95' Ka24DE wont rev past 4500rpm

[Ktt88]

Recently this S14 KA24DE has been feeling a bit sluggish (slower than it normally is)

Just noticed that it wont rev above 4500rpm, doesnt matter if its in gear or out of gear

Engine is completely stock, about 202,000km. Recently replaced the knock sensor and secondary o2 sensor.

Any ideas?

Solution: Exhaust had 2 cats on it. The primary cat off the header and a secondary cat after the secondary o2 sensor. The secondary cat was almost completely plugged! Replaced it with a straight pipe and everything is fixed :D

[l adam l]

Maybe maf? It usually won't Rev past 3k with bad maf though...just an idea.

[Ktt88]

Maybe maf? It usually won't Rev past 3k with bad maf though...just an idea.

I thought it might be the MAF, but the other threads explained it shouldnt rev past 2500-3000rpm if it was

[Ktt88]

so turns out i was mistaken; it actually wont rev above 5000.

Searched a bit and it might be the low grade 87 octane fuel i recently put in.

Going to fill up with 91 octane and throw in some seafoam and ill report back

[badass8]

Why would it be the low grade octane considering the ka24de never required a higher octane?

The easiest test is always the MAF. Either borrow one to test or simply disconnect the MAF's connector and see if anything changes. If your car idles better without the MAF then your MAF is bad.

[anti tyler]

Why would it be the low grade octane considering the ka24de never required a higher octane?

The easiest test is always the MAF. Either borrow one to test or simply disconnect the MAF's connector and see if anything changes. If your car idles better without the MAF then your MAF is bad.


That's no really true actually.. Since without any input from the MAFs at all the car goes into limp mode. It could possibly be a bad wire, signal/ground for the MAFs. As well as many other things.

[badass8]

That's no really true actually.. Since without any input from the MAFs at all the car goes into limp mode. It could possibly be a bad wire, signal/ground for the MAFs. As well as many other things.

But will it only go into limp mode if you are on the gas? then it limits the rpm(limp mode). IF you simply just disconnect the MAF wont it just change the idle IF it was bad?

[Ktt88]

So heres a little update..

I had a spare MAF from a 96' ka24de 240sx that I found in a junkyard, swapped that in and there was no change (it could have been bad, not sure)

I had to upgrade my fuel pump anyways since I have plans of swapping a sr20, put in a walbro 255.

Also, from idle; if i give 100% throttle it limits at 5000rpm. However if i roll onto the throttle the rpm will go to aprx 6000rpm.

any other ideas? this is killing my build.

[Frank_Jaeger]

Check FPR and fuel filter.

[cotbu]

I've seen this before, usually the speed sensor has been disconnected and the speed signal to the ecu has not been disconnected or viseversa. That is what i've seen on s13's. The other time i've seen this on an s14 was a fuel injector problem, upgrading injectors fixed the issue.

[Ktt88]

So little update...

Replaced the fuel pump with a walbro 255, nothing changed.

Fairly certain this is not fuel related. Makes more sense is MAF related.

[Frank_Jaeger]

Have you checked your fuel pressure at the rail?

[Ktt88]

Have you checked your fuel pressure at the rail?

What's the stock fuel pressure?

[Frank_Jaeger]

34psi at idle with vacuum. With vac line disconnected off fpr it should be 43.

[adams 02rs]

That's no really true actually.. Since without any input from the MAFs at all the car goes into limp mode. It could possibly be a bad wire, signal/ground for the MAFs. As well as many other things.

check your wiring.

[Ktt88]

check your wiring.

Grounds and power at the MAF are good

[adams 02rs]

Any codes being projected from the ecu?

[Ktt88]

Any codes being projected from the ecu?

Right now the ecu is throwing a code 12 (MAF circuit).

I replaced the MAF with a spare I had (not sure if its good or not), but no change in the issue.

[adams 02rs]

Had a similar issue were my maf signal and ground were crossed and threw the polarity out of wack, It seemed like it tried to ground back to the ecu.. Changed my ecu and harness, problem resolved. (it may be a fried ecu bud) try swapping them.

[Ktt88]

Had a similar issue were my maf signal and ground were crossed and threw the polarity out of wack, It seemed like it tried to ground back to the ecu.. Changed my ecu and harness, problem resolved. (it may be a fried ecu bud) try swapping them.

Interesting. Im doubtful that would be the issue since I rarely drive the car. Ill check the continuity of the MAF signal wire at the plug to the ecu and see if its good.

Ill try asking a friend with a working MAF to swap his MAF into my car and see what happens.

[adams 02rs]

Just because you rarely drive the car doesn't mean you won't have a fried ecu. That was my issue when some dude had wired the maf wrong and fried my ecu, my harness was pretty much butchered and it was shorting things out. SINCE you are going to ask a friend to use his maf, ask to try his ecu as well.

[adams 02rs]

Obviously it has to do with something with or in between your maf and ecu, those are primarily the two components that complete the circuit for it. I'm almost positive it's either a short in between the ecu and maf, a frayed wire, crossed wires, old beat up exposed harness, or a circuit board on the ecu is fried chicken and maf could be toast.

[Primo's Silvia]

Just because you rarely drive the car doesn't mean you won't have a fried ecu. That was my issue when some dude had wired the maf wrong and fried my ecu, my harness was pretty much butchered and it was shorting things out. SINCE you are going to ask a friend to use his maf, ask to try his ecu as well.

Had the same problem here :picardfp:
I was having some issue's with stutering and revving so i change the maf with 3 others but as soon as i tried the 2nd one the car went into limp mode and was undrivable :facepalm:, so i thought it was the harness so i grounded the ground wire from the maf connection to the chassis and it helped to get me were i began... Swapped the ecu and bam! Pulled like a horse!!! :drama:

[Ktt88]

So here a little update again....ugh. I went to the junkyard today. Put a MAF I found there in and theres no change, same issue.

Last night I also checked continuity of the signal wire going from the maf plug to the ecu, it was good. Along with the power and ground wires being good at the MAF.

The ECU is also now throwing no codes (code 55)

My only suspect now is the ecu or a hidden vacuum leak (does this make sense that it may be a vacuum leak?)

[ronaldo_fanbelt]

Mine did something similar. I cleaned the MAF and had the same issue until I cleared my codes. Clear the codes immediately after swapping or cleaning the MAF.

[cotbu]

The ECU is also now throwing no codes (code 55)

My only suspect now is the ecu or a hidden vacuum leak (does this make sense that it may be a vacuum leak?)
No!


Sent from my Highly Tuned Galaxy S3.4!!!

[Ktt88]

Mine did something similar. I cleaned the MAF and had the same issue until I cleared my codes. Clear the codes immediately after swapping or cleaning the MAF.

I cleared the codes, no change.

Every time I check now, no codes come up

[jerry_beans]

when mine did that i disconnected the speed sensor on the transmisson. try that!

[jerry_beans]

it was on my 95 s14 ka24de

[Ktt88]

when mine did that i disconnected the speed sensor on the transmisson. try that!

Ive already tried that, no change

[Clicky]

Spark plug gap
or spark plugs

[Ktt88]

Spark plug gap
or spark plugs

Replaced them with NGK BKR5E about a year ago.

Ill pull all 4 today and report back on their condition.

[Ktt88]

So I checked the spark plugs today, all looked the same; gap as within spec (0.044), NGK BKR5E. Torqued to spec

Was thinking about it and considered that I may be a bad TPS? does this possibly make sense?

Ended up testing it just to confirm. Harness side is all good.

When I tested the sensor, good is 1 ohm when closed, 10ohm when open

My results were 1.2ohm closed. 8.8 ohm open. Is this enough of a discrepancy to warrant a bad TPS?

Ohms also slowly change between 1.2 and 8.8 with partial throttle.

[Ktt88]

So I thought Id also throw this in.

If I give it full 100% throttle snapping it open. It will stop revving at 4500rpm always

But if I roll onto the throttle it'll rev to about 6000rpm, until i reach 100% throttle, when it will roll back to 4500rpm.

This is why I my suspect is the TPS, is my reasoning correct?

[Driftwire]

try using BKR6E plugs, stock gap and adjust the TPS. I believe the 6E were the stock plugs and ur running a 5E which is a hotter plug. Could be wrong on this.

[Ktt88]

Another update.

Adjusted the TPS according to one of the write ups on nico. I adjusted it perfectly. No change.

I even tried driving the car with the tps unplugged, drove the same.

Would it be worth while to look at the ignition side of things?

[Touge_Monster]

I had this same issue with my 92 s13. I borrowed a distributer from my friend and the problem went away. I then returned his dizzy and went through three autozone ones and it would not fix the problem. Finally I went to another used OEM dizzy and switched the entire upper harness and the car has had no issues since.
I would recommend replacing your distributer or harness with a known working counterpart and see if it helps.
Good luck!

[Ktt88]

I had this same issue with my 92 s13. I borrowed a distributer from my friend and the problem went away. I then returned his dizzy and went through three autozone ones and it would not fix the problem. Finally I went to another used OEM dizzy and switched the entire upper harness and the car has had no issues since.
I would recommend replacing your distributer or harness with a known working counterpart and see if it helps.
Good luck!

Ill try finding a working used oem distributer! thanks a lot for the recommendation

[Ktt88]

So I recently got my hands on a used working distributor unit with new ngk wires.

I replaced it all, set the timing right at 20deg BTDC.

No change at all. Im going nuts trying to figure out what this is...ugh

I tried driving the car adjusting the timing -/+ 5deg off 20deg btdc. The problem seemed to get a bit worse, with the car redlining at different rpms then 4500rpm

Any other ideas? I pulled the spark plugs; they look good but im going to replace them and see what happens.

Ill keep this updated.

[cotbu]

What is your speed during all your testing?

Sent from my Highly Tuned Galaxy S3.4!!!

[Ktt88]

What is your speed during all your testing?

Sent from my Highly Tuned Galaxy S3.4!!!

Its not related to speed, same symptoms whether im going 10, 20, 60, 100kmh; or at idle

[Driftwire]

Weak fuel pump.

[Ktt88]

Weak fuel pump.

Just replaced the stock fuel pump with a brand new walbro 255

[cotbu]

the only other sensor that could possibly cause a limiter is the knock sensor, try disconnecting that and do your tests again. remember pedal to the floor, the swing up on the tachometer is not the limiter the place it settles is, when the throttle is fully open.

[Ktt88]

the only other sensor that could possibly cause a limiter is the knock sensor, try disconnecting that and do your tests again. remember pedal to the floor, the swing up on the tachometer is not the limiter the place it settles is, when the throttle is fully open.

Ive started to suspect the knock sensor as well.

About 3 months ago I was throwing a code 34 (knock sensor code). I took the old one off and noticed it was cracked; fair enough. I replaced it with a brand new airtex/wells knock sensor.

I believe I installed it correctly...and its not throwing any codes right now besides a code 55.

Im going to replace the spark plugs, check resistance on each fuel injector, and inspect the knock sensor tonight.

Ill report back

[Ktt88]

So yesterday I inspected the new knock sensor I put in a few months ago. Looks to me good as well as the wiring being good (harness side and sensor side).

Regardless I unplugged the sensor and stuck a 560 kohm resister in the harness and experienced no change what so ever.

I also inspected all fuel injectors, they all had a resistance of 11ohm, which is within spec so I doubt its that.

Any other tips? I keep going back to thinking its the tps since whenever im at 100% is when the engine falls on its face. If im at 95% throttle, itll rev to aprx 6000rpm

[dudebuddy]

Check for vacuum leaks. make sure none of the hoses are kinked too.
I had this same problem and the guy who had the car before me just used straight heater hose. it was all kinked.

Also check to see if the catalytic converter is the culprit. It will sound like ass but remove it and try running it open. This is assuming that you still have the cat.

[Ktt88]

Already checked for vac leaks, found none and I also hear none.

None are kinked, this engine is pretty much stock factory.

I was thinking maybe the cat as well, its so rusted on tho I know that if i touch it the studs are going to snap. ugh

[dudebuddy]

spray on some pb blaster and let sit for 10 minutes.
i was worried about the same thing with mine before i installed the test pipe.
came right off, no breakage.
i'm willing to bet that it is the cat.
what are the emissions laws up there?

[Ktt88]

spray on some pb blaster and let sit for 10 minutes.
i was worried about the same thing with mine before i installed the test pipe.
came right off, no breakage.
i'm willing to bet that it is the cat.
what are the emissions laws up there?

I dont think you realize the level of rust we have here in Toronto haha. Ill try regardless.

Emissions tests are required every 2 years, cars pre 97 require a sniffer test. Cars post 97 require a obd plug in test.

[dudebuddy]

I can only imagine.
let us know what you find.

[Frank_Jaeger]

What did your fuel pressure end up being?

[Ktt88]

What did your fuel pressure end up being?

I did it a while ago..I think it was 34psi?

Ok so I think im narrowing in on what could be the issue.

Ive had this problem for pretty much as long as Ive owned it.

I remember the day I brought it home I noticed the front O2 sensor (single wire) was unplugged from the harness. I reconnected it and havent touched it since.

Now when the car was warmed up I unplugged it while it was running and saw no change. No change driving it either with the front O2 sensor unplugged.

Could this be the issue? Its weird that the only code im throwing is 55.

Anyways im going to replace it and see what happens

[MapleK]

Have you checked your ecu? Wonder if it has ever been replaced with an auto trans ecu... You said it's been acting like that since you've owned the car correct?

[Ktt88]

Have you checked your ecu? Wonder if it has ever been replaced with an auto trans ecu... You said it's been acting like that since you've owned the car correct?


If its not the front o2 sensor then im going to start looking into the ecu.

To the best of my knowledge (as well as the VIN #). The car has always been a manual ka24de. ECU code is 3C as well

[MapleK]

If its not the front o2 sensor then im going to start looking into the ecu.

To the best of my knowledge (as well as the VIN #). The car has always been a manual ka24de. ECU code is 3C as well

Should be ok then!

[Ktt88]

Im crossing my fingers its the front o2 sensor, itll make my day lol

[Ktt88]

Ok so update time...still havent fixed the problem

I replaced the front o2 sensor with a brand new NTK unit...no change

I took a video of what im experiencing

http://youtu.be/5VaEvw5_zMI


The first rev is 100% throttle snapped open

The second rev is rolling onto the throttle, then going to 100%

The third rev is again 100% throttle snapped open

[Ktt88]

Another update. I replaced the 3C ECU on the car with another 3C ECU from a known working car. No change in anything.

I also picked up a used TPS, going to swap that in tonight and see what happens.

[Ktt88]

So I swapped in the TPS yesterday, adjusted it via the nico writeup and still not change.

After I did the adjustment I backprobed the TPS connector (middle wire). With the ignition on I was getting 0.5v closed and 4.2v open. Is this normal?

I also went over the wiring harness again (esp the driver fender harness because I previously had to repair it), everything was perfect.

im serrrriously losing sleep over this, any other suggestions?

[dudebuddy]

catalytic converter?

[Ktt88]

catalytic converter?

Any way to test this without taking the cat off? Infrared temp sensor?

I also recently passed emission with flying colors

[dudebuddy]

fuel filter?

[Ktt88]

fuel filter?

Already replaced with a new z32 filter

[dudebuddy]

Check all the fuses you can get your hands on and try the air filter.
After everything else you have tried it'll probably end up being something stupid simple.
Some insane combination of Occam's Razor and Murphy's Law.

[Ktt88]

Check all the fuses you can get your hands on and try the air filter.
After everything else you have tried it'll probably end up being something stupid simple.
Some insane combination of Occam's Razor and Murphy's Law.

I guess i can take a look at the air filter, doubt it tho.

I know that when I eventually figure it out its going to be something very simple and stupid that I overlooked

[Ktt88]

Checked the air filter. I replaced it a few months ago anyways, looked fine.

Got a suggestion that If I advanced the timing to aprx 25deg btdc it could help. Changed how the car felt, but not any better.

Heres another symptom which I just started noticing.

Whenever I first start the car and do a hard pull. THe 1st and 2nd usually feel pretty good (how the car should be) and after that the car warms up quickly and the issue persists.

I was thinking could this be related some coolant sensor, I see 2 at the upper rad hose?

[dfyjdy]

Maybe maf? It usually won't Rev past 3k with bad maf though...just an idea. http://lifehealthus.com/image/images/123.gif

[Ktt88]

Maybe maf? It usually won't Rev past 3k with bad maf though...just an idea. http://lifehealthus.com/image/images/123.gif

Tested the MAF wiring and sensor. Also tried to swap in known good MAF's with no luck

Also tried cleaning the MAF with no luck

When I unplug the MAF with the car running, it idles like crap and wone rev past aprx 2500rpm.

Im fairly confident it's not the MAF

[Ktt88]

Another depressing update.

Thought it could be the coolant temp sensor, replaced it with a known working. Still no luck

[dirtrider375]

Another depressing update.

Thought it could be the coolant temp sensor, replaced it with a known working. Still no luck

I am having the same problem. Ive replaced knock sensor temp sensor plugs. I have a cap and rotor Im gonna do. Looks like some of the vacuum lines are skewed, but i dont think that is the problem. Gonna check some grounds tonight.... you ever figured out what is wrong with yours?

[Ktt88]

I am having the same problem. Ive replaced knock sensor temp sensor plugs. I have a cap and rotor Im gonna do. Looks like some of the vacuum lines are skewed, but i dont think that is the problem. Gonna check some grounds tonight.... you ever figured out what is wrong with yours?

Still havent fixed it, I think im narrowing down on the problem though.

Going to do a really good bleed on the coolant to get 99.9% of the air out. Then im going to inspect the cat (I think it may be clogged/plugged).

Keep me updated!

[dirtrider375]

Still havent fixed it, I think im narrowing down on the problem though.

Going to do a really good bleed on the coolant to get 99.9% of the air out. Then im going to inspect the cat (I think it may be clogged/plugged).

Keep me updated!

Hmm I tried to burp mine yesterday because its building up a lot of pressure but not overheating. So Im puzzled there too. And when I run it with cap off no bubbles. I am thinking it may be speed sensor but not sure. There is a write up where someone had a similiar problem and it was an o2 sensor went bad then they replaced it but timing was still off due to compensation.
If you figure it out before me PLEASe let me know.
Ill look for that post later.

[Ktt88]

Update! major progress. So I removed the front o2 sensor and drove the car. It felt perfect! Its definitely a clogged cat or something restricting exhaust flow.

[dirtrider375]

This is exciting news!!! Did it show the code for O2 sensor! keep me updated lol Ill have to try this. I have also seen that after replaccing an O2 sensor the Timing needs adjustment back to stock or something weird lol

[Ktt88]

This is exciting news!!! Did it show the code for O2 sensor! keep me updated lol Ill have to try this. I have also seen that after replaccing an O2 sensor the Timing needs adjustment back to stock or something weird lol

Sorry I should be more clear about that. I took the o2 sensor out of the manifold but still kept it plugged it

[dirtrider375]

Ok so i tried to unplug mine and had no such luck... I dont even get a check engine light when the key is on anymore. Im going crazy

[dirtrider375]

Sorry I should be more clear about that. I took the o2 sensor out of the manifold but still kept it plugged it

Ah oh maybe ill try that haha I just unplugged mine and no change.. that is weird thought.

[Ktt88]

Finally fixed!! Exhaust had 2 cats on it. The primary cat off the header and a secondary cat after the secondary o2 sensor. The secondary cat was almost completely plugged! Replaced it with a straight pipe and everything is fixed :D

[dirtrider375]

Finally fixed!! Exhaust had 2 cats on it. The primary cat off the header and a secondary cat after the secondary o2 sensor. The secondary cat was almost completely plugged! Replaced it with a straight pipe and everything is fixed :D

AWESOME glad to hear, I tried to take my O2 sensor out but still had same problem... did your rev fine in neutral?

[Ktt88]

AWESOME glad to hear, I tried to take my O2 sensor out but still had same problem... did your rev fine in neutral?

When I removed the o2 sensor it revved fine in any gear and in neutral

[dudebuddy]

Finally fixed!! Exhaust had 2 cats on it. The primary cat off the header and a secondary cat after the secondary o2 sensor. The secondary cat was almost completely plugged! Replaced it with a straight pipe and everything is fixed :D

the bolts weren't too rusty?

it's a shame that no one suggested to replace this initially...