help: 3sgte boost / "hesitation" at multiple point

[TWSTD]

Car:
1997 caldina GTT 3sgte

Mods:
running stock turbo @ 0.9-1 bar exhaust/filter/ FMIC/platinum plugs/ blitz dual SBC boost controller.

Problem:
My car seems to have developed a boost related issue. If you say floor it when boost comes on you feel multiple "hesitation points" throughout the rev range - maybe 5 or so times between 3500 and 7000 rpm? Almost like someone tapping the brakes. This is what i would imagine the ecu whacking heaps of ignition retard would feel like. Car also feels more slugglish than usual.

Possible causes:
The short section of hose blocking off the other WG actuator port recently came off and before i had realised this had occured i planted my foot a couple times and boost rocketed twice to 1.7 bar and i hit was i assume was fuel cut (vsv disabled so i cant have been boost cut right?) Could this have damaged the knock sensor which is now causing the above described problem? Note there is no engine check light on.

What timing aye - was gonna go put the thing on the dyno tomorrow morning


Anyone got any suggestions?

AL

[anthonym]

Sounds like an ignition problem. What plug gaps are you using?

Opening the second wastegate port to atmosphere effectively disables the wastegate alltogether but it's unlikely that this is the cause of your problem.

[TWSTD]

I cant recall but about 0.8 i think on the plug gaps.

Reason i suspected possibly the completely disabled WG could have caused the damage was through the high boost that it ran untill the ecu cut the fuel on those 2 very short occasions might have damaged the knock sensor?

[vvega]

just sounds like a knock sensor pull back
ive been thogh this issue a few times now
they get damaged or just fault out
there wont be a ecu light for it less its attually dies
otherwise it will just pull timing

could also be your knock sensor is fine and just doing its job
bad fuel ??
timiing incorrect
or even a big end knock developing

you may have damaged your delicate turbo shaft and now its grabbing

hell it could even be a wiring fault(hardest one to diagnose)
ive had that before too
sorry if ive been no help
but there are a few issues
just go though them systematically

v

[vvega]

I cant recall but about 0.8 i think on the plug gaps.

Reason i suspected possibly the completely disabled WG could have caused the damage was through the high boost that it ran untill the ecu cut the fuel on those 2 very short occasions might have damaged the knock sensor?

boost cut is done off the map
so yes you will still have it
and i doubt its killed ya knock sensor
more just a unpleasant coensidence

[Al]

Sounds exactly like what happens to my car when I've been for a spirited drive with our crap fuel.

You stamp on the gas and it hesitates then jumps in increments, afaik its just the ecu has pulled a huge load of timing.

[Twolitre]

It's quite common for old nissan coilpacks to split on the tubes and cause misfires, I highly doubt this is the case for you but might be worth a look to eliminate it as a possibility anyway.

[Farmer_dave]

Im with Al
Sounds like what my gt-t di when I ran it on crap fuel.

[TWSTD]

I run her on 98 the whole time aye... maybe i shd try a bottle of octane booster n see if it stops it?

[Al]

I run her on 98 the whole time aye... maybe i shd try a bottle of octane booster n see if it stops it?

octane booster is a waste of $$$$$, go tolulene, if that doesnt solve it, check ignition

[Farmer_dave]

Has it just started doing it? Bit strange if it has, bad batch of fuel maybe?? Mine did it when I ran it on 91. I thought that was detonation

[YeMs]

have u checked your fuel rail pressure etc? it could b sumthing as simple as a blocked filter or line? injectors all performing their task? could have sum extreme shitty fuel :S maybe its link plus and dyno time

[Al]

maybe its link plus and dyno time

you need something better than a link plus to run a gen4 3s

[TWSTD]

im pretty sure its nothing to do with fuel rail pressure - it doesnt feel like blocked injectors either - its more predictable. Maybe its a bad batch of fuel - who knows - frustrating tho - ill def just drive her real gently for at least this tank of gas.

[matt dunn]

im pretty sure its nothing to do with fuel rail pressure - it doesnt feel like blocked injectors either - its more predictable. Maybe its a bad batch of fuel - who knows - frustrating tho - ill def just drive her real gently for at least this tank of gas.

Yeah i'd say just use it till it' almost out of gas and try some new stuff.
Start with the easy cheap thing first.

[HERGTT]

If you say floor it when boost comes on you feel multiple "hesitation points" throughout the rev range - maybe 5 or so times between 3500 and 7000 rpm? Almost like someone tapping the brakes. This is what i would imagine the ecu whacking heaps of ignition retard would feel like. Car also feels more slugglish than usual.

Hey Al.....my GTT started doing the exact same thing today, and we(well Aaron) reckon that it is probably the spark plugs. They were already near the end of their life and I guess putting it on the Dyno yesterday used up the last bit of juice - SO....new spark plugs will be put in tomorrow - I'll let you know if there is any change with doing this.

The same thing happenend in Aarons RS, and the cause of it was incorrect spark plug gap, and the plugs were too cold. (Hotter plugs are needed for lower boost, Colder plugs for higher boost).

Mellissa

[TWSTD]

Interresting - let me know how ya go with new plugs....

Im running NGK iridium 8's with a 0.8 gap from memory....

[MrBob]

definately change you plugs (just chuck a cheap $15 set into verify). Your "high boost" run will most likely have cause some detonation and excessivly high temperatures... which has quite possible damaged your plugs

my 3sgte has done exactly the same thing many times when the plugs are nackered.

[MrBob]

Im running NGK iridium 8's with a 0.8 gap from memory....

further to my previous post... they may just be fouled. I ran these plugs for a while but they are too cold for the amount of boost you are running. Mine constantly fouled up and caused missing and hesitation... a 7 maybe a better choice.

[TWSTD]

i have some iridium 6's at home already that came with the car - will put those in tonite n try em out. I do have my suspicions re the plugs being the cause however as it is ONLY when im at about 0.3 bar boost or above that this problem occurs and does not seem rev related at all (i can happily rev to 6000rpm slowly without any sign of the problem).