Acceleration Problem from 1000-3000 RPM's; luctuating idle

[jwwpua]

I have a 1995 240SX automatic and am experiencing acceleration problems specifically from about 1000-3000 RPM's (most noticeable in 1st gear). From a dead stop, if I floor the gas it has trouble climbing from 1k-3k but once it's past that range it begins to climb much faster/smoother. This occurs the majority of the time, but OCCASIONALLY (10% maybe) it will climb this RPM range just fine!

Another problem that I noticed was that when idling, it will be steady at ~750 for even minutes at a time, but then I hear a noticeable drop in engine noise and it lowers to ~600 (occasionally sometimes down to ~500). It can then remain at this low RPM for minutes at a time. It's really just random the way it fluctuates from one range to another. (can takes seconds or minutes)

One last sympton I have noticed was that the accelerator petal sticks upon initial movement. Once I overcome the initial resistance, it is fine until I let off and have to start from a dead stop again. I don't know if this is related to the other problems but I thought it was worth mentioning.

I've been reading through the FAQ's on http://www.240sx.org and want to start trying some possible fixes. The problem is that I have no experience working on cars so I need some advice about the location of certain parts and the correct method of cleaning them or replacing them.

Here is a list of things I'd like to try:

[1] The first thing I was planning to check for was vacuum leaks in the hoses because several people have said that this would cause acceleration problems. What is the best way to find the leaks? Is it simply a tedious task of looking for cracks in all the hoses? Are there specific hoses that I should check first? Someone mentioned a 5" rubber hose from the BPT Valve to EGR Valve, but of course I have no clue what or where those parts are!

[2] Another suggested fix is to change the fuel filter. Autozone carries one for my car for $10. Is it pretty simple to change out?

[3] Someone said they fixed this problem by replacing their Air Feeder Hose which had a crack in it. Where is this located?

[4] Cleaning the mass air meter with Carb Cleaner. Where is this located?

[5] Looking under the "Sticking Accelerator" FAQ, someone said that it is caused by a dirty throttle plate. They said to remove the air duct, open the plate, and spray Carb Cleaner on both sides and clean with a dry cloth. Where is the air duct and throttle plate?

[6] Cleaning the AIV supposedly fixed this problem for one person. Where is the AIV and how is it cleaned?

Before going into detail about each question I have, do any of these solutions seem more likely to fit my symptoms? Please let me know what you think, and if you could explain in further detail how to do it, I would greatly appreciate it. An engine diagram would be very helpful as well!

Thanks

[el5y]

Definately change the fuel filter, mine was doing the same thing and all it was was a clogged up fuel filter. mine is a 93 however.

Eric

[jwwpua]

Another major problem that I somehow forgot to mention is that I've been getting only about 12 mpg! I think I used to get around 26 on a normal basis. Could a bad fuel filter cause this terrible gas mileage??

Definately change the fuel filter, mine was doing the same thing and all it was was a clogged up fuel filter. mine is a 93 however.

Eric

I just replaced the fuel filter today with the 300ZX one. I haven't noticed any faulty idling but I've only driven a little bit since then. I also haven't been able to test the acceleration yet either, but I'll be sure to update.

In the meantime, could someone let me know if a bad fuel filter could cause the terrible gas mileage? Thanks for the help!

[95nismo240]

ok im 95% sure its ur o2 sensor.... i have a 95 240sx automatic and it did the same thing. i got like 10mpg though. changed the o2 sensor which u can get from autopart store for like $12 and my car get like 25mpg city now. my acceleration is alot smoother also.

[ka24depower]

hey man i have a 1990 240sx and my cars doing the same thing.ive replaced the o2censor,plugs,plug wires,maf censor,injectors,and the cap and rottor button.my car still does the same thing but i was told to change the egr valve i went got one today i havent put it on yet but if it helps my car ill reply back and let you know.its worth a shot.

[jwwpua]

Well after changing the fuel filter (used the 300ZX filter), the problems seem to have been fixed. The gas mileage is much higher and it seems to accelerate much better.

Thanks for the help!