the strangest 4A-G problem yet?

**Vios-GT_07** · 13-03-2008, 01:08 PM

hi

this started about 4 weeks ago, as the car is more for weekend or going out with friends, so used 2 - 3 times a week, so i didn't really pay attention until recently.

1. exhaust note changed, like was a hole somewhere

2. started consuming petrol like no tomorrow, i mean barely 300 kms to the full 35 liter tank.. driving it like a grandma and that... i gave it a mild thrash one time, for about 50 kms, and the whole tank only did 250 kms before warning light came on

3. engine acts very strange.. upon deceleration with gear engaged, the car would lurch itself forward at 1500 rpms, as if the iscv has issues.. disengaging gears and the revs would blip up and come down.. idle is perfect, no erraticness

4. it'd rev very rough up till 3000 rpms, like it had rooted everything..

and now, the most puzzling piece of the puzzle

Error Codes!!! the mechanic with a scan-tool pulled out some scary error-codes stored in the ECU... this included

O2 sensor , TPS sensor, Crank Angle Sensor, Water Temp sensor, some ignition coil failure, ECU ROM Failure.. among a list of 12 or so error codes... the Check Engine light has never come on, and apart from it drinking lots of fuel, it's never failed me...

Checked and rechecked all sensors and everything on the error codes list, checked the loom, all wiring and earth, all fine... clear the error codes, disconnect battery and all that, the car runs fine again, and after a 100kms run, fuel consumption, exhaust note and engine behaviour is back to normal..

any ideas as to why the car decided to act stupid? i don't know to hope it'll happen again or not.. if it happens i'm fooked.. if it doesn't happen i'll eventually get fooked...

**Kedderz** · 13-03-2008, 01:50 PM

buldging caps in your ECU? The ecus are getting to the stage that parts may start to fail, I know recently around here tehre have been a number of 1jz ecus fail due to buldging/weeping capacitors, might be a case of try another ecu and see if that fixes it? Seems like a range of failures which MAY point to ECU.

**Vios-GT_07** · 13-03-2008, 04:12 PM

hm... ecu failure is a possibility...

i'll have a look if it throws back any more error codes or the car starts to act funny..

**parrot** · 13-03-2008, 05:34 PM

You have probably already done so, but if not, clear the codes first, then drive the car around and see what codes come up then.

You may well have lots of old stored codes from whenever you last disconnected your battery which are not relevent to your current problem.

**deviant** · 13-03-2008, 05:45 PM

ECU gone in to 'limp home' mode?

**psychofox** · 13-03-2008, 05:54 PM

if it's doing the "rev blip" at idle you probably have an air leak in your inlet system somewhere. all 4ags do it if they have an air leak. however, this would not explain the crap fuel consumption....

**MRMOPARMAN** · 13-03-2008, 07:09 PM

id start off exactly as parrot has said.. codes come and go all the time, especially if you've tinkered with the engine at some stage.

if your completely sure the earths and loom is ok, id be leaning towards the ecu also. especially if it goes good for a while then starts screwing up again. would you be able to borrow an ecu off another mate/members car and go for a quick burl? that would sort out whether the ecu is playing up or not.

visually check the ecu and the pin outs.. is there any bulging or melting round the plug area, or corrosion on the pins at all?

as deviant said it sounds like its going into limp home mode.

weird the check light didnt come on. does it actually work, ie light comes on when you first turn the ign on every morn?

. started consuming petrol like no tomorrow, i mean barely 300 kms to the full 35 liter tank.. driving it like a grandma and that... i gave it a mild thrash one time, for about 50 kms, and the whole tank only did 250 kms before warning light came on

what do you mean by warning light came on? obvious not the ecu light judging by other comments in the thread?

**Xaero** · 14-03-2008, 02:33 AM

try the sensor, if it's reading wrong, sending wrong signal to ecu, then the car will overfuel, and not run right, etc.

**Vios-GT_07** · 14-03-2008, 03:17 AM

Originally Posted by MRMOPARMAN

weird the check light didnt come on. does it actually work, ie light comes on when you first turn the ign on every morn?

what do you mean by warning light came on? obvious not the ecu light judging by other comments in the thread?

yes the check engine light works... if i disconnect the water temp sensor it will come on, and it lights up when i turn key to ON.

the warning light i mention is the low fuel warning..

**Vios-GT_07** · 14-03-2008, 03:24 AM

Originally Posted by parrot

You have probably already done so, but if not, clear the codes first, then drive the car around and see what codes come up then.

You may well have lots of old stored codes from whenever you last disconnected your battery which are not relevent to your current problem.

last diagnostic test was done at the service, which occurred at... 2 weeks ago from now.. and there was no codes whatsoever at that time.

yes i've cleared the codes.. and i'm driving the car around now.. i've just done 200 kms on it and the fuel consumption is spot on.. i'm doing the same freeway / city driving i always do, driving pattern and distance hasn't changed, but fuel consumption definitely has, and it's not that shitty consumption i'm having. Also, exhaust note is definitely the usual..

so my guess is... yes it must've been in "limp mode" while it had all the codes stored up. Strangely again, the diagnostic machine didn't register the car running in Limp mode.. Again i'll say this - all sensors have been checked, and none of them are faulty. TPS was checked to be spot on, CAS was plugged in and the diagnostic machine showed that everything is reading well within parameters.

i've added "check vacuum lines" to my list as the blip is intermittent.

**Vios-GT_07** · 18-03-2008, 10:52 AM

okay the car wasn't in limp mode.. it just ran pig rich for some reason

did another diagnostic test today and ... HOORAY!!! it had one error code... don't knwo if it's a good thing or a bad thing... the error code is for oxygen sensor..

i've decided to replace the o2 sensor, clear the codes... but also considering if it's worthwhile to take the ECU out and open it up to see if any of the capacitors are leaking.. but i'm told it's not entirely possible to visually inspect the ECU.. it should be bench-tested to ensure perfect running condition.. any thoughts?

**takai** · 18-03-2008, 11:21 AM

O2 sensor does make them run pig rich as well btw.

**oldcorollas** · 18-03-2008, 11:45 PM

why not put a multimeter on the O2 sensor and check it is working properly or not first??

then again, chances are it is fecked as they are not meant to last forever

**RT40Corona4AGTE** · 18-03-2008, 11:57 PM

you can check the capacitors with a multimeter set to measure ohms (resistance). All caps should read very high or read out of range. If they are low or shorted, replace them!

If in doubt of their capacitance value, grab a multimeter and measure them on the capacitance setting, if still in doubt, de-solder them and take them into your local dick-smith or radio-shack, etc. They should be able to tell you the values.

Or you could look up the value chart online and match up the codes to work out the values.

**CrUZida** · 19-03-2008, 09:24 AM

Checked to see if the catalytic convertor has collapsed?
Or the exhaust has received a blocked from somewhere else?

Have you checked to see if you have good spark on all 4 cylinders?

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