won't go above 5000 rpms

[maxxed out]

Hi all,This is my first time posting to this forum. I have a question about my 91 240sx SE coupe (bone stock). I am looking to start modding this car but I've had this problem ever since I bought the car. Ok, when I am accelerating, the car pulls strong all the way to ~5000rpms, then the engine jerks/stalls/shakes(usually an abrupt/violent stop), etc but continues to run, just not above ~5000rpms. It feels like a limiter but if I push the clutch in, I am able to rev it past the 5000rpms but just not when under load. This happens in all gears, not just 5th gear. The car is tuned up (new plugs/wires/etc) but no change. I read the part about 5th gear sensors and rev limiters in the f.a.q. but I don't think this is my problem. Any help would be appreciated. Thanks.:helpBobby

[apex_240sx]

hey i had almost the same problem in my 1990 240sx w/KA24E except mine wouldn't rev past 2000rpm with a load, but i could get the engine to rev up all the way to redline, just slower than usual, when in neutral or when clutched in. what happened in my case was that the driveshaft in the front of the engine that drives the oil pump and the distributor was almost snapped in half which caused it to go out of time at high revs under loads, so i'd check to make sure that either a) that shaft isn't snapped, or b) that the gear on the crankshaft that that gear drives off of isn't chewed up good or something.

[maxxed out]

apex, First off, thanks for your reply. Our problems are slightly different though. It has no problem with how quickly it revs under load, there is just a harsh jerk once I reach ~5000rpms. It just feels like a fuel cut or something like it.

[apex_240sx]

well then if it's just a harsh cut-off at 5000 rpm's, then i'd recommend something like checking the ECU codes to make sure everything is good. if that doesn't do it, then i don't know, obviously at 5000 rpm, something is shutting off in the fuel system, like your injectors or fuel pump, so if it's not the ECU then i'd take it to your local Nissan dealer and have them check it out cuz that sounds like quite the odd dilemma you're having

[GoofyATX240]

well then if it's just a harsh cut-off at 5000 rpm's, then i'd recommend something like checking the ECU codes to make sure everything is good. if that doesn't do it, then i don't know, obviously at 5000 rpm, something is shutting off in the fuel system, like your injectors or fuel pump, so if it's not the ECU then i'd take it to your local Nissan dealer and have them check it out cuz that sounds like quite the odd dilemma you're having

I know this is gonna sound dumb but my car did the same exact thing when my alternator was dying.Once I changed it it was fine.

[leper421]

I had almost same problem on my 91. I posted a posted a message a few months ago with almost the same subject . It would vary between 4750-5500, shake violently, and produce almost no power. It happened in every gear as well as neutral. My problem was a bad 5th gear sensor. It made my ecu think I was in 5th all the time, and apply the limiter when I hit 5500.

Quote »It feels like a limiter but if I push the clutch in, I am able to rev it past the 5000rpms but just not when under load.[/quote]

Are you leaving it gear or pulling it out when you hit the clutch? If you can get under the car I would recommend that you check the 5th sensor, since that is the onlything I know of that will trigger the limiting at 5500. There should be continuity in the switch when in 5th and an open circuit when in anything besides 5th.

[PabloHoney]

Easy fix, just unplug your 5th gear sensor.

[MaineExport]

let me jump on the band wagon too!!!

yup... 5th gear sensor = toast = wrong signal to ECU... probably wont throw a code though, so checking the ECU won't do too much.

[maxxed out]

Thanks everyone for replying to my topic. However, now I have a definite newbie question. Where is the 5th gear sensor located and will I do any damage by just unplugging it? Thanks for your help.

[leper421]

It the third electircal connector back from the front of the transmission on the passenger side. If my scanner was working I'd post you a pic . Nothing will happen from unplugging it, besides possibly fixing your problem. I've been driving around for months with mine disconnected. Much easier than paying the $60 the dealer wants for a new one.

[maxxed out]

Thanks leper, I'll give it a shot in the morning when its light outside.

[Mayhem_J30]

educate me, what's the purpose of a 5th gear sensor...especially on a manual?

[MaineExport]

educate me, what's the purpose of a 5th gear sensor...especially on a manual?

It acts as a backup to the speed governor. When the transmission is in fifth gear, it turns on the 5500 RPM rev limiter. The speed governor hits at just under 120 at about 4500+ RPMs.... so add another 1000 rpms and I'm not sure what speed you could reach with the speed sensor disconnected. I'd be scared to find out, as it feels like the car is about to achieve lift and take flight at about 115mph!

[sts76]

Had a nearly identical problem. Turned out to be cam timing. Both cams were 1 tooth off. I rebuilt the engine myself and even though the dots lined up with the links, the cams were not in the correct position.

[super_hicas]

im kinda having the same problem but my car just seems to lose power around 6000 rpm. i dont feel the push no more. you can totally feel the power drop.

[MaineExport]

im kinda having the same problem but my car just seems to lose power around 6000 rpm. i dont feel the push no more. you can totally feel the power drop.

That's becasue (assuming you have a KA) the horsepower DOES drop like a stone after 5500 RPMs. There is MUCH less pull at 6000 than there is at 4500. There is really no reason to redline a KA, you would do much better to shift at 5500.

[deviant516]

So basically... disconneting the 5th gear sensor takes care of the problem? I'm tired of hitting 110-115 and my engine just deciding it doesn't want to take me any faster. Come on!! We still got 2000 more rpm's to hit!

Anyways... I have no idea where the 5th gear sensor is located... and I have no idea how to get rid of my governor. Someone can e-mail me at [email protected] if they have the patients to help me out.

Thanks a lot guys.

-n00b 240SX owner :ylsuper

[Trppen37]

DUDE I HAVE THE SAME EXACT PROBLEM! i believe the 5th gear sensor might be right... my engine and transmission was rebuilt so theres lots of factors to determine the problem..but I believe that 5ht gear sensor is correct..

[Trppen37]

i disconnected the sensor...didnt do jack still revs to 5k and like the governor kicks in :help

[Nismo1182]

i disconnected the sensor...didnt do jack still revs to 5k and like the governor kicks in :help

Did you disconnect the right sensor?

Theres a neutral one, reverse, 5th and a 4th.

[Trppen37]

i disconnected the 3rd sensor from the front to back...it sits on top of the transmission while other others are on the side...so it may be cam timing "which im leaning towards to and/or coolant sensor if only I can find it! anyone kno where its at?

[Trppen37]

i also disconnected the first one..so the first and thrid are removed....should i remove that middle sensor and plug in the other two??

[spec-v5150]

i also disconnected the first one..so the first and thrid are removed....should i remove that middle sensor and plug in the other two??

That is what you get for getting those 180sx tailights before me. And for having a nismo shift knob:D