Very poor mpg 2zz

[MrChris]

Noticed that I'm getting very bad mpg on my 2zz  at donington this evening.

I will need to check wiring on the loom etc. But does anyone have any general pointers as to what I can check?

My exhaust has a fairly strong smell coming from it and it pops and bangs which I was not expecting.

Oh and my rear offside caliper was sticking which obviously won't help, but this can't be the sole reason for getting really bad mpg?

[Gaz mr-s]

Clean the maf.  Take out the plugs & check their condition.  Any codes/pending codes.?  Check for exhaust air leaks.

[MrChris]

Clean the maf.  Take out the plugs & check their condition.  Any codes/pending codes.?  Check for exhaust air leaks.

I'll go through these thanks. I did have an EML come on when it came back from MOT but I had the battery disconnected and it cleared before I could read it.

[Alex Knight]

Noticed that I'm getting very bad mpg on my 2zz  at donington this evening.

I will need to check wiring on the loom etc. But does anyone have any general pointers as to what I can check?

My exhaust has a fairly strong smell coming from it and it pops and bangs which I was not expecting.

Oh and my rear offside caliper was sticking which obviously won't help, but this can't be the sole reason for getting really bad mpg?

Can you please quantify what 'really bad' is?

What's bad in your opinion, may not be bad in another's.

[MrChris]

Can you please quantify what 'really bad' is?

What's bad in your opinion, may not be bad in another's.

Good question!

1 tank of fuel - maybe more (went from just under half full to full then back down to quarter/half).
70 regular road miles.
About 15 track miles.

[MrChris]

Went out and checked the exhaust and found two very slight leaks from the left two pipes right where the PPE manifold meets the head.

Will be checking coils and plugs when I get a chance. But does anyone think these two tiny leaks can make a big difference to the fuelling? Also, what is the best way to resolve this? Tighten up? Does it need a gasket?

[Carolyn]

I'd give it a new gasket.  But I don't think that will be the major cause of fuel consumption.

I'm thinking leaky injector.

[Joesson]

@MrChris said:

Does it need a gasket?


I might have misunderstood your question but a gasket is required between the cylinder head and the manifold.
That being an aftermarket manifold you may have used the gasket supplied with it. From my reading on here these are typically less than optimal and an OE gasket is recommended.

[MrChris]

@MrChris said:

Does it need a gasket?


I might have misunderstood your question but a gasket is required between the cylinder head and the manifold.
That being an aftermarket manifold you may have used the gasket supplied with it. From my reading on here these are typically less than optimal and an OE gasket is recommended.

I didn't do the install, but presumably a standard 1zz gasket would work from what you are saying?

[MrChris]

I'd give it a new gasket.  But I don't think that will be the major cause of fuel consumption.

I'm thinking leaky injector.

Presumably this means they're letting too much fuel in and need replacing?

[Carolyn]

Presumably this means they're letting too much fuel in and need replacing?

If it is an injector, it will only be one of them.  By pulling the spark plugs you should be able to see which one is running rich, by looking at the tips.

[Joesson]

I didn't do the install, but presumably a standard 1zz gasket would work from what you are saying?

Even more likely that the gasket supplied with the manifold was used then. As said, reportedly less than it could/ should be and could be a contributory factor on the low mpg, but a dodgy injector  is more directly related to that problem.

[KRAMSNEHPETS]

Last sat at blyton in mine. 125 miles just under 40 litres

[Alex Knight]

Good question!

1 tank of fuel - maybe more (went from just under half full to full then back down to quarter/half).
70 regular road miles.
About 15 track miles.

Do some pure road miles. Too many variables on track.

Do a circa 50 mile motorway run and measure your fuel consumption (60-70mph).

If your value is around 35MPG or more, you don't have a fuel consumption issue.

[AJRFulton]

For reference, when both me and my car were competitive.

In dry conditions - 40 litres (8.8 gallons)  would do me about 60-70 knockhill laps (1.26 miles so 75-85 miles) - so I get under 10mpg. That's a mix of maybe 75/25 on hot to cool laps.

My rule for fueling for a race was was 600ml per lap + 4.5 litres (to stop risk of fuel starvation and contingency). Call it 500ml per mile.

My car isnt road legal and is a fully stripped out race car. I'd expect a more road spec car, on more road going tyres to be getting between 10 and 15mpg on track in the dry. Maybe up to 20mpg in the wet.

As Alex says there are a lot of variables but 250-500ml of fuel per track mile would be, in my opinion, normal.

First thing I'd check is all of the spark plugs. They should give a clue to what's happening.

[MrChris]

Just pulled a plug and it's pretty slick. Presumably this points to injector replacement or refurb? Appreciate thoughts on this as it's something I've not dealt with yet.






Edit: A quick go on ChatGPT and some Googling seems to indicate this could be either piston rings (not good?) or the valve cover gasket and spark tube seal letting oil in... if so, easy fix. I guess it would be the valve cover gasket as there is no oil on the tip where the spark is made.

Edit Edit: I still need to check my MAF but using stock 1zz airbox on 2zz seems like a bad idea from what I can tell?

[Carolyn]

The electrode is a perfect colour - so it's not oil in the chamber, i.e. not rings.

Oil on the threads indicates the plug was not properly seated.  Oil on the ceramic indicates cam cover gasket.

[Alex Knight]

Spark plug oil seals I would imagine.

One of mine went on my 2ZZ, so I replaced all of them. About £15 each from Toyota.

[MrChris]

If it is an injector, it will only be one of them.  By pulling the spark plugs you should be able to see which one is running rich, by looking at the tips.

Just on the leaky injector side, is it worth getting my injectors refurbished or getting new ones? I'm guessing they're needing something as they've been in for a while (years).

[Carolyn]

If all the electrodes on all plugs look like the one in the pics, I'd probably rule out a dodgy injector.

[AJRFulton]

Totally agree with Carolyn, that spark plug looks pretty much perfect. The oil on the thread isn't something I'd be "too" concerned about either.

As a side, in 5yrs within the 2ZZ community, I've seen few reports of injector issues. I don't think that's injector related and I'd even say (going by spark plug) your engine appears fueled correctly. Too much fuel would leave a sooty deposit.

Could this problem be pre-injector?

Could a fuel line be frayed and opening when under pressure/heat? Tank leak? Faulty fuel gauge/sender?

[Alex Knight]

I am 99.9% sure that this is spark plug oil seal. It's fairly obvious from the picture, and the name of the part I think has failed.

[shnazzle]

I did replace the cam cover gasket when I did the valves. Maybe I didn't seat it perfectly? It was done at Ding Day (good times). 

But I have to say those sparks look as good as they ever did. 

[Alex Knight]

I did replace the cam cover gasket when I did the valves. Maybe I didn't seat it perfectly? It was done at Ding Day (good times). 

But I have to say those sparks look as good as they ever did.

I don't know about the 1ZZ, but on the 2ZZ then spark plug oil seals are not part of them cam cover gasket. They are a separate part.

[shnazzle]

I don't know about the 1ZZ, but on the 2ZZ then spark plug oil seals are not part of them cam cover gasket. They are a separate part.

Sorry wrong car haha. It's late