sequential issue and going ttc ideas please

right so over the last few months on and off my turbos have been acting up a bit, the old 2nd turbo not coming online, off the throttle bk on and there she blows, so i replaced the iacv few years ago becasue of this issue. I just bought and replaced the egcv, no difference and still intermittent and also find it now dont quite boost to 0.5 and only gets to 0.6ish 2nd tubro. took top intercooler pipes off as were greasy causing them to blow off under boost, cleaned, tighten up great. so i thought right ttc mod now to check as im thinking its a vac leak. car boosts perfect in ttc, 3rpm starts to spool, 4k sees 0.8 or matbe very slightly just under but i think this is due to my intake link pipes are shot, all swollen inside. so am i right in thinking it can only now be another duff vsv or could it still be a vac leak even ttc works great? many thanks

also is ttc safe? fueling wise i mean. ive just pulled the pressue lines off the 2 vsvs and plumbed straight into actuators?

A couple of years ago on mine i had the same issue and it turned out to be one of the vacuum pipes had come off, it was a small U shape pipe and you could stare at it for 10 minutes and swear blind it was connected when in fact 1 side had just come off. My symptom was second turbo wasn't kicking in, if i backed off the throttle a little then it worked fine. I have attached an image showing roughly where the pipe was.

Well I'm in the same boat with my stock car, at present it's in TTC just like the OP's. Same symptoms re the transition.

Scott, ta for the pic will check this area closely. I'm thinking of going through all the pipes, I have spare vsv's but can't be 100% these work fine (will try and test them via the Toyota manuals info). I have everything turbo side spare in fact and off of a low'ish mile car to swap over, ideally for trouble shooting you do one or two things and then retest but that's time consuming and time is at a premium for me at the moment!

For info, mine holds pressure in the pressure tank ok (got a hiss from the back pipes in Scott's pic) so think the tank and lines to it are ok. I think I've replace the ones near the BOV recently ie the easily accessible ones! Be interested to try and help resolve this. I'm happy to try one thing/vsv while someone tries another?

also is ttc safe? fueling wise i mean. ive just pulled the pressue lines off the 2 vsvs and plumbed straight into actuators?

Mine is stock so I think it's fine, just be careful with bpu and the fueling dip at the transition, it could lean out at those rpm's.

Well I'm in the same boat with my stock car, at present it's in TTC just like the OP's. Same symptoms re the transition.

 

Scott, ta for the pic will check this area closely. I'm thinking of going through all the pipes, I have spare vsv's but can't be 100% these work fine (will try and test them via the Toyota manuals info). I have everything turbo side spare in fact and off of a low'ish mile car to swap over, ideally for trouble shooting you do one or two things and then retest but that's time consuming and time is at a premium for me at the moment!

 

For info, mine holds pressure in the pressure tank ok (got a hiss from the back pipes in Scott's pic) so think the tank and lines to it are ok. I think I've replace the ones near the BOV recently ie the easily accessible ones! Be interested to try and help resolve this. I'm happy to try one thing/vsv while someone tries another?

Ditto, will be diagnosing mine very soon.

Well between us we should get there! Let's just keep this thread going with what sorts it for each of us.

Some pointers here (whilst the final cause was some wiring the bits he did test are I think relevant to us)

http://www.mkivsupra.net/vbb/showthread.php?328004-BPU-Supra-Boost-Issues-Solved&highlight=late+turbo

I was having the same issue and it was the iacvvsv. Test it to see of it clicks and of not then it's knackered

Another link to try!

http://www.mkivsupra.net/vbb/showthread.php?143867-4k-turbo-problems&highlight=iacv

- - - Updated - - -

I was having the same issue and it was the iacvvsv. Test it to see of it clicks and of not then it's knackered

 

/QUOTE]

 

Thanks, can you explain exactly how you tested it?

thanks for reply, great stuff. ive replaced all vac lines apart from the ones around the plenum and power steering and also the 2 running down the bk of the engine. all the rest of them are new all round the turbo system/y-pipe etc. my mate reackons just because it works in ttc it could still be a vac leak. my link pipes are also shot. il check that rear pipe later tho . thanks. ps i quite like ttc, like an old school single

Another link to try!

 

http://www.mkivsupra.net/vbb/showthread.php?143867-4k-turbo-problems&highlight=iacv

 

- - - Updated - - -

 

 

 

Thanks, can you explain exactly how you tested it?

When I picked my car up from srd he said if it happens again to just connect a power source to it and see if it clicks. If so it's good, unless it has an intermittent problem. I think it's in the work shop manuals how to do it, mine are packed away but can look next week, but if not check the supra tsrm app

also could it still be an actuator even tho its running fine in ttc, could it be a tired slicking actuator in sequential mode over ttc. maybe !!?

When I picked my car up from srd he said if it happens again to just connect a power source to it and see if it clicks. If so it's good, unless it has an intermittent problem. I think it's in the work shop manuals how to do it, mine are packed away but can look next week, but if not check the supra tsrm app

 

/QUOTE]

 

ta no worries I have the books, just being lazy!!

ta no worries I have the books, just being lazy!!

Will let you do the donkey work then

I had this same problem, very time consuming job to sort out.

Unfortunately I never actually knew 100% what the fault was.

First off I changed the EBV VSV, had no change and still done it occasionally. I then changed all the top vacuums hoses I could get to, whilst doing this I snapped one of the nipples off either the EGCV or Wastegate VSV so changed that as well which after I had done this it seemed to of cured it in the short amount of time I drove it.

I've been doing a load of things on the car with both side of the block off and I have changed every vacuum hose, so when the cars back up and running I should know 100% if it has been cured or not.

The pressure tank has a VSV which a lot of people forget about, not sure if that could be the issue for some.

I did not know the pressure tank had a vsv, I'll have to look on the part program for it. Anyhow I've been using ttc today, very different. One thing I noticed. when I pulled the pressure line off while in sequential mode I got very little air release. Today while in ttc I thought I'd try it, I got a blast of air. Does this mine there is zero leaks? If so where my vacuum going in sequential !

In theory the reason why people do the TTC mod is to see if they have a vacuum leak, even tho pressure is staying in the tank I still personally wouldn't rule it out but I'd start with looking at and testing the VSV's first mate.

I've read in previous threads before saying it runs fine in TTC but they still end up finding a very slight tear in a vacuum hose.

Cheers mate, going to go right through it all, going to changed every single vac hose and check every vsv also going to change the 2 turbo link hoses. Is the carchaoal canister anything to worry about leak wise or is it just vapour, thanks

In theory the reason why people do the TTC mod is to see if they have a vacuum leak, even tho pressure is staying in the tank I still personally wouldn't rule it out but I'd start with looking at and testing the VSV's first mate.

 

I've read in previous threads before saying it runs fine in TTC but they still end up finding a very slight tear in a vacuum hose.

But the car boosts great in ttc, if there was a vac leak wouldn't it not?

The car boosts later in TTC, all of the noise of a single turbo with non of the power.

The car boosts later in TTC, all of the noise of a single turbo with non of the power.

that's how TTC is to some degree yes, in this case it's useful to determine the turbo's are not gone and also stop any over speeding/stressing of the 1st turbo if the vsv's etc are malfunctioning to some extent.

We are all trying to get away from TTC via this thread!

that's how TTC is to some degree yes, in this case it's useful to determine the turbo's are not gone and also stop any over speeding/stressing of the 1st turbo if the vsv's etc are malfunctioning to some extent.

 

We are all trying to get away from TTC via this thread!

I'm not denying it's usefulness for diagnosing faults with the complex sequential system, when supraGZaerotop mentioned it boosted great in TTC I though he might have forgotten how the OEM set up felt

I did not know the pressure tank had a vsv, I'll have to look on the part program for it. Anyhow I've been using ttc today, very different. One thing I noticed tho was when I pulled the pressure line off while in sequential mode I got very little air release. Today while in ttc I thought I'd try it, I got a blast of air. Does this mine there is zero leaks? If so where my vacuum going in sequential !

This means you dont have a vac leak, if you left the engine off for abit before you tested, the vsv that you pull the pipe off is often the cause of 2nd turbo coming on late like 5000rpm

switched car back to sequential last night ready for today. have since tighten some hoses which were tight enough anyway to be honest. mainly all ive done since ttc was change a couple of small vac hoses around by turbo boost sensor, and i thought id spray some gt85 in to the egbv and let it sit over night, took car to work this morning, initially it was the same, few miles down the road i tryed it, noticed 0.5 first turbo solid & gave the throttle a good shove and was getting a soild 0.8, was shocked! not holding my breath but will see how it goes, wondering if running in ttc could it have freed something up? or did the gt86 in the egbv do anything. will keep updated

only i will say is, just how is the turbo system suppose to work in how it delivers its power, meaning when i build the revs slowly to 3.5-4k it still dont come online, i mean driving like miss daisy to 4k now, no matter what engine speed your doing, at 4k is it suppose to boost? because the way my sequential mode runs on my car is, first turbo genrates about 0.5 unless im pulling off low revs then its about 0.3-4, and if i give the loud peddle a decent shove its now boosting 0.8+ but no more than 0.9.