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.

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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

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.

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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.

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culloa18

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).

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?

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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.

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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!!!

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tapdeznutz

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/a...=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!!!

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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?