Avensis 1.6 4Afe Hesitation?

[johnny c]

my avensis just started this in the last few days,when it warms up,there is a hesitation.

if im driving along,and i lift my foot off,then gently press the throttle again,it jolts and hesiates,then gets a burst of 'power'.

im going to remove the plugs later and have a look,also can smell the cat if i rev harder up the rev range.

possible blockage?

[igormus]

my avensis just started this in the last few days,when it warms up,there is a hesitation.

if im driving along,and i lift my foot off,then gently press the throttle again,it jolts and hesiates,then gets a burst of 'power'.

im going to remove the plugs later and have a look,also can smell the cat if i rev harder up the rev range.

possible blockage?

hi matey

check with MAF and sparks -- the problem must be there.

regards / Igor

[johnny c]

changed the plugs and leads,still no better.

when its sitting idle,you can hear the engine is quite lumpy.

wondering would it be one of the coilpacks?

[johnny c]

anyone?

[tamsa]

It's a common problem for this car. I'm sure it's made in UK, not Japan. In uk carinas EU parts were used, and thats a problem.

So, your problem 90% is injector. Symtoms: then engine is hot, somethimes you lose power, engine becomes louder. After moment or two- everything is fine. During this moment stop, open hood and try to unplug injector:s connector. If engine is running the same- you found it. If engine revs drops, plug it in and try another. My suggestion-start with the second:) problem is inside injector-then it heats up, sometimes it just stucks, posibble because coil wiresbecame short wired. Replace injector, cleaning will not work.

The second problem could be distributor or comutator.

[tamsa]

I just said Carinas, but the engine is the same, 4afe. Good luck. If it will be injecror, you should look for the same color. In my engine i had blue (eu model). Pinks were from japan models, they dont fit.

[johnny c]

I unplugged the injectors and the engine note changed,so don't think it's them.possible diluted filter?

[johnny c]

Got it plugged on,showing that it's running very rich,and the O2 sensor it doing its job. Any ideas?

[tamsa]

Please correct: hesitation happens sometimes or always? I understood -somethimes.. in this case how have you managed to measure lean or rich mixture you have?

Does it happens only when driving (moving), or also in idle RPM ? Does it happens all the time you release throttle and then gently press again or just somethimes?

Who checked your O2 sensor? it's not like in other cars, it's special, unique to 4AFE and expensive.

Let's think: Rich fuel= too much fuel / too less air / spark plugs does not work correctly (does not burn fuel like it should, but i'm not sure about this if you have rich mixture-maybe, if part of fuel leaves not burned, o2 thinks you have too less fuel and gives cpu orders to increase rate?).

Fuel=cpu+pump +fuel filter+ injector + valve for fuel excess (fuel returning to tank) + O2 sensor.

Air=air filter+gas pedal with throttle + ICS valve + EGR valve

Re electricity i'm not sure, it depends if you always have rich mixture or not. But spark plugs also are worth checking.

Have you checked air filter?

[johnny c]

I always have a rich mixture,new plugs fitted,and I've checked them,and they are wet all the time.o2 sensor is showing that it's doing it's job,switching on and off.car is quite smokey because of overfueling,smells of fuel.

[johnny c]

When I lift off the pedal,it happens for a few secs when I put it on again,does it worse when cold than when the engines hot.

[tamsa]

have you bought car like this or it just happend?

do you have 'check engine' shining?

could be lots of reasons for that- have you been to computer diagnosis-will save lots of time, maybe belt alignment is wrong or they will see bad sensor?

all plugs are wet? new platinum plugs with 1.3mm gap?

check wires-damage or short (for short take water sprayer and spray on wires-if they are shorting, you will see and hear)

check if you have good spark

What about air filter?

Take out o2 sensor and clean it (carefull, it's expensive).

Was going to write a lot but someone already did:

http://www.aa1car.com/library/problem_hesitation.htm

Adding to this article it could be thermostat or themperature sensor problem (CPU thinks enigine is cold all the time)-check how temperature rises and if you have hot air blowing inside.

[Delboy141184]

ive got exact same problem with my carina which is a 1.8 7AFE.it has blue injectors.ive started a thread in the carina section about it.im 99% i have a injector problem and this sounds like you have one too.mine appears to be injector number 3 as when the missfire happens removing the wire from this injector makes no difference to the missfire but removing wires 1,2 and 4 make the missfire worse so im certain i have a injector problem with number 3.

[johnny c]

Are all your spark plugs wet?

[Delboy141184]

Are all your spark plugs wet?

all 4 of mine are bone dry and a nice brown color.its deffo a injector prob on mine anyway.im sure of it.......

[johnny c]

Mines seems to be an overfueling problem.all plugs are wet,misses worse when cold than hit,checked the injectors with a multi meter,1 read 14 ohms,the rest 17 ohms.

[tamsa]

If all injectors had 0 or infinity, your car would not start at all. overfueling is just a result of fault. better do a diagnosis, it will be cheaper than overfueling:)

[johnny c]

Diagnosis isn't showing up much at all,I'm putting in a new fuel filter 2mro.

[Delboy141184]

Diagnosis isn't showing up much at all,I'm putting in a new fuel filter 2mro.

failing injectors will not fetch up a fault code on this engine.its the way the ECU has been programmed.its daft really,you would think it would,but it wont,no amount of a failing injector will ever fetch up a fault code on this car.my bet is still on one (or more) of the injectors playing up.

wise choice to renew fuel filter anyway,cant do any harm what so ever,run a bottle of fuel injector cleaner through the engine too to see if it clears out any blockage.(add some to fuel tank and also,remove spark plugs and add a few drops (about a tea spoon full) of it into each spark plug hole too),start your engine when its all back together and watch the ''blockage'' and crap from your engine come out of the exhaust.

should run much better,but the injector,if thats what it is thats causing the problem which im certain it is,may still be fubard and need replacing,but its worth a try first.

[johnny c]

I actually removed the fuel pump,cleaned the pick up,and siphoned the fuel from the tank,put in new fuel,and I think it's running a lot better!so now I'm thinking I'll try the fuel filter,after that,I'll go injectors,I'm sure I could pick up a used set somewhere.

[Delboy141184]

mine has a identical issue to yours,god help us lol.let us know how you get on.

[johnny c]

fuel filter made no difference,so ordered a 2nd hand set if injectors from eBay,going to fit them later,hopefully they cure it!

[Delboy141184]

fuel filter made no difference on mine either (although it was very dirty) i fiited a second hand injector to mine and it cured the problem.takes about 5 mins to change.good luck.

[johnny c]

thanks fella,will post my result tomorrow,ha!

glad to hear you got yours sorted!

[johnny c]

Fitted the injectors,made zero difference,back to square 1 again.