Hesitation/stumbling during acceleration (sr20det)

[caall99]

car idles just fine. but when i go out to drive it it starts doing some weird shit. at anything more than 20% throttle (give or take) the car starts bucking randomly throughout the power band. i can reach the rev limit, but i will go through two or three bucking stages before i get there. one stumbling/bucking stage lasts about 300 to 500 rpm, and happens no matter what gear i am in. i know i am building boost cause my bov is loud as hell (still need to get boost guage). in between the bucking it pulls awesome! also i am running 87 octane until my tank runs empty so i can get a full tank of 93. could this have anything to do with it? am i hurting the engine? i'll stop driving it if i do. anyway, if u know a solution to the bucking problem please let me know. i was considering that the timing was off.

[kuramaya]

car idles just fine. but when i go out to drive it it starts doing some weird shit. at anything more than 20% throttle (give or take) the car starts bucking randomly throughout the power band. i can reach the rev limit, but i will go through two or three bucking stages before i get there. one stumbling/bucking stage lasts about 300 to 500 rpm, and happens no matter what gear i am in. i know i am building boost cause my bov is loud as hell (still need to get boost guage). in between the bucking it pulls awesome! also i am running 87 octane until my tank runs empty so i can get a full tank of 93. could this have anything to do with it? am i hurting the engine? i'll stop driving it if i do. anyway, if u know a solution to the bucking problem please let me know. i was considering that the timing was off.

could be tons of stuff

one guess is you are running too rich and it is bogging out..is there an aftermarket FP in there? How bout an FPR, How about Injectors, did the guy before have all that stuff and run an SAFC or PFC or something to tune out the fuel that you do not have now...also could be an air problem...or a vacuum problem..all vacuum line connected , all intake piping good? I wouldnt run 87, I only run 93 with Booster every tank and it keeps my knock down...I say Fuel or Vacuum....

[caall99]

i swapped the engine myself, and its a mint condition blacktop with probably less than 30k miles on it. its a real beauty... :boink: . it has the stock fpr, and everything else is stock on the engine. i also installed a big fmic, and 3 inch exhaust turbo back right after the swap. i have a hks ssqv, that is def not leaking. anyway the stumbling happens at random intervals during the rev range. in between the stumbling its awesome. how about resetting the ecu? or does a disconnected battery do the job? oh yeah, one last important thing i didn't mention. i was driving the car without a battery, because my stock one won't fit. the new slim pc680 comes in tomorrow. could the lack of a battery be a problem? i am also putting 93 in it tomorrow...

one last thing i forgot to mention. it started bucking more often after i took the silencer out of my exhaust. this might just be in my head, so don't hold it as a priority when diagnosing this problem

[kuramaya]

Running without a battery? I am not sure if that could cause it since I honestly have never done that. SO your fuel is good? Do you have a fuel pressure guage? I would be interseted to see if you are getting a steady fuel flow..that could also be a problem...is it noticebly rich? Black smoke? When you stop can you smell it? I run rich by choice, but only so rich as not to bog out 11.5:1 /12:1 is best for your blacktop. The silencers are known for throwing off the AFR on a car...I hate them and never run mine but keep it in the car incase a JP pulls me over I can say I was coming from a power test and forgot to put it back in....back the silencer..see your ECU is learning the mods you have..silencer in and out over a short period of time can confuse the ECU...since you are not running any piggybacks I would guess still its a vacuum leak or fuel somewhere...or that battery not being in..put in a battery
:D
late
daryl

[sr240mike]

No boost gauge?? Well that sucks. You could be hitting 17 lbs and not know it. First, search for "hesitation sr20det" cause this has been covered 1233124414 times. Check ecu codes, timing............................................ .....................

[Sil-EightyNY]

i had the same problem with my second car with the sr. I just did the swap and the same problem. I checked all the vacum lines and the maf and is still kept doing it until i drove down to school (100 mile trip) and the car kept getting worse and worse until its stoped 3 miles away from school. I towed it so my dorms with a maxima and poped the fuel lines and ne gas was coming out. The fuel pump kept making it bog until it gave in. Changed to a walboro and not it runs like a dream.

[Dousan_PG]

vacuum leak
safc/a/f problems

mine was dead coilpack! aesy fix just took a while to test it (my fault)
lost power above 20% too like yours

[caall99]

i forgot to mention that i can rev the engine freely in neutral, and there isn't any hesitation, prefectly smooth. its when i drive the car i get that stumbling crap. i think it might be related to the engine building boost. i am pretty sure i am not running 17lbs. the vacuum line is connected directly to the wastegate. its fast but not 17 psi fast. i actually have a walbro installed. i know i installed that correctly. i also cannot smell an over rich condition. there is no smoke whatsoever. completely clean exhaust. this boggles my mind... i am thinking about checking my timing today (15 deg right?). how do i test for the coilpacks?

it could be something as simple as a vacuum leak. except i wouldn't know where to look. someone tell me the different vacuum lines?

[kuramaya]

i forgot to mention that i can rev the engine freely in neutral, and there isn't any hesitation, prefectly smooth. its when i drive the car i get that stumbling crap. i think it might be related to the engine building boost. i am pretty sure i am not running 17lbs. the vacuum line is connected directly to the wastegate. its fast but not 17 psi fast. i actually have a walbro installed. i know i installed that correctly. i also cannot smell an over rich condition. there is no smoke whatsoever. completely clean exhaust. this boggles my mind... i am thinking about checking my timing today (15 deg right?). how do i test for the coilpacks?

it could be something as simple as a vacuum leak. except i wouldn't know where to look. someone tell me the different vacuum lines?

well first off..you should install abost guage sooooooon over 14 PSI with stock injectors and stock FPR is bad bad news....

Having a wlabro will not cause you to run rich if there is the stock FPR on...you will remain at stock flow...vacuum line to the plenum si where to look first, then make sure there are no open ones from previous accesoories like boost guage, boost control, etc etc...also check the BOV again and the stock recirc down by the intercooler...is the piping still hooked up that runs back to the intake for that? hard to trouble shoot from japan man sorry

[Dousan_PG]

test coilpacks? get an extra and change it one by one to see which runs good w/o it
or swap w/ a friend w/ working perfect sr

also what voltage a friend had problems under boost and his alternator was dead..go figure.

[270R]

This is off the s14 service manual I just read it dont know if it might be any help This is for a boost pressure sensor malfunction "when ECM judged to be malfunctioning (when the ecm thinks the boost press. sensor is malfunctioning) the duty of the wastegate valve controll soleniod is fixed at 20%". So maybe its the wastegate that is "loud as hell" and causing a rich condition. so check if you r boost pressure sensor is connected or somthin lol.......

[fliprayzin240sx]

double check both mechanical and ignition timing...gap spark plug to .028...basic.
The 87 octane is also killing you, run 93 octane. What rpm does it hesitate at? another thing to look into is could be a bad fpr or water temp sensor.

[caall99]

wow some people can't read posts very well... anyway.... my setup is not stock, and i was the reason for it, not a previous owner! i am not a newbie to turbocharged cars, so please don't tell me the obvious. i used to own a 1990 supra turbo so i understand all the fundamental concepts and even some of the more complicated shit. things i have done to try to fix the hesitation/stumbling/bogging problem:

*i checked for leaks in IC piping. there are none (tightened clamps anyway)...
*went from 87 to 93 octane gas. didn't change anything...
*cleaned the ka sohc maf. smoothed out idle a little more, but didn't fix driving symptoms...
*installed pc680 battery. car is more responsive, but didn't fix bogging...
*looked at spark plugs. look awesome, but didn't check gap (they are also the old ones that came with my blacktop)... when i check and change the gap what should i put it at?
*my hks ssqv doesn't leak either.

i also have a 300zx fuel filter and walbro 255 so my fuel system is a-ok. i still need to check my timing but i don't know what "loop" i am supposed to connect to. i have a direct connect timing light not a magnetic pick up.

recently the car has been shooting some white/blue flames out of the exhaust, followed by a loud pop-bang! i know there is a rich condition. but there is no smoke whatsoever, and i can barely smell unburnt fuel.

i run stock boost, because my wastegate is directly connected to one of the throttle body vacuum nipples.

thanks guys for helping me out

[TheSnail]

My money is on the plugs. All the swaps I have done, I change the plugs dispite some of the plugs looking new. Get some ngkR's for 12$, and I bet it will fix your problem. Get some SeaFoam while your at it.

[caall99]

why would i want to put seafoam in my 20000 mile sr20det blacktop? i think thats unnecessary wear on a perfect engine.

what should i gap the plugs to? and is it $12 per plug or for a set of 4?

[TheSnail]

Well when you said it ran smoother after cleaning the maf, I figure it wont hurt (fuelsys etc..). Its $12 for all four. Ask for either z31 (6heat range) or 240sx(7 heat range). I never had to gap them, they always worked great as they are.

[caall99]

the maf didn't come with the engine its an old ka sohc maf, so i knew it needed cleaning. the rest of the engine seems to be clean enough. where can i get these NGKs and what is the complete part number? would autozone have them? by z31 u mean the old school 300zx? also, is 6 colder than 7 or vice versa?

[TheSnail]

AvancedAuto, Pepboys, NAPA. Make sure they are NGK-R's The part number is something like BKR7e-11 or something similar. If I were you, I would get the 7's. If you stressing the turbo at 14+ psi and your engine is being filled with hot air, get the 6's.

[statik]

for future reference, driving the car with no battery is a very bad idea, a battery as like a voltage stabilizer for to the pulsating DC produced by the alternator, you will wind up destroying alot of electronic components.

[element240]

edit: dammit.... i should refresh my web browser more often.

[caall99]

statik, chill out, damn! don't u think i know this?? :doh: i drove the car like that once, for a quick test drive. and now i have a new battery, go tell a noob. these off topic and obvious responses do get annoying...

the snail, so i am guessing 6 is the "colder" plug then? and u said they are pregapped, if not what should i gap them too? is there a fsm in english for the s13 with sr20det?

anyway, thanks for the info :wavey:

[TheSnail]

.044 for heat range 7 or ngk iridiums. the 11 at the end of BKR7e-11 stands for 1.1mm which is = to .044 . Heat rang 6 I would gap them down to .032 since they are colder.

[statik]

statik, chill out, damn! don't u think i know this?? :doh: i drove the car like that once, for a quick test drive. and now i have a new battery, go tell a noob. these off topic and obvious responses do get annoying...


It was a word of caution, judging by the fact that you drove the car with 87 octane, no battery, and the plugs that came with the motor, I just naturally assumed you were a n00b and could use some advice, my bad

[caall99]

whatever, its cool man, i know i was a little too excited to get the car on the road. i was also thinking that i could work out some of the kinks before my battery came in, so when it did, i would be all set to go. also i forgot to drive my tank of 87 empty before i put the sr in, and there is no way to syphon out the gas through the filler neck. i took it easy on the car until it emptied the tank (which happened very quickly, and leads me to believe that the car is running super rich)
eitherway, i know my post count is low, but i have surrounded myself with turbos and cars for years now, so noob doesn't quite apply... :rolleyes: .

i am gonna try to check my timing, and get some new spark plugs. can anyone tell me where i should hook up the timing light signal wire? its not a magnetic pickup, its a direct connect, so i need something conductive to clamp onto. i hear there is a wire loop at the back of the valve cover, am i on the right track here?

[90rps13]

Also, check your TPS sensor. Could be dirty or just bad. Run it unplugged and see if it runs any better. I had similar issues and this was the problem. Yeah, and definitely stay off the 87 octane and get new plugs too. Good luck.

[statik]

take off the plug cover and attach the pickup around the first coil pack, you will have to pull back on some of the wire cover

edit: didn't see you had a direct connect, go borrow a timing light with an inductive clamp, or buy one, you will probably use it more than once

[YucA]

like dousan said, you should really check out your coilpacks if you havent. I also had the same problem, and it was the last coilpack that croaked...

[caall99]

so autozone and pepboys are both pretty retarded... unfortunately there is no advanced auto around here... none of the stores i listed have magnetic pickup timing lights... where else can i get the spark plugs? i am about to call napa.

also, is there anyway i can get a direct connect timing light to work?

[caall99]

sorry to bring my old thread back to life but i still haven't fixed the problem. when i rev it a tiny bit of BLACK smoke comes out of the exhaust and there is a ton of carbon deposit on the exhaust tip. also it smells super rich. the stumbling and hesitation is still there with more than 25% throttle, and occurs at about 3000 rpm and 4500 rpm. someone suggested TPS, could that be the cause? if the ecu doesn't know how open the throttle is and the throttle is in fact completely open, what would the symptoms be? possibly mine?

[TheSparo]

go check your plug gaps again, i had the same problem, gap them down to 28 it should fix it... just try it

[Eternal_240Sx]

when my tps was off the engine would start bucking around 3500 rpm. Like you I would be able to rev freely at nuetral, only when i was in gear it would do that. So check the voltage and make sure its right.
Look on the FSM. Just search for it in the search button, you should be able to find a link to it there.

[caall99]

i forgot to mention that i fixed my problem, it turned out to be a drop of salt water that got into the CAS during shipment. it clogged up a couple of the slots. i cleaned it with carb cleaner and now it runs like a dream. thanks for the help guys

[cmartin240]

How do you clean a CAS? Very interested.

[caall99]

well best thing to do is remove the whole CAS, this way you will have quicker access to all the slots on the wheel. anyway, all u have to do is take some carb cleaner and q-tips and spray down the slotted wheel. carefully scrub with the q-tip, don't forget the opposing side. also, don't risk getting any carb cleaner on the diodes. they might fuck up.

[sr20drft]

btw, for ngk plugs....... the higher the number the colder the plug....... ie 7 is colder plug than 6

[katinkid]

wow.... not a noob! 87 octane on that engine/ a full tank at that... and your wondering if that will mess up your engine. yah it can just bend a couple valves... my retard buddy did it first hand on his 93tt supra.

check your coilpaks, tps sensor voltage, ecu/chassis and engine grounds maybe one came loose when you installed your battery. check for boost leak between the head and the manifold, cracked gaskets.

pressurize you ic piping, if there is a slight slit in one of the couplers it could idle fine and under boost pop open, just a suggestion.

you say your not a noob but even the most experienced mechanics will take 2 or 3 times of just double checking things until they notice something different.

the problem is there, patience is virtue if you have the time....

your probably complain that you looked at this stuff already but like i said, maybe you notice something out of place by looking at all that stuff again.

grounds would be my first bet check the resistance with a multimeter on the ecu.

[racerx2k1]

wow.... not a noob! 4 year old thread.