Shuddering (boost Issues?)

[atomaly]

i've recently started feeling some shuddering, or jerking i.e "juddering" and the engine feels like its cutting in and out kindof..

starts at 100->110kph when you're trying to cruise, then once the car is quite warm it happens at lower speeds aswell!

when engines warm (i.e. 20 mins of driving) it happens pretty much on small to medium boost, but normally starts at around the range of 2500 RPM. i do remember its always had a bit of dip at that mark, but was never juddery and noticable til now!

if i give it full boost it wont shudder at all!

i've only noticed the juddering 'since' i got the car serviced and the oils were changed,

and also the gearbox was serviced (which fixed my 4th gear synch issue) (used Martini Oils (Sabaddin))

when its cold, its not really noticeable.

i also heard it could be my AFM playing up?

i was also thinking to change my spark plugs and check my coil packs.. (but it seems liek a boost related issue to me)

in regards to the BOV return pipe seal being perished... what would be the best thing to use to seal it off this time, and where would i get it from ?

(picccccccc)

[SilverECR33]

My brothers Rb30ET is doing the Exact same thing, and he has no BOV, hopefully the Fix is the same. Few things we have tried on his RB30

Fuel pump replaced, fuel reg replaced, pressures tested to rail.

Crank Angle Sensor replaced, Leads Replaced. Spark from coil but havnt replaced as yet. (dont know if its related but could be).

and we are looking for a spare AFM to test with. But issue remains with or without AFM.

Doesnt matter what boost we run, same issue, also we noticed it only happens when it comes onto boost (while cold) but when it heats up, does it earlier, and we have checked everywhere and found no intake leaks.

Hopefully someone can Shed some more light on the subject.

[atomaly]

My brothers Rb30ET is doing the Exact same thing, and he has no BOV, hopefully the Fix is the same. Few things we have tried on his RB30

Fuel pump replaced, fuel reg replaced, pressures tested to rail.

Crank Angle Sensor replaced, Leads Replaced. Spark from coil but havnt replaced as yet. (dont know if its related but could be).

and we are looking for a spare AFM to test with. But issue remains with or without AFM.

Doesnt matter what boost we run, same issue, also we noticed it only happens when it comes onto boost (while cold) but when it heats up, does it earlier, and we have checked everywhere and found no intake leaks.

Hopefully someone can Shed some more light on the subject.

the only other thing my mech did was put on a missing bolt to the turbo (i think (wierd lol)).. my cars got stock ECU and its quite R&R (until i can afford a PowerFC) i wouldnt think it would be ECU related though..

i'll be cleaning my AFM and changing spark plugs / checking coil packs when i get some time!

other than that. i'm pretty stumped.

[SilverECR33]

I used to have a VL a long time ago, and it did something like this, and it was ECU related. We havnt tried it yet on my brothers VL because we dont have a spare anymore. but its worth looking into, dont rule it out. Try using a mates ECU to test it.

[Hiney]

My RB25DET S14 silvia has just started doing the exact same thing as described above. i don't know what RPM its at as the tacho reads 133% of what it really is. but it sounds very similar

i have replaced the spark plugs and had the ECU re-chipped but the issue still exists. i will clean out my AFM with that electrical cleaner tomorrow, but apart from that i'm stumped aswell (and quite broke )

[Shiraz200SX]

try unplugging your O2 sensor.. had the same problem, would hesitate before acceleration, then trying to cruise it would shudder... will run fine with it unplugged. i have a power fc now, and dont run an o2 sensor...

[KB240RB]

Mines doing something similar. Runs smooth up to 7psi, but if you go to 10psi or higher, power will feel like it comes on and off. Its nothing with the ignition, i have new coils, ignitor, and plugs. Ive cleaned the MAF. ECU throws no codes. Timing is perfect at 15*. Only other thing i can think of is some sort of built in fuel cut. Does the RB25 S1 ECU have a built in fuel cut for when it reaches a certain MAF Voltage?

[atomaly]

try unplugging your O2 sensor.. had the same problem, would hesitate before acceleration, then trying to cruise it would shudder... will run fine with it unplugged. i have a power fc now, and dont run an o2 sensor...

i'll give that a go when i get some time to tinker!

i have a feeling it may have been unplugged before it got serviced... then he saw it ands like.. hmm better plug it in?? it has been running less R & R since its been serviced....

Edited November 24, 2009 by atomaly

[Hiney]

try unplugging your O2 sensor.. had the same problem, would hesitate before acceleration, then trying to cruise it would shudder... will run fine with it unplugged. i have a power fc now, and dont run an o2 sensor...

have done this and gone for a 15-20 minute drive, and it seems to have fixed the problem!!

will running with the o2 sensor unplugged have any adverse effect on either performance, economy or safety? (its not going to blow up when i hit boost)??

[atomaly]

have done this and gone for a 15-20 minute drive, and it seems to have fixed the problem!!

will running with the o2 sensor unplugged have any adverse effect on either performance, economy or safety? (its not going to blow up when i hit boost)??

aparantly an 02 sensor should be changed every 80,000Km and mines 5k past that.

i'll test mine tonight by unplugging it and let u know

aparantly it will turn ur car very R&R but thats about it! best to get it replaced rather than wing it without one.

Edited November 25, 2009 by atomaly

[Silo_Wagon]

O2 sensor pretty much is the feedback for the ecu to tell it how the mixtures are going.

So if its running rich the computer will sence it via the O2 sensor and then its next Mixture will be corrected. Same goes if its lean.

Only way to check them is while they are on the car with a oscilliscope, should have a fairly even rounded sine wave at idle going both positive and negative over the centreline. Once the revs are increased the sinewave will get much closer together.

I ran no oxygen sensor on the dyno and was getting 10:1 AFR. i am now running one and im hoping next time on the dyno to have a better mixture.

[KB240RB]

I always thought the 02 feedback only affected cruising AFR? Sopposed to keep the engine at 14.7 while cruising. After a certain MAF Voltage the ecu disregards its reading and goes strictly off the ignition and fuel map. Am i wrong?

[atomaly]

unplugged my O2 sensor and its running smooth, took it for a 30 min drive.. no shuddering issues of any kind, and running smooth as when i first bought it

i'm going for a longer drive tomorrow night! just to make sure!

(i have a feeling my mech plugged it in when going over car, as i think from memory i saw something unplugged but didnt really take much notice)

is there any issues with running it with no O2 sensor for long periods of time? or will it just mean it will run R & R ?

in any case i'd rather use more fuel than have my car feel like its a kangaroo

i'll be getting a Power FC eventually anyway

[SilverECR33]

hey mate, glad u figured out your issue. My brothers VL is now doing it on idle! Eeek. its gotten worse.. Same issue. going to try the o2 sensor tomozza.

[atomaly]

Okay bad news I took it for a longer drive tonight 1hr plus

and the issue is back! I turn the aircon on and I get engine check light come on.

I plugged the sensor back in. Light stays on. Turn the aircon on

and off goes the engine sensor light.

Something sounds dicky with the ecu maybe haha

any other suggestions?

I do know someone who had a similar issue and they replaced

pretty much everything until they got to the ecu and that was the issue!

Where too next hmmm!

[SilverECR33]

ok tried o2 sensor aswell, no change. looking for standard vl turbo ecu to try out.

[Benzino33]

hmm i got the same problem on my 33, but somehow it kinda fixed itself (the shuddering on take off), but the idle heart beat is still there. i just let my fuel run out to real low then put 98 in today, ran a lot better. im thinking of trying this O2 sensor thing, but not too sure..i did change mine about 6 months ago, to a 2nd hand one,if it makes a difference, does that ,mean my O2 sensor is screwed?

[atomaly]

i'm thinking it will most likely be either my sparkers or the coil packs..

its shuddering under load but its a bit erratic and sometimes doesnt happen...... and it definately only happens while its hot!

i'll post back when i've changed the sparkers and checked my coils

i really hope its the spark plugs.... and not the coil packs haha

Edited November 28, 2009 by atomaly

[Hiney]

it has definately fixed my issue. i have done just under 800kms since i unplugged the o2 sensor and have not experienced it since. i decided to just test, so plugged it back in and with in about 5km's it came back. so i will be replacing my sensor tomorrow and leaving it at that

i have also replaced my spark plugs recently with BKR7E plugs and gapped them to 0.8mm. the coil packs are pretty old but seem to be holding up just fine.

[atomaly]

okay got an update of the situation

payed a visit to scotty_nm35 today and cam (iamhe77) was also there!

we cleaned my AFM, and we changed my spark plugs.

now i know for a fact my mechanic told me shit, cos he obviously DIDNT look at my sparkers or coil packs (unless he forgot and just said stock )

i was told platinum plugs, with standard coils.

we opened it up and saw nice blue coil packs.... turns out i have SplitFires, and they are in good condition from what we could tell!

and the spark plugs were copper.. and model NGK BKR5E-11

we put the NGK BCPR6ES (0.8 gap) in! (first time changing plugs for me wh00p)

also found that my ECU boost sensor is damaged, the nipple for the small blue hose is broken off, and the hose was just plugged with a screw.

so i need to get my hands on a new one... anyone have one? (aparantly they cut the engine if the boost gets to high only?? so prob maybe not related to my issue as its always been unplugged)

the BAD news is that what we did didnt fix the shuddering..

BIG props to scott and cam for helping me out! u guys are awesome! i owe u one.

Edited December 6, 2009 by atomaly