OK folks, what would you suggest looking at to diagnose the cause of the following fault:

Vehicle drives normally on short journey
About 5 minutes into the return journey, car significantly loses power
Car drives but acceleration is reduced and car simply doesn't "feel right"
Arrive home, idles very lumpy, turn off engine
Attempt to restart engine - tries to fire but won't idle at all

No, it hasn't run out of fuel!

The car in question is a 3.0i turbo Mk.3 Supra. I'd like to check out a few things myself before handing it over to a garage, not least because I don't have home breakdown cover (wish I hadn't driven it home now!).

Side note: Of course it will probably be a write off because I just bought new tyres for it a few days ago. I wrote off my old Jag right after buying tyres (that problem was easier to diagnose - the car was incompatible with the sturdy metal barrier in the middle of the road). Way back I'd just bought tyres for my first mini when the gearbox exploded. I am tyre cursed.

TIA

Rob

Ok this will probably sound silly (but hey I'm not a mechanic) but a friend of mine picked up her car at the workshop some months ago with exactly the same symptoms. It later turned out that there was to much oil poored into the thing (way beyond max marker). One would expect the oil pressure light to at least indicate this but no it didn't. restoring the oil level to normal fixed this. It was no Supra though.

Again, not a mechanic- but it sounds like it is getting electrial and I doubt you are starving it for air... so it sounds like a fuel issue. Clogged fuel lines or a bad fuel pump.

I work in Technical training for dealerships, so let me ask some of the instructors..

I've got the same idea, clogged fuel pump or carburator. I've had this happen once to me, but it was with my motorbike. (still a petrol engine is a petrol engine) Turned out the carburator was clogged. After clearing it out all was peachy. Maybe your fuel tank is polluted?

First thing I would check is the fuel filter. Fuel injected cars require a fair amount of fule pressure. Water & dirt accumulation overtime will kill your filter and the car will run like crap.

I was going to do a big long reply in the style of Tom and Ray, with all the appropriate references, but then I realized you've never heard Car Talk and wouldn't get it.

That's very interesting, as I did top up the oil recently (probably over-filled a bit) - but since then I've driven about 800 miles without problem.

I'll check the level, though.

Rob

No, it MUST be the tyres!

My guess would be fuel pump. Last time I had one go out, I left work to go visit one of my friends (who just happened to be a gorgeous female) who worked near me. The fuel pump went out while I was there. To this day my boss is convinced I broke it so I could skip work and spend the rest of the day with her.

Sounds like an old standard problem. I just can't recall what
the other teams said the issue was.

Check the various electrical wires under the hood that go to ground. Especially in the harness -> ecu area. It sounds like it could have gone into "limp home" mode. (not sure if Toyota has that) Many manufacturers run the car EXTREMEMLY rich when this happens. Notice any milage problems?
Is the header glowing when you get home?

Sounds like it could also be:
-clogged fuel filter or lines.(or bad petrol)
-Catalyst has broken up and is plugging exhaust port
-problems with ide stableizer system being buggered up.
running far too lean after warmup (called the ?? IIC air valve?
on the supra)

Interesting that someone mentioned Cartalk. Here's an old
common Supra problem: http://cartalk.cars.com/Columns/Archive/1996/December/14.html

Ed
-used to be a rally mechanic
-supercomputer repairman

Sounds like a fuel type problem can you hear the fuel pump buzzing another far out idea is the tank breathers okay as your fuel tank might be drawing a vacum and causing probs next time it does it pull over and open the tank filler to cross that off the list.

I had the same problem with my 92' eclipse. The problem: sparkplug wires went bad. I would check those as well as the plugs. Also check the fuel filter to see if its plugged.

-Greg

Hey, I've had a Jag and a Supra (unfortunately only the normally aspirated 3.0i) too but I had the Supra first and then the Jag. Anyway to your problem; I don't think it's reduced fuel flow due to a dirty filter or such like as I imagine it would idle ok. If there's enough fuel flow to get you through a short journey there would be enough to enable it to idle. Things that spring to mind are:

(1) Engine partially seizing.
This is quite possible if it's ok again once it has cooled down. My Supra went through 2 sets of big end bearings while I had it (about a year). Mine didn't seize it just got knocky. I also know that the previous owner had the big end shells replaced too. The Supras do not have the reliability record of other Toyotas. Supra big ends are not easy to replace either 'cause you can't just drop the sump. You have to take the whole soddin' engine out. I'm not suggesting it's the big ends, that's just a for instance.

(2) Ignition timing going adrift.
If something in the engine management system is overheating then it might cause this but I don't think it's likely to be honest.

There are probably many other things that it could be. Modern cars are so complex. Maybe something else is seizing and putting undue load on the engine. Basically check everything you can. Is it an Automatic? If so maybe that's playing up. I don't think anyone can give you a definite "it's this" without looking at it. I hope you find out what it is and it isn't serious. Let us know how you get on.

thinfourth2's tank breather idea is a good one too.

Some other easy quick checks include:

1) check coolant level (if low temp sensors may not work properly causing timing problems)

2) spray a fine mist of water on engine while running (changes in idle or sparks from wires may indicate shorted wire)

3) CHANGE FUEL FILTER-if this has not been done in awhile it needs to be done anyway.

(My 2 cents)

Yeah, fuel pump sounds like a good guess.

I once had a hell of a time with the fuel pump on my GTI... the thing has two fuel pumps, one inside the tank and one outside. The mechanics replaced the outside fuel pump twice before actually trying to replace the inside one.

Funny thing is, the following week, they presented the exact solution (including the same make of car and the same symptoms) on Car Talk. Would have saved me a lot of trouble if they'd run that show three weeks earlier.

My symptoms were different than Rob's, though. I only had the problem when the fuel level was low (as the inner fuel pump only kicks in at low fuel levels).

Checking it won't hurt but she had the problem the very next day. The drive from the workshop to her home was about 5 minutes, the problem manifested itself the next day on her drive to work.

Pull the plugs and look at them.

Calvin

Either fuel filter/fuel pump, or the catalytic converter has come apart and is blocking the exhaust flow when it gets hot.

tanstaafl.

re reading the post if it is the first time the car has done it it might be the cam belt has jumped or something else timing related.

Anotheroption is go get hugo and his many cars and either steal one or tow your car away from your house and then call the AA

Or everyone should just drive diesels i understand them these petrol things are a terrible idea.

I think we should start a $$$ pool.

Yeah, with all these opinions, it sounds like a trip to an auto shop is the way to go..

Too bad we can't interupt OBD-II data with our empegs....

To much oil wouldn't create a problem of high pressure because the crank case is not pressurized.
This causes a problem because your crank spins in the oil like an egg beater. Cranks have really big counter balancers which would hit the oil in the reservoir many times per revolution. The result is introducing serious added effort needed to rotate the assembly.

Have you tried Re-Sync'ing?

Seriously, It could be heat induced, but then the problem should get better when it cools. Heat could affect wiring, vacuum or minor mechanical bits.

Your problem sounds very much like fuel delivery or spark.
Do you smell excess hydrocarbons from your tailpipe? This would mean incomplete ignition and electrical problems. Check the spark plugs. If it's wiring, I'd just take it in and have it fixed.

You'd hate to take it in for fouled spark plugs or clogged fuel filter though.

Good luck.

You might want to check the coolant temperature sensor. It's used to adjust the fuel curve based on engine temp. If it fails or is not reading properly, it could cause the engine to think it's cold and add extra fuel (kinda like a choke). Idles lumpy sounds like it's too rich... Have you noticed any black smoke?

Happy hunting...

This is a known problem. It's discussed here. in The FAQ. Try downgrading to 1.03 to see if the problem goes away. You really shouldn't be using beta software if you're not comfortable with these issues.

- john

Yeah, should have searched on "pump", huh?

try putting the old tyres back on and see if the problem goes away. Reinstall 1.03 developer and capture the output on the comms.

exhaust sensor thingy (tm) fualty and running the mixture inconsistantly?

try putting the old tyres back on and see if the problem goes away.

ROFL, good one. Reminds me of this old joke:

A Software Engineer, a Hardware Engineer and a Departmental Manager were on their way to a meeting in Switzerland. They were driving down a steep mountain road when suddenly the brakes on their car failed. The car careened almost out of control down the road, bouncing off the crash barriers, until it miraculously ground to a halt, scraping along the mountainside. The car's occupants, shaken but unhurt, now had a problem: they were stuck halfway down a mountain in a car with no brakes. What were they to do?

"I know", said the Departmental Manager, "Let's have a meeting, propose a Vision, formulate a Mission Statement, define some Goals, and by a process of Continuous Improvement find a solution to the Critical Problems, and we can be on our way."

"No, no", said the Hardware Engineer, "That will take far too long, and besides, that method has never worked before. I've got my Swiss Army knife with me, and, in no time at all, I can strip down the car's braking system, isolate the fault, fix it, and we can be on our way."

"Well", said the Software Engineer, "Before we do anything, I think we should push the car back up the road and see if it happens again!"

You could have a leaking headgasket. Sounds like what happened to my friends MR2

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