I have to figure out this problem!

Discuss topics related to the CA18DE and CA18DET series engines.
cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

also noticed my TP on nistune fluctuates from a low that i saw of 5900 to 7100. this is on the stock rom flashed to the car. idk if thats right or not but it might point to something you guys know of


User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

Wait, you know it doesn't just hold a constant AFR it idle right? It's going to sweep back and forth between lean and rich. This is how closed loop behaves on all vehicles with a narrowband O2 sensor. Also, what is the idle when it's cold and warming up?

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

IDK much about Nistune, but if the TP it's displaying is fluctuating like idling, and the AFR'S are fluctuating while idling, then what you're seeing is the ECU modifying the TP to alter the AFR based on the input from the O2 sensor.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

right i know that but it shouldnt sweep between 12-18 i wouldnt think. i just went out for a drive and disconnected the boost controller so it has just the basics pulmbed for vacuum with no change. it does feel like it loses power(engine not electrical) when accelerating or at cruise with no real pattern its completely random. it feels like something is pulling on the car from behind when driving. (almost exactly how it feels when towing something and the slack runs out) but its only for a second each time. AFRs arent consistent when its doing this but the "lugging" , well call it continues sporadically throughout the drive.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

idle is around 800-1000 it fluctuates

User avatar
louiswun
Posts: 119
Joined: Sun Jan 27, 2008 5:33 am

Post

What firmware version on your nistune ?
Is it feature pack version ?

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

nistune is 1.2.51 not the feature pack i havent sent it in for that yet.

boost_boy
Posts: 7162
Joined: Thu Nov 14, 2002 7:28 am
Car: B12 sentra w/built CA18DET, B12 sentra w/fully-built CA18DET, S13 coupe w/ CA18DET, S13 hatch w/CA18DET, 2002 maxima SE
Location: Miami, FL.
Contact:

Post

I've been watching this in silence for quite soome time and I'm with float on this one. Though you may have a license to operate and tune the Nistune system, I believe that's where your problem is going to lie. You may not want to hear that, but after working with CA18s for nearly 20years, if there was to be a mechanical or an electrical problem on the motor, then you would start with the crank angle sensor or suspect exhaust camshaft key. But in this case, sounds like the engine management is not happy, although I could be wrong.

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

cadet18 wrote:right i know that but it shouldnt sweep between 12-18 i wouldnt think...
Actually, that's about perfect. 12-16 is a bit more normal, but 12-18 isn't crazy. It's only at 18:1 for a brief moment, so the engine doesn't have a chance to lean stumble in that amount of time. What are your fuel trims?

User avatar
louiswun
Posts: 119
Joined: Sun Jan 27, 2008 5:33 am

Post

Did you tried a 100% factory ecu (stock rom had not been removed) ?
do you have another injector resistor to test ?

User avatar
r34 gtr
Posts: 8909
Joined: Sun Dec 29, 2002 9:33 am
Car: 98 Frontier XE 4x4
95.5 Audi URS6 Avant 5spd
03 BMW 330i ZHP 6spd
89 240sx base CA18DET
Location: Creepin' in your crawl space
Contact:

Post

Yeah I am with float in that the idle AFRs are probably fine and should have nothing to do with your driveability issue. I would concentrate on other things for the moment.

What does your ignition map look like? Is it custom? I know you mentioned using an LS coil setup. Do you get that stuttering-sandbagging issue with a stock ecu?

What are your cruise EGTs like when this is happening?

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

so ive tried the stock ecu with stock maf, 3 diff CAS, 2 diferent dropping resistors, the stock coil packs, the ls coil packs. all did the same whether stock ecu or nistune ecu with stock map. igntion map is untouched both times. also checked cts resistance checked good. cam belt timing was also confirmed. i counted the teeth BETWEEN the gears like i read on here. unfortunately i dont have an egt gauge. ive also done the tests per the fsm for all the components on the engine and all tested good. i have no codes in the ecu. ive checked continuity and for shorts to ground on the engine harness for all the major sensors and all checked good. the fuel pressure is set to 28 using a genuine nismo fpr. i have a year old walbro 255 in tank. i wanted to say it was the ecu as well but i cant reason that after trying all of these things and 2 seperate ecus. i really think its something weird electrical somewhere thats causing this. i just cant wrap my head around where. or some component i havent thought of is not quite failing but not doing something right that i cant test for. im drawing blanks on this one. at this point id be excited if it was a $1000 part if i knew it would for sure fix it. trying to think out of the box now for wierd scenarios.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

ill have to take a look at what the fuel trims are tomm when i get back from work and report back.

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

Base differential fuel pressure for stock injectors is 36psi, not 28psi. You're fuel pressure is set too low.

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

Also, any time you change injectors, you need to readjust the fuel pressure. Most injectors are rated at 45 psi differential pressure. So if you pull the stock injectors out, and don't adjust the fuel pressure to match the new injectors rated pressure, they won't have the correct flow rating and your tuning may be more difficult because they aren't actually flowing the amount of fuel that they're advertised for.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

i was under the assumption that stock fuel pressure with vacuum line off was 28. i jumped the fuel pump relay and set to 28. so for final adjustment i should see 36 with vacuum connected at idle? I set it to 36 and if definitely seems to like it better at idle. i let it warm up set there and it seems better. I dont have time to go for a drive before work but its going to be the first thing i do when i get home! If thats all it was im gonna feel pretty dumb but hey! we gotta learn sometime. heres to hoping that was it! Thanks!

also i assume if im using stock gtir injectors for my 440s then ill set to their factory pressure which i believe is 40 something?

Ken@PTUNING
Posts: 99
Joined: Thu Dec 24, 2015 5:29 pm
Car: '92 Nissan 240sx KA-T
Location: Manassas, VA
Contact:

Post

The base fuel pressure should be 36psi (2.5bar) done with the vacuum line disconnected on a stock CA18 fuel system. Connecting the vacuum line will bring it down, likely close to 28psi at idle (depends on how much vacuum the engine pulls). With a standalone, you can set the fuel pressure to whatever you want. I tend to stick to either 3bar (43.5psi, stock for the SR20) or 4bar (58psi) depending on the car. Likely, you'll have good results at 3bar (typical on most Japanese cars). It's high enough for good fuel atomization but not too high to lower fuel pump flow (fuel pump flow capability decreases with fuel pressure). Once your fuel pressure is set, scale your injectors accordingly (example, nominal 550cc injector that gets rated at 543cc @ 43psi or 627 @ 58psi on a manufacturer's spec sheet). If you need more fuel (less duty cycle), you could also up the fuel pressure to compensate.

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

No, you don't set the fuel pressure with the vehicle running. If you do that, even with the vac line disconnected, the fuel pressure will then be higher than it's supposed to be. This should help you;
how-to-set-your-fuel-pressure-via-an-ad ... 14558.html

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

ill set it this way now and see how it acts. i did 36 with the vacuum line off and finally got to drive it like that. only took it around the block but it felt about the same. its still rich under acceleration until you let off or hold a constant speed. ill go out and run it through today since ill have some more time and see what it does. just been super busy lately

Buddyworm
Posts: 416
Joined: Tue Jan 09, 2007 2:55 pm

Post

12-16 AFR is quite a sweep at idle. A happy CA running a stock/nistuned ECU should hover WELL within 1AFR either side of stoich when fully warm.

Where is your MAF located relative to your compressor inlet? How long is the pipe?

Also, you seem to focus a lot on the intake manifold when looking for vac leaks. Have you checked the rest of your piping?

User avatar
Izento
Posts: 438
Joined: Fri Dec 12, 2008 12:20 pm
Car: RPS13

Post

I'll say that my car (tuned on PFC) was always within 1 AFR when idling.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

maf is stock length away from the turbo inlet. ive checked the rest of the piping each time... no leaks. its gross and raining out here and ive got the front bumper and hood off permanently until i resolve this so no driving tonight.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

reset fuel pressure with the above link (thanks float), its running around 32 psi at idle now vacuum connected. it definatley made it run leaner at idle im back to off scale lean at idle on my wideband. what doesnt make sense is that the car is rich under part throttle though and i dont have any air leaks. you think its my fuel pressure regulator doing something weird while under load( i cant see fuel pressure while driving as the gauge is under the hood)? i also noticed that what i believe is fuel cut (the car violently stop accelerating and loses power until i pull back on the throttle) is occuring around 4k rpms with me not flooring it just accelerating a little faster than i would normally drive the car.

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

There's something wrong with the reading you're getting from the wideband. Most widebands max out about around 19:1. The car won't idle that lean. I don't think you're getting an accurate AFR reading. Exhaust manifold leaks? Has the sensor ever been dropped? If the Wideband is reading incorrectly, and then inputting that erroneous info to the ECU, it's going to throw your fuel trims way off. IIRC the stock ECU is capable of +/-15% fuel correction. If your fuel trims are maxed out, that's enough to make the car run poorly.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

the wideband is a separate entity on this car. it has no input to the ecu whatsoever. i looked for exhaust manifold leaks and didnt see any black or feel a leak anywhere. i might just go with an innovate wideband, noone seems to like the aem. i do think youre right about the car not idling there. It is holding idle now so thats good. i just cant figure out why its idling lean and running super rich when i give it a load without a vacuum leak. it almost seemd like the knock sensor adding fuel and pulling timing but i get no codes from it.

cadet18
Posts: 226
Joined: Sun Feb 05, 2012 9:46 pm
Car: 89 s13 coupe ca18det

Post

so im leaning into this being ignition related. it really feels similar to when i was having spark blowout issues on e85. while at cruise the car will hesitate and hiccup while running full rich. also i hear compressor surge when it does this every time. im going to dig around this ignition system and see what i can find. Thanks for sticking with me on this problem guys! If your ever up in the delaware area ill take you out to dinner just let me know. (plus itd be cool to talk CA stuff with someone) ive got to leave on another trip tomm which hopefully wont keep me out longer than a week but well see.

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

So if you don't have the wideband feeding a simulated narrowband signal to the ECU, do you have a regular narrow band hooked up? Where is the ECU getting it's closed loop signal from?

My point is that maybe it's NOT lean or rich at all. Maybe the wideband is failing on you. In my experience they don't just stop working, they just give erroneous information. Before you drop $ on the AEM, go pick up a cheap narrowband from the auto parts store and hook it up temporarily to the narrowband O2 sensor.

User avatar
r34 gtr
Posts: 8909
Joined: Sun Dec 29, 2002 9:33 am
Car: 98 Frontier XE 4x4
95.5 Audi URS6 Avant 5spd
03 BMW 330i ZHP 6spd
89 240sx base CA18DET
Location: Creepin' in your crawl space
Contact:

Post

I had my wideband O2 (NGK AFX) located in the stock narrowband location and it was too close to the turbo. Readings jumped all over the place. When I moved it to just after the downpipe, it was much happier and gave me accurate, smooth, reliable readings. Your experience may vary, but its definitely worth noting.

Also, as Ryan says, if you arent running a narrowband o2 sensor or emulating one with your wideband, there's your problem.

Buddyworm
Posts: 416
Joined: Tue Jan 09, 2007 2:55 pm

Post

r34 gtr wrote:Also, as Ryan says, if you arent running a narrowband o2 sensor or emulating one with your wideband, there's your problem.
Negative. As I said already, ECU defaults rich if it doesn't see the O2 sensor signal. If the components on the engine were working properly except for the O2 sensor his AFR's would be rich, but stable.




Cadet, can you post your current tune and what injectors/MAF is currently on the car?

User avatar
float_6969
Moderator
Posts: 19853
Joined: Mon Aug 26, 2002 1:55 pm
Car: CA18DET swapped 1995 Nissan 240sx (too many mods to list)
2015 SV Leaf w/QC & Bose (daily)
Location: Topeka, Kansas
Contact:

Post

It's on the first page. He's put it back to stock trying to fix this issue. He's used a stock map Nistune and a stock ECU. He's gotten his idle issues sorted out, but he's still having stumbling issues under load.


Return to “CA18DE / CA18DET Forum”