Also make sure the oxygen sensor is ok (if equipped)... O2 sensors usually won't affect the air/fuel ratio when the engine is cold (they need to be very hot before they function properly)...

EDIT - Looks like Murray beat me to it... I didn't recognize 'exhaust sensor thingy (tm)' first time around

Thanks. I'll check those out.

The starter isn't the problem in this case, but another very common Mk.2 Supra problem is a blown head gasket. I'm seriously hoping this isn't what's happened (no smoke or steam, and I did get a pressure test a few months back).

Rob

Thanks for all the ideas guys - as soon as I have a minute I'll start to check them out.

Alternatively, who wants to fix my car in return for a tuner module?

(Kidding!)

Rob

I second the catalytic converter.

Easy test : run the car for a bit a night (until it gets warm and starts exhibiting the symptoms) and then run it a bit more. Look under the car for a red glow. If you see it that's your problem. Fix=replace cat. A friend of mine started a brush fire with a hot converter in a field when working as a surveyor. Unfortunately the car was in the middle of the fire and didn't do well.

-Zeke

There has been an annoying rattle in the front cat for some time. Luckily my car falls just outside the manufacturing year from which it is illegal to remove the cats - so I have been planning to throw away the stock system and fit a free flow Mongoose system (+30BHP for £360).

Rob

The rattle could be the shield rattling becuase it seperated at its welding points, or it could be because the ceramic element inside it has cracked. Catalytic converters have a fairly long waranty on them if I remember correctly. I had a problem which was similar to yours, the catalytic converter had broken and the sensors down the line had been ruined. This messed the engines settings up. They replaced the cat for free, but I had to pay to replace the sensors behind it.

I am a mechanic, but on Nissans, rather than Toyotas.
on Nissans, the ECU has a basic memory and LED readout, so it can memorise intermittent faults such as airflowmeter, crank angle sensor, temperature sender etc. Reading it involves turning a switch on the side of the ECU with a screwdriver and noting the sequence of the flashing red & green led's. The key to the codes is printed on the case of the ECU and also is in the workshop manual.
Might be worth checking if your car has this Felicity
Other things to check: Air leaks, fuel pressure, and corrosion of pins in electrical plugs on airflowmeter, temp sender, and fuel injectors.

Will

Were you driving in wet weather by any chance?
If the then maybe your distributor cap/plug wires need replacing.

Happened to me before. I stuck a trouble light (100 watt bulb in a metal cage) under the hood for 5 or 10 minutes and the heat from that dried her out pretty good. She worked fine after that and the next day I sprayed her wires with a clearcoat type of wire dressing. Lasted for about 2 years like that. The next time I bought a new distributor cap and upon closer inspection the old one actually had a nice crack in it.... oops!

Sounds to me like your ECU is dropping into "Limp Home" mode. This is a direct result of the new tyre sensor going active

Turbo motors are low compression; if you disable the turbo, they become notoriously difficult to start, tick over like a cement mixer (if they tick over at all) and lack power. While driving like this, they burn huge amounts of fuel, smell very rich, and if you put your foot on the accelerator, will reward you with a whuff of black soot out the pipe and not much else. I can quote these symptoms verbatim since this is what happened on our Maserati Biturbo.

Given the way your car is behaving, this is also consistent with the ECU going over to LH; in this case, I would guess that the ignition advance has been fixed to a retarded value and the turbo waste gate has been dumped to safe mode (wide open, giving no turbo boost) to stop the engine going into detonation, which would knacker pistons and heads (and other whirly bits too). You do not really want to drive the car much further than you should like this if you can help it as is can cause large amounts of unburnt fuel to go into the sump and this will thin the oil and knacker the crank eventually. Whatever the problem is, I would recommend the first thing you do after the problem is sorted is to change the oil and filter ahead of service interval, and with good quality oil like Mobil 1 which is the dog's doo-dah for turbo engines.

Before you panic, I would think that you have not blown the turbo, since this is a progressive (usually) or instant failure on the road. For the engine to run OK and then get grumpy points elsewhere. Turbo failure is usually accompanied by oil consumption, exhaust smoke (blue, not black) and lessening of performance over time. It can also seize solid, but you would hear that (no turbo whine if the turbine is not rotating). Can you hear turbo whine as you accelerate, before the ECU goes off?

If you are driving for 5 minutes from cold before this starts up, then it sounds to me as if the ECU has just tried to go from cold driving/warmup mode (enriched mixture) having sensed the coolant temperature has reached sufficient level to switch over to the normal mixture mode. As it makes the mode change, it seems as if it is finding that one of the sensors/actuators normally used in normal mode is not operating properly. It then kicks into LH. Since turbo engines need special cold running management strategies, you sometimes find an extra injector to richen the mixture when the engine is cold to stop the charge weakening due to petrol condensing on the cold inlet surfaces. If the ECU went to normal mixture at correct temperature, then it will turn off the enrichment injector. It could be that for some reason the ECU then detects the mixture has gone weak (it looks at the exhaust gas oxygen sensor) and thinks "Ey up! I'm going to go into detonation and seize the turbo! Anchors out!"

I am almost willing to bet you have one dead injector on one cylinder. Pull all the plugs one by one and look at the colour of them all. They will probably look pretty sooty, except one of them. That will be the one with the dead injector. My money goes on this

There are other things that could have failed to make it do this:

- failed MAP sensor, which means the ECU is unable to determine mixture strength by measuring the Mass of Air going into the engine. It then goes to LH and guesses at the volume of air being sucked in by a predetermined value determined by the engineering team during development. Pretty rare, but it happens none the less. Unforch it is also an expensive component, but you should be able to get a replacement from a scrappy for a resonable price.

- collapsed fuel filter; this is cheap and easy to replace, and should be done regularly on injected cars. On a friend's Peugeot, the filter used to collapse and block off the fuel line, starving the engine. This usually only happens if the fuel pump is in suction to the tank, upstream of the filter. If you have an in-tank pump that pressurises downstream of the filter, it is not as likely to happen.

- failed fuel pressure regulator. This one is a classic on injected systems, giving the rough running symptoms you describe. Not cheap to fix, but easy. The regulator usually fails to limit the pressure by either bursting an internal diaphragm (low pressure, lumpy running or bad starting) or seizing (incorrect fuel pressure, affecting mixture strength, causing overheating or "flat spots").

- if you have a single coil directed spark ignition, you could have either a dodgy transformer (insulation brekdown causing low spark voltage, leading to misfiring) or a coil breakdown (gradual loss of power as the coil overheats).

I would suggest that you bite the bullet and get the engine onto a Toyota test system at the garage to eliminate the ECU as a problem. If it is going into LH then there will be a failure code recorded in the ECU to state what it detected to make it go into LH mode. The longer you run it in this mode the more likely you will cause damage to the engine (crank/oil, or pistons/rings) or the Cat (contamination) which will cause you problems with the MOT on emissions later on.

There used to be a very good family-owned garage called Chorley Motors at St. Neots towards Bedford which specialised in injection diagnostics. They had a BOSCH diagnostic system with a rolling road, so if they're still there give them a call, as I found them friendly and very knowledgeable, plus they call a stone a stone, don't baffle you with bull**** and charge a reasonable rate for repairs.

Rob,
Did you say "reduced acceleration" is your problem??

No problem! Install a 2nd turbocharger. Lemme me know if that solves your acceleration problem; I'll glad take an extra tuner! :-)

--Andrew

with a second engine!!

I'd suspect that on an older engine, but this one is all electronic and has no distributor.

I fitted NGK platinum plugs not long ago, and Magnecor 7mm leads which run (mostly) under a weather cover. Given that this engine ran smoothly on just five cylinders when I first got the car (one of the leads had popped off!) I don't think it would be as dead as it is with just damp. I will strip down the ignition system, though.

Rob

I'll bet it's gnomes.

I bet its Gremlins. They probably ate the Gnomes already.

One cylinder not firing?

/Pepijn

I couldn't track down the problem myself so I took it into the garage (convenient having one right next door to empeg!) - as I feared the head gasket has blown. Damn.

I'll be replacing it with an HKS metal gasket, otherwise the chances are it will just blow again. I also need to get a really good head skim, so if anyone can recommend a good machine shop in the UK let me know.

I'm keeping my fingers crossed that the head hasn't warped, and that there isn't any surface damage to the block. Of course with my luck...

Rob

One place I WOULDN'T take it is Ivor Searle in Soham, Cambridgeshire. They reckon they're the biggest remanufacturer of engines in the UK. Well this may be true but I had a very bad experience with them. I took my Supra Cylinder Head & Camshafts to them for machining of the Camshaft Journals, Cylinder Head and Bearing Caps. What a mess they made of it. I sent them a letter but got no response whatsoever. I should have pursued my case but I'd really had enough of the whole thing so I just ket it go and remedied it myself. Here's an extract from the letter I sent to them outlining the problems with the work they did for me:
...
(1) Location dowels only partially inserted in the cylinder head and misaligned by a considerable amount.

(2) Elongation of the dowel holes in the bearing caps due to the above.

(3) One dowel hole distorted so much (approximately 1mm) as to leave just enough material between the dowel hole and the journal diameter to form a knife edge. And creating a crack in the bearing cap between the same.

(4) Swarf particles up to approximately 2 sq mm in area each, embedded in the bearing cap mating face of several caps.

(5) One dowel very badly damaged and marked with a pattern very similar to that found on the majority of vice jaws.

(6) Camshaft journals which still had deep scores in their circumference after explicitly advising the 'Engineer' that I wanted all of the journals to have the minimum amount ground off to clean up.

(7) Two studs which appeared to have been removed with ‘Mole grips’, therefore having damaged threads which needed rectifying by me before they could be re-fitted to the head.

I was very keen to return the engine to a working state as soon as possible and therefore continued with lapping the valves in and cleaning the cylinder head and camshafts of swarf and lapping paste etc. To put my mind at rest I thought it would be wise to check the fit of the camshafts in the newly machined cylinder head and caps without assembling the valves into the head so that I could get a true feel of the bearings without spring compression clouding the results. I duly assembled each camshaft into the head and found that I couldn’t turn either of the camshafts by hand, even with the extra torque afforded by the cam belt pulleys. I therefore assembled each cap in turn to see which were the offending ones. As I fitted each cap in turn I measured the torque required to rotate the camshaft. Some could not be turned by hand but were less than the 6 lb.ft. that I could measure. Of the fourteen caps, only three, when assembled and torqued down to the correct value allowed me to rotate the camshaft satisfactorily by hand. The three worst caps required approximately 7.5, 23 and 40 lb.ft. of torque to turn the camshaft, these figures being attained with lubricated journals. I therefore spent approximately nine hours on the Sunday having to scrape in each bearing cap by hand, not something I expected to have to do after having the assembly machined by ‘experts’ in this field of engineering. It was obvious from the pattern of the high spots on the caps’ bearing surfaces that the caps had been distorted when fitted to the head for subsequent machining of the bearings. This distortion was most probably caused by clamping down on the swarf which I had found embedded in the mating face of the caps....

This was back in September 1997 so maybe they've improved since then but I don't think I'd risk going to them again. I hope you have more luck finding someone decent.

Yeah I think I'll avoid that place

Rob

I'm disappointed you didn't fit the old tyres first. If you had I don't think you would have to have gotten the head machined.

Osselli Engineering, without a doubt.

Thanks, I contacted them for a quote.

Rob