Hello, All:

I have a 95 200sx SER with 134,000 miles on it.

I recently purchased the vehicle from the original owner and he said the car has only been driven 15,000 miles in the last three years. Three years ago is the last time a major tune up was done (15,000 miles ago). So the car has been doing a lot of sitting over the last few years.

My problem, is that when I accelerate in 1st and 2nd, below the 3 or 4k rpm mark, the car just seems really sluggish. It seems like when I put the pedal down, the RPMs go up but the car doesn't move much. After the 3/4k rpm mark, the car just takes off. If I go WOT, the car is sluggish/hesitating...then BAM it just takes off for some reason. It's like some insane lose-VTEC it seems like. The power is not smooth at all. The car is driveable, however, but I know there is a problem with it.

So I searched and searched and it seems like it MIGHT be my o2 sensor. I plan on taking the o2 sensor off, driving around, and see if that was the problem. The only problem, with it being the o2 sensor, is that I am getting around 30mpg in the car. The car gets really good gas mileage. I was under the impression if the o2 sensor is bad, your car would have bad gas mileage??

Anyone have other suggestions or ideas as to what I could try??

I also considered adjusting the trottle cable, thinking that might have something to do with it?? I have no clue.

Thanks!

::EDIT:: I ended up fixing the problem. It was my BPT valve. Feel free to scroll down and read my adventures ;) First thing I would do is pull the codes. If you are having similar symptoms as I did, I'd clean the BPT/EGR Valve and the TB. Knock sensor replaced, TB/BPT Valve cleaned + a full tuneup really made my car back from the dead. It pulls like new.

-G

Try throwing a new fuel filter on there.

Try throwing a new fuel filter on there.

I ordered all the tune up parts for it a week ago and they should be here tomorrow. I will replace those and report back if that fixed the problem. Also, tomorrow, I will disconnect the o2 sensor and see what happens. I had a question about this: Should I unscrew the o2 sensor or just disconnect it from the wiring harness??

Most of the other threads I read involved the person ALSO having bad gas mileage, that's why I was hoping it could be a specific problem or possibly rule out some things.

Something I also didn't mention is that my idle is fine. When it's cold, it may start out at around 1.2k, but once it warms up it stays at a constant 800rpm.

Thanks

-G

I ordered all the tune up parts for it a week ago and they should be here tomorrow. I will replace those and report back if that fixed the problem. Also, tomorrow, I will disconnect the o2 sensor and see what happens. I had a question about this: Should I unscrew the o2 sensor or just disconnect it from the wiring harness??

Most of the other threads I read involved the person ALSO having bad gas mileage, that's why I was hoping it could be a specific problem or possibly rule out some things.

Something I also didn't mention is that my idle is fine. When it's cold, it may start out at around 1.2k, but once it warms up it stays at a constant 800rpm.

Thanks

-G

Let me know if anyone else has soom ideas...I'm going to be working on this tomorrow, but I am going to bed now.

-G

plugs, wires, fuel filter, reground everything in the engine bay (including maf), clean egr...problem will be fixed

when my o2 sensor was shot i was still getting 30mpg.

Don't unscrew the O2 sensor unless you have an appropriate bolt to go in the hole, otherwise your exhaust will get loud to a whole new level! Just unplug the harness connector, and see how you do. Out of curiosity, have you checked timing? Also, are you smelling fuel (a possible symptom of an over-rich condition)?

Hope this helps!

Darrin

Don't unscrew the O2 sensor unless you have an appropriate bolt to go in the hole, otherwise your exhaust will get loud to a whole new level! Just unplug the harness connector, and see how you do. Out of curiosity, have you checked timing? Also, are you smelling fuel (a possible symptom of an over-rich condition)?

Hope this helps!

Darrin


I replaced the spark plugs/wires, rotor/cap, fuel/air filter today.

I also tightend the throttle cable.

When I was changing the spark plugs, I noticed thee old ones were Autolite spark plugs. Another thing I noticed was a lot of oil on each spark plug. Most just had it on the top, but spark plug #2 (which was the hardest to get out) had oil on the bottom of the plug. I am assuming this had something to do with my problem. I can see a little pool of oil at the bottom of the socket.

I didn't know how to get the oil out, so I just installed all 4 of the new spark plugs.

I drove the car around for about 20 minutes after I replaced everything and the car does feel more smooth.

I still have a problem. Almost exactly at 2,000 rpm, I am getting hesitation. When I put the car in neutral and slowly give the car gas, once it hits 2k rpm, it hesitates and kind of stays there for a second and then once I give it heavier gas and it gets past 2k rpm and continues up.

I am noticing the hesitation almost exactly between 2k - 2.3k in the RPM range.

I disconnected the 02 sensor wiring harness and it didn't seem to help. What was odd, however, is that the CEL did not come on after I disconnected the 02 sensor. Maybe it was because I only ran the car for a few minutes??? I don't know, but that may be a problem too.

I have yet to check the timing because I don't have access to a timing light. I considered buying one on ebay or something. No, I haven't been smelling gas that I know of.

All in all, the tuneup seemed to get rid of the obvious hesitation issues I had. I only drove the car for 20 minutes, but it does seem like it is still hesitating a little and when in neutral it is more noticeable.

I was considering cleaning the TB as the next step.

Well, that's the update. Thoughts?

-G

did you fluch the motor to make sure all the sludge is out of it? another check your tps voltage and maf voltage i would suggest the regrounding on that. also check your ignition timing.

did you fluch the motor to make sure all the sludge is out of it? another check your tps voltage and maf voltage i would suggest the regrounding on that. also check your ignition timing.

What do you mean by flushing the motor?? I changed the oil, that's about it.

reground , reground ,reground

thanx

when i have a motor that has either been just starte dup and not driven or that has been sitting for god knows how long when i do the oil change i put some kerosene in the motor let it idle for about 3 mins then cut it off and do the oil change....or you can buy that crap you dump in th eoil....either way it helps break down sludge.

What about pulling codes? [rolleyes]

Your're describing what mine is doing with a bum knock sensor. I'm still searching for what resistance and/or voltage values I should have at the KS connector...

Update!

I did pull the codes and had a knock sensor code.

Knock sensor is fixed and now getting 5-5 codes(all is well).

I still have this hesitation issue.

Since my first post, these are my attempts at fixing the problem: complete tuneup, MAF/TPS voltage check, knock sensor replaced, O2 sensor check.

I'm thinking that cleaning the EGR valve would be the best next step for this problem. If that doesn't work, I guess clean the throttle body, then maybe the IAC valve, but if all that doesn't work idk.

to summarize my problems: the car is only hesitating at predictable points between 2k-2.3k rpm.

-G

Try plugging off the egr vacuum tube and go for a drive. if it makes a difference then check your bpt valve and see if your catalytic converter is plugging up. too much egr will bog it down at 2000-2500 cruise speed.

I think he fixed it:

http://www.sr20forum.com/showthread.php?t=175874

It was the bpt.