Zack342

iTrader: (89)

today i had my car dynoed with some of the guys on here from the Northeast chapter. my car is a 99 SE-L cail spec. it has 98,156 miles on it. i have owned the car for about 7 weeks and i have done about 4000 miles. i only use synthetic oil and i also only use 93 octane fuel. a couple weeks ago i replace the rear O2 sensor due to an engine check light and the engine check light has since went away. i have also added the warpspeed y pipe, jwt pop charger and catco highflow cat. the car runs and drive pretty well although it feels a bit slower than when it was stcok but i just thought that was in my mind. i have no ecu codes and everything seems to be in good shape. well anyway had car dynoed i was the first max to go max HP was about 160.98 fwhp and max torque was 181.49. i would be ok with these numbers if the dyno graph looked smooth but its terrible. i have the file scanned and i can e-mail it to someone if they can host it for me. please help with any info was to why my #'s are so low. after the car was dynoed 3 other maxes with intake,y pipe and exhaust all did 180+HP and 190+ TORQUE. 2 of them had 160+k and one had 123K. what's wrong with my car ?

Zack342

iTrader: (89)

here is the graph
http://www.imagestation.com/mypictur...7&from_album=1

MAXRB8

iTrader: (19)

Just guessing.... bad knock sensor? Anyone?

UTIMaxima

iTrader: (2)

I don't think a knock sensor would be responsible for 20 hp.

Zack342

iTrader: (89)

one of the kids who also had his car dynoed suggest it maybe the knock sensor but we tried to read it off the ECU and there is no screw to turn on the 99 ecus so we then went to autozone where they read the ecu and got no codes?? could it be i need a tune up or bad coilpacks i have heard that the 99's have bad coil packs. at this point i just wanna drive the car into a tree, how dissappointed would you be if your car was making 15 less hp than cars with 60,000 more miles. i mean i treat it well good gas and expensive oil changes. i let it warm up for a couple minutes even if i am late. i may just sell it and get a neon srt-4 . i saw a couple at the dyno meet today, 260hp and 280tq at the wheels with just mopar stage one package and exhaust.
can anyone explain why the graph is so unstable and not smooth.......

WhiteMax96

Have you ever had a bad knock sensor on your car? I don't think so. When your knock sensor is toast, your PCM fall into a safe mode. It means that the spark is retard. So if the spark is retard, it means less performace. You will feel a bad knock sensor between 0-3500 rpm approx.

When you floor your car, do you feel some kind of lag between 0-3500 rpm, like someone is holding you?

DAVE Sz

iTrader: (2)

Wanna bet? Look at athe dip on the graph at 3.5krpm. Don't the cali spec cars dyno lower than other anyway?

Zack342

iTrader: (89)

if it is the knock sensor wouldn't there be a code when we read the ecu with the code reader? could it be coil packs or bad plugs. the last major service on the car was the 60k at nissan

zazon

iTrader: (4)

fyi my i had a coil pack problem and you can definately tell theres a problem at all stages of the throttle.

Mishmosh

iTrader: (3)

A bad coil pack would cause a misfire condition which anyone should easily feel. I bad KS can definitely cut you back 15% or so. Although it doesn't give a CEL, it does give a code with a code reader. I would try another autozone just to confirm that the other one read it right. Don't know what kind of plugs you have but it's something to check. The only other thing I can think of is a clogged cat. Were your O2 sensors bad for very long?--running rich is definitely not good for cats.

njmaxseltd

iTrader: (19)

Change your fuel filter and spark plugs and do the dyno again. Your Cali spec is not going to make the same HP that Fed specs will. You should be close though.

ScarfaceTHX

HOLY CRAP.

Throw in a few valium or xanax next time you fill up.

UTIMaxima

iTrader: (2)

I know what the knock sensor does. I have had a bad one, and after I fixed it, the difference wasn't that noticeable. Not a difference of 20 hp anyway.

Zack342

iTrader: (89)

the cat is a week old i installed a new one when i did the Y pipe. the pervious owner had the 60K service done at nissan so i assume that they are NGK's being as that is what the dealer ship would use. if the majority of people think is the know sensor then i will have it changed. but i just wish i knew if this was a definate solution to my problem. the 02 sensor was bad for about 2 weeks before i had it replaced it was a p0135 code, or 0901 "front heated oxygen sensor, rear bank" after i reaplced that the car felt much better or back to normal. what concerns me is why neither or my curves for HP or TQ are smooth is it an ignition thing? i would really appreciate any help that could point me in the direction of the problem.

Ceasars Chariot

iTrader: (16)

dont drive the max into a tree, you will get things worked out man !

Zack342

iTrader: (89)

tree = simple solution to a pain in the A$$. paid $6600 for max. nada on mad = $10,000 with the mileage.
but i wouldn't do that.
i just want my 15 wheel hp and a smooth curve.

Mishmosh

iTrader: (3)

Did the others have different looking graphs? It seems to me that on your graph, the raw data is being mapped. I believe that the software usually smooths out the data to make a smooth line for tq and hp. I would NOT replace the KS if you do not get a code for it. Please pull a plug and see if they are the appropriate NGK and heat range. It is not unheard of for dealers to put something else in (cheaper). Courtesy Nissan sold me one step colder plugs as "stock" for my 1995!

Zack342

iTrader: (89)

i can pull the plugs tomorrow and take a picture, i don't know what else it could be. thanks for all the info guys i appreciate all the comments and don't mind my whining, i am trying to vent. its kinda upsetting see a car with a 166,000 miles doing 182 fwhp with intake,y-pipe and catback. with nice SMOOTH power band and graph. and then you car which was the newest, 99 and lowest mileage doing 160 fwhp with a graph that looks like a polititian's polygraph test. i wouldn't mind if there was a problem that i could identify and resolve but its not knowing is the worst part. so far its down to , knock sensor, plugs , fuel filter, i am not sure what else it could be. i don't wanna modd the car anymore if its not responding well to the bolt ons......

charancon

Someone said something about graph smoothing, isnt that what's written on the top right corner ? Anyone know what that means ?

futhermore, is it possible to get a bad KS without a cel light or a code ? at all ?

Zack342

iTrader: (89)

who knows????

mansurxk

iTrader: (14)

its int he faq's the knock sensor can function intermittently, and yeah to the person who claims the knock sensor wont make that muc idfference, sure as hell does, when mine was bad you could floor the car and it wouldnt chirp the tires, and after i changed the snesor, i could peel at half throttle,

zack is your gas mileage down?

charancon

Anyone know how to replace the knock sensor with a resistor (550k ohm) to test it ?

Imobejoas

iTrader: (1)

I noticed you said that the y-pipe installed is fairly new. Have you reset the ECU and driven around a bit to let those readings settle? That could account for some missing HP.

WhiteMax96

Don't replace your knock sensor but just use a ohmmeter to see if the resistance is ok or overload.

Dave B

Looks like it's time to buy a Chiltons manual ($20) and a $10 volt meter and start testing the obvious problem areas like coil packs, MAF sensor, knock sensor, etc. It's all in the book and it's FAR cheaper than blindly replacing parts. Pull the plugs and let us know the brand. The gap should be 0.039-0.043 and they should be NGKs.

BTW, a bad knock sensor WILL throw a code without any other codes being present. It did it in my car.

Also, Cali-spec cars do make less power unfortunately. 5-8fwhp seems to be the norm. You may want to look into the "swirl valves" and make sure they're operating correctly. The swirl valves are something the 95-98 Maximas don't have and the valves have been known to cause power problems if they don't open under full throttle.


Dave

Nealoc187

iTrader: (23)

That looks like the ECU is pulling timing to me, for whatever reason.

I've seen dynos of cars that should be dynoing 170s and 180s dynoing in the 140s and 150s because of the timing pull as a result of knock sensors, thats 30ish hp right there in some cases. This could very well be a knock sensor or some other reason why the ECU is pulling timing.

n2oMike

Sometimes knock sensors get overly sensitive. They think the engine is knocking when it is not, and retard the timing. To the computer, everything seems to be working correctly, so there is no code.

My car had a small hesitation under 2k rpm, didn't seem to pull as hard through the rpm range. The fuel mileage also dropped off 2-3 mpg.

I replaced the knock sensor (even though there were no codes) and everything was fixed. It felt MUCH better in the low-mid range, and pulled harder on the top end as well.

Good Luck!

Zack342

iTrader: (89)

ok since i have been a bit worried i woke up early this morning to go check the plugs. like i suspected they are NGK's . they do however looks like they could use a replacement sometime soon. i took some pics of them for you guys to maybe assist in determining what could be wrong
http://www.imagestation.com/mypictur...7&from_album=1
http://www.imagestation.com/mypictur...7&from_album=1
http://www.imagestation.com/mypictur...7&from_album=1

Zack342

iTrader: (89)

i should also note that i have been observing pretty good gass mileage considering how i drive i do all higway miles at about 80-100mph and i usually get about 350 miles to a tank. tomorrow i am going to go to the dealer and get 6 new plugs and trying replacing them to see if that helps. as far as i can tell the car runs extremly well no hesitations at any RPM, no hicups, it drives pretty good considering what the power band looks like. i am going to change the plugs. since they have about 98,000 miles on them. i know nissan didn't change them at 60K . they told my dad when he had his 60k tune up on his altima "they inspected them". they inspect alot of sh*t and chage for it. i should also note my ECU does not have a screw in the side which i can use to turn it for self diagnostic on the car. i am going to give the plugs a try, then maybe the knock sensor. then i have will have to shell out the $100 to have it dynoed. hopefully there will be some improvement. if not in HP atleast in the way the power is delivered.

Zack342

iTrader: (89)

what does "ghost" refer to when talking about the code 0304 i notice in this post his dyno graph looks similar to mine

http://forums.maxima.org/showthread....68#post2870568


also another thing that i am curious about my TQ doesn't seem that bad at 181 it was only off by 10 or some from the other maxes ?

Dave B

Your plugs look completely fine. They're not the problem.


Dave

Zack342

iTrader: (89)

believe it or not i was hoping that they were.well i guess then i don't know what it could be maybe that is all the car is capeable of as sad as it is. i was wondering if it could be a Exhaust Leak, or a grounding problem. i don't know if anyone remembers when installing their y-pipe there is a a "ground Strap" that connects your exhaust where the cat bolts to the y-pipe. the strap then connected onto one of the exhaust hangers. when we installed my y pipe we snapped this strap and i never re-installed it . i just got one from autozone and i am going to install it in a little while and see if that make any diffrence.

i am open to suggestions if anyone wants to throw in there 2 cents . i mean there car is in excellent condition. bearly any rust, doesn't leak oil, drives very well. if i hadn't have had it dynoed i would have never suspected any problems......

charancon

Ok, regarding your plug coloration. If indeed what I see is also what you see when looking at the plugs. Am I right to assume that the electrode is has a white deposit on it ? Both Haynes and NGK say that this is due to carbon deposits starting to accumulate on them. This is caused by a weak ignition, bad fuel system or incorrect mixture. The color your are looking for in a plug is as if they were kinda rusted, a browny type of color. This is what I think. I removed mine about a week ago and they were a nice brown color with no deposits on them, yours look white to me...

IMHO...

Charancon

Zack342

iTrader: (89)

there was some white build up of some sort on the plug, there was also black suit of some kind as well.

i have also reinstalled a ground strap in the y-pipe/cat intersection and that may have help a bit. right now my plans are to get a full tune up and hope for the best i will have to wait and see what my mechanic says with regrad to this matter. in all honest the car drives pretty well and its liveable , its sucks that its not acting as it should but there is nothing i can do...

SteVTEC

If you're pulling 181 fwtq then I doubt your knock sensor is bad. If the knock sensor is dead you will EASILY drop 20-30hp/tq and have trouble passing 4-cyl Honda Accords!

It's probably one or a few smaller things. Tire pressure, alignment, air filter, plugs, coils, dirty throttle body?

99 Cali-specs are just as quick as Fed-spec and earlier 4g Maximas and "should" dyno just as high (around 160fwhp/175fwtq stock). I saw one dyno for a 99 cali-spec at 155 fwhp and that was with an O2 sensor code I think too. 99 cali's aren't any slower But yeah, if the swirl control valve is stuck closed (only used during cold start I think) it'll be blocking up your lower intake manifold and hurting your low/mid-range a little but your top-end A LOT.

And I agree with whoever said to not just go throwing parts at it. First get the right tools for the job. An OBD-II scanner is essential for troubleshooting these cars as far as diagnosis and figuring out exactly what's wrong. You can check for an 0304 (or other) code, and also see what the timing looks like. You should be getting 25* at WOT and redline. If you're only getting 20 or so then timing is getting pulled.

BTW my 99 Cali-spec does have a screw for diag mode on the ECU. Yours should too. But the main reason I got my OBD-II scanner was because flipping the screw was a PITA and the scanner lets you datalog too.

I have an Auterra and a bunch of other folks do too.


www.auterraweb.com

Zack342

iTrader: (89)

thanks for the info steve, i wish i had ready your post eariler, i just bought a knock sensor off of ebay !!! oh well it can't hurt to change it. in all honest the car doesn't drive as if there is anything wrong with it at all, not problems accelerating, 1st gear goes really quick as does 2nd. would plugs, dirty throttle body or even alignment cause the unsmoothe graph. i did reground the y pipe and i think that may have helped a bit believe it or not. i am going to go to the track an see what kind of #'s i can get. i don't wanna go back to the dyno until i can do something that i think will make a diffrence in power. the 181 torque was a bit odd but i didn't know what to make of it. horsepower was down atleast 15 and torque stays pretty good but i don't know why the graph is so terrible, i wouldn't mind if the 161HP was nice an smoothe but the power delivery on the dyno was so terrible, at this point i am open to anything . i haven't cleaned the throttle body, it is due for a tune up, tire pressure should be 32 32 last time i checked and it doesn't seem to need an alignment but i don't know for sure. well i will wait for the knock sensor, and have it intalled same time i have a tune up the car now has 98,200 miles approx. i am going to have a full tune up at 100k. yeah when we cracked the plastic it didn't look like a screw so we just went to autozone and had them read the ECU no codes. thanks for the info

Zack342

iTrader: (89)

has anyone dynoed a car with a bad knock sensor? i am curious because i would like to compare graphs.

Zack342

iTrader: (89)

just checking in and hoping someone can point me in a definate direction.

Zack342

iTrader: (89)

bump.........

EZEMaxima

Change your fuel filter and clean out your throttle body. And make sure that your air filter is clean. I also suggest throwing in some fuel injector cleaner if you don't want to spend more money on getting them professionally cleaned.

But like what the rest of the guys said...your car would dyno a little lower compared to fed spec.