacuum circuit, including that vacuum transport plate with the sensors on it (Only vacuum line back there is FPR)
-AIV valve removed completely
-Vacuum nipple under TB plugged
-Vacuum line on the side of manifold plugged as well

New parts:

-Water temp sensor
-O2 sensor
-Spark plugs
-Accel spark plug wires
-New-ish ignitor
-Intake manifold gasket

Now it does stumble at idle, and that I can understand being associate with the IACV, but it was ok before the motor swap (I used the same intake mani from my old motor). Could the hesitation be cause by that as well? Plugs might not be gapped properly?

Just throwing anything out there because I haven't seen a definitive fix for it.

[pr0ject TRUENO]

Well, since you have no idle valve anymore, your idle speed is basically dependent solely on your throttle opening. Try adjusting your throttle plate and see what happens. Tighten up the throttle cable.

[Ninjabread]

See, I'm not too too worried about the Idle for now, and the IACV is still there, not sure what you meant. It's still connected to that tube on the intake piping. I'll get pictures of my bay up.

Right Now I'm more worried about the hesitation / missfires. Misfires happen down low from 1-2.5k and hesitation is anything higher than that. Someone had mentionned to me that my fuel pump could have crap the bed.

[Ninjabread]

So, today I also decided to check ECU before going any further.

I got:

11 Crank Angle Sensor (does this mean i need a new distributor?)

13 ECT Sensor (which is brand new... could the fact that my temp gauge wire isn't hooked up be causing this?.)

21 Ignition Signal Circuit (what could this be?)

34 Knock Sensor (luckily, I have another one)

[mtx450]

Any resolution to this? My car just started these same symptoms tonight. It drives sort of fine at regular throttle, and then when full throttle is applied, or more then 25%, it sounds exactly the same as it did in that video. I also noticed that the EGR isn't moving with throttle anymore, like it used to. That could be it, but then again, the car has already had injector issues. Gonna do some testing tomorrow.

[240sxScores]

yea id like to know what happened to this too. I have a bad idle untill the car is finally warmed up but then theres a jerking in the engine when im at cruising speed in the car that makes the hole car jerk, it gets really damn annoying.

[mtx450]

Originally Posted by mtx450

Any resolution to this? My car just started these same symptoms tonight. It drives sort of fine at regular throttle, and then when full throttle is applied, or more then 25%, it sounds exactly the same as it did in that video. I also noticed that the EGR isn't moving with throttle anymore, like it used to. That could be it, but then again, the car has already had injector issues. Gonna do some testing tomorrow.

Originally Posted by 240sxScores

yea id like to know what happened to this too. I have a bad idle untill the car is finally warmed up but then theres a jerking in the engine when im at cruising speed in the car that makes the hole car jerk, it gets really damn annoying.

Heh, sorry I didn't post back. I figured out what it was. Very weird actually.

I painted my VC and then replaced the gasket (obviously) and put the VC back on. I then tried that shitty engine cleaner (didn't really work, needs elbow grease) and then hosed everything down. I covered a lot of stuff up, but didn't (idiot) cover up anything by the spark plug wires. Water got into the top of the spark plug and caused no spark. I just took out the plugs and cleaned them and it went back to normal.