Hiro Protagonist

Don't think the idle speed is meant to be manually adjusted via the screw on a 7AFE.

Owning a 90s FWD Toyota does make me practically invisible to the cops even with an almost certainly illegal exhaust, lowered, 17s, personalised plates, and spotties in my front grille (an actual factory option, just only in Europe) Been driving for almost 15 years and I've only ever been pulled over for an RBT (as in by a cop driving around) once, and that was because I chucked a u-ey outside a pub (was picking people up). Numerous roadside booze-bus ones though (and passed all with flying colours, because I'm a good boy) but also driven past plenty too without being waved in. Car has never been searched, not even so much as had the bonnet lifted or ride-height checked.

If it goes away for good, then yes it was most likely the cause :P If not, them time to keep ticking things off the list. I do notice a little flat-spot just off idle in my 7A, the old shell was worse though and could possibly be a stretched throttle cable, check to see if the butterfly moves straight away when you press the pedal or if there is a slight delay from a loose cable (you do need _some_ slack there, but not much).

Another possibility is that the plates have been flagged for whatever reason (noise complaint, used to be owned by a hoon etc etc) so the cops automatically pull it over whenever they see it.

The older systems use the wax-pellet valve (or a bi-metallic strip), newer ones went to a thermoswitch sender and a rotary valve. The newer valves also control all the idle-up functions too so can adjust for air-con, power-steering, electrical loads etc etc, they also don't tend to have an idle adjustment screw (unlike the old "dumb" systems). They get called different things depending on the engine (cold-idle valve, aux air valve, idle-speed control valve etc) but they all do the same job - open up an additional passage through the throttle to let extra air in to the engine when the throttle blade is shut. Another thing is that maybe we have different definitions of "hunting" or "surging" idle speeds. To me, any idle speed that doesn't stay stabilise is "hunting", even if it stays at a particular rpm for several seconds.

How much did they charge to do the seal? I probably should have done mine when I did the CVs (just because I had free access) but didn't have the time to order in new seals, it's a relatively simple job.

The easiest way to determine if it is an idle-valve issue and not a vacuum leak is to take the intake pipe off to expose the throttle body, and then stick your finger over the hole for the bypass whilst the engine is warm and idling. If the idle stops surging then the issue is in the ISCV (and either a faulty valve, sensor or air bubble), if it continues then the issue is a vacuum leak downstream of the throttle (or with the MAP sensor or TPS).

For a 4AGE, there is no temp sender for the cold idle - it is literally a wax-pellet valve like the thermostat which opens and closes a bypass passage in the throttle body to up the idle. I personally have fixed a hunting warm-idle problem in a 4AGE (a bigport in my wife's old AE82 Twincam) TWICE purely by bleeding the cooling system AND NOTHING ELSE. Over the years of being on forums and Facebook I have seen countless other times when a hunting or high idle problem for those engines has been fixed by bleeding the cooling system (and it is really noticeable on 4AGEs due to the big difference between cold and warm idle speeds). Remember too that an air pocket might be stationary when the engine is off, but when it is running and coolant is being pumped around things get stirred up, which can result in intermittent contact between the coolant and the wax-pellet/sender/whatever. Usually it is a persistent high-idle that doesn't drop when the engine gets warm (also symptomatic of the wax-pellet valve dying of old age and being stuck permanently open, like a dead thermostat) but it can cause surging if it is borderline. It is actually a slightly different cause compared to a vacuum leak one (which is extra air causing the idle speed to rise about the ECU's preset limit causing it to pull fuel out) but can be hard to differentiate if you don't know exactly what to look for. Yes, other issues such as a vacuum leak or faulty sender/valve can also cause similar symptoms (and I'm not discounting any of them in the slightest), but the air-bubble trapped in the throttle body causing inconsistent/high idles is something that is common across most of the transverse A-series Toyota engines (moreso in MR2s but Twinkies/SXs do suffer it too), and it is almost always suggested as the first answer because it is free, easy, doesn't require any disassembly, and is very common especially when people also have coolant leaks or have recently replaced a radiator/thermostat/hose/etc and introduced air in to the system (in my wife's case it was both - air was in the system after fixing a leaking water outlet on the end of the head and replacing a heater hose that had burst).

For a 4AGE, there is no temp sender for the cold idle - it is literally a wax-pellet valve like the thermostat which opens and closes a bypass passage in the throttle body to up the idle. I personally have fixed a hunting warm-idle problem in a 4AGE (a bigport in my wife's old AE82 Twincam) TWICE purely by bleeding the cooling system AND NOTHING ELSE. Over the years of being on forums and Facebook I have seen countless other times when a hunting or high idle problem for those engines has been fixed by bleeding the cooling system (and it is really noticeable on 4AGEs due to the big difference between cold and warm idle speeds). Remember too that an air pocket might be stationary when the engine is off, but when it is running and coolant is being pumped around things get stirred up, which can result in intermittent contact between the coolant and the wax-pellet/sender/whatever. Usually it is a persistent high-idle that doesn't drop when the engine gets warm (also symptomatic of the wax-pellet valve dying of old age and being stuck permanently open, like a dead thermostat) but it can cause surging if it is borderline. It is actually a slightly different cause compared to a vacuum leak one (which is extra air causing the idle speed to rise about the ECU's preset limit causing it to pull fuel out) but can be hard to differentiate if you don't know exactly what to look for. Yes, other issues such as a vacuum leak or faulty sender/valve can also cause similar symptoms (and I'm not discounting any of them in the slightest), but the air-bubble trapped in the throttle body causing inconsistent/high idles is something that is common across most of the transverse A-series Toyota engines (moreso in MR2s but Twinkies/SXs do suffer it too), and it is almost always suggested as the first answer because it is free, easy, doesn't require any disassembly, and is very common especially when people also have coolant leaks or have recently replaced a radiator/thermostat/hose/etc and introduced air in to the system (in my wife's case it was both - air was in the system after fixing a leaking water outlet on the end of the head and replacing a heater hose that had burst).

One of the reasons my old one lasted so long is that I had a complete history on it, my old man owned it from new back in '97.

You mean clutch release bearing. FWDs don't have spigot bearings.

There were still carby Corolla models thru till ~October 1992 or so, EFI started to be introduced back in 1991 (apart from 4AGEs which obviously were EFI from back in '86). Skipped straight from carby to MPFI though.

It's just a thermo-switch (or in the case of the older 4AGEs, a wax pellet). When there is an air-pocket around the ISCV, there is insufficient heat transfer through the air for the correct coolant temperature to be measured, simple as that. Just google 4AGE idle air bubble and scroll through page after page of people who fix hunting idle problems by bleeding the cooling system. Front-engine A-series engines are meant to be bled by the radiator cap. There is no other designated bleed point in the system (like a header tank or bleed port - MR2s are obviously different due to radiator being at the other end of the car and mounted low). It's not as bad as a VL Commodore (which had the radiator cap so low that air-pockets would form in the HEAD), but it is a recognised thing.

They're both 4AFCs so no worry about EFI :P. Don't think there were any revisions done to the FC over the life of the AE92 so should be no need to mix-n-match anything apart from the flywheel as stated. And all xAFx engines have a 6-bolt crank so no issue there (4AGEs have 8-bolt)

Wasn't so much stuff wearing out as it was me trying to chase a niggling issue that turned out in the end to be wheel bearings. CVs and gearbox oil were fine and didn't really need to be changed, but I wanted to cross them off the list as they were things I could do myself at home rather than paying someone else labour. As a comparison, my previous shell did 405,000k on original brake rotors, gearbox, clutch, CVs, wheel bearings, engine, the whole shebang. Treat them right with the usual preventative maintenance and these things will run to the moon and back.

Trust me, anyone who has ever owned a 4AGE will have experienced the air-bubble in the T/B at some stage causing a hunting idle speed. Gas is a poorer conductor of heat (convection) than liquid (conduction) too, remember.

Every little bit of help you can give the system counts. If it isn't enough, then you can cut the bottom off a soft-drink bottle, duct-tape the neck to the radiator filler neck, and then fill it with water/coolant and run the engine. It just makes a mess when you finally get the system bled and have to remove the bottle with some water/coolant still in it. Coolant doesn't go all through the throttle body anyway, just the base of it for the ISCV. It's not much higher than the cap

And then last Monday was wheel bearings :P (although at least I didn't do that myself)

If you're getting the axle seal replaced they have to pretty much drain the box anyway, might as well take the opportunity to fill it up with gear oil instead of ATF. Only needs about 2.5L of gear oil so it won't break the bank. Unless you fill up via the breather on top of the box or with a pump it's hard to really overfill it anyway as the excess drains out the fill hole before you get a chance to tighten it up. This is all fresh in my head because I changed the gearbox oil in mine last month, followed 2 weeks later by changing the CV axles (which meant that half the new oil I put in got dropped anyway).

Fill plug is on the front (radiator) side of the gearbox about halfway down, just under and to the right of the clutch slave cylinder boot. Will be an 24mm hex-head, if you look straight down beside the coolant overflow bottle you should see it. I'll take a photo of the workshop manual when I get home if you need any more guidance

Some Toyota manual 'boxes do actually call for ATF, but the C50/52 isn't one of them.

Checking gearbox oil level is simply by removing the fill plug (when it is cold) and sticking your finger in the hole - the level should be just up to the bottom of the hole. Diff oil is shared with the gearbox. Got a photo of the pipe you're referring to? Again I don't think any of the power-steering components or piping get that far over the engine bay, they're all concentrated around the steering column (naturally) and the driver's side of the engine (where the pump, reservoir and "cooler" are), unless it has somehow leaked internally in to the rack (which would be a rather large amount of fluid to lose)

What colour is your coolant? Leaks from the thermostat or water outlet on the end of the head will run down to the top of the gearbox and then find their way around the housing and drip on to the ground. That leak spot is a long way away from where you'd expect a power-steering leak to be.

I actually have a spare 7AFE head (and thus PCV valve) sitting around, maybe I should pull it apart to show how the internals work... I had a quick look through the 4AFE/7AFE Toyota workshop manual this morning (the actual proper Toyota Australia engine manual), unfortunately I think the PCV valve gets classed as part of the Emissions system (which is chassis-specific) so wasn't covered.

The 55mm thing is irrelevant now as I've got a second set of AE111 rotors which are the correct centre-bore. Also, all aftermarket rotors that I've found are 55mm rather than 54mm. The plan is to machine the mounting bosses on the pad carrier to re-centre the rotor, only needs to be ~2-3mm or so. Much prefer this to running a spacer as the rotor would be close to falling off the 55mm step (the rotor has a lead-in chamfer on the centre-bore so half the thickness doesn't make contact)