At the end of last article – way back in May 2023! – we got our project Celica GT4 back on the road, warranted and registered.
To be honest, since then our project GT4 has sat in the garage for well over 6 months, and the WoF ran out. Time has not been our friend, but early in January, I decided it was time to drag the car out of the garage and take it for a WoF check.
I was informed that the car had driven 25km since its last check and sadly that sounded about right. We need to get this car out more and use it! After it (thankfully) passed, I took it for a reasonable drive. To start with, it wasn’t happy; there’s some jerkiness in the drivetrain between 3-4000rpm, and the car just didn’t feel right. But after 30km of driving, it was feeling a whole lot better. The jerkiness was still there, but not as bad. Mile after mile, the car felt better.
By this point in our project, I had honestly thought I’d be into prepping the car for painting, or something other than mechanical issues. But no, this whole article is about mechanical issues on our 1993 Toyota Celica GT4.
Project Car: 1993 Toyota Celica GT Four | Clutch adjustment
One thing I really need to do is adjust the clutch. It takes up almost at the floor and makes it very difficult to drive the GT4 smoothly. I hate that. On checking out some YouTube clips, I see that even though the car has a hydraulic clutch, Toyota fitted an adjustable rod under the dashboard. That’s the good news; the bad news is you have to be a yoga instructor to get to it. Once home and in the heat of a January day, I had my head under the dash and my legs up and over the headrest. Trying to see what I was doing was less difficult than trying to get my arms in there to loosen off the adjusting bolt.
Sadly, with scrapes on my hands, adjusting the clutch made zero difference, so I crawled under and adjusted again. After another test drive, still no difference. I shouldn’t admit to this, but I then realised I’d been adjusting the clutch switch, and not the actual pedal adjuster. Doh! Once I adjusted the rod, the clutch was 100% better, and the car much smoother to drive.
Another sunny Sunday, I took the GT4 to Remutaka Forest Park for a drive to see how the GT4 was feeling. This would be the furthest I had driven the car (not joking), as I’ve been a bit cautious about its reliability up until now. That Wainui Coast Road is a great test of a car’s handling, and while it may be 34 years old, the GT4 does bloody well on the twisty bits. That engine is still underperforming below 3000rpm but once that turbo kicks in it goes pretty well, I thought. I’ve ordered a boost gauge to chuck in the car; gut feeling is there might be a wastegate issue, as it should have more pull than it does.
Still, I was really happy with the car, and after that one drive, and felt I could drive it anywhere and get there, and back. That was a milestone moment.
Another day in the garage, I decided to pull the spark plugs just in case the jerkiness is related to electrics and not fuel. All the plugs look almost new, they are Platinum and are supposed to last for 100,000km, so I won’t be replacing them. On the other hand, the spark plug leads look decidedly dodgy, so I’ve ordered a set of those. I’ll replace the coil at the same time, since it’s only $30. I thought the shunting around 3,000 might be a fuel filter issue, but probably not since the car picks up and goes after 3,000rpm.
My boost gauge arrived and I checked it in to find I was getting a maximum of 2psi of boost, and not the 10 or so I should be. I think I found the performance issue!
Project Car: 1993 Toyota Celica GT Four | Wastegate jammed
On talking to a Toyota MR2 owner who has the same 3SGTE engine in their car, they felt the issue with performance might be down to boost, so one day we removed the O2 sensor on the dump pipe and put a bore scope down there.
His thoughts were confirmed – we could see the wastegate was jammed open, letting out all the turbo’s boost. Our GT4 has had a replacement Kinugawa CT26 turbo fitted, with a standard Kinugawa wastegate. That wastegate is adjustable but getting to it? Almost impossible. It’s behind the turbo, close to the engine block. There is zero chance of removing the wastegate’s arm and adjusting it, and besides, I need to find out why it is jammed.
You know what that means? To get to the wastegate, I’d have to remove the dump pipe, turbo and exhaust manifold. To get to those parts means removing the lower engine covers, radiator, alternator and a whole lot of other bits.
That’s not even all the parts I had to remove to get to the wastegate, but it had to be done. You can see the valve cover in the photo; obviously, I didn’t need to remove that, but while waiting for new gaskets to arrive, I decided to remove it, sandblast it, and paint it. Previously, someone had tried to repaint the valve cover with it in place and only managed to get silver overspray everywhere.
Back to removing the turbo etc. It took me four hours on my own to finally get it out. For example, there are two nuts under the exhaust manifold holding on a heat shield, and you can only get one nut out. The other one has to be wiggled down bit by bit while removing the exhaust manifold, so you can actually get to the nut.
Then there is the banjo bolt on the engine, holding on the turbo’s oil-feed pipe. Someone – possibly at the factory – had torqued this up to Herculean numbers, and I had to get a very long power bar on it to crack the seal. What a mission.
But in the end, I removed it all from the engine bay and took a look at the wastegate. It still wasn’t budging, so I removed the dump pipe to reveal the wastegate and found it had been jamming against the gasket. Such a great feeling to know what was going wrong. But that wasn’t all; I could also see marks on the side of the dump pipe where it had been scraping. I’d need to grind that off a bit to make sure that wasn’t going to happen when it all went back together.
So essentially, that was it. I was pretty confident of knowing what had been happening, and those who troubleshoot car issues will agree that’s most of the battle won, right there.
I had already heard over and over on the New Zealand GT4 Owner’s Facebook page that you should only use a genuine Toyota gasket for that turbo to dump pipe join; aftermarket gaskets are fine everywhere else, but if you replace this one with aftermarket, it will blow in six months. So I ordered one, but they are only available ex-Japan and would take about six weeks to arrive. The genuine gasket is around $100, so not too bad for cost.
Project Car: 1993 Toyota Celica GT Four | Engine bay tidy
That was fine by me; one of the things I’ve been meaning to do with our GT4 is tidy up the engine bay, so that time would allow me to do that. Not only sandblasting and painting some brackets and things like the valve cover, but close to the engine block and near the turbo are the “heater hoses from hell”, as they have been named. It’s a suitable name; you can only get to these two hoses by removing all I had just removed. Would I be replacing them? Hell yes! I do not want to go through this process again in my lifetime. I found a set for $50, a bargain for my peace of mind.
While restoring the valve cover to its original glory, I hunted down new gaskets. In a stroke of great timing, Repco were offloading some, so I got the main rubber gasket for $16, and the smaller rubber gasket between the spark plugs for $6. I bought two of each, so have spares if I need them. I also ordered some new valve cover bolt sealing washers; this time it was Supercheap with them on special, for $12 for the set. I also went off to that excellent store of Coastal Fasteners. I don’t know if Wellingtonians know how lucky we are to have a place like Coastal Fasteners, where you can go buy just a single nut. They have so much stock of nuts, bolts, screws etc, and a whole lot more. I got some Allen-key bolts for the valve cover; the existing Philips head screws were thrashed out and looked terrible.
While mucking about with the valve cover, I found a weird thing in the middle of it; a hole with a steel mount that sat inside, and I couldn’t work out what it was. A quick check on the GT4 Facebook page told me it was for the throttle body mount bracket to bolt onto. I didn’t have the bracket, so I went hunting in the boxes of stuff that came with the car, and couldn’t believe it was there. A quick sandblast and paint, and it was ready to go back into place.
By the way, if you’ve ever been tempted to buy a sandblaster but weren’t quite sure if it would be useful – it is. Mine is not a huge cabinet, but it is one of the best things I ever purchased. No more sanding with paper for hours, and then getting lines in your paint. That throttle body bracket took less than a minute to sandblast and came out looking great. Nuts and bolts? A quick sandblast removes rust etc in seconds. They come out looking like new.
Another thing I wanted to do was to replace all the exhaust manifold and turbo to dump-pipe nuts, as well as the nuts between the exhaust manifold and the turbo. I got genuine Toyota ones for all these, and they were not ridiculously priced.
While still waiting for the turbo gasket, my heater hoses from hell turned up and took minutes to install.
Project Car: 1993 Toyota Celica GT Four | Reassembly
At last that genuine Toyota turbo gasket turned up, so I started to put everything back together. That new gasket didn’t hit on the wastegate at all, so that was a great start. I had already ground a little of the dump pipe away, so the wastegate was not jamming on the side of it. But the wastegate was hitting the dump pipe at full extension of 90 degrees.
I was sure this was going to be an issue, so did some light grinding of the dump pipe – but it still hit when on full extension. On and on I went with no luck. Since our GT4 is fitted with an after-market dump pipe, I went and got the original cast iron dump pipe and attached that to the turbo – and the wastegate arm still hit on full extension.
In a “doh” moment, I wondered if it actually needed to go to full extension, and it doesn’t. I had wasted a lot of time for no reason. I found this out by attaching the wastegate arm and setting the preload as per the Kinugawa video.
Once the preload was set, the arm didn’t reach 90 degrees and didn’t hit the dump pipe, so I could go on putting it all back together. After reattaching the exhaust manifold, it was time to get the whole unit into the car. Apparently – and I have to agree – the best way to work on the turbo etc on this 3SGTE engine is to remove the dump pipe, exhaust manifold and turbo as a single unit. That sounds good, but it’s bloody heavy to lug around. I can’t imagine how heavy it would be if using that original cast iron dump pipe.
I carried it over to the car and tried slipping it into place. A lot of wiggling, but no. The studs for the oil feed pipe were hitting the oil feed pipe and I couldn’t find my torch to see what I could do, or what I needed to lever to make it slip down home. It would have to wait until tomorrow.
Another day and for some reason, the entire unit decides that yes, it will go into place today. After months off the road, I start putting all the hoses etc back on and, without putting the radiator back in, start the car up – just to make sure it will start. It does, and the idle is perfect. I continued on, getting the radiator back in but no alternator yet, and start it again, and no water is spurting out yet. A good sign. Everything goes back into the car, and it’s time to go for a drive and check turbo boost.
There is no change – I am still only getting a max of 2psi of boost. Can’t write the words I said, but basically I closed the garage door and walked away, as most people would. The next morning with new enthusiasm, I removed the vacuum lines from the wastegate actuator to see if I would now get full boost, and I do! At last the car is getting the amount of boost it should, although it’s still gutless below 3,000rpm, struggling to even get up hills.
So it seems like perhaps it’s the VSV unit, that controls the wastegate? But then in a moment of clarity, I put the intercooler back on, the one that came with the car but was fitted with a blow-off valve. I left the BOV disconnected so it was shut and went for a drive – and got full boost, with the vacuum lines reconnected to the wastegate actuator.
Progress! At home, I blew some compressed air through the ‘old’ original intercooler and some brown specs of something came out, but no idea what it is. The intercooler is really just a 2” pipe that goes through a radiator, so highly unlikely that anything could jam it up – but something has.
But now I have a new issue. There’s an exhaust manifold leak and I feel I need to get this sorted before I muck around any more with intercoolers. Of course, it’s coming from the left side of the head, under the alternator. The only way to get to that nut is to remove the belt and take the alternator off. So I do and find the nut not quite tight. Problem sorted, I go for another test drive, and still there’s a bad exhaust leak.
At home, I can feel the leak coming from the same place, so again, remove the alternator and try retorquing all the exhaust manifold nuts to factory spec. Starting the engine with no alternator on, and the exhaust leak is still there, and it’s bad.
I look over everything again, trying to figure out how to fix this – without having to remove all the turbo, dump pipe etc again. But, there is no way. So again, I removed the whole exhaust manifold, dump pipe and turbo.
Well, I would, but again the oil feed pipe to the turbo is stopping the whole unit coming out as well. I decide to remove the banjo bolt on the block, that feeds oil to the turbo. I had already had this off previously and had tightened it up to factory specs, but now it just won’t move, even with my biggest power bar on it. I can’t get my rattle gun in there as a socket extension won’t slip past all the pipes etc.
Eventually, with a lot of whacking, the banjo bolt loosens up and is removed, and yet the whole exhaust manifold/turbo/dump pipe will not come out. It’s another day of closing the garage door, and looking at it next weekend.
My next attempt on the next weekend, and for some reason, the whole unit comes out very easily. Looking at my barely used exhaust manifold gasket and one side has separated. Luckily I had a spare, so put this on and go through the long process of getting the whole turbo/dump pipe etc back into the car, and torque the manifold nuts up to factory spec.
Time for another test drive, and my exhaust leak is fixed. That’s one problem sorted. While the car is definitely getting boost over 3,000rpm, below that, it’s still a bit of a dog. On a light throttle opening on the flat it’s just fine, but try and go up a hill or give it a little more gas, and the engine starts to shudder. Not only that, but there’s now a water leak somewhere, and since there’s zero room in the engine bay, I can’t actually see where the leak is coming from.
For the performance issue, after a discussion with some knowledgeable 3SGTE owners they suggest it’s worth trying out a Map Sensor and also the Air Flow Meter (AFM) – our model of Celica GT4 with the 3SGTE engine has both. I borrow spare units that are known to work ok, and they are an easy thing to replace – but there is no difference to the car’s performance under 3,000rpm.
Clutching at straws now, and we’re keeping thoughts of a vacuum leak out of our minds. There are so many vacuum lines on this engine, it’d be like finding like a needle in a haystack trying to locate a leak. I check the engine’s timing at idle, and it’s set at 8.5 degrees, where it should be 10 BTDC. That’s not enough to make a real difference to the performance issue we are seeing, but it may be worth fixing that anyway. And then, someone asks if I have bridged the TE1 and E1 terminals before checking the timing. I had no idea! Apparently, unless you bridge those two terminals on the diagnostic block in the engine bay, you can’t set the base ignition timing.
On doing this, the timing didn’t move more than 1 degree, but I set it correctly anyway, in the hope that this would fix my low-down lack of performance. A test drive shows no improvement, but it does show the water leak, and it’s a lot worse. On getting home, I can see a spray of water, meaning at least that I could now trace the leak to its source.
I do that, but while it’s not one of the heater hoses from hell, it’s just about as bad. No, I don’t have to remove the turbo etc again, but the AFM and so many other hoses and bits have to be removed to get to this water bypass hose:
I do get to it eventually, but it’s got such a sharp angle on it, the spare (straight) new water hose I have kinks when I try and use it. That means hunting at somewhere like BNT to find a replacement, and that means another weekend where the GT4 is not running.
Project Car: 1993 Toyota Celica GT Four | What now?
I’ve been adding to this article on, and on, and on – hoping to end with some good news. But at the moment, there’s no good news other than I have turbo boost, but the car is otherwise almost undriveable. It simply won’t go up a hill unless it’s running boost, and sucking a lot of gas. Since Wellington is pretty much hills everywhere, that’s not a good option, as I’m not keen to keep the oil companies in profit just to drive the GT4.
So I am going to stop here, and next time I pick this up, there will be far better news – I hope.
