240sx bogging
 

Mods: cat back exhaust, stage 2 clutch and light flywheel.


1995 240sx the car idles fine and under slow acceleration the car will rev up
but any acceleration past like 15% throttle the car stocks bogging really bad
and will die if not brought back to idle. No check engine light on. Last thing
changed on the car was the clutch and flywheel was about 4 months ago.

Things i have tried cleaned the maf,replaced fuel pump and filter,replaced plugs and wires,check ohms on injectors and pulled plugs off one by one but made the engine get worse,checked for vacuum leaks,checked fpr, hooked up fuel pressure gauge got 40psi idle 50 55psi when bogging, pulled exhaust off and ran just headers to see if the cat was clogged.

Any idea would be helpful

anyone with an idea?

Ohm the knock sejsor, should be ~550k ohms. If not. Replace or bypass. Check fuel pressure. Check O2 sensor and CHTS.

Did you mess with ur ignition timing or pull the distributor out? Also check intake system and make sure you have no leaks, ka's dont like any air leaks especially after the maf

checked the ignition timing which was good. Did a fog test over engine bay no leaks.

Try cleaning the maf and check for possible loose grounds on the engine, if the ground on the rear left of the cylinder head is loose, it will cause a problem like that. The bracket that holds the o2 sensor wire also mounts there, possibly do a compression check also see if you dont have a burnt exhaust valve

Thanks for the help.

Replaced the Maf 2 days ago also I checking the grounds by removing them and removed any dirt/grim still the same. Guess i will try a compression check next.

get a wideband o2, that'll help you determine if the bogging is caused by too much air, or not enough.

Put new distributor in and car now runs fine but when i press the pedal more then 50% the car picks up and then acceleration is very slow.

Knock sensor. Did you check it?

No i didn't wouldn't that trip a code?

Yes. But no check engine light.

K I will check out the volts and ohms today

You still have an EGR?

Yes I still have the egr

So i got my hands on a scan tool and got P0325 and P0110 but when i went to reset the codes they were gone? Drove around for 30min checked and got code P0325 this time i stopped the car to reset it but it was gone again. PO325 is the knock sensor and PO110 is intake air temp right?

replace the air intake temp sensor

I was going to say it might be sticking, but if you're getting codes for the AITS and knock sensor, change those... The knock sensor is easy if you fish it in with a coat hanger or something... You don't have to take your intake mani off like the FSM suggests.

The knock sensor is troublesome on these cars. Bypass it

/?/..................

Already bought both 100$ shipped

Thanks for the help everyone I will let you all know how it goes when the parts are in.

also something minor to check is ur plug gap make sure ur gappings are correct

Well both parts came in today installed them cleared the codes started it up drove it around and it did help a little bit but still doing it. The knock sensor was cracked down the side of it.

Ever check the cylinder head switch? Injector seals?

What the temp switch? Haven't checked them yet

Cylinder head temp switch. Two sensors on the front of the head near the rad hose outlet. One has one wire. That's for the temp gauge. The other has two wires. That's the cylinder head temp switch. If it goes bad it can make the car run real screwy. It's only about $8 .

I will take a look at it as always thanks for the help.

From the looks for where it is I might as well change the coolant or is the fluid level not up that high when not running.

The coolant always does touch the sensor. When the car warms up and the thermostat opens . The sensor changes resistance with temp telling the ecu how to trim the fuel and timing. The one on my girls car was cracked, causing a high idle, hesitation and hot running. When you remove it not much coolant comes out.Dont use Teflon tape or any other sealant on the sensor.

Well I replaced the temp sensor and got new plugs and gaped them. The car sounds better but still does the same thing half throttle or wot the car bogs anything less car is fine idles fine revs all the way up fine. No check engine light or any codes.

What's the tps voltage set at? Maybe take the injectors to get serviced and flow checked.

anyone else think that maybe ohm/voltage checking the tps? mine didnt throw a code but i changed it and problems went away!

Tps is like 2 weeks old

I'd start de looming the engine harness looking for brittle, burnt, or cracked wiring next. The temp sensor you replaced has two wires right, what voltage did you set the TPS for? Ever replace the o2 sensor?

Yes two wires on temp sensor. TPS was installed. By a shop would think they put it in right as the reading were bad on the original one. The o2 sensor I have never replaced.

sounds like a tps plug is unpluged or needs adjustment

I will check to see what the shop set the new TPS to. Im guessing I check ohms when closed and then open volts on power wire is what 5v and then ground?

Just checked the the o2 sensor got the car to normal engine temp and the computer said it was "open-loop" shouldn't it be closed when idle at normal temp?

Yes it should be in closed. TPS voltage should be right under .5V . Back probe the middle wire and check the voltage. Mine is set at .45V. The O2 sensor is a service item to ne changed every 15K miles. It's only $15. I don't want to see you keep throwing parts at the car so hopefully that is it.

Going to replace the o2 sensor today.

O2 sensor in and car is sill doing it. The car runs better and starts right up fast now but still bogging. It it means anything the tip of the sensor was white.

Any word on the TPS voltage? Are you absolutely sure you have no vac leaks? Was the mafs and dizzy new or used? Does it only bog under load or also when free revving in neutral?

Have not checked the TPS volts yet. Yes 100% no vac leaks mafs and dizzy are new. Yes only under load but fine revving in neutral.

So today i was checking all the basic things again some for third time and first i checked the injectors i just drove the car and now the car is cold the first 3 injectors were all around 11.8 .4 off was the most but the forth was at 15.8 then i tuned the engine on and put my ear on the end of a screwdriver which was on the injector could hear the clicking of all the injectors but that forth one. So i was guessing it was bad but after a drive around engine warmed up i tested them again all were around 12.8 and all were clicking like they were working. Could a injector work and sometimes not work.

absolutely can change with heat. sounds like a bad injector. I thought so, thats why i recomended having them serviced and checked. grab a used one to check before running ot and buying a new one.

Any point in getting rebuilt injectors or are they not worth it.

Seafoam! Jk

I would start with one that you know is good and see if that is your problem. Might even be a bad injector driver in the ecu. Rebuilt injectors are fine too.

Taking a working one from friends 240sx on monday

The injectors in my friends car are 2 months old. Put in one working injector from friends 240sx and still doing it so I then put in the other 3 injectors. I can feel a power difference but still bogging at 50% throttle or wot. Still no codes or check engine light.

did you lube the new o rings for the injectors? New o rings?

New o rings yes there was some lube on the injectors how much is needed?

Doesn't take much lube. Really starting to sound like a wiring or ecu problem. Ignition timing is correct right?

Make sure you are gettin good voltage at the injector clips.

Going out this morning it does it when I rev around 4k 4500k

Friend said it could be a sensor on the transmission?

So its rpm based or throttle position based?

Whats your fuel pressure reading at? Could be a bad pump or bad wiring for the fuel pump. Check voltage going to the fuel pump.

Couldnt tell which it was will look more in to it tomorrow.

No fuel pressure gauge hooked up last i checked it was 40 psi at idle. Fuel pump is around a month old will check it out tho thanks

You need a dedicated fuel pressure gauge, fuel pressure will change after the car is warmed up. You'll especially want to see what your fuel pressure is reading around the problem RPM range. I'm not so concerned with the fuel pump but more so the connections / wiring for the fuel pump. A loose ground, wires with high resistance, will cause fueling issues for sure.

thanks for the help will check it out tomorrow and post the results.

Driving it around today it might not be rpm or throttle position its different for every gear and sometimes just goes limp in first from a stop

Do you mean the ground on the fuel pump like taking it out again? or is there another ground outside the tank?

The tps is set to .73 closed 4.23 wot

Not good. You'll want it at 0.45 closed.

So to change the voltage you loosen the two screws and move the tps unit?

Yes, make sure you test the entire range of motion as well. Move it and make sure the voltage continues to go up, if it dips down randomly or cuts out, you may need a new TPS.

Closed its .45 wot 3.97

WOT seems a little low, it should be around 4.45 - 4.55v.

Here's a good article: KA24DE : Checking TPS and adjusting idle : Nissan Articles

set the wot to 4.5 and then closed was .97 now its set to .48 wot 4.04 best i could get it could it be bad it like a month old? It helped but still going it. Going up hill makes it bogs worse.

Going to hook up a fuel pressure gauge next.

Try swapping in a working ECU.

Well i gave up and a shop now has had it for about about 5 days no luck.

Any word from the shop yet? I think mine is having the same problem that you are describing. I was happening earlier this year, I switched out the mass airflow meter, and the spark plugs and the problem almost completely went away, but now its getting worse again. I'm goning to start testing the advice from this feed, and see what works, but let me know what you learn from the shop.

They still have it cant find anything yet

Shop called and they ran out of ideas. Great lol now what

I've been doing my research, I havn't had time to start palying with it yet, but one thing I have found that seems to give the same symptoms as we are experienceing is the EGR unit. It can go faulty, or get clogged and cause hessitations. The EGR and EGRV can be cleaned replaced or removed to fix the problem. Like i said i havnt tested it yet but you might want to try it, seems like its getting good results...

Checked the egr valve you can get your hand under it and push up on it and if the engine starts to idle bad (which mine did) then the egr valve is working.

Did you ever try another ecu?

Couldnt get my hands on one to just swap. Might have to just buy one

Same thing with mine , it was a bad maf plug connection.

Thank god for safe mode

So i cut it off and did this
http://i278.photobucket.com/albums/k...k/smallmaf.jpg

Like a baws. now it runs perfect

Ya I was thinking about the same thing but didnt because i thought it would have given a code. I will have to steal or idea and give it a try thanks for your help.

I just noticed last night that the air temp sensor on the intake just past the filter was missing the wires/pug that connects to the plug that goes to the ecu. i have the part on order and i'll let you know if that fixes my problem any. if you have and aftermarket intake u might want to make sure that yours isn't like this too. im thinking that when my maf went bad, the shop might have accidently knocked the wires of the sensor and it got lost somewhere and thats why only half of the problem got fixed the first time around in my case

Well bought a used ECU and no luck. Also hooked the MAF connecter right to the MAF nothing drove the car around don't see any difference. Wow this is crazy there most just be a loose wire or half broken wire sending a bad signal or something.

Start de looming the harness. Wiggle test the connectors with a ohm meter to check for bad connections. I'd start with the Maf and work back. There is a gremelin in there somewhere.

One thing I haven't seen you check, the tps voltage. Does it go up smoothly all the way from closed to full open? I've had this problem, right at quarter throttle the voltage dropped then came back near 3/4 throttle.

Set the tps to .48 4.04 with the new on didnt see anything jumping in volts.

Im having the same exact issue wtf..

tman by any chance is yours manual or auto?

My car is manual