Missing at idle only

[Turbo_Turtle88]

I just picked up a 90 240sx se. I am having an issue at idle only. I have replaced the plus, wires, cap, and rotor but its still missing on at least one cylinder maybe two. Need some ideas on what to check next.

[ultimateirving]

first narrow down which cylinders are missing, Disconnect each injector plug one at a time. The engine should start to limp, if you disconnect an injector and the idle doesnt change thats your bad cylinder.

After you've figured out which Cylinder(s) are not firing. You can start checking to make sure its getting fuel, and spark.

[Turbo_Turtle88]

Its the 3rd cylinder and it's getting spark threw the wire I just need to check the plug

[Turbo_Turtle88]

It has to be fuel not spark I guess the next step is a new injector.

[culloa18]

That sounds right but itS a ka or sr

[Turbo_Turtle88]

Ka sohc stock motor

[culloa18]

Did u check engine codes

[Turbo_Turtle88]

No check engine light so no codes

[culloa18]

Ur light on ur dash might not work so still run a check when the cars off and on
Do you know how to check your codes???

[cotbu]

No check engine light so no codes
This is a false statement. If, you are not OBDII and even if you are? You should always check codes. It's the first step in diagnostics.

[chung]

I had a similar problem on a dohc KA, it was a fuel injector, try pulling the connector off each injector one at a time and see if the idle gets worse, if it idles the same as if it was on then that's injector needs to be changed...

[pacotaco345]

If the check engine light doesn't work in the first place then you won't be able to check the codes without a reader anyways.

[culloa18]

If the check engine light doesn't work in the first place then you won't be able to check the codes without a reader anyways.

False because if the dash check engine light is burnt out it has nothing to do with the red light on the ecu

[soryu]

^True
Check engine light should come on when ignition is set to acc.
No engine light = bulb out . ecu still has codes.

[Turbo_Turtle88]

I know the check engine light works cause it comes on when you first start up the car like all the rest of the lights on the dash

[sterlinge]

Did you check compression?

[Turbo_Turtle88]

yes I did all cylinders were right around the 150psi range and not even 5 psi difference in each cylinder

[culloa18]

U could be off timing

[Turbo_Turtle88]

It must be timing cause the new injector didnt work.

[culloa18]

Even a single tooth of the dizzy or timing chain could cause this type of problem

[culloa18]

How does the dizzy and the rotor look

[cotbu]

It's getting really hard trying to teach you new set of noobs, the basics.
anyway once more OUR OBD1 Cars only trigger the ecu dash led when there's a serious problem. Normally the codes just get stored (in the ecu), no check engine light. so we have to manually pull codes (argue all you want).

It must be timing cause the new injector didnt work.
This means you didn't test correctly. Even if timing was off it would still trigger spark and injector pulse, albeit the wrong time.

It gets ridiculous sometimes! 1 injector doesn't fire and you believe it's timing that's stooping that 1 injector from firing?

[Turbo_Turtle88]

Well I dont really know what else it could be if fuel pressure is correct, new plugs wires and plugs, new cap, new rotor and a new fuel injector on the 3rd cylinder. I have checked compression, check to maker sure I'm getting spark. Checked the pulse of the injector. So what else could it be? An engine only needs air fuel and spark to run. If I know I have spark and fuel and air wouldn't just effect the 3rd cylinder it would effect all of them.

[cotbu]

You see when you have a problem like this and you approach it wrong, you could potentially mess something else up.

Your first step should have been, check for codes. do that now.
I would like you to recap so I can get an idea of exactly where you stand.
You've played with the distributor so we might have to set timing again with a light.
Are you still able to start the car? and Is that 1 injector still not firing or is it the spark plug? I don't know if you narrowed it down correctly too the #3 fuel injector.
So, if you can get a video up it would help along with the recap.

[tapdeznutz]

i have a 1990 sohc ka as well. sometimes you just have to put up with shit unless you want to play with it forever. my idle sometimes is low even after warmup. i ended up adjusting my idle higher at the throttle body to able 900rpm. that is livable with me unless i get tired enough to dig into it again. just asking.

on a side note COTBU, what does it mean when i have my timing set at "correct stock timing of 15 degrees" but i get what i believe is knock at low rpms? then i adjust timing back to 10 degrees and the knock is slight is not gone at the low rpms, i guess around 1500-3000rpm? thanks for the help.

[cotbu]

Probably low octane,.or pour crank case ventilation. Just a guess.

Sent from my Highly Tuned Vibrant!!!

[tapdeznutz]

Probably low octane,.or pour crank case ventilation. Just a guess.

Sent from my Highly Tuned Vibrant!!!

sorry about that but to clarify i always run high octane. as for poor ventilation, how do you increase it? i have the oem intake system on with k&n drop in filter

[Turbo_Turtle88]

http://s873.photobucket.com/albums/ab295/revolt911/?action=view&current=VIDEO0036.mp4

Here is a video

[cotbu]

OK 1st we need to know if it's spark or fuel. Take out the spark plug, check for fuel on it, then check it for spark. If we get spark we're good.
The injector, ohm it, check for battery voltage, lastly remove rail visually check for spray. You could also do a combination of swapping wires to injectors and spark plug leads to help narrow it down.

You may need a second opinion on the compression test, or do a leak down test.

PS an alignment shop did the same thing to my SR same cylinder even. I had a broken rocker arm, sounded like knock, but my Rpm, vacuum and idle was a clear indicator of a problem.

Sent from my Highly Tuned Vibrant!!!

[Turbo_Turtle88]

okay I just check the codes. I did have one code stored it was 41. 41 - Intake Air temperature sensor would this cause it?

[cotbu]

I don't think so, unless it supplying voltage for the number 3 injector. Clear the code and get testing. Check the codes again when you're done.

Sent from my Highly Tuned Vibrant!!!

[Turbo_Turtle88]

cotbu- pm'd

[Turbo_Turtle88]

rechecked spark. = good
checked injector resistance = good
Check injector pulse = good

I havent removed the injector and check if spraying. need for find some way to do it without spraying gas everywhere

[cotbu]

Get 4 soda bottles, Remove rail, place injector in bottles. Unplug other injectors if using 1 bottle method.

Sent from my Highly Tuned Vibrant!!!