PhillyMAx

iTrader: (1)

Have about 90K on my 97 SE. I had my knock sensor and rear 02 sensor replaced a few months ago at the dealership. I'm getting great mileage, about 25 - 28 mpg on the highway, but my acceleration has suffered immensely; it's lagging around 2K - 3K rpm.

Spark plugs were replaced at the 60K tune-up. Oil, fuel filter and air filter were just replaced a few months ago. Any ideas on how to remedy this? Should I run a can of octane booster to see if that helps?

Zirafa

Reset your ECU - perhaps they didn't do that when they replaced sensors at the dealership. Also while you're at it check if you got any codes stored in the ECU. This should help:
http://forums.maxima.org/showthread....hreadid=104931

PhillyMAx

iTrader: (1)

I recently replaced my EVAP canister as well. That previously caused my CEL light to come on. The codes were for the EVAP system, as well as the knock sensor. I know the knock sensor is sometimes a ghost code if anything else is wrong with the car. I've since reset my ECU, but it isn't helping my acceleration. The car gives me a hard time whenever I want to go past 80.

Zirafa

Do this just to make sure your KS is good:
---------------------------
The KS may be checked with an ohmmeter.

1) Raise the hood. View the engine from the driver's fender. Look into
the deep valley between the cylinder banks and below the intake manifold.
Identify the KS as a black item fastened to the block by a single vertical
bolt. A wire harness wrapped in black leads toward you, out of the valley.
That is the KS sub-harness.

2) Follow the KS sub-harness to it's nearest connector. This is connector F121.
It is located near the upper right-hand corner of the valve cover of the forward cylinder bank, as viewed from the front of the car.

3) Disconnect F121. You have to do a "press the latch and wiggle and
pull" to disconnect it. F121 has only two pins; if you see more than two
pins, you have the wrong connector. Use a digital ohmmeter capable of
measuring more than 10 Megohms. You want to measure the pins of F121, not
the sockets of the matching connector. Measure the resistance between a
good ground (such as the battery negative terminal) and pin #2 of connector
F121. On my car this is the highest of the two pins, the one closest to
the front of the car. The factory spec is 500 - 620 Kohms.

njmaxseltd

iTrader: (19)

Clean your throttle body and try to flush the entire intake system with cleaner. It makes a huge difference down in that RPM range when your whole air intake plenum is nice and clean.

You can get your car to run and ingest air intake cleaner while it's running. It's prefectly fine to do, read the instructions on the can it tells you so. Problem is some cars don't run with the intake and MAF disconnected, ours being one of them. But you can get around that.

Cleaning the intake this way gets deep into the intake system and cleans everythig out.

Disconnect the intake at the TB and pull it back so just a small crack is open. The car will have to detect some air flow at the MAF or it's gonna stall on you and throw a CEL. Get a can of cleaner and spray into the TB while you blip the throttle. It's gonna choke a bit, so keep the RPM's up. You'll see dark smoke coming out the tail pipe as all the crud is removed and burnt up. Run about 1/2 the can of intake cleaner through the system, the exhaust will start to clear up when the intake is clean. Then turn the car off and put everything back together. You'll feel a big difference in throttle response and power in the lower RPM range.

Good luck!

bb0ys

What type of cleaner are you talking about? Throttle body cleaner? I was thinking of taking apart my upper intake manifold and cleaning it, but if i can get some of it clean by just spraying a 1/2 can of something into the TB while running the engine, tell me what this stuff is and I'll try it!
thanks!

njmaxseltd

iTrader: (19)

Air Intake Cleaner, same stuff you clean your throttle body with. Read the instructions on the can, it explains both ways to clean the intake. One being with the engine off, and the other while the engine is running. Depends on the car, ours being normally done while the engine is off, but you never get anything cleaned deep inside the air intake path that way. Follow my write up and you can clean the entire intake path right down to the valves.

PhillyMAx

iTrader: (1)

Thanks, I'll give that a try as soon as I have time. I cleaned my throttle body pretty good about 6 months ago, but maybe it needs a little fine tuning.

bb0ys

All this time i thought it was bad to get that stuff inside the the intake! When I cleaned my TB with the spray can and a rag I tried hard not to let any drip down past the TB and into the engine. Can anything bad happen from spraying the Throttle Body Cleaner straight into the TB while the car is running and someone keeps tapping on the gas?

EDIT: Is it better to do this when the car is warmed up? It seems like it would be so the internals are hotter and burn better...or does it not matter at all?
Thanks! this is a real helpful tip!

njmaxseltd

iTrader: (19)

I think a warm engine, warm intake manifold and plenum will clean up easier then a cold one.

rmb

Only warm. You don't want that gunk that's left plugging up your cold main cat.

-RMB

bb0ys

Score 1 for my common sense guessing!
thanks again!

MAXSRB

Thanks alot njmax named guy. I will clean it your way since it is the smarter thing to do. Now my question is about my knock sensor....i just checked the ohms using zirafa's method (checking the pin on the F121 connector) and i got 0 ohms constantly on one pin and 1.1 M ohms from the other pin. When i turn my car on I still got 0 ohms on the first pin and I got up to 2.1 megaohms on the other pin. I had not let the car warm up, but as it was on longer and longer the ohms just kept going up. Whats the deal? It seems my knock sensor is working but its about 4 times the ohm rating it should be.... please help
Oh and yes i did check my ecu twice and both times i got 0304 - Knock Sensor....i know that sometimes it can spit out that code even tho something else is wrong with the car. I wouldn't want to spend $160 on the sensor and have it do nothing. My symptoms are slow acceleration and horrible gas mileage.