no power below 3000 rpm, but cam timing is on point

[f s t caz]

I did a search for this and came across C-rad's post in which he describes seemingly the exact same problem i'm having now.

If i accelerate from a stop, the car stumbles and about falls on its face until 3000rpm, then its fine, then boost kicks in perfect at 4000rpm. If I'm sitting still and blip the throttle it is very sluggish. If I go WOT while sitting still, the engine stumbles, bucks, misses until its gets past 3000rpm at which point it revs fine.

C-rad started by looking into his tps and then found it to be his cam timing was off. When i assembled the motor 2 days ago, I did so w/ the valve covers off (the 1" hex on the cam get makes putting the belt on 213098123x easier b/c move the cam w/ a wrench on that hex is much much easier than turning a cam gear by hand) and the belt practically fell into place. i was shocked and amazed and must have turned the engine over 10 times to check the position of the marks because i couldn't believe it didn't put up a fight at all. needless to say, after reading c-rad's post, i went out and took the front covers off and checked my marks. all perfectly aligned. I then counted teeth again. 48 teeth on the belt between the exhaust cam and the crank pulley marks, 39 teeth on the belt between the intake and exhaust cam marks. I wish it was as easy as repositioning cam gears.

I checked for codes, came up w/ a 55.

vacuum at idle is roughly 18in

ignition timing is set to 15*

Now I'm trying to check my TPS to see if maybe its just out of adjustment but not throwing a code. Idle switch works properly: continuity when released and none when depressed

throttle sensor though, i'm getting strange ohm readings but can't figure out if its my $10 multimeter or my throttle sensor, but i can't come close to any of the specified resistances

could it be something other than my electrical components, like more along the lines of my modifications? It currently has:

freshly rebuilt - 165psi+ on all cylinderscp pistonstomei head gasketwalbro 255 (stock fpr though)dsm 450cc injectorsz32 mafsocketed and chipped ecu - programed for the z maf, 450cc injectors, higher boost/rev/speed cut - but not fine tuned to the carfull brm exhaust - no catssauto "equal length" manifold and elbowGTiR t28

The problems do lessen in severity when the car warms up - read engine about stalls below 3000rpm if reved when cold, but still exists even when at operating temperature.

What engine speed does the 2ndary butterflies open up at?could i just be running super rich down low from the not-fine-tuned chip and the walbro w/o an adjustable fpr? I pulled plugs tonight when I did the compression test and they aren't fouled.could i have just lost my low end from the equal length manifold? it's been so long since i had the log on, I cant remember what it used to be like. I remember the lag and waiting for the boost to come w/ the GTiR, but certainly don't remember the stumbling.

so if someone has some advice, some insight or could point me in the right direction, i'd greatly appreciate it.

[Chris859]

I would like to know how you fixed this problem if you get it figured out. My 240sx has been doing this same exact thing on my almost stock ca18det. It has been frustrating me so bad trying to figure this out! I am about to just give up on the ca ecu, sensors, electronics, etc and go with a standalone fuel/ignition setup.

[UMS_CA18DET]

with the TPS you dont check resistance you check Voltage.

Closed should be around 0.2VWOT should be around 4.3V+

[float_6969]

I mean you no offense, whatsoever, but I think your cam timing is still off. I COULD be an engine temperature sensor as well, but I really don't think so.

There have been COUNTLESS people (myself included) who SWORE that the cam timing was right. They poured over the entire car trying to diagnose the problem. When they finally redid the cam timing, it fixed it.

If you're not getting any codes, and you just replaced the timing belt. Reset the belt again. And make sure you pull the crank pully and lower timing cover. And you're right, pulling the valve covers makes the job very easy. You can just stick a big wrench on the cams and turn them. I would HIGHLY reccomend getting a second set of hands for this job. It makes it much harder to screw up.

[boost_boy]

walbro 255 (stock fpr though)= Bad for business! Ryan should have picked-up on this one. don't be screwing around with the tps too much especially if you've never moved it. Be wary of all the things you've added that's not stock and work around those components, especially the fuel pump and regulator. One of my customers had nearly the same problem and he lives in Port St. Lucie, FL which is about 2 hours from Miami. I drove to him to do his car and he encountered a similar problem and even drove the car to my house for me to check. Everything checked-out okay, but since the time when I did his car and told him to change his pump, he swore to me that his pump was fine, so I didn't sweat. Making a long story shorter, he changed his pump, he's extremely happy, and now he's running low 14s/hi 13s on a relatively stock set-up. Final answer, Nismo adjustable fpr for you............

Dee

[Darius2250]

with the TPS you dont check resistance you check Voltage.

Closed should be around 0.2VWOT should be around 4.3V+

is that with the engine running or just sitting and not running?

[UMS_CA18DET]

should be able to check it with the key turned to ON.

[f s t caz]

I mean you no offense, whatsoever, but I think your cam timing is still off. I COULD be an engine temperature sensor as well, but I really don't think so.

There have been COUNTLESS people (myself included) who SWORE that the cam timing was right. They poured over the entire car trying to diagnose the problem. When they finally redid the cam timing, it fixed it.

If you're not getting any codes, and you just replaced the timing belt. Reset the belt again. And make sure you pull the crank pully and lower timing cover. And you're right, pulling the valve covers makes the job very easy. You can just stick a big wrench on the cams and turn them. I would HIGHLY reccomend getting a second set of hands for this job. It makes it much harder to screw up.

I went back last night and counted teeth on the belt using a permanent marker and put a dot on each tooth and a line on every 10th tooth. unless the fsm can be wrong about the number of teeth, or if the american version of the CA i purchased the nissan timing belt for has an extra tooth, then i just can't see how its possible.

i've been waiting for my turn with the fpr. i saw that its hit or miss on problems with it. Thought maybe i got lucky with a miss, but perhaps not.

[tyrannix]

somethng to try: dont count the teeth, just use the white marks on teh belt (Assuming they came with it and you didnt make them) and match up the marks on the gears (with the gears pointing where they are supposed to of course)

CJ

[f s t caz]

somethng to try: dont count the teeth, just use the white marks on teh belt (Assuming they came with it and you didnt make them) and match up the marks on the gears (with the gears pointing where they are supposed to of course)

CJ

unfortunately, the belt has about 10,000 miles on it, so the marks are the ones that I made

[boost_boy]

Of course if the belt has marks on it, you'll want to reference them, but the only thing you need to worry about is if the cam gears are lining up when the #1 piston hits TDC. If they are lining-up on both exhaust and compression strokes, then there's no need to toy with this area. Try the FPR and see how she acts.

Dee

[Chris859]

Boost boy, the previous owner did install the 255lph pump in my 240sx. And my setup is stock, asside from 3" 5zigen catback, no cat, hks bov, and ka24 throttle body(or, at least I was told...). Its possible my ecu had been tuned in japan on the swap, before I got the car(It came with an aftermarket cold pipe on the smic, with a sticker on it that says "TBO tune japan") - unfortunately I have no idea, as the ecu has no markings or stickers on it. I am also willing to bet the timing belt on my ca was never changed - as the previous owner didn't take care of the car very well. Do you think the nismo fpr will help my running problems as well?

[f s t caz]

nismo fpr goes on tomorrow.

here is where the cas sits for 15*

I took it to two master tech friends to look at. both agreed it most likely had to do w/ timing - either cam or ignition. One said CAS could be bad and/or teeth inside the CAS or exhaust cam could be worn and to take a look at that. Doesn't appear to be worn down on either end, however. Also said to loosen the bolts and advance it and see if it made a difference. Advancing it as far as the bolts allow significantly reduces the bog/miss when blipping the throttle and/or going WOT but i won't drive it like that to see how that goes.

There are a few CA's local from what i hear. should I go on a quest to find another CAS to try out?

[boost_boy]

Boost boy, the previous owner did install the 255lph pump in my 240sx. And my setup is stock, asside from 3" 5zigen catback, no cat, hks bov, and ka24 throttle body(or, at least I was told...). Its possible my ecu had been tuned in japan on the swap, before I got the car(It came with an aftermarket cold pipe on the smic, with a sticker on it that says "TBO tune japan") - unfortunately I have no idea, as the ecu has no markings or stickers on it. I am also willing to bet the timing belt on my ca was never changed - as the previous owner didn't take care of the car very well. Do you think the nismo fpr will help my running problems as well?

If your ecu is badged, then it has been chipped, but for what? If it has been chipped and it's for upgraded components and yours is stock, that's where you might want to start (With a stock ecu). Just because and ecu is provided with your engine set doesn't necessarily mean that that ecu is tuned for modifications on that physical motor.

Dee

[boost_boy]

caz, I don't like the position of the CAS. It seems to be a bit retarded. Be wary of your idle as well because your base idle has to be within spec to set your initial ignition timing. I normally start at or around 800-850rpm to set base timing.

Dee

[float_6969]

I missed the upgraded fuel pump part. It is possible that it's over running the stock FPR, but when mine was doing it, it wasn't as consistant as what you're complaining about. My AFR's were all over the place.

From the look of the CAS, there is something wrong if that's where it's setting at 15*. It should be smack dab in the middle. The CAS is suspect, as is the exhuast cam's teeth for the CAS. They are infamous for having problems. And did you count the teeth between the crank and the cam, AND between cams? I once had the cam spacing dead on, and the crank off by one tooth and the car ran poorly because of it.

I'm not saying it's not something else, but it just sounds like cam timing to me, I could be wrong though.

[f s t caz]

From the look of the CAS, there is something wrong if that's where it's setting at 15*. It should be smack dab in the middle. The CAS is suspect, as is the exhuast cam's teeth for the CAS. They are infamous for having problems. And did you count the teeth between the crank and the cam, AND between cams? I once had the cam spacing dead on, and the crank off by one tooth and the car ran poorly because of it.

yeah. i marked and counted teeth on the belt between the crank and cam, and the exhaust and intake. 48 and 39

I checked the CAS - the inside stars points are still boxed and not worn to points.

if thats too far for the CAS, then what would the problem be? cam timing still?

[boost_boy]

yeah. i marked and counted teeth on the belt between the crank and cam, and the exhaust and intake. 48 and 39

I checked the CAS - the inside stars points are still boxed and not worn to points.

if thats too far for the CAS, then what would the problem be? cam timing still?

Okay, let's do this, you will need the FPR regardless if it's the CAS or not, but I think the gurus are with me onthe CAS's position. Go back to my previous post and your idle. Where does your idle sit currently? The CAS has the ability to be problematic without the computer sensing it. As long as the CAS's photodiode don't miss one of those 360 slits on its timing wheel, the ecu won't trigger a code for it. The crank angle sensors do wear and get out of calibration. This usually happens when you have or have had a worn camshaft, dropped the CAS, or have left it loose while the engine is running. If anything, just try another one. Again don't listen to these fools about your cam timing. They're trying to make you think you're crazy or something; especially float

Dee

[f s t caz]

just started it up. it was cold, so it idled at about 1000rpm, then dropped to about 850rpm after a minute or so and held steady. It's a little too late to wait for it to warm up and report the idle warm, but don't think it's much below that.

[f s t caz]

nismo fpr installed, set to 36psi, symptoms still exist.

going to try to borrow an ignitor and a cas tomorrow.

also got a s-afc to fine tune the fuel and should be going to the dyno tomorrow or the next day.

all this so i can sell the car in the next two weeks.... but it needs to be running right when it changes hands.

[f s t caz]

sigh.

Tried:Nismo FPR set to 36psiChecked cam timing, marks line up, teeth count is dead on.timing is set to 15* at ~750rpmswapped out CASswapped out ignitor twicepressure tested intake system.disconnected maf and reved and had same effect.pulls no codes

could this be eprom related or knock sensor related? It has been socketed and it does have a chip for the 450cc injectors, the z maf, higher boost, higher rev, no speed cut. could there be an issue there? Or could the engine be pulling timing from a bad knock sensor but not tripping a code? iirc, it only sends a code for a knock sensor open circuit. I intended on purchasing a new knock sensor until i found out the price. wishing i would have now... bout to take the socketed ecu out and put my factory one back in and just use the s-afc i hooked up last night instead.

[boost_boy]

I would put the stock ecu back in. If you've done all that and it's still acting-up, that chip could be causing you issues. Oh yeah, your knock sensor is just fine or it will indeed flash a code, regardless. Dee

[f s t caz]

disconnected my socketed ecu today and plugged in the factory ecu. started it and it died right away. sat there puzzled for a second, then changed the output for the maf on the S-afc to 7 and started it up again and it purred. blip the throttle and it glides to 3000rpm.

the eprom won many battles, but it appears i've finally looks like the tides are turning. going in right now to get it tuned on the s-afc and factory ecu. looks like i'm in the market for a eprom chip w/ just speed cut and a higher boost limit.

[f s t caz]

got it tuned and posted the dyno sheet in the sticky. Its running in the best condition its been in while i've had it, so now it's ready to sell

Don't want to clutter up the CA forum with another FS post, so if you're interested in a RHD CA powered hatch, find my post in the classifieds section

[anumeric]

Chris glad to hear you got things worked out and it running good. Good luck with the sale. Let us know if you find some goodies while your over there.