2jzgte - strange surging boost when cold

[PlacentaJuan]

lately i have noticed my car acting funny, especially after cold night and trying to drive it in the morning.

the expected boost isnt there, and if i keep my foot into the 'boost zone' or increase throttle it will come on suddenly and surge and after i close throttle it will happen again, until the car is quite warm (5-7mins of driving.)

i never drive hard when cold so its only ever the first turbo working (stock sequential system and stock boost on first turbo)

its like the boost is taking an extra second or two to come on, and when it does it comes on a lot more suddenly than normal, it feels like the engine is even about to stall but this maybe because of the loss of expected power.

in the zone before the spiking, the engine seems to rev freely and normally.

the only 2 major things that have changed before this was happening is:

1/ high pressure hosing the engine bay at car wash. i didnt directly spray wires or solenoids but im sure everything got wet.
i noticed something similar happening after driving away but since i knew there was likely to be water in the system i didnt boost the engine until i was confident the water had evaporated (about 20mins of driving) and then everyting was fine. - this was about 3 weeks before the spiking problem

2/ changed oil brands. from shell ferrari crap to cheaper nulon brand(both fully synthetic bro) have noticed that the nulon oil seems to change colours a lot more quickly (go black)


another thing is that i am using a colder spark plug range, (iridiums) which are probably coming up to 9months old now. i noticed when i first installed them that the engine was kind of stuttery when boosted cold, but this went away after about 2 minutes of warming up, the car drove fine when off boost though.

because the engine revs freely i have ruled out fuel pump/fuel problems.

if the turbo was siezed it would stay siezed even when hot? so i have ruled out turbo problem. (maybe sticky wastegate acutator on second turbo?)

any ideas?

[The Count]

i got the same prblem
i noticed it when i did a service i used a slightly thicker oil for the hotter weather 15-40 instead of 10-30

[PlacentaJuan]

i havnt checked the oil thickness, the shell is 5-40 and the nulon is 10-40, what does that mean im easily confused by oils.

do you think the thicker oil may be stopping the turbro from spinning freely?

[The Count]

maybe
but im half way thru a single conversion and the front turbo was chipped on one of the blades

but honestly from having a quick 1JZ soarer before i put the 2jz in my merc the best oil is mobil 1 ..10-30 3 litres of that and 1 lt of lucas oil stabilizer

last service i was kinda broke and used nulon 10-40 it was crap

[Draven]

err, doesn't the 2j take more than 4l of oil?

how does it drive off boost? I've had vaguely similar symptoms in 2 past experiences.

1 was caused by the timing belt slipping a notch - drove like a pig down low, came on strong after a lot of hesitation once boost hit.

The other was when the 2nd turbo was in the process of eating itself. Everything was fine off boost and below the threshold for 2nd turbo coming on. When 2nd turbo should come on there was the same hesitation, followed by a bit of a sputter then suddenly a LOAD of torque up to normal boost/power levels. Perhaps an inspection of turbo #2 is in order?

[brett_celicacoupe]

this is funny actually


my front turbo wastegate is seized open

by seized i mean takes 5mins to close after fully boosting it.

this situation very much gives you the symptom you described. in my case it was fully open and while in sequential mode it wouldnt make full boost until 6krpm

for the time being im running it in true-parallel mode. it probably lags a little more then it should but i dont have time to fix it at teh moment.

ive been trying to figure out how to lube the shaft without disassembly of the entire car. i was thinking spray the shaft as best as possible then connect the wastegate reference line to the manifold so the vacuum pulls it closed

[PlacentaJuan]

yes my 2jz fills up to the half way mark on the dipstick with a filter change + 4l of oil.

since the car is cold i dont boost it enough to engage the second turbo, the hesitation is happening well before that. i havnt been flooring it until the car is warm either way and dont think i would like to even for a test.

the front wastegate (no1 turbo) is only active once the both turbos are online so it shouldnt affect anything while the car is in the rev range for the no 1 turbo only...?

while the car is in sequential only using the no 1 turbo, its the no 2 wastegate (pre-spool valve) that ocntrols the boost for no 1.

that is an idea though i will run the car in TTC mode for a while and see if this changes anything.

also the problem goes away completely once the car is warm, but im not sure how to interperet this.

[brett_celicacoupe]

the front wastegate (no1 turbo) is only active once the both turbos are online so it shouldnt affect anything while the car is in the rev range for the no 1 turbo only...?

unless the no 1 wastegate is still partially open from the last boosting event.

[PlacentaJuan]

yea but this problem happens when the car is cold and been sitting in the garage/driveway/carpark all night.

unless maybe its not heat that would be unsticking it but the application of pressure - ie trying to actuate it as i drive unsticks ot or something.

coz i allways give the car a bit of a boost before i get TOO close to my house then i just idle it to cool down.

well if no1 is sticking then it should still do it on TTC (not too keen to boost the car to 17psi though) but ill see how it goes.

[big_zop]

5-40 refers to the viscosity of the oil. 5 is for 'low' temp and 40 for 'normal' operating temp.

What these different temps are is dependent on manufacturer for which they might tell you if you ask - probably something mentioned in that 'optimum oil temp' thread (will post a link if i find it). but i can tell you anything you want about the additive that is used to change that value if you want.

[-GT-]

I think you're potential issue no 3 in your first post warrants some checking; you said this started (or similar symptoms) after going a range colder on the plugs? And the issue goes away once the engine is warm? Does it feel like it could be missing as it comes on boost?

Might be worth chucking another set of the original plugs in to see if it goes away? Quick and easy to rule out at least.