I'm trying to get to the bottom of what has gone wrong with my car and many other's cars. It seems in the past few weeks alone there have been many posts with odd dyno curves, or excessively slow MPH's at the drags. Please post here if your car either A) dyno's low on the dyno, or has an odd torque/hp curve to it or B) runs slow in the 1/4 mile, with more emphasis on MPH then ET, because MPH has more to do with the power of the vehicle rather then driver skill and error, or C) if you have data for both.

Also please post your current modifications, and what you have tried to do to correct the problem, succesfully and unsuccesfully. And also when you started noticing the drop in power.

Please DO NOT post here only if you "feel" your car is being slow with no track numbers or dyno numbers to back it up.

I guess I'll go first. I've never dyno'd, but I have had a significant drop in MPH from last season to this season (november, to march). Last season, even with bad launches and missing gears my lowest MPH's were usually around 92 MPH at least.

But, for the past 2 weeks I've been to the drags with similar results. The first week I was posting 89-90 MPH trap speeds, never making it out of 15.3 with most the runs 15.4. During the very last time I was at the drags all of my runs were solid 15.5's except for one which was 15.49, which is close enough to 15.5. Except, my trap speed was 88 MPH, for all 3 runs, yet I launched well and I shifted perfectly. Having a 4-6 MPH drop in MPH like this is very significant. My car has 70,000 miles on it. The 60,000 mile service was done.

My go forwards fast modifications include a cone K&N "pop" style filter, cattman Y pipe, Stillen B pipe, ACT clutch, home made polyurethane rear motor mount and Quaife differential.

I tried running it once without the air filter, with almost no change in MPH or ET whatsoever, so its not the air filter. I havent tried

The car still "feels" smooth, good idle, feels like decent power on the street, yet the track numbers just arent adding up.

I do not know if this is related or not, but my "hesitation when starting problem" seemed to have subsided. Perhaps something has happened?

One thing that will make me very happy is my MPH's goes back up to consistent 93-94 MPH (or higher).

 

I know that when my Friend Stephanie's Maxima had problems starting it turned out to be her Mass Air, she also complained of the lack of power.

I am having problems myself, sometimes with a high dose of octane booster I get some of the power back, off and on, but the problem is still there. No codes showing, yet. No starting problems though.

 

I too have a power loss just like eric and VeeTec do......I dynoed 160hp at the wheels in a fully N/A modded 5-speed.

Car starts perfect and runs perfect.....power just isn't there..

 

Can't help you on the 4th gens but several 5th gens (myself included) are seemingly having problems with our VIAS intake manifold not opening at all. My 2K 5spd w/intake, y-pipe, and cat-back should definitely be able to run faster than 90.0 (that's my BEST so far and yes, I CAN drive!) My best quarter mile was 15.51 @ 90.0mph similar to what you are doing now.

 

I had a kinda low dyno.. but I since cleaned my filer and my car feels stronger now

 

Well, I'm adding myself to this list. Sorry Eric, I dont have numbers to back me up, but you know you have a problem when you are a 95 5spd(intake and ypipe), had an awesome launch, perfect shifts and still only put one car length on a 97 auto with only intake. Also, barely pulling on a stock 98 VTEC accord, in 3rd gear!!!!! I'm gutting my cat this week, hoping this will do something. Clean air filter, tb, new fuel filter, plugs have all been performed.

 

I think there should be some things added to this post.

What city? If the city is a larger metro area, the "winter" gas could be affecting the performance of the car. Winter gas can do lots of nasty things to cars like kill gas mileage, performance, knock in hot weather, etc.

What kind of intake setup? Cone filters that need to be oiled tnd to get cleaned WAY too often. Over oiling of the filter has a tendency to coat the MAF "hot wires" therefore reducing performance. This is why I like my HKS intake. The filters are disposable and I don't have to worry about over oiling.

When was this lack of power observed? Was it noticed this winter or was it noticed before winter? Did performance go down a few weeks after oiling your filter? Going by butt dynos is worthless. Somedays my car fells weak and I've noticed this while going to the track. Then I get to the track and my car continues to run consistent 14.7s@95mph+. It's just constant exposure to the same car.

Are you running OEM NGK plugs? Few cars care about which plugs you run, but the VQ Maxima is an exception. I don't know why, but it's true. I tried running Bosch Platninum plugs and my car felt flat, slow to rev, and detonated up top. I pulled the plugs, checked the torque, and the gaps were perfect, but the plugs showed sign of detonation. I tossed the plus and got the expensive factory NGKs. Immediately my car was far more lively, revved quickly, and pulled nicely at all rpms with no detonation. All I can think is that the Bosch plugs can't keep up with the advanced ignition system of the VQ. Many Japanese mechanics say that you can't run German plugs in a Japanese motor. I guess it's true.

With all this said, I think it's a faulty MAF. MAFs are notorious to killing performance in other cars and many times they don't throw codes either. Have any of you guys tried swapping MAFs with another Maxima? If it's not the MAF then try the ECU.

Goodluck and hopefully we can find the problem.


Dave

 

Near Baltimore maryland. Track is pretty much sea level.

Dave you know what is funny I was just about to post about this. I remember before that when I first put my intake on there was a crap load of oil stuck to the MAF screen no doubt. I wasnt sure how to clean the MAF wires but I'm sure they are affected. With all that stuff all over it, certainly its getting wrong readings.

From http://forums.maxima.org/showthread....s+air+cleaning Daniel B. Martin says "MAFS stands for Mass Air Flow Sensor. The MAFS is located just downstream of the air cleaner. It measures the amount of air drawn into the engine. For more information about the function of the MAFS and a test procedure, please refer to the Chilton repair manual (page 4-16) or the Haynes repair manual (page 6-9). The MAFS is a vital engine control sensor. It is also sensitive, easily damaged, and expensive.

The Maxima factory service manual makes no mention of cleaning the MAFS. The dealer probably won't even consider it; he wants to sell new parts rather than rejuvenate used ones. One "motorhead" magazine described rehabilitating a dirty MAFS by cleaning it with carburetor cleaner. If the DTC implicates the MAFS, you could try this. However, this should be reserved as a last resort measure."

For me, my car always "felt" OK, but after going to the track it proved otherwise.

No, I got some autolites, but I was running these same plugs last season. I guess I'll just have to break down to buy the NGK's, they are sooo expensive and see what happens.

I agree, I notice alot of people here are running the cone style filters. A dirty/oiled MAF will not necessarily throw a code either. Maybe if I can swap out mine for a "virgin" MAF. I know a few people who may let me borrow theirs. Is there any difference between the years, or the transmissions in the MAF?

But, what still doesnt correlate is I was running OK trap speeds before, and I HAVE NOT oiled the filter since the last time I was at the track. Infact the last time I oiled the filter may have been well over 8 months ago. Maybe something got dirty or broke.

I'm also pretty sure that the MAF is NOT ignored during WOT like the O2 sensors are, right?

In any case, today I'm going to clean the TB (even though it probbly wont do anything about the WOT) replace the plugs, the fuel filter (even though it was done before, but it was an aftermarket filter) and see what I can do about the MAF. I wish I had some way of testing besides my butt.

 

The MAF just may be my solution....the car has been running REALLY rich for seemingly no reason at all.....I cleaned and re-oiled my filter at the end of last summer...but my car was in the shop for 2 months in the fall not being driven....and I noticed the power loss in the middle of the fall....hmm....something to check out...too bad MAFs cost MUCHO DINERO!

 

OK I tried tackling this one by one. Today I bought some throttle body cleaner and went to work. My throttle body was actually very clean. I sprayed the stuff in there and nothing that was crappy came out. But then, I did something else. First I got the top lid of one of those sealed Glad containers. I then filled it up with TB cleaner and proceeded to to clean the MAF screen. Wow, there was alot of crap on there, mostly grease. I looked from the rear end of the MAF and sure enough, there was crap caked up on the MAF filaments. They seemed 1/2 greased with the grease holding some particles on it. So the next part took *****. Figuring that I would hopefully do more good then harm, crossing fingers, I very carefully and very gently sprayed the MAF filaments with TB cleaner from both sides.

I then put everything back together and went out for a spin after the typical choke choke choke startup. After nailing the throttle a few times to blast the residual crap out of the system I immediately noticed a difference. The car did indeed feel alot better then it did before. Infact, when I shifted 2nd gear hard (NOT powershifting) it spun so hard into 2nd gear harder then I've ever remembered it. Doing this satisfied my butt dyno. It also feels that I got back a considerable amount of torque.

I'm going to hold off on the expensive spark plugs and the other stuff for now.

I'm really hoping that this was my problem. So far it adds up though- no idle problem, no starting problem, no engine codes, and the car feels fine other wise. Also, no odd MPG figures, probbly cause the car is running slightly lean. Theres only one way to be sure though, is to go back up to the drags and to see my MPH as I really have no other way of testing.

 

ya the MAFS's are very sensitive, hopefully that's what it was.

 

Eric, Im so happy for you and hope this solved your problem!!! Only the track will tell! I might as well check this out on my 95 as well. Are there any other details you can give me on how to clean the maf sensor?? Thanks, Steve

 

Eric-

I hope it worked out for you. I too checked out my MAF this evening just for fun (my car is running really well, knock on wood). Anyhoo, I pulled my MAF and I too noticed the MAF screen was actually black with carbon. I cleaned it off and the residue was pinkish just like the K&N filter oil. SOB!!! I haven't run a K&N filter (panel) since last May, but the residue is still there!!!! I too had to grow some big fury ones and I cleaned off the two MAF elements with a Q-tip (from behind the MAF screen). Neither was very dirty at all. I buttoned everything up and my car feels even more lively?!?!

What really scared me was the pink residue. I can completely see how the MAF elements could get coated in the oil after long term use. This could possibly be the one of the sources of the low powered VQs.

Next on your list is to get new NGK plugs. Bite the bullet and spend the cash.


Dave

 

So all i need to do is put tb cleaner on the maf sensor and that will clean it right up?

 

so you think it's k/n causing all this, hmmm.

 

This is the ONLY thing left on my car that could possibly be robbing power....I hope this situation is only with K&N filters that have be cleaned and re-(OVER)oiled by the user....not original K&Ns.....cross your fingers for me guys....I just ordered a new MAF from Courtesy Nissan.....and a NEW popcharger filter...cuz mine is getting kinda ragged....

 

My original K&N came overoiled. I remembered that. And, I ran a panel for a while too and that also came over oiled. I hope this is your problem too BriGuy....but I took another spin around the block, and even with my leaky Y pipe after I cleaned my MAF the car feels 10 times better. It spins hard into 2nd gear and feels like it gained a ton of power back. I'll be watching MPG figures as well.

Hopefully when I get the Y pipe fixed, even more power will come back.

Although I'm still not clear if a MAF with oiled elements would give lean or rich results.

 

This should be stickied! I'm going to check my MAF tommorow.

 

'


It would make a rich condition, my car has been running REALLY rich...and getting bad MPG...think about it this way....if your car was running a little lean...you'd actually see an INCREASE in power....not a decrease....plus It's almost certainly engineered so that if it get's ****ed up the car will run rich....a safer condtion.

 

so, is there any type of harm caused from using TB cleaner on the MAF? just want to know before I try it

 

Oh yea I was gonna put that- I guess me and BriGuy will be the test pigs right now unless otheres want to join the boat. I'm going to see if there were any effects in cleaning the MAF. Once we get some concrete numbers, and take the test of time, then I'll have more definitive answers. So right now, if you are "unsure" I would not recommend doing it.

 

yes if you think about how they work, they heat up to get a reading of the amount of air passing around that, i would imagine oil would make it have to heat up more for the same amoutn of air, thus thinking the car is getting more air and giving it more fuel for a rich condition, rich=loss of power.

 

Uh-oh, this thread has got me re-thinking the K&N sitting on the end of my CAI, and I've never cleaned my MAF. I'll check my MAF tonight. I may have to start looking for a replacement non-oiled filter element for my CAI.

DW

 

Yep, oil and grim on the elements will definately insulate them to the point where they are getting incorrect readings therefore making the car believe it being run in hot conditions therefore backing out timing and possibly dumping more fuel in the cylinders to prevent detonation in an attempt to cool the banks.



Dave

 

Ok, I just cleaned but I "believe" to be the mafs. This is the piece right after the intake with the sliver screen and little sensor sitting in the middle, correct? If this is the case, my wasn't dirty at all!! I was hoping it was so this would be my problem. For some reason mine was really clean. I took my car out for a spin and really couldnt tell a difference. I can bark 2nd pretty good, but that really proves nothing. Tomorrow afternoon I am going to gut my cat.

 

i went to the track with a brand new filter about 2 months and i was running REALLY bad. my times were 15.5@89, 15.7@87, 15.9@86. b4 i changed my filter, i had my old k&n which was turning gray from being exposed to cali weather. with that old filter i ran a 15.4-15.5@88-89mph consistently. weather was pretty much the same ~80 degrees, same track(cali speedway), and my mods stayed the same. the only other thing that i thought might have caused my off times were my loose belts. my belts would let out a loud squeal after every gear change. could that have been a factor? also i noticed my cat>bpipe is leaking heavily now..it makes a rattling sound at low rpms...

btw here are my mods
-vb
-cai
-ypipe
95' GXE with 150,500miles.

 

i just pulled my MAF off and looked at it. The screen had some black residue on it and the filaments didn't look that bad.

But i couldn't get the screen off to clean it off with a q-tip. How'd you guys get yours off?

Also there was like oil sitting at the bottom of the intake plenium right behind the maf when i pulled it off. just a little puddle.
My car has been sitting for a month due to the clutch going out.

 

you have to take the MAF completely off to fix it.....you get at the filament from behind....be VERY careful...and use some TB cleaner.....

 

i did pull it all the way off. It's sitting right here infront of me on my desk. THere's screens on both sides and i don't have the big fury ones (as dave puts it) to cut the screen open or force on it to much. The only other possible way other than spraying or going through the screen, is it looks like it threads through the top. But i don't see a way to pull it out through the top becuase the smooth flat black piece on top is like glued down.

 

Guys, can someone please help me?? Ok, I just cleaned but I "believe" to be the mafs. This is the piece right after the intake with the sliver screen and little sensor sitting in the middle, correct? Did I pull off the wrong part. Mine only has a screen on one side.(The side closest to the intake.) On the side of the piece it says
"{- {- {- FLOW". Did I clean the right piece? I didnt have to take the screen out it it was only on one side.

 

it's the right piece, the 95-up's have a screen on one side. it's scary to clean it though, but you can get one otu of a junked car for like 50 bucks i hear.

 

Ok, I am going to clean mine today and see what happens.

All I need is gumout or something like it right?

Here goes nothing.

 

I just cleaned my MAF. Wasn't that dirty, some carbon on the mesh screen, that's all. I sprayed (more like blasted) it with electrical parts cleaner, spraying mostly in the direction of the normal flow. Sprayed some in the back, too, the open side with no mesh. Also wiped the screen so it shined gold again. No biggie.

No more K&N over-oiling worries. I'm good to go

As for how the car felt afterwards, I'd like to say it felt a skosh more smooth, but then, that may just be a psychological mind game: I cleaned it, so it must be better

DW