Intermittent Problem With Rb20

[DannyC33]

Hey guys.

Just need some help with my c33 laurel.

bit of back ground.

its a stock rb20 silvertop outta the laurel so runnin all the laurel electrics and everythin.

ive noticed recently that its having a strange issue on cruising throttle and acceleration between idle and 3200 rpm.

basically what it does is itll take off and then itll feel like its surging or struggling for fuel.

but soon as it gets to 3200rpm or i give it a boot full youll feel it kick and take off like theres nothin wrong.

almost feels as tho the timing is retarding itself and then just gets over it.

now when cruising say sittin in 5th gear at between 60-80ks

itll randomly start chuggin and feel like the you bunny hopping almost, again on light cruising throttle. but soon as you put the foot down

it goes away again.

another thing.. when this hesitation happens there is suddenly considerably more load on the engine.

ie vac gauge goes from say 20in vac to about 5 in vac and the exhaust note changes drastically gets alot deeper and sounds more strained.

strangest thing is my hr31 coupe with rb20det redtop eccs did exactly the same thing and i chased the problem since day one replacing sensors and stuff and could never figure it out.

even after multiple times at boost worx shaun could never figure it out. and i put it down to the fact they never actually road tested it and drove it under light throttle because he said it never happened on the dyno

and even the dyno sheets say the same.

last week i had an issue where the car just simply didnt want to start. so i sent it to boostworx after checkin a few things myself and couldnt figure it out.

they charged the battery (as i killed it tryin to start it) and after testing the cas and fuel pressure it simply just started...

not sure if this is related to anythin. but thought id throw it out incase it helps any one.

cheers guys.

Danny

[The Mafia]

I had the same issue with my r33 engine. Struggles at cruise, goes ok at boost. Idles rough sometimes etc.

Put a timing light on and the timing mark was jumping around all over the place.

I think it was struggling at cruise because the stuffed cas was advancing the timing too much. Causing pre ignition. The timing is already super high at cruise. It was ok at boost because the timing drops back considerably.

Changed the case with a known working one and all the problems went away. Also, the mark didn't jump all over the place when we checked it with a timing light.

Try another known working cas.

Every 3rd timing light flash the timing would be in a random spot.

With the new cas it would jump every 20th flash or something like that. A lot less that's for sure.

[DannyC33]

hmmm. will try that. i have tried a different cas before on my hr31 but didnt make much difference how ever it was just from another hr31 that had had its motor pulled out coz it spun a bottom end bearing. so may have been on its way anyways.

ill see if i can find another cas. will also get the test light on my car tonight to check the timing.

i did notice on my hr31 when i tried to time it, itd be all over the shop and basically looked like it was sittin at about 40degree advanced. and with the cas turned as far retard as it could go it would only drop to about 30 degree. how ever it never pinged.

will check it tonight.

[The Mafia]

I thought that would be alarm bells to something being wrong?

Dude, a cas as timing isn't there for decoration. It's the most crucial part of the engines functionality.

Brin advanced 30 degrees could have killed it.

[DannyC33]

yeah it did ring bells and i realise its a crucial part hence i sent it to get tuned properly. and it returned no issues.

engine in the skyline ran fine other then the hesitation which the laurel is now also doin.

i believe it was probs doin what you are sayin and it was flashin at the wrong point. because when i retard the timin it drove like a pile of crap and felt like it was very retarded timing wise.

another reason why i didnt believe it was givin a correct timin reading is because when i changed the timin belt i made sure everythin was perfectly lined up (mate from darwin whos qualified mech actually did the work)

and it was perfect. still the timin gun read 40degrees and bounced around the place from 0-40 (forgot to add that part to the last post)

[d3vic3]

Sorry to dig up a thread, but ive been searching for months for someone with similar symptoms and found nothing as close as this.

My rb20det is doing the same thing.

on partial throttle(off boost) it will splutter and go rich and retard until i put my foot down and get into boost. sometimes idle will just drop off and sound like its miss firing then the ACC opens up and restores the idle somtimes.

But some times i have no symptoms at all.

the problem is much less while the car is coming up to temp. once its hits the warm point about (69deg) the issues begin.

also after an ecu reset it will be good for a few days and then gradually go back to this.

i have another CAS i can try but im not 100% sure its good. but ill see any way.

if not, im next to swap out TPS and MAF.....

I get no ECU error codes.

I have replaced/cleaned or checked the following:

coilpacks replaced

fuel pump replaced

fuel filter replaced

plugs replaced

AFm cleaned

AAC cleaned

split vacuum lines replaced

IACV removed

cleaned and added an earth point

replaced O2 sensor x2.

replaced batter

replaced battery

Checked TPS voltage

AFM voltage seems good.

reset TPS

checked for boost and vacuum leaks

reset timing - but dont remember taking notice of it jumping around - will recheck that. was previosuly unsure of 'normal behavior' from the timing.....

had compression test a while ago and one cyl was down a little but still fine.

If some one has solved this prob i would be so very happy.

Edited February 23, 2012 by d3vic3

[cherring]

Given that the OP didn't post again I'd say that the CAS probably sorted him out.

[rob82]

All issues in this thread sound like incorrect 02 sensor operation. Bad cas usually cause issues at higher rpm high load where ignition timing is crutial.

Its hard to diagnose a bad 02 sensor without ecu data. There is a few things you can check though. Put a multimeter on the signal wire and check that the 02 sensor oscillates between about 100mv and 900mv check at no load at about 2500rpm.

[DannyC33]

hey car came off the road not long after i posted last.

problem was not the cas.

its still doin it now and gettin worse. ive replaced my 02 sensor with a brand new one. and another known workin one.

after talkin to a few old school mechanics and a few tuners ive been told that it could be the knock sensors.. they are likely working fine but somethin is confusing them. could be outside noise, could be bad wiring. reason they say its the knock sensors is because obviously a knock bein sensed will cause the ecu to go into r and r mode. also knock sensors only measure between 1500-3500 rpm. any higher or lower in the rev range theres a substantial amount of radiant noise which can confuse a knock sensor.

when i get around to it. (hopefully in the next week) ill be by passing the knock sensors all together via a 460k ohm resistor soldered inline with the knock sensors.

basically that will tell the ecu that there is no knock ever so if it does fix it then, ill replace the wiring and the knock sensors (seperately so that i can pinpoint which was the issue incase it happens again)

[rob82]

hey car came off the road not long after i posted last.

problem was not the cas.

its still doin it now and gettin worse. ive replaced my 02 sensor with a brand new one. and another known workin one.

after talkin to a few old school mechanics and a few tuners ive been told that it could be the knock sensors.. they are likely working fine but somethin is confusing them. could be outside noise, could be bad wiring. reason they say its the knock sensors is because obviously a knock bein sensed will cause the ecu to go into r and r mode. also knock sensors only measure between 1500-3500 rpm. any higher or lower in the rev range theres a substantial amount of radiant noise which can confuse a knock sensor.

when i get around to it. (hopefully in the next week) ill be by passing the knock sensors all together via a 460k ohm resistor soldered inline with the knock sensors.

basically that will tell the ecu that there is no knock ever so if it does fix it then, ill replace the wiring and the knock sensors (seperately so that i can pinpoint which was the issue incase it happens again)

The knock sensor aren't active at light load. Nissans strategy is to detect knock at low rpm high load and if substantial knock is detect it will revert to a completely different ignition and fuel map. The values in this ignition map are only slightly retarded at light load but quiet a bit more retarded at high load.

Can you confirm the cruise mixtures with a wideband are correct ie 14.7:1?

[DannyC33]

i havent had the checked on the laurel. but i know with my r31 coupe everythin was fine. literally every single test turned up no issues.

only thing i didnt change/test on the coupe was the knock sensors.

[DVS JEZ]

When u do the knock sensor bypass u should do it at the ecu, wire in the resistor then ground the other end of the wire

[DannyC33]

yeah thats what im gonna do. ive got the pin out. been told to cut the wires bout 100mm from ecu plug, wire in resistor and then earth them to the same earth the ecu uses.

[DVS JEZ]

Sweet. U should run it on the dyno to help diagnose the issue

[SargeRX8]

Changing the knock sensor with the plenum on is impossible. Try unplug one and leave the other in. see if it's one or the other. I did this to confirm the knock reading I was getting on startup was the rear sensor near the starter motor.

[d3vic3]

if you just unplug the offending knock sensor, will it run ok? or do you need to fool the ECU into thinking its active.

cause if the ECu is just going to throw a code cause the sensor is not responding, i can live with that.

i have a consult cable and all that. is there a program that will show if knock is being detected and hopefully narrow it down to this???

[DannyC33]

Sweet. U should run it on the dyno to help diagnose the issue

yeah i had my hr31 coupe on the dyno many many times and turned up nothin.

for the sake of a couple resistors im gonna give it a shot. and once i get my nistune ecu done ill send it to get dynoed to see if they can see anythin else this time,

[GTSBoy]

yeah i had my hr31 coupe on the dyno many many times and turned up nothin.

for the sake of a couple resistors im gonna give it a shot. and once i get my nistune ecu done ill send it to get dynoed to see if they can see anythin else this time,

If you Nistune it you can just make the knock maps the same as the main maps so that if it does detect (falsely) knock, then it won;t stuff up the timing. You'd soon notice the difference between having proper knock maps and copied ones if the knock sensors are the problem.

[DannyC33]

hmmmm thats a f**kin good idea... and i didnt think of that.

cheers, saves me dicking around with cutting wires and shit

[d3vic3]

So i did some thinking and some more reading.

Danny mentioned about knock sensors reacting to false knock or outside noises they confuse with knock.

i had a look around the engine bay and noticed the intercooler pipe was touching the cam cover. i figured it may be vibrating against the engine and messing with the sensors.

I cut out a piece of rubber and put it there and went for a short drive.

no more symptoms. solid idle and no hesitation or R&R

ill do some more driving before celebrating tho....