ka24de running lean

[jrb92se]

so i changed out my plugs and i had my father inspect the old ones (hes a mechanic) there was alot of white build up on them he told me this is caused by the engine running to lean and then yesterday i was changing out my exhaust mani gasket and took the o2 sensors off to get the heat shield out and it was also covered in white build up. so now to the question: what could be causing the car to run lean its a 96 ka24de with a three inch catback it has recently been rebuilt and it seems to run great i dont notice any problems driving but im concerned this could lead to problems in the future any suggestion on how to troubleshoot this will be a big help thanks (i tried searching before posting)

[goodstudent]

no sweat JB I have the same symptoms...I am running a JWT Stage 2 set of cams and a Nismo AFPR, stock pump and injectors with an Autometer FPG set at 46 lbs and I notice a light ashy residue also. I expected a little more tan in there but it seems pretty much light grey. I changed out both O2's, the knock sensor and cable, plugs, rotor and cap but the same result. I am running a hotshot header to a Random Tech 2 1/2 cat through a full 2 1/2 magnaflow exhaust. I do get good mileage and over 100 mph the car is rock solid so I do not know what else I need to do. I am converting to a Greddy system, so I will be changing to a Sard FPR, 210L Pump and Injectors...so hopefully that might help it. I do wonder if I am doing any damage to the cat but the exhaust seems to flow very nicely...rock on with it just keep an eye on the plugs often...oh yeah...98 SX SE

[Bigvinnie]

This is typical of KA24de's with stock ecu tune. As you add devices such as intake filters, headers, CAT back exhaust, high flow cats, the KA runs closer to stoich and lean earlier in the power band and moves further away from rich.The stock ecu tune is already a some what rich tune till about 3000RPM, then it becomes closer to stoich at 5600RPM.When ever you add devices that increase the O2 (such as intakes, and exhaust systems) then youve added power by burning more O2 in the compression stroke while fuel remains the same from it's ecu tune.Exhaust systems inparticular will show more signs of leaness especially since the EGR system is consuming less exhaust gasses to the intake charge, and the O2 sensor is recieving a weaker signal (less exhaust gas to read in the volume of piping offered). 3" cat back exhaust systems will do this through the method of almost no back pressure or resistance to the EGR system.Pretty much the same effect that a high flow 2.5" cat, and cat back system would do. (We can use mine as an example since I have the DC sports header, CATCO high flow, and pacesetter cat back all in 2.5", and I myself am runnign a bit on the lean side).Honestly I wouldn't worry about it to much. Just make shure that your distributor is set at 20BTDC, and use 91 octane at all times to prevent detonation. If you still feel uncomfortable, hit up DeviousKA and get a stoich tune with increased HP....

I am also willing to gaurantee that installing the 3" exhaust has also thrown the reading off on your O2 sensor, less back pressure, less exhaust gass and O2 element to read. I honestly wouldn't worry about it.

EDIT: if you don't want a tune from devious you can always get an SAFC, and wide band O2 and toy around with your car.


Modified by Bigvinnie at 12:59 PM 5/14/2006

[jrb92se]

thanks for the good info and speedy reply guys

[MikeMurphy]

I dont believe bolt-ons would have any significant effect at all on your AFRs.

I would however check your fuel pressure. If your running a higher milage car, replace the fuel filter with a Z32 fuel filter and then throw in a walbro fuel pump if need be. The fuel pressure is a constant culprit.

Your MAF is going to read an increased amount of air your engine is ingesting so I dont understand why people think bolt-ons automatically run the engine leaner. I also dont see why anything would change regarding the O2 readings on a stock manifold with a 3" cat back.

I would be willing to bet that your fuel pump is tired and your filter could use replacing.

[goodstudent]

Bigvinnie, Good looking out I will change out the filter and pump this weekend. As I think back there have been a few times when I caught the smell of fuel from up front but found no leaks or wet spots anywhere. I rushed out and got an injector o-ring kit and checked all the pentils...I guess the filter and pump were too simple for me to see...I really felt the Nismo AFPR was the ticket with just a cam and an intake port job, but at 100k, the pump should go just to be safe...no excuse for the filter, this will be the third one...my badd!

[Bigvinnie]

I dont believe bolt-ons would have any significant effect at all on your AFRs.

Do you seriously think that bolt on's don't make a leaner mix?Do you ever look at dyno charts with the A/F ratio's?A fuel filter that is plugged will more than likely make the engine sluggish and decrease pressure through the fuel line, technically less power will be made on the bottom end and the engine will feel slow. The engine he has doesn't have any problems or symptoms other than having a lean mix. If you have ever done EGR block off on a KA you will defenitely tell that the mixture is much leaner, especially since there is more air in the compression stroke than hot exhaust gasses.

I myself have no problems making power and my engine is a bit lean. My electrical is up to date, and I recently installed a 300Z(z32) fuel filter under 7000miles ago, I'm still lean.....
Modified by Bigvinnie at 4:08 PM 5/17/2006

[matt4pl]

ditto, im running mad lean myself. i have ITB's with a header, no cats, 2.5" exhaust. stock fuel system and prolly the original fuel filter (changing it out this weekend). my car would overheat pretty badly too after i did the itb's though, and i did have the smell of gasoline in the engine bay.

[3dKa24]

Hey matt4pl your running ITB's man, I'm druling..I would love to hear those ITB's thundering near redline. Thats so sweet!What numbers are you putting down?I'm on the Northside of Chicago (Uptown) Good to see a fellow Chicago-EN on this forum.Also are you running stock injectors, and pump?Elaborate on your setup I'm interested.

[jrb92se]

i wrecked the car in this post and now i smell gas in hte engine bay of my s13 because it has a leak

[matt4pl]

yup, stock fuel system, and it cant be maxing out cause no way am i putting down anywhere near close to where it maxes out. dunno if s13 cams would have anything to do with the overheating...

there are the itb's:http://img.photobucket.com/alb...5.jpgits my finalized plenum...

and heres a short vid taken soon after i got it running, with my prototype plenum:http://smg.photobucket.com/alb...t.flv

[Bigvinnie]

yup, stock fuel system, and it cant be maxing out cause no way am i putting down anywhere near close to where it maxes out. dunno if s13 cams would have anything to do with the overheating...

there are the itb's:http://img.photobucket.com/alb...5.jpgits my finalized plenum...

and heres a short vid taken soon after i got it running, with my prototype plenum:http://smg.photobucket.com/alb...t.flv

Sounds and looks like a cool setup. How were you able to run the stock ecu without the IACV? This route seems very interesting to take.The majority of engine temp could be caused from your leaness. You could possibly readjust the stock TPS and use an SAFC to fine tune and bring it more into stoich. I do know that advancing the ignition timing, and a lean setup such as yours could show for alot of overheating.You can always use water wetter to resolve some of the overheating issue.

[3dKa24]

Nice man, did you custom fab that setup? if so thats some skills.Let me know if its on sale at any time or if your up to fabbing another give me a quote im down with dropping one of those. Did you get those tuned anywhere, Also whats up with a dyno.

I also am running hotter than usual also, not overheating though, after the s13 cam swap fans stay on about 15-20 seconds after I turn off the car, sometimes though usually after hard driving though.

[matt4pl]

i cant weld but i have a buddy who can so he made the plenum for me. the itb install is fairly straight forward too. as for overheating, im chocking it up to leaning out but im gonna have to look into wiring too cause my fans dont turn on at the temperature they're supposed to, possibly meaning the ecu isnt getting a good signal from the temp sensor, which in turn also controls mixture. got a fuel pump, O2, and fuel filter going in soon, after i clean up the engine bay.

as for running without IAC, i used the adjustment screw on the actual gixxer itb's to make it idle at w/e rpm i wanted. thing is it has no decel control then and backfires like mad all the way down from w/e rpm i was running at when i let off.

got a bunch of things on the menu to fix on the car this coming week, so we'll see how it goes. 3dka24de, since ur in chicago, hit me up on AIM, same name as on here