Acceleration seems fine immediately after startup but seems bogged minutes later

[jwwpua]

My 1995 240SX seems to accelerate pretty good (not sure if it's actually "good") right after startup, but after just minutes (if even that long) it is bogged down.

It's most noticeable from a dead stop. First gear definitely feels the worst/slowest. It just drags through until about 3k or 3.5k rpms, where it seems to have a LITTLE more power.

It is by no means terribly slow. It just feels sluggish and not as peppy as it should be. If I floor it from a dead stop, it very gradually starts to speed up. Like I said, right after starting it up is when it seems to have the best acceleration.

Any suggestions?

thanks

EDIT: Could this cracked hose (which has been taped) be the problem?





Modified by jwwpua at 2:14 PM 7/3/2006
Modified by jwwpua at 2:15 PM 7/3/2006

[smokin240]

Most common problems with those symptoms are spark plug wires and dirty or malfunctioning MAFS. There are alot of topics on this, search and you'll find answers in more detail.

[jwwpua]

Added pics of a cracked hose in the original post.

[rogoman]

My 1995 240SX seems to accelerate pretty good (not sure if it's actually "good") right after startup, but after just minutes (if even that long) it is bogged down.

The temperature sensor for the ECU might be defective. When the coolant is cold, the ECU richens the mixture; if the sensor is bad, the mixture will still be rich after the motor is warmed up.

Also do an ECU code readout for possible fault codes.

[jwwpua]

The temperature sensor for the ECU might be defective. When the coolant is cold, the ECU richens the mixture; if the sensor is bad, the mixture will still be rich after the motor is warmed up.

Also do an ECU code readout for possible fault codes.

I'm not sure how to access the ECU. Here's a picture. What steps should I take from here? (assuming I'm looking at the right thing)


Modified by jwwpua at 3:11 AM 7/4/2006

[sicride]

Obviously first step in diagnosing any lack of power issue is to check for the obvious. Air filter cleanliness, spark plug condition and wires. Once you verify these are all fine then you can start looking at other issues such as said ECU temp sensor, or MAFS read outs (slightly more complex issues to test). Obviously if there is a check engine light that would be your first step.

How easily does the car start? When starting the engine do you first let the key set in the ON possition for a moment and then crank the engine? If so it doesn't sound like you have a temperature problem necessarily since the engine would have a hard time reaching proper temps in that amount of time but it could be a tired out fuel pump.

To answer your question about the cracked tube coming from the valve cover- no. This is your breather aka PCV valving this could be removed and the car should still RUN ok. If that tube is clogged it's a POSSIBLE cause but not likely.

[sicride]

Err. To do an ECU readout there would be a port to connect a diagnostic tool to, most likely underneath the dash by the steering wheel. Pep Boys Auto Zone and Advanced Auto Parts would be able to do this sort of testing for you for free usually.

[jwwpua]

I checked the ECM and got a code 34 (Knock Sensor). I reset it and drove it for a day to see if it came back. It did. Does this mean the knock sensor is bad and needs replacing? Or can it mean something else that just needs adjusting?

Also would a faulty/damaged knock sensor fit with the problems I'm having?

To answer your question, it starts just fine from what I can tell. It does that little shaking thing but I heard that's common with this particular car. Starts within a couple seconds every time though.

thanks

[smokin240]

Hmmm maybe grounding issue?

[ArdmoreS14]

Yeah the FSM says to check engine ground. Loosen and re-tighten engine ground. Glad you figured out you can check it your self. Remember that cause not all codes turn the check engine light on. Since the 95 is the OBD-1, auto zone and those other stores cant check it, only a nissan dealer or shop can, with atleast a $50 charge.

[SPEEDingMoNK-S13]

HEY i have the same problem which i have been trying to find the time to fix. i cracked that same exact hose while trying to put my rocker cover back on, it just kept spliting when i went to reattach it. i also have the same symptoms lack of power from time to time, code for the knock sensor. ive had a ***** of a time trying to get a replacment hose for it from nissan. i have a hose on it atm but its just a piece of regular hose that is clamped on. so lemme know what did and didnot work and ill do the same. -- peace

[winez31]

my z31 does the same thing but way way worse. my car starts and runs fine till it hits a certain temp then dies. i have to keep ving it gas to keep it running but once it get to 3krpm it runs fine. and im running really rich. things ive replaced fpr fuel pump injectors fuelpump relay maf fuel filter and still does it. im just waiting for a new ecu. mine started out like yours and ended up like this.