Misfire at idle

[andrewxxcarlson]

Hello all,
New to 240s, not new to forums nor wrenching.
89 Coupe (Ill try to get a picture up)

Too start, I am usually strictly opposed to buying modded cars. As the work does not usually meet my exceptable standards. Bought the car from an older gentleman (55ish), who has owned it with his son for the last 10 years in California. Spent the last 2 years on non-op. Said stock, original motor, 120k...what?? 120k and the odometer works? Yes. Im a skeptic of course. But I've been around this long enough to know, this motor was original with 120k. 4k was the asking price and 4k is what I gave him. Rust free, couple exhaust leaks, a misfire. But nothing I couldn't handle. Came kitted as well, fairly well done too. A Touge RB silvia kit. Looks pretty, not sure its the style I'm gonna go for, but its also came with the original pig nose body panels, and also my much sought after silvia front end.

Moving on, time to register and get this bitch ready for smog. First impression...eh, clunky in the rear (Kaaz 2-way diff) what feels like its borked but ill get more into that later. Misfires at idle on I believe 2 cylinders. Under load above 1500rpm misfire is gone. Idle is solid at 750. Done all the maintenance that youd normally do with any car with unknown history.
-Spark plugs
-Wires
-Cap & Rotor
-o2 Sensor
-Oil
-Coolant
-Fuel filter
-Fuel pump tested at 48psi before the fuel rail.
-Cleaned MAF
-Cleaned throttle body
-Properly adjusted TPS, .5v idle, 4.3v WOT
-Properly timed @ 15 BTDC
-Cleaned up some vacuum lines running to AIC
-Seafoam in gas tank and through brake booster.

Doing a cylinder balance test shows that when cylinder 3 and 4 wires are pulled, there is m00t change in idle compared to when pulling 1 and 2 cylinder wires. I have good spark on all 4 cylinders. Compressions numbers are 170 160 175 180. So if I have compression and spark, so that leaves the fuel side, like I said fuel pressure is fine. I do believe I'm running rich, smell fuel on plugs after compression test. I've noid tested each injector connector and I'm getting solid signal. Putting a stethoscope to the injectors all injectors click on and off across the board, no difference between them. I have ordered 2 injectors to see if that will correct my issues.

Problem number 2, Kaaz 2-way diff, this is my first time ever driving something that locks this often, it turns me on. YET, it makes noises. YES, i know these make noises. Can hear wheels bind on slow turns, but what I do not find normal is the clunking/popping. Its really more of a popping, kinda like a worn ball joint or tie rod. But when the diff pops it much more violent and its numerous times. If it was like one or 2 pops ya I understand. But is this how its really supposed to be? My 10 years in the field tells me this is a little excessive to the majority LSD 2-way diff noise.

I apologize for making this a long intro, just tryina get this thing on the road and smogged. But this is my intro, I am looking for any advice or experience anybody has had with these symptoms, and I'm glad to be apart of the zilvia forums.

[rawgarage]

kaaz be poppin bro

[KAT-PWR]

Check injector o rings

[andrewxxcarlson]

Waiting on another injector.

[andrewxxcarlson]

Okay, replaced two injectors, the others "seem" fine. O-rings have been replaced. No leaks in that area. Still not convinced I've found all the vacuum leaks even after smoke testing. Misfire at idle its more subtle but not quite gone. Idle fluctuates ever so slightly, maybe 2-300 rpms. Driving is pretty much the same although I've noticed a better low speed on/off throttle response. Less bucking.

I notice when I open the throttle to around 1500rpms and hold it, I can get it to miss and hear continuous popping in the exhaust. Which kinda makes me think I may have a bad spot in my TPS?

Any thoughts?

[Dboyizmlg]

Tow it to my house.
I can find, and fix the problem

[andrewxxcarlson]

Originally Posted by Dboyizmlg

Tow it to my house.
I can find, and fix the problem

Tow it? This 89 would make it there no issue. Any tips other than unrealistic situations?

[andrewxxcarlson]

So dick'd around a little more today. Noticed when I spray brake cleaner around the underside of the EGR valve car wants to die. Don't know if leak is coming from EGR valve or other surrounding areas. Also noticed that when I push up on the diaphragm the car tries to die, but does not. So that brings me to a new issue I don't really need advice on. Even if I fix my misfire (hopefully from the leaky EGR) I will still definitely not pass smog.

Gonna pull the whole EGR system, replace valve, pull upper plenum on intake manifold clean out passages and drill out a broken stud in the head causing a massive exhaust leak and hope the miss is gone.

[andrewxxcarlson]

UPDATE, intake manifold has been removed, egr passages cleaned, egr valve cleaned and vacuum tested. Same issue still exists. I have good spark, I replaced 2 injectors, don't know if the other 2 are leaking..ill pull the fuel rail off and prime the pump and see if any leaks out. Pretty sure I don't have anymore vacuum leaks though, idle only fluctuates when it misses. I've sprayed around and found nothing. Fuel pressure is good. Timing is good. Spark is good. Compression is good.

Anybody know specs for MAF signal wire?
Also, if my tps was calibrated correctly can it still be bad? Wouldn't i notice a loss of voltage with throttle sweep?

[andrewxxcarlson]

UPDATE, went to check smog numbers today.

HC (PPM)
MAX MEAS
83 36
65 11

CO (%)
MAX MEAS
.53 .53
.44 .04

NO (PPM)
MAX MEAS
559 41
516 697

Why are my NOx so high at 25mph? I also currently have code 32 for EGR valve not opening, I cleaned it, moves freely, doesn't leak. Why is it doing its job at 15mph but not at 25?

[inopsey]

high temp produces high nox

[andrewxxcarlson]

Originally Posted by inopsey

high temp produces high nox

Thanks I am aware.

[andrewxxcarlson]

Update, EGR solenoid is supposed to have battery voltage at idle, and then drop to 0-1v racing the engine. I have the opposite. I have .7v at idle, and battery voltage while racing engine. Point to a bad ecu? Doesn't seem like it would just flop if the terminal was bad..??

[andrewxxcarlson]

FIX, vacuum hoses swapped on the 3 vacuum hardlines. Swapped them to there correct locations and EGR functions.

Now to fix my idle. Idle stays around 800+-100. Can feel and hear random misfires. Any ideas? Refer to my original post for already replaced parts and actions taken.

[zombiewolf513]

injectors.

[Jefro240]

Vacuum leak will cause a misfire. I was going to say make sure your BOV isn't leaking but from your post I assume your on a stock KA. EGR stuck open will also do it. Use propane to test for leaks, if the rpm rises or smooths out then you found the leak.

[andrewxxcarlson]

Originally Posted by Jefro240

Vacuum leak will cause a misfire. I was going to say make sure your BOV isn't leaking but from your post I assume your on a stock KA. EGR stuck open will also do it. Use propane to test for leaks, if the rpm rises or smooths out then you found the leak.

I'm constantly searching for vacuum leaks. Can't find any, yet it is hard to notice when RPM changes at idle due to the fact that idle fluctuates every few seconds. Tried smoke testing to no avail. Will look for exhaust leaks before the cat but I'm pretty sure I already took care of those.

Got updated smog numbers today after getting the EGR code to go away.

HC (PPM)
MAX MEAS
83 12
65 10

CO (%)
MAX MEAS
.53 .03
.44 .03

NO (PPM)
MAX MEAS
559 129
516 621 FAILFAILFAIL

Any tips or tricks just to get it down 120 PPM or so?