Scott Vincent Grissom

I appreciate your help in advanced guys!
driving the car and with an open throttle the RPM will drop from 3k to 2k or 2k to 1500 and not when its changing gears. I have poor acceleration, horrible gas mileage and this issue mainly occurs when its warmed up. When its cold it operates normal, strong acceleration, revvs up to 3k and changes gears normally, but after about 30 minutes of normal driving, stepping on the gas doesnt even move the tachometer, it stays at 2k at 40 mph up to 60 mph and I feel a strain. If i floor it the RPMs will fly up to 3k but it will also fall back down.

Replaced:
ECTS
cleaned the intake
Cleaned Throttle body
New MAF
cleaned IACV

added lucas fuel system cleaner, still acting up
fuel filter is not clogged (fuel came out when i held it)
No Check engine light
Car idles at about 750 in park, 500 in gear

Acceleration is intermittent, i step on the gas and it goes, but ill get a boost of power and sometimes a reduction of power. Its annoying to drive... and its terrible on gas
220,000 miles

njmaxseltd

iTrader: (19)

I've seen this first hand on a Lincoln, car seemed to drive ok upon starting out, but lost power once it was warm. Turned out to be a clogged cat. Took quite a while to figure it out.
Do check that, although you should be getting a cel for catalyst efficiency.
The MAF sensor could be an issue as well, but my vote goes to the cat.

Amerikaner83

iTrader: (17)

Agreed. Once warmed up, the cat will not let full flow of exhaust gases through, causing backpressure that you can feel with the car being sluggish.

dwapenyi

iTrader: (3)

Curious about this.......if the cat is clogged, why do you get strongish power when the car is cold? Clogged is clogged hot or cold, no? Or does the platinum and other precious metal elements inside the CAT change shape as the car warms up? Or does the ECU which starts to rely on the O2 sensors when warmed up dial back power b/c the O2s are detecting too much dirty exhaust from the clogged cat?


DW

Amerikaner83

iTrader: (17)

Once the car goes into open loop mode and pays attention to the output of the cat (which is when the engine is warmed up), that's when it happens, yeppers.

maxed_out_99

Do you have an auto?
Sounds like a trans issue to me

Scott Vincent Grissom

its an automatic, and the strange thing is sometimes when its warmed up it runs really nice, but not after long will it begin to act up again. stepping on the gas feels like im stepping on air. The car has shut off on me a couple times...but since i added fuel injector cleaner and changed the MAF and KS its been a LITTLE better, but after about a day of good driving the problem is back. Still sound like the cat? I do not have a code though, does it matter?

maxed_out_99

whats the condition and level of the trans fluid? (check it in park or neutral while its warm and running)

original trans?

i would start by hooking up a fuel pressure gauge. it should read around 32psi at idle and around 38-40 with the vacuum line unplugged.

then check fuel volume this is done by cranking the car and unplugging the feed line from the filter and measuring the fuel in a measuring cup. im not sure of the spec but if either of these are not within spec i would condemn the pump. especially if you said that the fuel system treatment "made it a little better".

just because fuel comes out of the filter doesnt mean its not plugged. if it was completely stopped up you would have a no start situation.

check fuel pressure and volume and report back.

Scott Vincent Grissom

if the issue is intermittent, and only when its warmed up, which is most likely the case?
bad cat?
fuel filter?
tranny?

I do not have any codes....doesnt the cat throw a code?

after I replaced the MAF with an OE replacement, and the KS, I got codes for both of those but I had them cleared, as I had just replaced them.

Scott Vincent Grissom

i also smell gas, and the exhaust does seem to be expelling in a light pulsation...still could be the cat? my mechanic cant even figure it out. Pepboys claimed the MAF, replaced that, still have an issue. If a fuel filter is clogged, will that be an intermittent issue or no?

maxed_out_99

did you read this??

maxed_out_99

if you smell gas you have a leak.
the fuel pressure test would have showed you that.

if the exhaust is "expelling in a light pulsation" the cat is not clogged


the fuel filter will not cause an intermittent problem its either clogged or its not.
just like your stomach its either full or its not your never intermittently hungry.

Scott Vincent Grissom

Sorry, yes I did what you said, and the tranny fluid is at the correct levels, and the fuel pressure & volume was too. :/

however, I havent replaced the filter, or got a chance to check out the cat...is there any diag for a cat? visual inspection or anything?

Scott Vincent Grissom

Hmm okay, Ill have the fuel pressure test done again, by a mech. Since we can rule out the Cat and the filter. if is fails the pressure test does that mean i need a new pump? I dont know if i mentioned but, at idle, it idles fine, revvs fine and idles at about 750-800, when in gear it drops to about 500-650. if i keep my foot on the pedal when i feel little or no power, the engine "catches up" and delivers the right amount of power, but usually after a day of driving it that way, it will barely want to push above 2500. Its like somethings dirty, or being forced to give the power

maxed_out_99

This is the exact reason that diagnosis is so expensive.
Check the fuel pressure in 3 places to rule out what the problem area is.
T it off before the filter this will determine if the pumps working properly

Then after the filter to determine if the filter is clogged

Then after the injector to rule out a leaky injector

Then 1 more time before the regulator to determine its working order

Scott Vincent Grissom

Is the TPS a possibility?

maxed_out_99

well yeah but usually the symptoms of a faulty TPS will be a "dead spot" which will resemble a "hesitation" or "stutter" not an intermittent loss of power

Scott Vincent Grissom

gotcha. I just wish i knew WHAT the problem is. Ive spent so much money chasing possibilities, that havent worked, I dont wanna put another dime in. I toyed around with the cat and heard no noise, with the engine running or after shaking it with the engine off. How about relays or fuses? could the fuel pump relay be out? I guess i'll switch out the fuel filter in the mean time since its an easy and cheap fix..

maxed_out_99

yeah throw parts at it instead of diagnosing it


im done

Scott Vincent Grissom

...if you keep beating your head against that wall youre going to have to post in the trauma center forums...those diags are expensive.

I just put the fuel filter in. if it doesnt help, well, it can only help. Ill get the fuel system pressure tested asap and report back! thanks again

Amerikaner83

iTrader: (17)

maxed_out, think of it this way...fuel filter is maintenance anyhow. OP is doing maintenance that may or may not help this particular situation, but will help in teh long run.

dwapenyi

iTrader: (3)

Yup. OP, can we assume all regular maintenance is done on this car? Plugs, air filter, etc?

I'm starting to think you have 2 or more issues with your car.

1. A bad coil. Your light pulsation observation at the exhaust suggests that one of your ignition coils is iffy. Not completely bad but well on its way out.

2. O2 sensor
What's the status of your O2 sensors? If they are all old, I would then try changing just the front one only, the one before the cat. My theory (which I've tested) is that the 4th gen ECU relies on just the front O2 to fine tune air-fuel readings. the other O2s are somewhat secondary, making sure everything else (3 back cylinders, cat) are OK so to speak.

I've replaced just one O2 on my friends I30 car after doing a complete maintenance (oil, air, plugs etc). After the maintenenace his car still was acting strange. After the single O2 change his car was a bat out of hell

3. Ground issue.
Add you own home made ground kit like I did. I bought 4 battery cables (for like $30) and followed the instructions here;

http://forums.maxima.org/4th-generat...nding-kit.html

Even though my car was OK before I added the ground kit, when I added the kit my headlights became brighter and my Bose stereo sounded way better. Before the ground I thought one of my Bose amps was sounding a bit off and was about to go. After the ground kit that iffy sound was gone.

With a 13+ year old car your grounds can get sketchy. You can also fix/clean your grounds for 0 dollars by un-screwing and re-screwing in your ground points, like the negative battery cable where it connects to the trans and engine, other points like the valve cover grounds, and the screws behind the headlights that screw to the inner fenders etc. Un-screwing and re-screwing all those will dislodge rust, making the grounds more solid.

Hope this helps

DW

maxed_out_99

See the thing is I just walked him through the fuel system diagnosis but I guess he just didn't want to listen

maxed_out_99

yeah your right a fuel filter is a must even if you dont have any problems with your max im going to be installing a z32 fuel filter here in the near future

DBear

I wouldn't rule out the TPS. I had similar symptoms on my Durango, and that's what it turned out to be. My first thought was transmission, since it felt like it was lugging. It was pretty constant, though. It's easy enough to test, anyway.

SterlingMistMax

A bad coil will act up intermittently sometimes the car will run fine when its cold and start acting up when the engine is hot , i know this from past experience. my gf has a 2000 maxima . it was giving us the 1320 code but wouldnt give the code for what coil it was . i told her to keep driving it since there was no code for what coil it was . on a hot day it started really acting up . she came home the one day and told me she was afraid the car wouldnt make it home from work it was losing power so bad . the next day i took it for a ride it drove fine till it got nice and warmed up after i gave it a nice kick in the *** . got it to do the same thing to me and the ses light was flashing like crazy and finally was able to get a code for the #4 coil . and ive read on here that just cause a coil test good doesnt mean its good .

Scott Vincent Grissom

no, i just work full time. so when i get home its night time....and so i try and do my own diag hoping for a solution until i can lug over to a mech. i agree with your diag, could be the fuel pump since when i step on the gas, it goes and then GOES and then i let off the gas and the RPM drops fast. It def seems like a fuel pump issue...or the cat like others were saying...I just need to get the fuel pressure test done so i can rule some things out. I do not have any CELs...the last one i had cleared and it was for the KS and MAF but i just had them both replaced

maxed_out_99

ive been doing this for a career for a while now so to me it sounds like it may be a fuel problem, not for sure though, thats what diagnosis is all about re read what i posted to eliminate the fuel system. fuel system problems usually dont throw codes.

if everything is in spec let me know, post a video, and we will go to the next area and try to eliminate that until we come to a conclusion

im saving you ALOT of money dude cuz im a nice guy

get yourself a fuel pressure gauge and a "T" fitting there is no need to go to a mechanic you have one right here

there is some other really good info in this thread already

Scott Vincent Grissom

ok agreed, I will go out and buy one, and come right back. Thanks, I appreciate it. As a recent update, the engine last night sounded like it was sucking air, it was really quiet and the RPMs didnt get above 2k. The hose on my air box connecting to the manifold,(farthest from the firewall) has a broken clamp, so the hose isnt tightly attaching to the airbox, and one clamp is missing on my air filter box....make any difference? I was told it does not...

Amerikaner83

iTrader: (17)

isn't that where the MAF connects? I would think it DOES matter, you need steady metered flow of air getting in.

maxed_out_99

does your ses light work?
you should have a million codes if you have a vacuum leak

Scott Vincent Grissom

Yes the CEL works, because it just came on I'm having it scanned today. and the hose I'm talking about, I was told by a mechanic is just a "breather"

maxed_out_99

That would cause a major issue
I believe you found the problem

jholley

iTrader: (13)

That is your crank case breather hose. That vacuum line removes excess pressure in the crank case during acceleration.

Scott Vincent Grissom

Ok, sweet but what does that mean lol so could this really be my issue? Could this trip the CEL for a bad MAF because that's what the scanner read. P0100. And I just had it replaced (aftermarket though, does it truly matter??) Thanks I'm glad I took this picture Nd posted it. The hose goes on, but it can come off really easily with a light tug.

SterlingMistMax

why is it yellow? did it break off and somebody glue it back on ? hopefully fixing this will solve your problem . but only a test drive will be able to tell for sure

Scott Vincent Grissom

Yeah I attempted to use epoxy, maybe I just need a new hose, air box and OEM MAF? everyone telling me I can't use aftermarket MAF and I'm beginning to believe them

SterlingMistMax

Id try getting that fixed first then see how it runs . buts it is usually best to stick with the oem nissan parts .

dwapenyi

iTrader: (3)

Just get the entire box from a junkyard.

DW

Scott Vincent Grissom

I got a factory MAF from a dismantler since the CEL came on for it. still no change, the RPMs still drop and acceleration is still weak especially up a hill, downhills usually arent an issue. I'll be posting a video soon. Maybe I need an airbox now?