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