Jump to content
SAU Community

Rb20Det Lag/bogging

teteous

By teteous,
in Engines & Forced Induction

 Share

Recommended Posts

teteous Apprentice

teteous

Posted
Posted (edited)

Issue with my r32 rb20det skyline is that under acceleration it will accelerate between 2-3k RPM, bog down severely between 3-4k RPM and boost hard between 4-5k RPM and bog down again after that.

I have changed plugs/gapped, replaced and cleaned AFM, changed fuel pump/filter, confirmed correct timing.

Using consult cable I get a code 34 (Knock sensor - Not reading correct resistance) and no other codes.

I cannot find any vac leaks and everything is tight and connected..

I have a feeling because of code 34 it might be going into some type of limp mode but am unsure.

Also, when it bogs down the timing drops to 0-5 degrees..

Any feedback would be appreciated.

Edited by teteous
Link to comment
https://www.sau.com.au/forums/topic/427267-rb20det-lagbogging/
Share on other sites
GTSBoy Grand Master

GTSBoy

Posted
Posted

It's probably switching back to the knock fuel and ignition maps (the standard ECU has a proper set and a set it switches to when knock is detected). And the R32 ECU also then has the ability to pull even more timing out if it continues to have knock while on the knock map. This will make it as doughy as all get out. So, if your knock sensor is faulty (and let's face it, you can be pretty sure that it is!!) then it may be registering false knock and making the ECU spaz out.

Replace knock sensor with new one, or with ~500Ohm resistor, and see how you go.

teteous Apprentice

teteous

Posted
  • Author
Posted (edited)

Bought the car in not 100% running state, been slowly fixing it as listed above and this is the point I have gotten to.

So no idea on previous history. Is running a r34 turbo/gtr radiator, turbo back exhaust, constant power feed to fuel pump, air con/heater removed, everything else engine wise is standard.

Heading to Jaycar today to get the resistors, will putting the resistors directly into the ecu pin outs for both sensors work?

Edited by teteous
teteous Apprentice

teteous

Posted
  • Author
Posted

Only if you disconnect the wiring out to the sensors.

Ok, so i cut both 23/24, added the 470 ohm resistors to both and grounded the other end to a ground on the ECU.

It made a difference in the revs as soon as I did this as it was on a cold map (1700-2000rpm) and instantly dropped to hot map once the resistors were in.

But it still gives the knock sensor code 34 even after clearing, as soon as I start the car and the code re-appears.. Any ideas would be great.

david69 Community Regular

david69

Posted
Posted

when I got my skyline it wouldn't rev past 4500.the previous owner changed the usual crap that everybody changes when they don't know whats going on.ended up the fuel filter sock was full of brown crap.Old tank with a lot crap in it. I cleaned the fuel pump sock then I changed the fuel filter,problem solved,its worth a try.cheers

teteous Apprentice

teteous

Posted
  • Author
Posted (edited)

I don't know if 470 is close enough to the original sensor's impedence. Have a google around for what the best resistor value is. You may need to series or parallel another resistor on there to get closer.

Yea I was thinking that too so I read all the threads i could find and they either said 470, 500 (which isnt a actual resistor impedance) or 1M ohm.

I ran two of the 470's in parallel and it still has the code & hesitation (but reduced the idle weirdly), I guess I can try in series if that may make a difference. I guess next step would be to try another known working ECU..

when I got my skyline it wouldn't rev past 4500.the previous owner changed the usual crap that everybody changes when they don't know whats going on.ended up the fuel filter sock was full of brown crap.Old tank with a lot crap in it. I cleaned the fuel pump sock then I changed the fuel filter,problem solved,its worth a try.cheers

I shall try that, I have another Bosch 040 laying around so I guess I can just swap that in and see if it makes a difference, it could be contributing to it :)

Edited by teteous
GTSBoy Grand Master

GTSBoy

Posted
Posted

Not. Not 2x 470s. A 470 and a something else to get you closer to 500. Like a 47, or preferably something around 30 ohms.

And there is always the possibility that there is a damaged track inside the ECU to consider also. If that were the case, you could hook up whatever you liked and get the same result. I don't know if the knock sensor circuitry/tracks in a Nissan ECU have EVER been found to be faulty, but there's always a first time. Have you tried another ECU, just in case?

teteous Apprentice

teteous

Posted
  • Author
Posted (edited)

Thanks GTSBoy,

I have limited understanding of resistors, but wouldn't running x2 470's actually reduce the value by half (ie 470/2 = 235k ohm).. So really I should get x2 1M ohm resistors & run those in parallel to make exactly 500k ohm (but twice the wattage?).

Or alternatively run the 470 with say a 47 as mentioned in series?

Edited by teteous
GTSBoy Grand Master

GTSBoy

Posted
Posted

Any two resistors in series simply add the resistance. So a 470 and a 47 = 517. That might be too high, so you could use a 30 instead of a 47 and get 500 exactly.

Two 470s in parallel gives you half the value of one of them (so you end up with 235 like you say), but this is useless to you. Yeah, you could get two 1M resistors in parallel, but I was assuming that given you already had the 470s it was worth starting there.

Jaycar's 510 ohm jobbies might do.

What would actually be smarter would be to get a variable resistor that works in your desired range and try adjusting it around the 500k mark and see if the fault code goes away. Could be tedious. But worth a try.

But one thing I think you have to be prepared for is that the problem may not be that the knock sensor resistance is actually out of range. There may be some other problem.

More swaptronics is also an option. Try to obtain another ECU and some knock sensors and see if swapping them out helps.

teteous Apprentice

teteous

Posted
  • Author
Posted

Thanks for all the info,

Got the 30 ohm & 1m ohm resistors (only $0.46/pack of 8 so why not..) and i'll test these out tonight. Hopefully being closer to 500 ohms will get it running again.

My mate is looking for a spare ecu, so if this fails i'll go down the swapping ecu's route.

bananaweesle Contributor

bananaweesle

Posted
Posted

how to you have the resistors connected u can use 1m ohm and connect both knock sensor wires together connect to one side of resistor then connect the other end of the resistor to a good ground. code should definitely go away after that.

teteous Apprentice

teteous

Posted
  • Author
Posted (edited)

how to you have the resistors connected u can use 1m ohm and connect both knock sensor wires together connect to one side of resistor then connect the other end of the resistor to a good ground. code should definitely go away after that.

Ill give it a go, I have pin 23/24 cut at the ECU loom which I soldered separately to each wire x1 470 & x1 30 ohm resistors in series. These both have the same ground of pin 50 (Ground control unit) - This is a known good ground as I have my SAFC connected to this ground also.

Edited by teteous
teteous Apprentice

teteous

Posted
  • Author
Posted

470k ohm resistor?

Just double checking. Also try 2 new resistors as i have seen them not work the first time

Ok ill try a couple more, I first tried 470's on each knock sensor, then tried 470 + 30 in series. After those failed I tried connecting both of the knock sensors wiring from the ecu together, attaching a 1M resistor and grounding that to the chassis but still have the same issue.

I've tried another ECU and same issue to rule that out.

  • 3 weeks later...
  • 2 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Duncan
      R33 GTR running -9 with no tune

      By Duncan · Posted

      Sounds like you've got an interesting adventure ahead here with local support if you have trouble! My guess is that, unboosted, you will be OK with a small upgrade like -9. What will happen is that once the stock ECU sees more airflow than it expects it will add a heap of fuel and pull a heap of timing to be safe because it can't understand how it could get that much air without there being an issue. You will see clouds of black smoke and it won't pull hard through the midrange and top end. So, overall it will be a bit frustrating but should be OK. If you are still nervous set the base timing back 2o through the CAS, but it will be even more sluggish everywhere. As said above through...this is not my guarantee your engine won't be blown into a million pieces, leaving you looking for very hard to find parts A better idea is get a computer with logging ASAP, wire in a wide band O2 sensor and a use remote tuner. I've done multiple cars this way and while it is not as good as a specific tune on a dyno they can get it 90% right. I'd suggest if you can afford an R33 GTR these days you can afford an ECU and tune. And if you can't afford that you sure won't be able to afford the rebuild if it goes bad in the meantime,.  
    • Duncan
      New kid on the block

      By Duncan · Posted

      Yeah it would be nice if someone took the time to put that sort of information together, but there are a lot of variations in looms. I think you are making this way hard for yourself if you just want to get it running....sourcing an SR20 with the right wiring will be a billion times easier than matching the RB loom to an S15 chassis. If you do end up going this way, you just need to trace every wire in the loom with a multimeter, 95% of them will go to a location you can confirm at the ECU.....and then post it up for the next person who needs it  
    • Duncan
      Coolant leak?

      By Duncan · Posted

      Just top it up with water, and keep a general idea of how much you added. It is normal for water to be pushed into and pulled out of the reservoir through the cap, and it should not be more than half full or it will be likely to overflow when hot. Any decent mechanic can do a pressure test of the cooling system to confirm if you have a leak. Keep in mind if it is only leaking a little and when hot it may well evaporate before you see it hit the ground
    • GTSBoy
      Coolant leak?

      By GTSBoy · Posted

      I'd ask the shop what they used and use that. Mixing coolants is sometimes OK, sometimes not, and you have know the details of each coolant to know whether it's a good idea or not.
    • Chupapy
      Coolant leak?

      By Chupapy · Posted

      Is it alright to top up with just another green coolant?
×
×
  • Create New...