cas sensor limp mode ????

[archaeic_bloke]

what do u mean u swapped them? with each other? or with new ones?

they have a specific placement, the front one needs to be in the front exhaust and the rear in the rear.... just making sure.

i would say its not maf's... car wouldnt shut off by itself.....

can u get a wideband sensor in there to see the A/F? engine shuts down to prevent serious damage at times... or maybe its ur ECU faulty....

[gtrjon]

i put in two brand new ones. i know they are specific to front and bak. the clips are different so i know i didnt mess them up. i know i was running extremely rich with the old o2 sensors cause i failed air care. but with the new o2 sensors i just passed air care today with flying colors so i think i can rule out the a/f mixture making the car turn off. sometimes the car will run fine it will idle fine and pull hard but than randomly it will just enter limp mode where i cant rev above 2500 rpm and if i push in the clutch or put the car in neutral when this happens the rpms will fall and the car will turn off. my mechanic thinks i have a wiring problem and thinks i should get a new harness and just re do the entire thing? i dunno if this will solve my problem though? do you think it could be a bad ecu? also my hicas light is always on but i do not think its related. also when the car enters limp mode and dies when i restart it one of my accessory belt squeels.

[jdms13rhd]

I think I met you at Alan's shop before we went out to mission. I had that plum 180SX that night. I think its you...??

What you really need to do is spend a couple nights and just read over the GTR FSM. Everyone with a skyline should read it and try to understand the factory diagnostic.

Since you have replaced some parts and the MAF wiring is supposedly correct which i assume it is or you would for sure get a codes for them and other symptoms, I would try the following before running through the fsm.

Try opening up the ECU. Take the back plate off and see if it has had a rom chip installed. You can easily tell if its aftermarket if there is a chip bed soldered in. OEM ECU's dont plug in and out. I have had several nissan RB cars run like crap when they get to canada from bad maps on the rom tune. If you see a aftermarket chip in there, get a OEM ECU and give it a shot.

Temp sensor. Are you having this problem when the engine is cold and hot? If its only on one or the other then you should diagnose that sensor. How to is in the FSM.

Since you are not getting codes on the ecu it could be a mechanical problem. Things like intercooler piping. I've had GTR's with the similar symptoms as you refer to with nothing visibly wrong with the intercooler piping. Sometimes dirt can get in the joint causing a leak thats near impossible to check out without removing everything, cleaning it and installing it back on the car. If you get around to doing this apply pressure to each rubber coupling/pipe (roll it in your hand). Sometimes there can be a slit from a rock hitting it or rubbing up against something causing a boost leak. A boost leak can be like a "limp mode", wont let you boost at all.

Another thing could be the wiring. Like you said. I know your looking for a harness but i always say fix the problem rather then swapping things like a harness. Again, if you read the FSM it will run you through an entire diagnostic. If you did that you would find the problem 100% guarantee it! The eng harness is pretty basic and redundant. All the grounds are in a series. Then the pin out for that specific sensor can be tested with a meter from the ecu plug and the wire at the sensor your testing.

Could also be something in your fuel line. When its in a limp mode you can try checking pressure to see if there is a problem with the delivery. Could be a pump problem (listen?) or crap in the fuel line. I've been there at least once.

Can check the key in the exhaust cam. I had once on my rb25 silvia the key hole strip out causing the car to feel like it was going in a limp mode. It would go in and out of the problem till i figured out what it is doing something like what you describe.


One thing you can let us know to help you further, is describe what this "limp mode" is doing for ya. Is it a fall on its face with no throttle response (like a boost leak), or does it just run perfect but not go over the RPM you are telling us of? Any more detail and I might be able to think of a few more lil things. But like I say, read the FSM. Its all in there. It describes two problems in the chart. There is only one answer. At the end you have a solution or at least something to eliminate. Pretty easy for the do it your self'er too, just time consuming to learn it. Lots of back and forth crap. :P

I dont think its your O2 sensors. I can pull an o2 from any of my oem ecu cars and still bag it up and down the street :P If anything, you would run rich as the ecu wont use that parameter to increase/decrease injection pulse via O2.

[gtrjon]

yea thats me from allans shop. well my ecu is chipped so i guess thats the next thing ill try with a stock ecu and c how it goes. and the problem occurs most when the car is fully warmed up. i am thinking it could be tps sensor as well?

[gtrjon]

when i say limp mode i mean i cannot rev above 2500 rpm. i can drive the car fine until i get to 2500 rpm than the car will shake and bounce off almost like its the rev limiter. the car pulls fine just limiter at 2500 rpm and if i push the clutch it the car will stall. its mostly an idle problem. if i am crusing on the highway it rarley goes into limp mode and i can drive it fine. but when in the city in stop and go traffic the car doesnt idle and stalls and turns off every 5 seconds

[Shane_Sawatzki]

sorry to revive this thread but I have a couple questions and I figured they seem to match gtrjon's situation almost exactly.

1) did you ever fix this problem jon?

2) how do i pull codes from my car? I have nistune and had the car tuned by someone else because I dont really know how to use the software on my laptop, Can I connect to nistune through my consult port and just read the codes?

This is what my car is doing :

The 2500 RPM limp mode is happening randomly when iv been driving for 10-15 mins ill pull up to a light after having no issues, sit at the light and randomly while i try to drive away I get this limp mode, it doesnt happen all the time but i decided to video it today when it acted up... its strange it did it once 2 months ago... and nothing untill this week it has done it 2 times this week

so in the video, I pulled into a parking lot after hitting limp mode randomly, and for the first 20 seconds I was trying to rev it, giving it full throttle and the revs were kind of all over the place and it didnt want to rev, almost like no throttle response + limp mode.

after I shut the car off, I started it again and try to rev and I hit the 2500 limp mode a few times and then I let it idle for a few seconds and when i reved it again everything was fine and I drove it home with no problem.

here is the video, sorry that its vertical

[gtrjon]

dude that is the exact same problem i had. like literally the exact same ****. my car would die after it went into limp mode if i pushed in the clutch and it would be completly random. like no pattern at all. I never fixed the problem I do know that my motor had bum compression in two cylinders 60 and 85 but i dont think that caused it. the guy i bought it off had ztune replace both mafs and resoder the harness so i kinda eliminated that. ztune also replaced the tps. I never fixed the problem because i ended up pulling my motor and i am in the middle of a big build. Im hoping i figure it out or it will go away when my new motor goes back in or else im ******. i thought it could be maf related despite ztune replacing them because i replaced them again and it didnt go into limp mode for a day but then it came back. but that could just be it being random. I hope you figure it out man it sucks so tough and makes me not want to drive the car. my ideas were cas or tps or mafs but those are just my guesses. no body on here really seemed to have any idea. I tried pulling codes off my ecu but there were no codes. im not sure how to pull codes off nistune but if its the same as the stock ecu just google it its the same for alot of nissans. pm me if you ever figure this out. good luck

[gtrjon]

o also my alternator ended up dying on me and my hicas was all ****** before it died so i thought that might be it too. i didnt end up replacing the alternator yet as i am in the middle of my build but i thought that might be it

[Shane_Sawatzki]

hmmm I know the motor is good, compression test 2 months ago before it was dyno tuned was 160 across.. the car runs and pulls friggin hard except for when this happens .. im kind of lost, im thinking something electrical coil packs? ignitor?

[Skym]

Sometimes ECU can go into limp mode if the Nistune board dislodges itself from socket or the cable to Nistune board unplugs itself. If hit a bump in road and problem shows up, then that probably would be the cause. Also engine would run very rich.

If unplug both MAF's, then start engine and it idles normally, bingo MAF problem. Only stock ECU can run without MAF's up to a 2500rpm revlimiter.

If you fit known good MAF's and problem appears, check MAF plugs (sometimes people pull on the wiring, not the MAF plug itself when removing MAF plugs from MAF's and wiring gets pulled out of the MAF plug) and check ECU plug, as can get same problem or ECU is not seated correctly in ECU plug. Or ECU plug is warped due to being tightened down on a angle. Sometimes there's a wiring problem between ECU, MAF's. Check MAF voltage for both MAF's at ECU plug with multimeter.

Easy with Nistune. Plug Consult cable into laptop when it's off and then plug into Consult port on car (plug goes one way only). Boot up laptop, open Nistune program and click on Consult button on far right at top. Then click on Display > Consult Display and the error code should be shown under "ECU messages" if there is any and can clear them, reset ECU, check TPS is touching idle contact + see TPS voltage in realtime, etc.

But you'll need to install USB drivers, Nistune, etc (should be shipped with instructions).

Also can datalog sensors, so can playback and see what is causing the problem. Should be obvious.

[MarusGTR]

o also my alternator ended up dying on me and my hicas was all ****** before it died so i thought that might be it too. i didnt end up replacing the alternator yet as i am in the middle of my build but i thought that might be it

I hope you find the problem especially since I hate mysteries like this. Do you have a build thread? I'd like to know your GTR a little better

[gtrjon]

I hope you find the problem especially since I hate mysteries like this. Do you have a build thread? I'd like to know your GTR a little better

dont got a build thread yet my progess is kinda slow since im a student in university. ill give you a hint its a built bottom end with a r34 crank a tomei oil pump and a big single bw s300x 91-79 with about 10gs in supporting mods im shooting for 650awhp or where ever my tranny shits out. once i dyno it ill have a build thread for you with lots of pictures