Never seen this before, maybe anybody at that.....help please

OKay, so Im new to this site and loving it that there is an active 240 group in wisconsin! Ill start by saying I have a 1991 nissan 240sx coupe with a ka24de engine, has about 180k on the engine. I rebuilt the engine about a year ago, and it still sits. Now for the problem I am having. The engine will just shut off while driving. Doesnt matter if its up hill, braking, corning. Happens at all diffrent rpms, mostly seems to happen when I get on it, or while I shit. When the engine shut off if I have it in gear it will buck and try and pop start it self with no success. All the electronics work, rpms, radio, lights etc... Also the cars idles varries, 1000 - 2500 rpms .Now I did some searching and found many "like" what I have but not really like what I have. Today I started to unplug some of the sensors to see if any effect it the engine. What I found was wierd. Idling I unplug the tps, it drops a bit but nothing to kill the engine (tps is new, maybe 1 month drivng on it. Next I unplug the IAC and it sets down to 700 rpms ( correct idle!) That also is new, same time as tps. I took it for a drive and no killing but I have to play with the throttle when slowing down, because iac is unplugged. I park it and plug it back in and it jumps back up to 1-2.5 rpms. Also I know I have a bad speed sensor, its unplugged now. Yes I have the part, waitting to put it in. I also have a consult cable, plugged it and got Ign signal primary. So I looked up how to fix it and it said replace coil. Well the coil pack was replaced same time as tps,and iac. It should be good. I have the fsm but I dont really know how to us my mulimeter.....maybe I just need to know how to work it to run the test but Im kinda lost. I have also replaced the dizzy, rotor,wires and I have the no gap plugs. Any suggestions would be great.

I may have had a similar problem before.

Quick Q- Does the car stumble before it's about to die, or does it just seem to shut off real quickly?

one second Im joy riding and bam, hard to say. kinda stumble then out. I thought it might have been fuel pump so i replaced the fuel pump, the whole thing.

Sounds like a wiring problem, either from the coil itself, or signal wire from the CAS. That is if the consult is actually reading correctly. Its an old car and the wiring is know to go bad. If i were you, i would test the coil per FSM (using the ohms setting and checking resistance in the coil). Also i would check continuity (resistance) from the coil wires (not the big wire that goes to the dizzy cap but the harness wires) and dizzy plug wires all the way to the plug at the ecu. While doing so, wiggle and bend the harness to see if you can get a fault to happen.

It sounds like you need to adjust the IACV and throttle stop screw to the correct rpm at idle.

Quick Q as well- When the car dies, do you lose all electronics? Does it start rite back up? How long after initial start up does it usually take to it fall on it face and die?

If it stumbles then I personally would be taking a look into the fuel pump wiring. Check and/or replace the relay (You can swap the AC relay for the FP unit). I rewired mine myself because I had problems with the stock setup before.

The other major thing is to check over all of your grounds, and to inspect for any wires that may have been caught on anything or worn down. Check out the low hanging fruit, you know?

Does the engine run smoothly when it is running good?

Wish you were closer, then I could offer some help in person.

I had replaced the coil, and control. Reading now how to use the mutimeter, plan on checking grounds. I had tried setting the idle via unplugging and what not. Thought I followed the fsm for setting it. When it dies its just the motor, everything is still on. I thought maybe some sort of safe mode to save itself. It doesnt usaully start up on the first key turn, maybe 2nd or 8th. It happens at random, some times I drive and hour others 5 min. I thought it could be fuel but I have new fuel filter and new injectors, yes i lube before insertion. I had replaced the head gasket, so I just pulled the motor. The lines looked good. The AC is out so Ill try swap. Yes it runs smooth, so so nice, its been the whole winter.

Nelson240 wrote:

yes i lube before insertion.

Okay, okay. Like the guys said. Sounds like a wiring issue. One thing to check right off the bat...make sure your main engine ground, on the rear driver's side of the head, is securely fastened and not corroded. That is the main ground for your ECU, Coil, the works. If it's loose, you will get an unexplained, random issue with the motor not running correctly. Theboy has the right idea...start the engine and perform the wiggle test.....grab the harness in various areas and firmly shake it to see if it acts up/duplicates the fault. Keep us updated...it's gotta be something simple bro.

Also, was the car converted to 5 speed from automatic? Check the number on the ECU to see which it is. An automatic ECU on a manual car can cause an erratic idle.

So, dont know how to us this facking thing! To many settings on this thing, time to YouTube multimeter!

That's my ground, cant I just make my own out of some 8 gauge wire. Cant beleive they used that! Going to change that this week if I get off early. I'll also pull the ecu numbe, I dont think it was an auto 307.photobucket.com/albums/nn295/stonedrhyder/IMAG0171.jpg

I found that the stock 240 relay sucks. if you really believe your fuel pump is the issue (it sounds like that would be the probable cause) run a jumper wire to a relay in the trunk, then wire that directly to the FP. Just my 2 cents but this will also be nesisary if you ever decide to do any further modification to your FP

Last night I changed my ground on the back of the engine, also cleaned the spots. If it doesnt rain all day Im going to try and look at the plate my coil is on. Im pretty sure its not the fuel pump.

Checked the coil connections, all good. I had replaced the control module on the coil, and the coil. Going to check ecu relay, and fuse. Hope its not a short some place in the wiring. I've done some searching and found that there is some little white box. Near driver side fuse panel. It's called the "timing control unit". Could that be bad or is that something different?

well fuses looked good! started to take appart the wires, wow. So in the wires that go over the valve cover there is a splice. 3 wires into 1 that goes the the tps i think. all grounds look good, going to test the control module today. I have new plugs, wires, cap, resistor, fuel pump relay, ecu relay, and control module. I also ordered my secondary air valve in hopes that will fix my idle problem. I cant quite understand how to use this mutimeter, if i put some pics up of it can anyone help me or explain to me how to do these test? I know its code 21 primary igniton, I have the FSM in front of me and dont understand the procedures.. one other question is i order these spark plug wires from NOLOGY Hot wires, are these to much of an upgrade for my car? They say its a spark 300x greater than normal wires, dont want to blow up.

Do me a favor and take a pic of your intake where the plastic part. Section meets your lower intake. And around that area

I took the box out and replaced it with a cone. I'll go get pics now and post them later tonight, thanks!

wait, you mean lower part of intake manifold? or where the intake air filter box is?

All of it

was rainning, will get them in the morning

okay so just got back from taking some pictures, here they are
Left side
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right side
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this is the splice i foiund the spice goes to the throrrle position sensor.

if you need more pics i will take them and post them up

i just picked up a known good ecu on the way, it was $20. Thanks nick z for helping me out so fast. No, I didnt test my ecu but i figured ill need a 2nd one for when I send mine in to jim wolf to remap it to my engine. I also got a blue e mange system for $20 .

i would start checking those vacuum lines that might be were your problem lies.

already replaced all lines when I pulled motor

ok i have a couple more question about Diagnostic procedure 27 in the FSM. I had some time today to perform the test/tests.
1.)I checked all the connections 1st to make sure they are connected and snug.
They checked out fine.
2.) Check Power supply by checking voltage between terminal A and ground.
11.96 volts
3.) Check ground circuit bu checking harness continuity between terminal B and terminals D, I.
got the beep, so continuity is there
4.) Check harness continuity between terminal b and engine ground.
got the beep, so continuity is there
5.) Check Input signal circuit between terminal C and ECM harness 3
got the beep, so continuity is there
6.) Check output signal circuit between termianl G and ECM harness !
got the beep, so continuity is there
7.) Check components - Ignition Coil, Resistor, Power transistor
Ignition Coil was 1.3 ohms says it should be approximately .7ohms ......bad or good?
Resistor was 2.08 says it should be approximately 2.2ohms........ good or bad?
Power Transistor checked out okay with the chart


If you look at the wiring on the Diagnostic Procedure 27 there is a connection called F8 and F9, where is that located??? maybe that is loose. Are those readings in step 7 ok? should I replace the sensors that where high in resistance?

this is for code 21 - ignition signal

bump for the weekend