6G Celicas Forums

OK here goes, I am at the stage where I am going to scrap the car I am so sick of it. Have posted on another forum but had no luck so hoping someone can give me an idea.

The car is a 1995 convertible (uk) 2.0 gt manual which is the 3S-GE engine with 70,000 miles and full toyota service history.

The symptoms are, from cold it will hesitate but not always straight away, could drive half mile before it does it. When it does I can have my foot to the floor and nothing happens. Then it surges and the car will run perfectly. EXCEPT if trying to drive at 20 or 30 mph it runs rough like its in the wrong gear. Driving at 35 and above it runs perfectly, Just to add to the problem, occasionally if I reverse and stop the idle will fluctuate and stall.

Jumping the diag pins shows no faults!

So far I have changed complete throttle body with sensors from a car that was known to run perfectly.
Fuel filter, water temp sensor, air temp sensor, spark plugs, distributor cap, rotar arm, thermostat.

As far as I can tell all vacuum hoses look OK

I am stumped for ideas.

Help appreciated.
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This post has been edited by Fujifilm: Aug 28, 2014 - 2:57 PM

My car (7A-FE, 285k) had a very similar issue. It would hesitate from a stop and occasionally stall when COASTING to a stop. At around 2,800 RPM (my cruising RPM) the car would jerk violently and would be unresponsive if I slammed the gas down (did so just to test). I suspected TPS and replaced it, along with a tune up (cap, button, wires and plugs). The problem went away completely for a couple of weeks, but then I started experiencing similar issues - hesitation, surges and very poor idle. After a 3 hour highway trip I replaced my fuel filter and again, the problem went away completely. Keep in mind that these separate occurrences may be completely unrelated - the symptoms were all similar, however. What sucks is that you already replaced these parts. Do you know from first hand experience that the donor car was running properly? If not, maybe they got rid of the car for the same reason.

Have you had ANY improvements since replacing the parts you mentioned?

Thanks for reply, strangly I had same as you, everytime I changed a part the problem seemed to go away for two days. I have changed throttle body and sensors twice so chances of three being faulty are slim but not unheard of. I am now thinking on the lines of a dodgy injector. Just clutching at straws.

The car has no mods fitted, my biggest problem is I do not know if it did it prior to buying it, the guy said it run perfectly, the first time I drove it I ran out of fuel on the way to the garage less than a mile away so the tank was totally dry.
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This post has been edited by Fujifilm: Aug 3, 2014 - 3:41 PM

Good luck with it all my friend! Keep us posted on what you find out.

check timing, check tps, check spark plugs, wires etc. make sure toyota used the right parts.

Did you ever retard your timing?(distributor). This can cause a rough idle. A dirty throttle body and intake manifold can do the same. That's good there are no vacuum leaks. Where you live it must be cold. Driving a car til it runs out of gas is bad. You can overwork the fuel pump and burn it out since it is not pumping gas. Let me know if your problems persist. And maybe a coolant temp sensor? It may be defective and telling the computer that the engine is already warm. The computer is supposed to add extra fuel when cold to "choke" the engine until it reaches operating temp.

This post has been edited by Timothy: Aug 10, 2014 - 7:05 PM

I also say check the ignition timing by renting a timing light. you clip the wire to the no 1 (far left) spark plug wire then the light should flash just as the little mark on the crank pulley hits 10 BTDC. If not you rotate the distributor till it does.
also, you didn't mention the Ignition coil and the condenser(small capacitor) inside the distributor. if these have never been changed in 20 years they definitely make a big difference in the quality of the spark.

also when was the timing belt last done? if the timing was set wrong by the position of the crank and cam with the timing belt it could act a lot like that.
and how about the fuel filter? if you've never changed it yourself you should.

This post has been edited by VavAlephVav: Aug 10, 2014 - 9:41 PM

Apologys for not getting back sooner...

Just to recap, I have eliminated throttle body and sensors, changed it with a known working one, changed fuel filter, spark plugs, distributor cap, rotor arm, air temp sensor, water temp sensor, thermostat.

The mileage is just short of 70,000 and timing belt was changed at 60k by Toyota.

Not getting anywhere I decided to chuck in a tin of injector cleaner into the tank. For three days I had no surging in the morning and idle was ok, at 30 mph it was better but not good.

Half tank of fuel later I am getting the surge but not as bad, I have had it cut out twice after driving for ten minutes, at 20 or 30 mph it kangaroos quite badly.

I am now thinking either its injectors or the filter in the tank, I am positive maybe wrongly that its fuel related. My next planis once I have used most of the fuel to pull out the fuel pump and check filter. Not sure if there is anything I can test.

If that fails I will remove the injectors and have them reconditioned.

If that fails I will just break it for parts as I am now sick of it
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Injectors dont fail intermittent like that.

Check the ignition coil

I have no symptoms of ignition coil failure ( i dont think ) no problems starting, mpg seems ok.

The reason for me thinking ijector is because one may be leaking or partial blockage or? I have no idea just clutching at straws, as the problem is only occuring from cold for a few minutes where I get the surge, then most of the time at low revs at 20 - 30 mph where it kangaroos or runs rough, at 35 and above it appears to run faultless.

also, if your system was badly gunked up that cleaner may have nocked a bunch of crap loose and has re-plugged up your filter.
don't be afraid to change it again, but if your pretty sure the fuel is your problem id take the pump out and inspect the sock there as well.
and if you jump Fp to B+ in the diagnosis plug you will give full 12v to the fuel pump (you'll hear it), if that makes it act better you may have a weak pump.

Had time to have another go ati it again today, I took your suggestion and took out the fuel pump, the sock is a little dirty on about an inch strip, but petrol flows in and out of it so I am thinking its OK, nothing floating about in fuel tank. So I then tripped out Fp and B+ I did not hear any difference but car performance is greatly improved and the exhaust burble/popping is reduced.

I need to try it in the morning from cold to see if that has improved.

Your help is much appreciated.
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After driving for a few days with the fp and B+ pins tripped out the car is 95% improved, no hesitation, I can drive at 20mph, acceleration is spot on.

So my question is what part do I change or need to look at, as far as I can tell all this has done is bypass the open circuit relay, so what have I proven or eliminated. The pump seems ok because the car is running ok. The relay only opens and closes and the car starts on the button.

If I remove the jumper from Fp and B+ it goes back to the same problem. The best way to describe the main problem is, imagine you have an auto and in first gear the car is revving but not going any faster or changing gear, then suddenly it changes gear and goes like the clappers.

Thats what mine feels like except its manual.

But with the pins shorted its right.

Any ideas?

sorry I lost this post for a couple days
If jumping the fuel pump to full power makes it work better you probably have a weak pump, so you'd replace the fuel pump itself.
when you jump those pins you are giving it the full 12 volts. its a dc motor and so the computer adjusts the voltage from maybe 8v-12v as needed.
you might read up more on it here
http://bgbonline.celicatech.com/94_6gmanual/94_6gmanual.htm

I would follow the step-by-step on the fuel system to be sure, maybe it could have something to do with the fuel pressure regulator.
I wouldn't be afraid to replace the fuel filter again, both the regular one and the sock thingy if your system looks dirty. Do yourself a favor and always run Top Tier Gasoline.
http://www.toptiergas.com/

also you can get a reman fuel pump from the factory brand, Denso, on Rockauto.com for about $90. which is a pretty sweet deal.

This post has been edited by VavAlephVav: Sep 2, 2014 - 9:57 PM

im not aware that the Celica has a fuel pump ECU that controls voltage to the pump. there is nothing in the drawings.

The MKIV Supra does have a fuel pump ECU and most Supra owners bypass that with a relay and constant power. Since im running 2 pumps in my supra i did something similar with 2 relays.

hmmm, I haven't had time to fully investigate how this works. somebody else told me jumping Fp to B+ gives full power to the pump

Fujifilm - did you replace the fuel pump?
Did it solve the problems??