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Old 08-25-2014, 09:02 AM   #1
Ktt88
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95' Ka24DE wont rev past 4500rpm

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

Last edited by Ktt88; 10-25-2014 at 12:48 PM..
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Old 08-25-2014, 09:09 AM   #2
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Maybe maf? It usually won't Rev past 3k with bad maf though...just an idea.
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Old 08-25-2014, 09:13 AM   #3
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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
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Old 08-29-2014, 12:50 PM   #4
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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
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Old 08-29-2014, 02:32 PM   #5
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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.
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Old 08-29-2014, 04:45 PM   #6
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Quote:
Originally Posted by badass8 View Post
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.
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Old 08-30-2014, 10:12 PM   #7
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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?
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Old 09-13-2014, 05:51 PM   #8
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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.
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Old 09-13-2014, 08:05 PM   #9
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Check FPR and fuel filter.
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Old 09-14-2014, 08:20 AM   #10
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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.
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Old 09-18-2014, 12:33 PM   #11
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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.
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Old 09-18-2014, 11:13 PM   #12
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Have you checked your fuel pressure at the rail?
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Old 09-19-2014, 06:45 AM   #13
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Have you checked your fuel pressure at the rail?
What's the stock fuel pressure?
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Old 09-19-2014, 06:59 AM   #14
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34psi at idle with vacuum. With vac line disconnected off fpr it should be 43.
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Old 09-19-2014, 07:02 AM   #15
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Quote:
Originally Posted by anti tyler View Post
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.
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Old 09-19-2014, 07:10 AM   #16
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check your wiring.
Grounds and power at the MAF are good
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Old 09-19-2014, 08:25 AM   #17
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Any codes being projected from the ecu?
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Old 09-19-2014, 08:27 AM   #18
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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.
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Old 09-19-2014, 08:31 AM   #19
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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.
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Old 09-19-2014, 08:33 AM   #20
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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.
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Old 09-19-2014, 09:12 AM   #21
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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.
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Old 09-19-2014, 09:18 AM   #22
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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.
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Old 09-19-2014, 09:53 AM   #23
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Quote:
Originally Posted by adams 02rs View Post
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
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 , 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!!!
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Old 09-20-2014, 01:44 PM   #24
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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?)
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Old 09-20-2014, 06:29 PM   #25
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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.
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Old 09-20-2014, 07:17 PM   #26
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Quote:
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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?)
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Old 09-20-2014, 09:30 PM   #27
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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
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Old 09-20-2014, 09:53 PM   #28
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when mine did that i disconnected the speed sensor on the transmisson. try that!
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Old 09-20-2014, 09:53 PM   #29
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it was on my 95 s14 ka24de
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Old 09-21-2014, 09:18 AM   #30
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when mine did that i disconnected the speed sensor on the transmisson. try that!
Ive already tried that, no change
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