During the last week or so I've noticed an odd problem at WOT or close to it. The car will accelerate and suddenly it will feel like it bounced off the rev limiter for a split second, the AfR meter leans right out and then suddenly everything is good to redline. Happens infrequently so obviously hard to troubleshoot. Any ideas?

 

Sounds like a miss......

 

This feels a lot stronger than a misfire. Unless all 6 cylinders are misfiring at the same time. Feels more like a fuel cut . Like one bounce off the rev limiter

 

Hmm... So you think it could be electrical, as in some environmental factor is causing a relay/wire to screw up, stopping fuel to the cylinders for a few ticks?

Some misses are really dramatic, from what I've heard on Car Talk. The only misses I've felt, however, were in a friend's 4-cylinder Mazda Protege, which was more like a stutter than a "push the gas and the car feels like it jerks backwards instead of moving forwards" that others have consistently described.

You are a car-savvy guy, knight, so it's kind of worrisome that your car is doing something that even you are like ! Obviously, it's not an Air problem, so that leads to either a Fuel or Spark problem. What've you done to kind of play with it or diagnose it?

 

On a higher hp car a miss would be more prevalant...no?
The lean out seems weird though and first thing I would think is fuel cut.

Any other data logging you can do? Maybe fuel flow logging?
Is it at any random RPM or specific?

 

seems to be completely random. I havent had much time to trouble shoot. In fact I havent even scanned for codes. GOnna try to do that saturday morning. Just wondering if anyone has had something similar happen. Just wondering if it could be something like CPS or maybe the junkyard TB I bought a while back.

 

Well, things took a small turn for the worse today. Took the car into my mechanic to replace my toasted drive shaft. I had attempted the removal of the old one a few weeks ago but it was in there pretty good. It was freaking hot that today so I said F it and put the car back together...

Anyway, on the way home with the new drive shaft everything seemed fine but then suddenly the car felt like it was going to stall out on the highway, leaned right out, sputtered something awful and then the tachometer stopped working. The car made it home alright though. Seemed to run fine all the way home but no tach. I stopped in at a store to pick something up and had a really hard time starting the car. I got home and I pulled the CPS code p0335. I also noticed my timing is only at 12 degrees. No wonder my car sucked at the track a few weeks ago.

 

check your MAF. i have a working extra one if you need.
if that thing is all wack, it would run it lean or rich.

or it might be the TPS.... is the tranny shifting weird too?

 

My car is doing this exact same thing how did you fix the problem?

 

Gravedigger

 

Lol really though this sucks

 

I actually have not fixed the problem. It seems to come and go randomly. I replaced the fuel pump a few days ago thinking that made it go away, but a few days later it started sputtering again. Going to try the fuel pump regulator soon.

 

I Had similar issue on my 3.5 and I think it was the injector harness, found a corroded knock sensor pigtail.

65$ from z1 auto. I'll post link later.
Crappy part is you have to re-pull all your intake off to do it.

Also could be A maf. Can you datalog?

 

Fyi my issue may or may not be gone because mine was also intermittent and I haven't driven the car, because summer car. So grain of salt.

 

I can datalog, just too lazy to do it. I'm in the middle of setting up a new laptop. Had windows 7 installed but most software I have wont work. So I am installing "xp mode" Just haven't added any of the software like zeitronix or greddy or autoenginuity. It's not the MAF, I have 2 and they both cause the same problem. One is almost brand new, the other is my original.

Right now i can't rev past 4k rpm, most of the time. I can sometimes. But now, I am also getting random surges, especially at a stop light. I'll start to accelerate and I will squeal the tires without trying, or the car will buck with a fuel cut. I know there is a fuel cut because the wideband slams down to 21 instantly when this happens. I put a can of seafoam in the gas tank and for 3 days i thought the problem was solved. But it came back.

 

The fuel cut was evident to me also, afr and fuel trims both cut. The knock sensor could cause this if the wires are randomly shorting as mine were, its speculation but made sense once I found it.

And could be maf wiring, not just the sensor, a datalog of the mafs would show issues if present.

Can't rule it out

 

I had a similar problem a couple of month's ago. I had all the symptoms you had except the Cut off at high RPM. The problem would happen one day, then not occur for another week or two. After a while it happened more frequently. When i had it checked out it was my TB. I ended up getting a TB off RockAuto.com for $84. When installed, the problem was fixed. My mechanic is a genius at this stuff but he is on vacation till the 22nd. When he comes back i will shoot this by him to see if he has any thoughts (If u don't have it figured out by then). I usually bring my car to him. he checks, tells me whats wrong & what needs to be replaced, then i go order the parts and do the repair myself.

 

I've replaced the TB and the accelerator (TPS sensor)

 

Someone please correct me if I'm wrong, but the tachometer reading is sent directly from the Crank Position Sensor. If the Crank Position Sensor were to fail or be on it's last leg, then it would cause timing to be out of whack, engine speed not to be displayed, throttle input lag or choke, as well as other symptoms. The crank position sensor sends a lot of information to a lot of different systems to make sure everything is working in harmony, and if the car is mechanically doing something different than it thinks it is doing electrically, you are going to experience some anomalies in it's operation.

I would strongly suggest testing the Crank Position Sensor, and both Cam Position Sensors to make sure that they are working within spec AND that they are clean and clear of debris, build up, or damage to the sensor area.

-Nathan

 

It's not the crank position sensor or the harness, both were replaced in the summer. The car is not throwing any codes except for secondary o2 sensors (headers). The Ses does not flash, so there is no misfire. It has to be something that doesn't throw an Ses code.

I took a video in cabin tonight on my way to work. I will post it when I get home in the morning

The car starts first try, no problems there, it cruises at any given speed with no problem as well. There is only a problem under load while accelerating. If the cps is bad it takes 30 seconds to start the car and it stalls randomly. Been there done that

 

Fair enough. Mine was bad, but it didn't hesitate to start up, but my tach never stopped working or any of that. My timing was just way off.

The tach not working really confuses me I guess. Just seems like an odd symptom that one would think would allow for a pretty controlled group of test subjects, but I can't think of any that would cause those problems and not throw a code. At least, not off the top of my head. I'll keep thinking and let you know if I come up with anything.

-Nathan

 

Good points though Nathan! And knight, no ses doesn't mean no mis fire my friend. Mine was misfiing like crazy and took forever to finally trip the cel, its common for the vq to have misfires without codes.

Not saying that helps diagnostics here.

Which harness did you replace?

 

Crank position harness and sensor. The pins rusted out so both were useless

Anyway, here is the link to the video. ****ty quality ****ty audio...

 

So just the crank PIGTAIL, if I'm interpreting that correctly? There could potentially still be an issue in the main harness or wires feeding the CKPS, right? Or did you replace that stuff too?

I have to side with dj420 here, the tach dropping off is a beautiful pointer towards the CKPS, which could cause this exact issue IMO. Could be a slight break in a wire or something?

You twisted whatever wiring you replaced as well I'm assuming?

 

Do you happen to be going 120mph when this happens?

 

Geez man, that's friggin terrible! Much worse than I expected it would be.

Did you get a new Crank Position Sensor from the dealer or from an auto parts store?

Not sure how similar the situation would be, but I replaced a crank position sensor on my 03 Spec V when it went bad and it worked well for a couple months and then went bad again. I decided then to go ahead and replace it with an OEM one from the dealer and it worked perfect and I never heard from it again.

That does look like it's in a pretty bad state though, let me brainstorm a little more and see if I can think of anything else.

-Nathan

 

Also, there could possibly be an issue with the sensor plate that the CKPS receives it's magnetic input from. If there is debris, build up, or a bit of that plate missing then it might cause problems. Though, I don't think that would affect your tach at all.

Just brainstorming and thought I'd pass that along.

As for the wiring channeling for the tach, the white wire from the CKPS goes directly into Pin 95 on the ECM, and that circuit outputs to a very vast number of other output pins, but 95 and Pins 65 and 85 are the only ones that are tied into the signal outputting to Pin 34, which is the tachometer. So they may all tie in and coordinate together to send the tach signal, but those are the only inputs for it.

65 and 85 are Bank 1 Cam Position Sensor and Bank 2 CPS, respectively.

One of the other outputs is to the fuel injectors though, which is why I think that it could be the culprit. If the CKPS is sending a faulty or intermittent signal especially when a high load request is being made, then it may cause a signal interrupt for the injectors and cause them to understand that fuel is being cut.

Based on that logic though, it could also be argued that there is a possibility that the Throttle Control Unit is the malfunctioning party, though, as far as I can work out, it would not explain the erratic or dead tachometer. But it may be something you'd want to test.

Anyways, sorry for the sort of all over the place post, just brainstorming and wanted to pass it along to you in case it helps. Cheers.

-Nathan

 

The tachometer is not dead. It bounces off whatever RPM it happens to be at when the car starts bucking. During the video I was at probably 1/2 throttle and never got over 80kph, because that is about 4k rpm. If the CPS was acting up and the car was driving like you saw, there would be a code. I've had my CPS drop out on me twice since i have owned the car and it causes all sorts of problems not shown in the video. Like hard starting, random stalling while driving and at stop lights. It is a brand new dealership CPS and dealership harness, which is maybe an 18" harness which hooks to the engine harness. There was no soldering done. This was done in August 22 if you read all the posts. Because I had the pins rust out on me twice I used a De0X wire paste on all the connector ends, and shrink wrapped the connector to make sure it stays dry. IT IS NOT THE CPS. The throttle body has been replaced, and the accelerator TPS sensor on the pedal has been replaced. Now the fuel pump has been replaced and a FPR is on order. I have a new knock sensor in my basement, but I don't have the harness so that is on order. I guess that is the next thing to change

I also have a full engine harness which I intend on replacing in the spring. Can't do that right now because my Greddy Emanage blue is spliced into the old one, and I am replacing it with the EMU and Surra's patch harness. Too effing cold right now to do that without a garage.

 

Tps sensor on Tb been re calibrated it checked? Sorry if I missed that.

And for clarity, you keep saying CPS is good, CPS = Cam sensor.
CKPS = crank sensor. Which are you referring to? The Cam sensor won't cause this but a crank sensor or wiring could.

 

My apologies, I must have misunderstood. I remembered reading that your tachometer stopped working and your timing was at 12*, so my mind immediately went to the CKPS.

I shall reexamine my thinking and get back to you if I come up with anything new.

-Nathan

 

OK, let's start again.
I have replaced the CRANK position sensor twice, and the harness twice. (the harness is an 18" long harnes, there is no soldering involved) I have replaced the TB and yes it was calibrated. I have replaced the APPS sensor on the gas pedal, and yes it was calibrated. I have replaced the fuel pump. The car is no longer throwing any codes except for secondary o2's (headers). The SES is not flashing when the AFR goes all wonky with the fuel cut. The tachometer is reading as well as can be expected for a ten year old car. You can watch it hit an invisible redline when it starts to buck due to the fuel cut. The timing is back to normal at 17*.

 

If it was my car id replace the injector wiring harness for 60-70 bucks. Includes knock sensor and throttle body wiring as well. Cheap thing to eliminate, especially for you who can pull the intake apart quickly and easily

 

If I had a warm place to do it...

 

If you find one lmk Ray, I need to do some work on my bish too but no way I'm doing it in this weather

 

I had one and sold it last week. The engine harness I have has one. Its intertwined with the main harness and a ***** to get off the car without cutting tons of electrical tape and loom.

There are a few on fleabay

 

I meant a warm place to work.

Z1autosports sells the brand new harness, OEM Nissan part, around $60-70, in stock

 

Well, for ****s and giggles, I decided to replace both Cam Position Sensors. Took a few minutes to figure out how to get the connectors off. Any way, while investigating I noticed that my front back o2 sensor harness is stuck to my front header. It's probably shorting out when I drive. But not all the time.
Rechecked the codes with autoenginuity and still only showing o2 codes.

I have a week off end of March, so I will be replacing all 4 o2's the knock sensor and the full engine harness. I hope that solves it.