high idle issue ka24de-t

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slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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Hello everyone,I have been scratching my head on this for a while, and I have tried numerous tests and wire inspections. At this point I need a hand or another perspective so to speak. I have a new ka24de-t, after fixing the other little problems I have had that go along with a full build, I am stuck on this one. I have had the intake off, cleaned and inspected all of the mechanical idle components. The part that has me scratching ,my head at this moment is the voltage at the air regulator(this is the nissan part name). At the EFI sub harness I get 10.5 volts for a split second with the key turned on, thats all, it disappears as soon as the meter reads it. (the battery voltage is 12.75 so its full charge). Per the factory manual(which I bought offline) it should have battery voltage for 5 seconds after the key is turned to the K.O.E.O. position.
Any help or incite would be greatly appreciated, the vehicle has had a tune done by enthalpy. the list of mods is as posted.
bored .020 over 8.5 :1 compression ratio
a multi layer steel head gasket
Brian Crower v2 cams (262)
the maf is from a 300zx with the last numbers reading n62
the injectors are 75lb hr.(I have wired in a resistor pack)
the fpr is a fully adjustable fuel lab regulator(fp is at 50psi with vac line off)
timing is at 20 btdc
the turbo it a t3/t4 50 trim stage 3 turbine wheel.
pauter rods
ross pistons
toga high volume oil pump
oil cooler

Please guys who have been building these cars for years I could really use a hand here.
blaster ss coil(with resistor wired in)


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D-UNIT
Posts: 787
Joined: Mon Jun 23, 2003 10:37 pm
Car: a 91' S13 (15.014 @ 94.56mph NA) KA-T

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Seems like you got a pesky vacuum leak. Bust out the brake clean and spray the main culprits. Brake booster line , pcv hoses under intake manifold , rubber injector bosses etc. spray bc while engine is running if you get a stumble , even a light one that might be where the leak is. Further inspection will be needed. Also if you have a vacuum gauge you can instantly tell if there is a leak. I'm pulling -23 psi at idle and -25 on decel. if your pulling less than -20 psi at idle you might have a leak which would cause high idle.

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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I forgot mention that I have replaced 98% of the rubber on the motor and removed all excess coolant and vac lines from the intake manifold. But I did not replace the brake booster line so I'm going to check that when I get home from work. I do have a vac gauge with my boost gauge when I give it a little gas and let off it drops to like -22/-23 on the gauge. thank you for the insight, your help is appreciated greatly. And I always wondered what a good vac number would be at idle so thank you for the numbers as well.

chillmieste
Posts: 381
Joined: Mon Aug 12, 2002 2:22 am
Car: 97 240sx KA-T
Location: Ft lauderdale

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if u cant find a leak why not just adjust the idle control valve? it has a phillips screw on it pretty easy to adjust, check out fsm

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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I have a fsm, and I have tied to adjust the idle screw. When I adjust it all the way in the lowest i can get it is 1100-1200 rpm, and if I adjust it up, it will go up from there...just being a pita.

chillmieste
Posts: 381
Joined: Mon Aug 12, 2002 2:22 am
Car: 97 240sx KA-T
Location: Ft lauderdale

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wow thats odd i can adjust my idle to low 700s with my idle control valve maybe urs is defective. I would try another one since ur kinda stumped. I have seen people loosen it to much then it f*** with the spring and cant ever get a good idle. did u have an idle issue before u put on the turbo kit? since u have good vacuum readings I doubt ur computer is reading extra air.

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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The car has been a five year project and it never had an idle issue before it took it all apart,go figure.
I was just out messing around with it. I pulled off my brake booster line and threw a plug over it, with it on or off the idle is now at 900. Its a little hard to work on the car ,I work third shift so I'm always racing against the clock so to speak. Anyway, after I got it nice and warm my a/f was around 16.5-17.3 bouncing around, it was extremely erratic for quite some time and hard for me to even get a reading. Sometimes it would drop to 12-13. Idk if it helps any but it has an enthalpy tune. I will be getting a designated vac gauge to plug in because I was sitting at a good old 15pis of vac at idle...lol I am trying to give out as much info as I can. I have a new air valve on order and I'm just going to order a new iac as well at this point. Thank you for the help guys I really appreciate it. Sorry if it seems like I'm all over the place but I think there is a chance I'm loosing it...haha

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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Worst case scenario is my valves are not seating properly....and i really hope that's not the problem. Ah I guess I can bust out the clt tester and listen for leaks too at this point.

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WDRacing
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Car: 95 240SX, 99 BMW 540i, 01 Chevy Express, 14 Ford Escape
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Check your TPS voltages and confirm the throttle cable is allowing the tb to fully close.

liquid_cool
Posts: 1700
Joined: Sat Jul 05, 2008 3:02 am
Car: 1990 240sx ka24de-T swap 8.6:1cr ,duelsprings ,ti retainers,supertech pistons,K1 H-beems balanced internals ect ect.

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could allways adjust the throttle plate via the hex screw and 8mm nut..i donot use an IAC and adjust my idle there..works fine...you might want to see if you have a leaky injector allso..sometimes that adds to a slightly higher idle.

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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I know it has been a while since I have posted anything, but yere is an update. I have the idle problem corrected, but now I seem to have another problem. I seem to have a problem with the car leaning out past 5500 rpm. I have a perfect 11.5 af all the way up to that point, but after that she starts to lean out. I have hard wired my walbro 255 with 10 & 12 gauge wire for the power and ground. Also I have a 300zx tt fuel filter as well. Any insight would be very helpful. The pump sat for 4 years before I installed it as well.

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WDRacing
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What are the numbers like when it leans out?

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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Iwill go all the way to 13.2 and I'm sure more if I kept on the throttlIe it would continue to lean out. I dont feel like pushing my luck so I usually back off at around 12.3. it sucks because at the lower rpms,its a dead nut 11.5.

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WDRacing
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What's your fuel pressure at right now with vac and without?

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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Its set at 50 psi without the vac line on, and at about 40-45 with it on.

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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The pressure is set per enthalpy.

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WDRacing
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The only things I can think of are either your fuel pressure is dropping off or your tune isn't adding enough fuel. Any way to monitor your fuel pressure while driving?

How much boost are you running? Perhaps you're starving the fuel rail, although I've seen guys run over 20psi on the factory rail...

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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Enthaply says that the tune is linear.I don't know anything about tuning at all unfortunately, but I'm assuming it changes the a/f according to the air coming in. So if I'm thinking correctly, the computer should change the amount of fuel coming out of the injectors according to the amount of air the maf detects.

And wd, I have a gauge on my fpr. I am going to get a line that's about 3 feet long and zip tie that mofo to my windshield wiper, or ill have a buddy hold the gauge while I do a 3rd gear pull. Does that sound like a good idea?
Also thank you for your help. It is greatly appreciated.

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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I have it turned down to low boost which is 13psi.

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WDRacing
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The rail shouldn't starve at 13 psi, so that's not the problem.

The fuel pressure idea is exactly what I would do. Let me know what the results are, I'm hoping this is the problem because I'm not sure what it could be otherwise.

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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Alright guys, I finally have had some time to puts with my car. I ran an extension line on my fuel gauge and zip tied it to my windshied wiper (ghetto but works) and did a few test runs and the results were as I figured. The fuel pressure shoots up to over 60 psi and stays there. I won't run it all the way to redline because I don't want to run that high of rpms at a 13 to 1 afr. But as always it starts to creep right at about 4800 rpms. I talked to Martin at enthalpy and he is going to retune my ecu. This is the only thing I can think of at this point. Idk if it is because I have cams (bc stage 2) and maybe the wrong map got flashed to my ecu. All in all its been crappy not knowing what's going on with my car and if this fails I may just bite the bullet and get a mega squirt 2 and a dyno tune. Any thoughts on it vs aem ems? :gotme

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Jmoore124
Posts: 278
Joined: Wed Dec 12, 2012 4:22 pm
Car: 1995 240sx Ka-t
2003 Saab Linear turbo conv
(Sold) 1989 S13 red top

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I would bet it is the cams causing the problem.
Martin is a great guy, he will get you squared away.

slip'n'slide
Posts: 25
Joined: Sat Jan 29, 2005 8:32 am
Car: 1991 Nissan 240sx coupe

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So I finally pulled my car out of storage this week. After racking my brain for the last few months about what could be causing my problem I could only come up with one possible solution. I could slap myself in the face with a 2×4 for this one. So I know I had good fuel pressure and I had the tune checked, everything was how it was supposed to be so it was something on my end. Well I was thinking that maybe my air filter was either too restricted or it was disrupting the maf with turbulent air. I took it off and now it runs great. Sorry for my noobness. I figured since it was an hks large filter it would be good... nope I was wrong. It was the air filter.......thanks for all the replies everyone. I really appreciate you taking time to read my post and take time out of your day to try to help me with my problem. Hopefully ill be able to post up a vid soon once I figure it out.

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WDRacing
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Man, gotta hate those easy fixes that you find after tons of troubleshooting! Thanks for the update dude! Hopefully she brings you lots of enjoyment this summer!

WD


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