Lots of carbon coming from a 4AG

**Nim** · 13-03-2006, 10:23 AM

It just sounds like it's riching out up high for some reason. Get it on a dyno with A/F ratios. Beninca has one.

Have you checked the ECU to see if it's giving any error codes? Perhaps it's going in to limp mode for some reason.

Perhaps the knock sensor is going off and messing up the timing? (I'm just guessing now)

**phrostbyte** · 13-03-2006, 11:23 AM

30psi, I'll give it a shot, just to make you happy

.

Nim, yes, it is richening up, that is quite obvious to us. Quite frankly I don't see the point of doing a dyno run to confirm it. It's a stock ECU, meaning there is no kind of A/F ratio tuning that can be done.

ECU isn't going into limp mode and gives no error codes on diagnostics mode (we used to have a misfire problem (shit plugs), was so cool, the check light would flicker every time it misfired heheh).

We do have an o2 sensor, which actually should detect the carbon and lower the ratio... Might try changing that. I had another thought yesterday that it could be the TPS, as it's a TPS for a late model AE92 bigport, and the resistance at certain throttle points seems different than with an early TPS.

No knock sensor Nim, only 4AGZE's had those

.

Kev.

**MWP** · 13-03-2006, 11:29 AM

Fuel related things to check are:

- Fuel rail pressure
- AFM/MAP sensor
- TPS
- Coolant Temp & Air Temp sensors

It sounds like youve checked everything else, so im betting on a dodgy coolant temp or air temp sensor.

**RWDboy** · 13-03-2006, 01:11 PM

Originally Posted by 30psi 4agte

TRUE. I think it is still likely to be burning the fuel in the cumbustion process but most likely not all of it(hence the excess carbon of a uncompleted burn). Like i said im prob wrong and it may not be his prob but i have seen this before and it may well be worth a shot!

Dude if the combustion process is *incomplete* (ie not getting full burn) then you will get PETROL coming through the exhaust ...

NOT carbon (maybe a little carbon but nothing significant) but the thing you will notice most is the FUEL smell..

NOT CARBON!

You only get *lotsa* carbon if the mixture is TOO rich, and burns COMPLETELY!

Again - INCOMPLETE burn means FUEL is a significant 'byproduct'

COMPLETE burn means CARBON is a significant 'byproduct'

**oldcorollas** · 13-03-2006, 01:22 PM

for plugs, 0.8mm is good.. although toyota recommneded 1.1mm, 0.8mm is (often) better

you will also get carbon if the fuel does not burn.

by burning, you assume the carbon goes to CO2 and the hydrogen goes to water.

at high temps, long carbon molecules will break down and if this provides a carbon activity of one, you will get solid carbon as a result..
fwiw, we use various carbon gases to do this in the lab, methane, propylene etc..

so it's not raw fuel, and it's not burnt... it might just be decomposedcarbon chains

complete burn means only CO2 and H2O. incomplete burn means CO and H2O. if rich enough, also means some non-burning = solid carbon, but solid carbon can result from burning too

**RWDboy** · 13-03-2006, 03:55 PM

From my experience, a car with poor ignition will smell like fuel (with some carbon from the exhaust and of course a discoloured exhaust gas) and a car that runs quite rich will blow good chunks of carbon through and the exhaust will be quite dark.

Which is why i'm leaning towards the side of there being a rich mixture, rather than effed ignition.

I usually mean by "incomplete combustion" that not all of the combustible material actually ... combusted. But i do realise that the more proper definition of incomplete combustion refers to the case where not all of the carbon chain was converted to CO2.

**oldcorollas** · 13-03-2006, 04:18 PM

fairy nuff

agreed

**30psi 4agte** · 13-03-2006, 06:51 PM

RWDboy
Well i guess old corollas cleared that up! you can get carbon from the exhaust when it has not completly burnt!

**RWDboy** · 13-03-2006, 07:24 PM

Pretty much yeah

It's more a matter of 'quantity' though, i wouldn't expect lots of carbon (as was described) when ignition is breaking down.

**30psi 4agte** · 13-03-2006, 07:40 PM

I agree with ya . You woulnt expect heaps but one persons version of heaps can end up being a bit of smoke by another person and without seeing the smoke its hard to judge.In this case it does sound excessive.

**phrostbyte** · 13-03-2006, 07:51 PM

Excessive is talking lightly, if you hold it at 5000RPM when not under load, all you can see at the back of the car is a massive black cloud.................

**75Ta22LT** · 08-10-2007, 09:50 AM

Hey guys, what plugs are you all running in the 4ag's?

was pissing out steam and fuel from the exhaust, gasket blown between # 1 & 2

We've just dropped a new ACL monotorque gasket in. (torque will be checked after run in, single torque my ass)

Won't fire on 4 under load... barely does at idle.

currently got some BCPR5ES - 11's in, tried BCPR5EY - 11's aswell.

I do have some BCPR5EP - 11's (platinums)

No noticable difference between them..

However, running twin webber's, 42DCOE's / 33mm Chokes.

Should I consider hotter plugs?

Had a quick chat to one of the guys at the local dyno, he said run some BPR5ES / 5EY's.

Didn't get a chance though, they have a larger diameter than what will fit in the spark plug recess..

Reset the cams as per DOHC specs, (#1 inlet and exhaust lobes pointing away from each other at TDC) - new timing belt.

Its over fuelling pretty hard, still needs a good tune (and maybe rejet), and with the cams in there I don't expect it to idle perfect.

Installed a fuel pressure regulator - between Facet sold state pump and webber inlet - set to 2 pound - no noticeable effect.

Its fouling plugs like crazy (definitely fuel) within the first minute of running (hot or cold).

Any suggestions? or just stop being a cheap c*nt and get it on the dyno?