ALi-B

iTrader: (1)

Not to be confused with the 1AZ-FS which is more conventional.

I don't work with much Toyota stuff so DENSO's take on direct petrol injection and Toyotas attrmpt at getting itto work is a bit of a learning curve compared to the VAGs and BMWs with similar tech.

Main problem is a CEL reporting bank 1 cat efficiency. It also occasionally logs post cat sensor errors (reading/switching plausibility) on both bank 1 and bank2 post cat sensors. It's had both new post and pre cat oxygen sensors on bank 1 and a post cat sensor on bank 2. No difference. Live data is in conclusive (it varies depending on which equipment I use).

Also it vibrates at idle when warm like one cylinder is slightly down on compression; compression have been checked, new correct spark plugs have been fitted (pretty much unique to this engine). Performance below 3000rpm is lethargic with flat spots, and emissions swing about from normal to excessive in terms of Co and HC

Imo the cat(s) is ok, but is either marginal or being overwhelmed by the poor running.

I think it's s a fouling issue that is preventing smooth running in stratified or lean mode as when in homogenous mode (3000rpm + ) it seems ok.

Thing is we have EGR, swirl flaps and injectors to consider here. None of which is easy to get at.

Knowing the big VAG FSI lumps suffer from fouling, I'm thinking along these lines. So just wondering if anyone has had experience with this engine.

By the way for the uninitiated : this is a petrol engine

TIA

ditchmyster

iTrader: (7)

Turn the little idle screw on the carbs clockwise and that should sort it, if that doesn't do the trick look for a banana up the exhaust pipe.

Matteeboy

EGR valve and swirl flaps in a petrol; eh?!

ALi-B

iTrader: (1)

Yep. That's modern direct injection petrols for you. All the big manufacturers are at it....ticking time bomb for those who bought them to avoid diesel complexities.

The Denso system is doing my nut though...it needs to be driven is a particular pattern to confirm the faults...this is a cut and paste from the bulletin:

12 times stop/go??!!!! I kid you not! Not to mention "bank 1" being cylinders 1 and 4. And "bank 2" being 2 and 3. The Motronic MED 7.x seems far more logical.

Its not as if I'm doing this for the money...its my mates car...Toyota just want to dump a new cat on there without addressing the running issue which I'm 90% sure is the root cause!!

daveyj

iTrader: (1)

Pretty much every Vauxhall Petrol engine from the late 90s to now has or would have had an EGR valve fitted. I've blanked every one I've owned.

ALi-B

iTrader: (1)

Can't do it now as its required for the stratified/lean-burn operation. At idle it runs on something like 80% EGR

daveyj

iTrader: (1)

The price of keeping the pipe end clean sadly.......make the business end less efficient. If that story about turning water into wine never came about, do you think we'd have EGR valves today? Sorry, not helping your dilemma I know.

Based on my limited "enthusiast mechanic" experience I'm leaning toward an injector(s) issue. Like you say, the CAT is the symptom rather than the problem.

Matteeboy

If either of my petrol cars have one, I shall burn them.
They are the scourge of modern engine reliability.

ALi-B

iTrader: (1)

Yeah, I'm thinking along that...with this stratified charge, the injectors have to direct a spray of fuel into a pocketed area of the combustion chamber so the air fuel mixture is concentrated by the spark plug. I belive the swirl flaps contribute to it mixing in this area too. The area of the combustion chamber outside of this "pocket" contains little or no fuel.

So if the air isn't mxing correctly (blocked inlet ports) or the injectors aren't spraying the correct pattern, its not going to burn the fuel properly. Diesels using the same techniques just smoke a bit more (and block the DPF )....With a petrol however, I'm guessing will produce more hydrocarbons (unburnt fuel) which the catalyst will have to burn off and if excessive cause its demise from overheating (the exhaust doesn't smell nice after a sedate trip round the block).

Thats the theory at least; Inlet off and decoke, injectors out and find someone who can test/clean them. Should be fun.