GTT Knocking

[BZG Wagon]

I have a GTT which intermittently knocks between 3000rpm and 4500rpm under boost. I'm using 98 octane, the plugs look sweet and I'm at a loss to what else could be causing it. Normally the knocking is at its worst the first few minutes after the car has just started.

It also occasionally surges - badly if the engine is cold (on the odd occasion I have done that), otherwise it will feel like boost is patchy through the rev-range.

I've taken it to Albany Toyota twice but they have failed to identify it both times & their last response was if it doesn't go away, learn to live with it; its NZ petrol. However I'm worried that it could be damaging the engine over time and I don't know any other GTT owners personally who have the same issues .

Alternatively can anyone recommend a good mechanic in Auckland that could diagnose what the issue is?

[Santa'sBoostinSleigh]

have you got a boost gauge?
what boost is it running?

[BZG Wagon]

No, I don't have a boost gauge unfortunately.

[WCKWGN]

have you even installed a boost controller to it yet or is it only running at factory boost ?? 9 - 10 psi

is it something with the oxy sensor possibly and that once the engine warms to temp that it is adjusting the fuel/air mix correctly, but when cold not get the right mix??? had a similar prob on my 1990 gtr celica, and if you have driven it there to get the prob looked at , only that it happens but it only on cold starts?? i got a 97 gtt and no worries with engine with running heaps of boost on factory internals

in dunedin we only have had 98 available for 2 years now so i had to run mine on 96/95 for 3 years and the ecu's were orginally meant to be run on 100 octane in jap land so i doubt crap fuel theory on a 255hp engine on 98 octane, could just be the way it is getting mix by the ecu which if you have a stuffed oxy will be giving false readings and would give a similar problem.

diagnostics test on cold engine... or start the wagon and leave till has warmed to safe temperature for hot road running levels and take it for a skid on boost through the rev ranges to to see if the prob has gone or still exists

or your engine is pooped and you may become a member of the dead 3sgte engines



tried mr revhead he very very knowledgeable on things ?

good luck

[slighty_sykotic]

Think you will find the oxygen sensor is purely for crusing, and will not adjust mixtures during WOT or when its cold etc.

Doubt its the oxy sensor.

I'd plumb in a boost gauage, check the boost, and go from there.

[strx7]

have you even installed a boost controller to it yet or is it only running at factory boost ?? 9 - 10 psi

factory boost on a GT-T is like 14psi.......

[Santa'sBoostinSleigh]

yes factory boost is 0.9-0.95 bar from memory (which is about 14psi)
not that most caldinas will see this on a daily basis due to fuel etc

but anyways, if you get surging boost, you better hope its not freeboosting, otherwise you WILL join the dead 3SGTE society
take it easy until you know what boost levels you are running

i had a problem where the wastegate actuator had perished, and basically was not opening the wastegate
symptoms were: surging power/boost, no boost cut etc

if this in fact is the problem, and you keep driving around with your foot flat down, you basically will blow your motor

[99gtt]

have you even installed a boost controller to it yet or is it only running at factory boost ?? 9 - 10 psi

factory boost on a GT-T is like 14psi.......

The boost on a factory caldina is 10.7 psi you will only see 13 - 14 psi with exhaust mods

[strx7]

on a thread a few months back a number of people who own caldina's said their factory boost - with no mods wasaround 14psi. perhaps they all had wastegate problems???

[Mr Revhead]

iirc they peak around 13-14psi and drop back, and i also think they run to different boost depending on the gear, at least the auto ones do...
im sure its been discussed on here before

[Stu-]

Haven't seen mine hit 14 before, gets to around 11-12 max and it has to be pretty well loaded up.

[AJz]

iirc they peak around 13-14psi and drop back, and i also think they run to different boost depending on the gear, at least the auto ones do...
im sure its been discussed on here before

yea thats what mine does, and thats with 2.5inch system. wasnt really much different when stock either.

[BZG Wagon]

yes factory boost is 0.9-0.95 bar from memory (which is about 14psi)
not that most caldinas will see this on a daily basis due to fuel etc

but anyways, if you get surging boost, you better hope its not freeboosting, otherwise you WILL join the dead 3SGTE society
take it easy until you know what boost levels you are running

i had a problem where the wastegate actuator had perished, and basically was not opening the wastegate
symptoms were: surging power/boost, no boost cut etc

if this in fact is the problem, and you keep driving around with your foot flat down, you basically will blow your motor

Scary Sh*t. Thanks for the replies.

I initially had a problem with the sensor running into the cold air box (the mechanic who did a pre-purchase test broke one of the wires). Similar symptoms, knocking, patchy boost etc but after fixing this it almost went away - from knocking under any level of acceleration to the issues I have now.

I guess the question now is where to from here?!? A mate at work reckoned I should send it straight back to Toyota and tell them to diagnose it properly. I just spent $800 on getting the waterpump and cambelt done and he said the car shouldn't have come back running the way it is. Im wondering if it could be an issue a bit out of their league? Maybe I need to take it so a specialist of some sort?

What ever the problem might be, is it something a fancy diagnosis machine is likely to pick up? How hard would it be for a mechanic to check what boost its running?

Oh yea - no boost controller, no boost gauge, factory exhaust and air-filter. Car was running fine the night before I had a pre-purchase check so I've been hoping its something simple, and not a coincidence the whole thing turned to mud the day I bought it.

[strx7]

sounds to me like a sensor or something is either unplugged or faulty or something along those lines

[cynakyl]

yeah boost on cal's is funny. I think fivebob figured it out to being poor boost algorithms or something like that and you need a really good (read hks etc) multi stage boost controller i think to fix it. My caldina is completely factory and it peaks at nearly 15 and drops back to 12.5ish or thereabouts...