Acceleration Probs.

[Sidewayzzz]

Alright, first things first ... 91 Ka24de.

After near 5 months of no issues with my 240 .. some shit has to start today...
Driving around town, when suddenly (not after spirited driving either .. ) I start to accelerate from a light, and I notice that at some particular throttle points (all of them besides WOT and off the throttle anyways) im bogging and losing all power .. either spark or fuel.

So I drive it some more, fill up the gas a little more (water possibly, maybe my gauge is lying to me as usual and im empty, who knows) and the problem doesn't go away...

So I stop by the house, clean the plugs, check the gap, check the wires, yadda yadda, check all my connectors...after all that mess, I fire it up, and its all good. Drive it around for 3-4 minutes .. no problems.... then they start again...bogging, missing, loss of power unless im at WOT..

Now I've replaced the TPS 5~ish months ago, so i'm doubting that.. and i'l explain why.

First things first, I have no thermostat, so when I say my car is heated up .. thats just means that my temp has moved passed the first bar, and has at least heated up a little.

What it appears to be doing to me, is anytime i'm in open loop (not using stock ECM readings after the car has heated up) im bogging, etc.. When in closed loop (using ECM and very few sensors) i run absolutely fine, no hiccups, nothing.

As far as I know (and correct me if im wrong) open loop only utilizes three more sensors, Oxygen Sensor, Coolant Tempature Sensor, and the EGR system.

The problem is intermittent at best, when the car starts giving me the accelerating problems it isn't a constant thing. Sometimes I can go partial thorttle and it will accel ... most of the time though, it will bog unless i floor it and go WOT (wide-open throttle).

I'm clueless...any help is appreciated.

[usdm180sx]

Did you check the distributor cap and rotor? They usually need to be replaced after 75k miles.

[Sidewayzzz]

Knew I forgot to mention something, Yeah .. I checked them ... looked fine.
I couldn't think that it could be that anyways ..

I can't stress enough that until 4-5 mins after I start it up, it runs 100% perfect..just like it always did, just like my 240...

It's after those 4-5 mins (heats up, goes into open look I BELIEVE) that it just goes to shit ......

:smash:

[driftkid316]

wow, i noticed the same thing in my stock sr today. well it happened only a few times then really bad today. exactly as you described, the same thing is happening to me. at WOT im cool, but when i try to just drive normally it happens. im also running no thermostat too. i wonder if this is the problem, ive been meaning to put one in, its annoying how long it takes to warm up. i was thinking i needed to clean my injectors or something. but yea, someone help us.

[TURBI]

I have the same problem and I was told that my pressure plate is the problem because my motor has been rebuilt but I only bought a new clutch disc and used the same 15 year old pressure plate which was already really soft.

[driftkid316]

yea mine has a new act clutch and pressure plate and today flywheel. i dont think it has anythinkto wiuth it. but still not sure what is the problem

[TURBI]

So has anyone found out how to fix our bogging problems yet?

[Sidewayzzz]

i tested the tps and coolant temp sensor today .. fine
tested the o2 .. no change of voltage whatsoever, unplugged the fucking thing and guess what ... problems are gone...

check your o2 sensor, if your getting a constant voltage.. its bad.. it needs to change voltage rapidly.

[TURBI]

So the o2 sensor is bad? Wouldn't the motor shut off if the o2 sensor is disconnected? Can the car run well without it? Buy a new one and replace it, yes?

[driftkid316]

well i went drifting last night and it was giving me this problem more than ever. at times kepping it at WOT would nothing at all, the revs would just drop and car would die. and it wouldnt stay on for a minute or two. i would start it up and it would just die. so i tried disconnecting the o2 and reseted the batt. it seemed like it helped kinda but i dont know if it was just coincidence that it didnt feel like giving me trouble anymore. but thruout the night it kept giving me the hesitation problem, sometiems real bad, sometimes not. so im still thinking its the injectors. anyone else have any ideas?

[TURBI]

Damn! So it might be the injectors too? I hope someone can help out with this for sure so that I don't have to toss this newly rebuilt motor.

[TURBI]

So will the motor be damaged if I drive with the o2 sensor unplugged and what can I use to clean my injectors? Injector cleaner spray or can I use seafoam?

[Sidewayzzz]

i've driven my 240 w/o the o2 in for almost a week now. I can't say wether it will/will not damage your motor, because I don't know and even if I did know, im not bold enough to say wether it will or won't :P.

Anyways, what unplugging the o2 should do, is force your car to run in open loop (pre-determined maps from the ecu) it will run rich, but it will run and it shouldn't stumble. If it still is, you have other problems...try your TPS/CTS. (throttle position sensor, coolant tempature sensor)

[Sidewayzzz]

To be honest and try to help you guys, when i've got a problem with any car, I break it down to three areas.
1) Spark
2) Fuel
3) Compression

Usually, I will compression check first, if its okay..I pull the spark plugs, put them in the wires, and hold them against the block while someone tries to start the car. If I see the spark firing from the plug, I know im good in 2/3 areas. Lastly (very dangerous, you can try this but I don't recommend it) I will pull the fuel rail and DISCONNECT THE CHARGE WIRE FOR THE DISTRIBUTOR (so theres no chance of a spark) then I will have someone snap the key a few times and watch to see if all my injectors spray.

Thats how I test for the 3 vital things to make an engine run.

After that, if your car runs but doesn't run well you have to figure out 1 of 2 things. Am I getting too much/too little fuel or am I getting weak spark? Once you figure that out you figure out what could be causing that.

The way you test this is completely up to you, but how I figure it out is I use the FSM and knowledge of motors to figure out what sensors control what. If im too rich you troubleshoot things that effect fuel..such as ECU/TPS/CTS/Sticky or Leaky Injectors/Fuel Pressure Regulator <- that kind of stuff. If you run very low spark or sparatic spark I would check the coil, (by voltmeter) distributor cap and rotor, check spark plugs for gap, check the wires to make sure they are transferring a complete and strong spark.

When it comes down to it, a motor needs 3 things to run (not talking about oil/gas/etc...so don't be a smartass :P) fuel, spark, and compression. Find your missing links to that equation and you should be able to figure it out from there.

[Sidewayzzz]

Dirty injectors can cause bad gas mileage, but when he says cleaning them I believe he means having a shop clean them. They do this with very high pressure liquids being fed through them with a cleaner in it to clean them. You can't really do that yourself. I doubt dirty injectors will cause the kinds of problems your describing. Check your TPS there is a very good guide on how to do that at www.240sx.org, use the search function you WILL find it. Check your CTS by opening the PDF file to your FSM, you will see it needs to be between 2.93 and 0.33 k ohm's. Check the ECU for codes, now I don't know how to do that .. its really weird with the nissans but the FSM will tell you how to do that too (factory service manual if I haven't previously stated) uh...check the Ignition Coil for proper ohmage .. your car hestating on anything besides take-off can't be any of your drive-train .. such as your pressure plate .. so whoever told you that was bullshiting you.

Try those things, let me know, i'll help you as best I can.

[HalveBlue]

So will the motor be damaged if I drive with the o2 sensor unplugged and what can I use to clean my injectors? Injector cleaner spray or can I use seafoam?

No, you will not damage your motor from running without an O2 sensor. The O2 sensor monitors your exhaust gasses for the amount of oxygen it contains. It uses this measurement to adjust the air/fuel ratio to improve you fuel effeciency and, I believe, to reduce some of your emissions.

Seafoam should be fine to clean your injectors.

[TURBI]

Thanks for all the advice guys! I'll try'em out.

[Natty]

No o2 sesnor won't hurt anything other than your mileage. Get a universal BOSCH unit and save yoruself some cash.

My car bogs down pretty badly as well. I belive it is the fuel pump but I can't confirm this.

[ledzeppelin240]

Hmmm..Your O2 sensor is a way more accurate way to control fuel suplly as well as it helps with emissions. Running no thermostat is stupid...You engine is less efficient, it might overheat, cause excess cylinder wall damage, etc...