fuel cut/what feels to be a speed gov.?

[Sideways~S14]

Evan why dont you actually post a video so they can see the problem your having

[idriftnsj]

I am sure swaping the ECU will prevent any RPM or Speed govenor from kicking in. The problem is that all of us that are having this problem had cars that would run fine all the way up to 6500 in any gear (except 4000 in 5th) and 115MPH all day long 24/7.

Then something changed. Now we can only go to about 4000 - 4500 in any gear. And no where near 115MPH.

Cutting the wires for the 5th gear and speed sensor do nothing. The OP of this thread can trace down to the day that the problem started. This is not a unique problem either. A number of us suffer from it.

Does anybody have a scematic of the INTERNAL working of the ECU? I would bet that there is a weak part that has failed and eventualy will fail in all ECUs of this era.

In my case I CAN'T swap to a re-done ECU. It is not allowed at our track. I MUST remain stock. I can repair as needed but can not upgrade. Eventualy I am sure we will figure it out.

check the mass sensor connection ,tps connection,air temp sensor some ka24 e's have them they r located on the side of the airbox,then check the gear sensors under the car on the transmission .make sure u pull the rubber boots back on them to see if they are connected they tend to corrode and break inside the boots

[Vegascorbin]

Thanks for your input, however all of the above was checked for the first time over a year ago. And the trans wiring is not connected at all. It is disconnected where it plugs into "engine harness 2".

Generaly, but not allways, a bad MAF or AIR Temp sensor will show as not able to rev past 3000. This problem shows up at 4000 to 4500.

[justin240]

i personally have veiwed this problem as a challenge and i have fought it a few times on open roads, when it does cut you can hear the pitch change in the exauhst when you left off or press the gas like its trying to go but something in the transmission or drive train is keeping it from doing so, also right after it cuts i put in the clutch and let the rpms drop below 3k then let it out and lay on the gas, the original cut happens at about 85 but for the second try i can usually make it to about 90, i do it again i can make it to 95 ect.

[justin240]

oh and when im goin down hills it usually doesnt even happen, i accelerate all the way to 115 without even skippin a beat

[bikerskater]

see mine even happens going down hill but it rained the last few days and it didnt do it at all and i was messing around burning (making me feel like i had more power then i did lol) and burning 1st to almost 7 2nd to almost 7 3rd to almost 7 and 4th to about 5500 so idk its weird how it just wants to turn it self on and off?

[bikerskater]

heres a video of 1st and 2nd http://www.youtube.com/watch?v=HKlGW4NB8H4

http://www.youtube.com/watch?v=s8xmn54rHyA

[Vegascorbin]

Ok. Aperently it has something to do with the engine being under load.

I know that the fuel system will use pre-set values until a certin load is reached and then it will use "active" monitering of the sensors etc to decide on the fuel etc.

While most of us have checked / replaced the sensors there must be at least one we are missing or is somehow testing good but failing under load/stress.

Thoughts?

[bikerskater]

ya but see minie does it even when not under load ill take a video of that tomorrow

[Vegascorbin]

Can you edit the video to improve the lighting? I am haveing a hard time figueing out what it is showing.

Audio would be helpful also if possible.

[Vegascorbin]

Also has anybody tried changeing the Power Transistor that is near the coil? Saw a referance to that part in another thread and got to thinking.

It is possible that it just can't operate at the speed we need it to anymore.

[idriftnsj]

its a single cam thing

[bikerskater]

ill take a better video tomorrow

[bikerskater]

also i was reading this http://www.240sxforums.com/for....html

and i remembered that my friend had just put a analog cluster in right before i bought and hadnt really driven it with it in so i was wondering iif that could possibly be the problem cause he said it never did that when he had i. also any try an auto ecu?

[Vegascorbin]

My son was discussing the problem with his friends the other day and one of them suggested that it could be caused by our aftermarket Tac.

We are going to try disconnecting it when we get things back together. Torn down right now for a little body work and battery tray repair.

Can others watching this thread let us know what type of Tachometer you are running?

Thanks

[justin240]

i think it may also have something to do with the power usage in the car, i drove 60 miles the other day and for almost all of it i had my parking lights and fog lights on as well as my heater blowing and stereo on, and my car cut at 85 every time i accelerated, without fail, however my passenger started to complain about the heat so i turned the fan off and the cut didnt happen till about 90, so i turned everything off ( lights, stereo ect.) and drove for about 10 mins at about 110 with not even one single cut

[bikerskater]

ya i thought that to still may be the problem but idk cause i have tried and it still cut out but it maybe a power problem, but as of right now my problem is solved because i was on a mountainess road/hwy just crusing and some truck came around the corner with his highs on and halfway iin my lane and i went off into the diitch head on at about 50-55 and my car iis completely done but i will still try and help you solve this problem

[Vegascorbin]

So Sorry to hear that. Send photos so we can do a proper memorial.

Any chance of finding out who it was to possibly get compensation?

[bikerskater]

the car in my sig is my first 240 but my parents took it away so i bought myself a new one and it was the one ii got ran off in
Modified by bikerskater at 12:55 PM 1/30/2009

[Vegascorbin]

Sorry for the slow response. Had to welcome my first Granchild in to the world.

bikerskater: Your car looks fixable if someone wanted to spend the time and effort on it.Most people won't want to but I think it could be fixed.

Back to the original problem.

We had taken the Battery out to do some body work and in the process had to remove the ground wire that attached the harness to the chassis by the battery(headlight side). When we went to put things back together we fired up the car and then verifyed that the timing was set right (we had tried a diferant setting that did not work). Then we werer able to rev the car to 6200 in netural. That is at lest 500 to 800 RPM higher than we had been able to before. It was a motor cut not rev limiter.

Here is the kicker. I realised the next day that WE NEVER RECONNECTED THE GROUND WIRE WE HAD REMOVED! Just plain over looked it. That tells me we have a grounding and or voltage problem that we have yet to find.

Interesting.

[bikerskater]

ya i starting to think it maybe a power problem but as for my car goes the entire frame was like --------- -------------- if you understand what i mean lol along with needing a entire new front subframe but im getting a shell from my friend for so its not all bad

[justin240]

well i fixed my prob wit the cut...... wrecked my baby about a week ago, came over a hill on a corner and lost traction, slid into the ditch and rolled it about 8 times, went about 400 feet down the highway flipping and rolling the whole time, completely totaled, but i am getting a new one for 1600, runs with a few problems (exhaust leak, lights wont go down, etc...) this one doesn't have the fuel cut, not that i have seen anyways, so im kinda off the hook, good luck though

[Vegascorbin]

So based on the experiance with those that follow this thread, the only way to fix the fuel cut is to wreck your car.

justin240 I hope you were not hurt too badly. Sorry to hear about your crash.

Question, those that have seen this problem have any noticed that it happens only with the Mitsubisi dizzy or does it also happen with the Hitaci?

[bikerskater]

sorry to hear about that....back on subject now lol i did a motor swap today with my friend he had a sohc and blew iit so i gave him mine we did this swap ini like 7 hours we're pretty stoked by that and we drove for a lil and he left and went drifting for a lil and he said it didnt do what mine did but idk ill have to see for myself tomorrow if it doesnt do iit now or not

[Vegascorbin]

Let me see if I have this right:

your friends car did not cut out but he blew the motor;Your car did cut out;you took your motor and put it in his car and it did not cut out.

PLEASE confirm that it is not cutting out and if possable provide a detailed list of what went with your motor into his car, including harnessing and ECU etc. That would be VERY valuable information on tracking down the ultimate problem and therefore THE fix.

Thanks

[bikerskater]

the only thing outta my car was the engine the harness and ecu were from his but we did change the distributor cap with his cause for some reason it broke? along with when pulling i found a lot of grounds missing on my car that he had all of and hooked all of them um i was even missing the fuel injector grounds come to find out and we also for got to hook them up in his car (because we were so excited first full motor swap lol) that when he tried to start the car it wouldnt start like no fuel we checked spark and everything we also sparyed starter fluid and then it started up just fine but then wouldnt start again afterwards but connected those started up after a few trys and idleed wered then drove fine and everything afterwards

sorry for the block of text

[240SXCL]

Its funny, i got my shell from a friend for free and salvaged my fastback parts into it. I cranked up the timing on the dristributor a bit and I was able to go over 116mph in 5th and it was still going (SOHC). Could there be something wrong with my car? The speedo seems to work fine but I'm not entirely sure if its accurate at that speed. I was around 5400 rpms...

[jmac636]

240's have been known for having grounding issues. It's best to get some 8 gauge stereo cable and some ring terminals and start grounding everything. Remember there's gaskets between head, intake,block,injector rail, etc. So making sure your grounded can't hurt.

[Southerngentleman]

Ok, so I'm new to this site... but been in auto repair for awhile. I have a '90 240sx M/T, non ABS, with basically the same prob. (fuel cutout at 75mph) any gear. The speedo does not work. Tach works. does NOT cutout when on jackstands, ... yet th ecm seems to know the cars speed... werid... SO... short of wrecking th car, swaping th motor, What is the fix???? Has VSS code... When I clear codes it WILL top 75mph for the first mile or so, then I guess it pops a code again. PLEASE LETS SOLVE THIS! p.s. I have searched, and read this post over & over....

[Southerngentleman]

a bit more info, I unplugged the bulk trans plug (near battery, grey plug, 6-8 wires?) and car acts different. hits a limit earlier, 3400rpm-4200 and every gear.

Has anyone just replaced the speedo that HAD this prob?