PDA

View Full Version : ka24de bogging issue


Mitsubayati
06-22-2011, 01:54 AM
I've searched about this problem for quite some time and did a lot of diagnosis and trial work, but nothing has helped so I'd like to see if someone can come and help me.

Description of Problem: My car is a 1991 240sx. The motor is a rebuilt ka24de that I purchased off of a friend. the motor ran beautifully without a single hiccup just seconds before we started to pull it from the old chassis. So I know it ran perfect before I swapped it into my shell. Before swapping, I changed the oil pan for one tapped with a return line bung, changed the fpr for an aftermarket unit since my friend took his off of the motor, routed the vacuum lines differently, then added stock header , added the downpipe and the aiv system that was on my chassis originally. Not to mention, I connected the egr pipe to the mating opening on the header.

Start up: First time I went to start the motor, she fired up without a problem, fpr was pretty much already set at the correct pressure since it was a used item so that wasn't touched. When I went to gas it though, the instant i pressed down on the accelerator, the motor would bog and completely die or come close unless I let off again. If I played with the accelerator I could get the rpm to climb until around 2500 when it would stop hesitating and rev up like it did once before. If I leave the car to idle it will die in a matter of seconds. On top of that, if the engine was warmed up it would bog less but the problem was still noticeable.

What I have done so far: I have gone through just about all components related to spark. plugs, wires,cap and rotor, ignition coil were all replaced with working units from my dd. Nothing changed. Then the MAF was swapped with no change as well. Then I moved onto fuel. I checked the fuel pressure going into the injector rail, it would show good pressure and never drop when the motor was bogging so I assumed there was no problem with the fuel pump or fuel filter. On a side note,I replaced the fuel tank and fuel pump before i had the new motor in. They were used items and replaced the old tank and fuel pump since the car sat for so long. Today I pulled the motor out just enough to get at the vacuum lines. I routed them correctly after looking up every picture and diagram just to make sure I had the right setup. I put the motor back in place, bolted her down and same thing happened again. I was so sure it was the vacuum lines but they had no effect.

If anyone has any helpful suggestions, they would be greatly appreciated. If you know what you are doing and would like to come over that would be the greatest. If you are certified and can fix this I will pay you for your time. located in Norcal. I know its something simple because KAs are just stupid like that. Any help would be great. Thanks for reading.

roboticnissan
06-22-2011, 01:57 AM
Sounds like vacuum to me. Did you remove any lines for the swap? Got a friend with dohc to.compare all lines.

Vernal
06-22-2011, 02:09 AM
it stalls when trying to idle cold, but no stall when warm? a video would be nice :/ Straight dohc to dohc swap?

Mitsubayati
06-22-2011, 11:01 AM
roboticnissan: I already routed the vacuum lines correctly behind the motor. I compared the ones in front to my dd and they are routed correctly as well. So I don't know how else it could be vacuum lines. when I first swapped the motor I thought the way lines were set up wsa incorrect so I changed them, but I realized I was wrong and changed it back yesterday. all vacuum lines should be correct now.

Vernal: When its warm it either takes longer to stall or it won't stall, but ya pretty much when it's warm the symptoms go away. I'll try and take a video to post it. it is a dohc to dohc swap.

FrippS
06-22-2011, 11:17 AM
just had a similar issue with my sr.....the wires going into the plug for the maf were all taped up, i untaped it and the ground came right out of the plug, so i soldered and heat shrunk and retaped. fixed the bogging instantly. hope this helps.

Mitsubayati
06-22-2011, 11:20 AM
FrippS: So yours would bog all the way up to 2500 rpm then rev fine past that? How were they taped up? It was to the point where there was no ground wire attached to your maf plug you are saying? I'll go take a look at the maf plug.

FrippS
06-22-2011, 11:32 AM
yes it would bog at the low end and then if it made it above i'd say 2500 to 3k rpms it would stop bogging. i think mine is a single cam MAF, there were 3 wires all taped together really tight, when i unwrapped it it just seemed edgy and the black/white wire came out of the plug with really no effort. so i pulled the little thing out of the plug (which was a pain in the ass, unless maybe there is a tool for it) and then re did it, put it back and reconnected the other wires since i cut all of them. used solder and then heat shrink tube and then taped back together, not as tight as it was, just enuff to keep moisture or any crap out of it. then plugged it in And it was all gravy.

Mitsubayati
06-22-2011, 12:00 PM
I really wish that was my problem, but I looked at the maf plug and it seems to be wrapped as it comes from the factory. Doesn't look like it was tampered with.

Mitsubayati
06-22-2011, 12:16 PM
Do you guys want to hear something hilarious!? So I left the MAF plug disconnected and started the motor and she revved up without any problems!!!!!! This is the first time I started the car today so she's cold as ice!!! Where do I go from here??! I'm sorry, but I'm so excited this finally runs right lol

PIN GIO 2
06-22-2011, 12:57 PM
i have same issue problem as yours, i worked on it since 3 moths now, nothing good find problem But i just read this thread gave me good hint then i checked firewall where is harness connecting ground on cylinder head was loose bolt then i tighten it and it all goood runs now! hope this help you find it problem :) good luck

skizsystem
06-22-2011, 01:15 PM
Do you guys want to hear something hilarious!? So I left the MAF plug disconnected and started the motor and she revved up without any problems!!!!!! This is the first time I started the car today so she's cold as ice!!! Where do I go from here??! I'm sorry, but I'm so excited this finally runs right lol

ive had a problem very close to yours before. from what i know when you unplug the maf the car goes into safe mode. i did that to my car and my car started running, it was rough but none the less it was running. my problem was a bad maf. if you already checked your maf i would check all the wiring.

Mitsubayati
06-22-2011, 06:06 PM
I checked the maf by replacing it with the one on my dd again and still nothing. checked power going to the maf and it reads 12 volts when the ignition is in the on position and 14 volts when running as did my dd. The signal from the maf was the same on both. I added a ground and ran it to my chassis but nothing changed either!

If the car runs fine without the maf plugged in can i rule out vacuum lines or fuel being the problem? sounds like a wiring problem

slidevertable
06-23-2011, 10:30 PM
i have a similar problem when i turn on my car 91 ka24de, it turns on but if i let it idle on its own it dies but if i rev it and turn my ac on it idles fine but when i try to drive it it boggles untill im at 3000 rpms then it runs fine i thought it was my throttle body gasket and replaced it but was unable can i get some input

Mitsubayati
06-26-2011, 09:31 PM
Ya, I fixed mine. It was in fact the vacuum lines. It hesitates a little bit but it runs fine now. Slidevertable, I would check your tps and your coolant temp sensor, because I was able to replicate the same rough revving issue by disconnecting those two on my running dd. lmk if you need anymore help.