3sge bouncing idle and overheating.

[lojik]

Having a few possibly related issues with my celica at the moment.
It's been overheating lately, I have reverse pressure flushed the radiator, and replaced the thermostat with no effect.
The revs have just started bouncing at idle. Normally between 1k and 2k rpm. I've read this may be bubbles in coolant flowing past temp sensor...
The ECU is throwing codes 25 (AFR LEAN) and 26 (AFR RICH). O2 sensor could be shagged?

Any ideas on which direction to start troubleshooting? (yes I've tried the search button)
Cheers.

[slide86]

i would be checking to see that the thermo fan is operating correctly and cutting in when it should be. you have replaced and fixed the most common things, check the fan next/

check for vacumn leaks. does the engine run an airflow meter? look for any leaks in the air intake system AFTER the AFM. this would cause the engine to idle erratic and give the codes that you have stated.

[urantia]

sounds like a blown headgasket too. Both of those symptoms will cuase that.

but yeah see what happens when you sort out those error codes first. O2 shouldn't set those codes off on it's own. Might need to check your fuel flow, blocked up fuel filter will set off exactly those codes.

[Jorrs]

kinda sounds like a 02 sensor though your comp would throw u that code ? wats the condition of the senor by visual inspection ? and a BHG could be a possibilty though u can test that in many other ways.. and yeh the fuel filter may need a changing, if i remember with my last 3sge car the fuel filter was buggered and the idle was up and down. there are many things to test with the problems u have stated !

[AndyTTR]

my gen 1 3sge used to idle up and down like you described unless i bled the cooling system properly.

After the water pump failed and the engine overheated the car would randomly overheat despite changing the thermostat, reco-ing the radiator, new thermostat etc. In the end it was decided its either a BHG or a cracked head.

[lojik]

Thanks for the replies guys.
I had a quick look last night.
Took rad cap off and started the car, I have bubbles coming out of the filler. (could be bubbles caught when I refilled the radiator after the flush?)
Had a bit of smoke coming out the back, was hard to see in the dark, but it looked pretty white to me. These all signify a BHG yes? I dont have any oil water mixing going on.
Pulled the plugs out and they all looked similar in condition and deposit color. What other tests can I do to check this? Compression?

I havent had a look at the o2 sensor yet, I'll do the fuel filter as its due for a newie anyway.

Thermos are working.

[SilverGhost]

Thanks for the replies guys.
I had a quick look last night.
Took rad cap off and started the car, I have bubbles coming out of the filler. (could be bubbles caught when I refilled the radiator after the flush?)
Had a bit of smoke coming out the back, was hard to see in the dark, but it looked pretty white to me. These all signify a BHG yes? I dont have any oil water mixing going on.
Pulled the plugs out and they all looked similar in condition and deposit color. What other tests can I do to check this? Compression?

I havent had a look at the o2 sensor yet, I'll do the fuel filter as its due for a newie anyway.

Thermos are working.

Yep, sounds like you have a BHG between one of the cylinders and your cooling system. Oil galleries may be intact hence the lack of oil mixing with coolant. As the cylinder is on the intake stroke is sucks water through the breach and combusts it creating the white smoke, ( is a large part steam) and on the compression stroke blows gases into the cooling system hence the bubbles.

Radiator place can test the coolant for combustions traces (cant remember the name of the test) but it only takes a minute and will let u know 100% if its a BHG.

[mtp_69_i]

run the car for a bit then switch it off and pull each spark plug in turn and stick a *cold* screwdriver into the spark plug hole. If there's condensation on your screwdriver then chances are you've blown the head gasket.