91 240sx KA24de idle 2k, dies when throttled - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Andrewdrazin · 01-29-2023, 12:39 PM

im at a lost,
i have a 91 240sx with a rebuilt ka24de.
when started, idle jumps to 2k rpm for about 3-10 seconds and than will bog down. at any time i hit the throttle it will try or it will die immediatly.
things i have tried or replaced.

1. checked timing, and distributor(used manual to verify tdc). installed new cap, rotor, plugs(gaped at 0.045), and wires.

2. checked vacuum leaks. when motor was rebuilt i replaced all vacuum hose/lines. cleaned IACV. checked for leaks with carb cleaner around the hole intake, none found. hooked up vacuum gauge and at idle of 2k it shows 15 IN HG, when the throttle opens the gauge jumps to 0.

3. checked fuel. installed remanufactured injectors 270cc, fuel regulator, fuel filter. checked and verified incoming fuel was on the correct line for the fuel rail. checked fuel pressure, pressure is at 30psi. i can here fuel pump prim too.

4. installed new TPS and set with a voltmeter to 4.80. installed new knock sensor. new battery. tried new MAF (from O'reillys). tried a different coil. checked grounds. new temp sensor.

5. checked ecu for codes. all i get is 55.

any other suggestions would be vary help full to me. thanks for reading

parkrat · 01-29-2023, 01:11 PM

mine had similar issues, it was a bad brake booster since its hooked up with vacuum. bypass the booster and see what happens

Andrewdrazin · 01-29-2023, 01:32 PM

unfortunately i did bypass the brake booster and no luck.

foreverdeath · 02-01-2023, 08:18 AM

Nissan motors uses MAFs, vacuum leaks will make them go lean lose RPM and die. what you have here is meter air out of control and the ECU is trying it best to bring it down by pulling time down because the TPS is telling the ECU it should be idling.

Too get that high of an idle you really only have 3 places to look the idle air control valve (IACV), IACV-FID (fast idle control) and the throttle blade. First place I would is the IAVC on the back of the intake manifold. Take it off and clean it with brake cleaner, they tend to get clogged and stuck.

If that doesn't handle it the IACV-FICD may be bad or not plugged in. its on the inside of the intake so its a plane to get to. check the FSM for more info https://www.nicoclub.com/service-man...neral%2FEC.pdf

Afterword, there should be a screw visible on the passenger side of the IACV, it maybe covered with a wax plug, this sets base idle.

KApasa · 02-01-2023, 02:25 PM

Another thing to do/check is if you have a shop or buddy that has one of those smoke machines that detect vacuum leaks. Had my engine hunting idle during prep for smog, and even though I replaced all the hoses; one of the hoses heading to the charcoal canister got frayed against a bracket that wasn’t easily visible to me. Pinhole leak was found quickly with the machine and that was the solution.

AKADriver · 02-05-2023, 11:25 AM

You can also toot flammable stuff like starting fluid/ether or nonchlorinated brake cleaner here and there around the vacuum hoses and clamps and see if it makes the engine rev up when you hit any of them.

Andrewdrazin · 03-02-2023, 07:26 PM

thank you for that link foreverdeath. i will take a look at this.
i have cleaned all of these components and tried adjusting over and over.
im curious about the throttle blade. are you meaning the throttle butterfly or the four blades on the intake that has some sort of valve/ actuator? i have already cleaned the butterfly. but would that valve/actuator cause this issue.
im thinking i might take the intake off again.
but this problem sounds like a vacuum issue??

thermogod · 05-18-2023, 09:31 AM

i think he means throttle butterfly, and it 100% sounds like a vacuum issue.

i had a 1700rpm idle and it would die under throttle. I adjusted the two nuts on the throttle cable that adjust throttle butterfly position at idle. this extended the throttle cable a bit, which closed the butterfly a bit more and dropped it down to 1100. this was after cleaning my IACV and using the brake booster hose to do a vacuum leak check (found some uncapped shit from previous owner's EGR delete)... and that vacuum leak was the reason my KA would die when throttled.

i thought i had a leak from the lines under the intake manifold so i removed it, did new gaskets and found a leak under there as well.

just make sure you adjust the throttle butterfly AFTER fixing vacuum leaks

01-29-2023, 12:39 PM	#1
Andrewdrazin Join Date: Feb 2017 Location: California Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	91 240sx KA24de idle 2k, dies when throttled im at a lost, i have a 91 240sx with a rebuilt ka24de. when started, idle jumps to 2k rpm for about 3-10 seconds and than will bog down. at any time i hit the throttle it will try or it will die immediatly. things i have tried or replaced. 1. checked timing, and distributor(used manual to verify tdc). installed new cap, rotor, plugs(gaped at 0.045), and wires. 2. checked vacuum leaks. when motor was rebuilt i replaced all vacuum hose/lines. cleaned IACV. checked for leaks with carb cleaner around the hole intake, none found. hooked up vacuum gauge and at idle of 2k it shows 15 IN HG, when the throttle opens the gauge jumps to 0. 3. checked fuel. installed remanufactured injectors 270cc, fuel regulator, fuel filter. checked and verified incoming fuel was on the correct line for the fuel rail. checked fuel pressure, pressure is at 30psi. i can here fuel pump prim too. 4. installed new TPS and set with a voltmeter to 4.80. installed new knock sensor. new battery. tried new MAF (from O'reillys). tried a different coil. checked grounds. new temp sensor. 5. checked ecu for codes. all i get is 55. any other suggestions would be vary help full to me. thanks for reading

05-18-2023, 09:31 AM	#8
thermogod Join Date: Apr 2023 Location: away from anything with a roof Posts: 21 Trader Rating: (0) Feedback Score: 0 reviews	i think he means throttle butterfly, and it 100% sounds like a vacuum issue. i had a 1700rpm idle and it would die under throttle. I adjusted the two nuts on the throttle cable that adjust throttle butterfly position at idle. this extended the throttle cable a bit, which closed the butterfly a bit more and dropped it down to 1100. this was after cleaning my IACV and using the brake booster hose to do a vacuum leak check (found some uncapped shit from previous owner's EGR delete)... and that vacuum leak was the reason my KA would die when throttled. i thought i had a leak from the lines under the intake manifold so i removed it, did new gaskets and found a leak under there as well. just make sure you adjust the throttle butterfly AFTER fixing vacuum leaks __________________ *yeah, that's a great steak, but it's not Cypher's steak.* Last edited by thermogod; 05-18-2023 at 10:30 AM..

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01-29-2023, 01:11 PM	#2
parkrat Join Date: May 2017 Location: Manitoba, Canada Age: 24 Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	mine had similar issues, it was a bad brake booster since its hooked up with vacuum. bypass the booster and see what happens

01-29-2023, 01:32 PM	#3
Andrewdrazin Join Date: Feb 2017 Location: California Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	unfortunately i did bypass the brake booster and no luck.

02-01-2023, 08:18 AM	#4
foreverdeath Zilvia Junkie Join Date: Sep 2012 Location: va beach Age: 30 Posts: 321 Trader Rating: (3) Feedback Score: 3 reviews	Nissan motors uses MAFs, vacuum leaks will make them go lean lose RPM and die. what you have here is meter air out of control and the ECU is trying it best to bring it down by pulling time down because the TPS is telling the ECU it should be idling. Too get that high of an idle you really only have 3 places to look the idle air control valve (IACV), IACV-FID (fast idle control) and the throttle blade. First place I would is the IAVC on the back of the intake manifold. Take it off and clean it with brake cleaner, they tend to get clogged and stuck. If that doesn't handle it the IACV-FICD may be bad or not plugged in. its on the inside of the intake so its a plane to get to. check the FSM for more info https://www.nicoclub.com/service-man...neral%2FEC.pdf Afterword, there should be a screw visible on the passenger side of the IACV, it maybe covered with a wax plug, this sets base idle.

02-01-2023, 02:25 PM	#5
KApasa Join Date: Aug 2019 Location: SF Bay Area Posts: 6 Trader Rating: (0) Feedback Score: 0 reviews	Another thing to do/check is if you have a shop or buddy that has one of those smoke machines that detect vacuum leaks. Had my engine hunting idle during prep for smog, and even though I replaced all the hoses; one of the hoses heading to the charcoal canister got frayed against a bracket that wasn’t easily visible to me. Pinhole leak was found quickly with the machine and that was the solution.

02-05-2023, 11:25 AM	#6
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 41 Posts: 3,369 Trader Rating: (1) Feedback Score: 1 reviews	You can also toot flammable stuff like starting fluid/ether or nonchlorinated brake cleaner here and there around the vacuum hoses and clamps and see if it makes the engine rev up when you hit any of them.

03-02-2023, 07:26 PM	#7
Andrewdrazin Join Date: Feb 2017 Location: California Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	thank you for that link foreverdeath. i will take a look at this. i have cleaned all of these components and tried adjusting over and over. im curious about the throttle blade. are you meaning the throttle butterfly or the four blades on the intake that has some sort of valve/ actuator? i have already cleaned the butterfly. but would that valve/actuator cause this issue. im thinking i might take the intake off again. but this problem sounds like a vacuum issue??