Technical excessive fuel and hissing noise?

[billathome65]

I've noticed that my car is using a lot of petrol the air filter is clean and there is no smell of petrol but I have noticed that when I accelerate there is a low sound like a hiss as if there is a vacuum leak??

Any ideas of what to check and if a leak I describe could result in more fuel usage???

Cheers

 

[Ziggy122]

A Vacuum leak can do just that

The car wants to know a set volume of air going in to set correct fuel

It does that fine, but the long term trims are saying, the burn isn't correct its leak
Thats because the Vacuum leak is letting air in when it shouldnt
so it puts more fuel in, to balance it


Also you must remember the outside temperature has dropped, and this will also incure a lower MPG Figure

Go on youtube - Ericthecarguy - Vacuum leaks it'll help you

Ziggy

 

[billathome65]

Ok ta I just watched the youtube video and am pretty sure I have a vacuum leak

Will use WD40 rather than carb clean though just hope it's not a big fix.

Only issue I have now is he said about resetting the ECU problem I have is Isn't that done via a code or something? If so I don't have a code?

Cheers

 

[billathome65]

Checked for leak earlier however was unable to find anything?

Sounds like the hiss is only happening on the move as i'm accelerating any thoughts?

Cheers

 

[fingers99]

Base of throttle body.

 

[billathome65]

Hi fingers already checked the throttle base. The strange thing is, the hiss does not happen when you just rev the car, it happens as it's being driven and you put your foot down to accelerate it's got me stumped.

The car drives perfectly and gets decent acceleration for it's age but I have noticed it struggled to get up the acceleration from 60 to 70 on the motorway the other day so I was unable to overtake unless already at 70 just wouldn't respond to the throttle so foot was down to the floor?

It could just be that it's an old car so worn.

 

[fingers99]

Dry and wet compression test (cheap compression testers on eBay) would tell you a lot about the state of the engine.

Also worthwhile checking the cam timing -- one tooth out will make a lot of difference.

 

[billathome65]

Dry and wet compression test (cheap compression testers on eBay) would tell you a lot about the state of the engine.

Also worthwhile checking the cam timing -- one tooth out will make a lot of difference.

Cheers Fingers will look into it more.

 

[portland_bill]

Are the engine mountings ok? If engine is moving too much on acceleration, could be straining hoses or joints, allowing air in.
Check exhaust for leaks, especially at manifold. If air is leaking in before the first lambda sensor, this will cause it to over fuel to compensate to get the right reading.

Check all air hoses, flex them to look for cracks. Especially the hose to the brake servo.

 

[fingers99]

Just a thought -- cam belt tensioner on its way out might cause a hissing noise/allow belt to jump a notch.

But it is just a thought.

 

[billathome65]

Chucking it down today but when we get a break in the rain I will give it a good check over failing that it's going to be a trip to the garage at some point to get it on a test unless their is a way for me to check for codes myself?

I have Throttled up from engine bay and noticed no discernible or excessive movement of the engine. And as it does not have the hiss when just sat being reved it is a little baffling why would it only his on the move?

I have checked the obvious ie gaps at seal on doors and air blower it is definitely not that but when I throttle down to accelerate it will hiss for a few seconds maybe more or less.

Thanks for the info guys it is helping

BTW Fingers just noticed your over in the pool I was born in Garston moved to Speke then over to Manc many moons ago. Good to see a local guy.

 

[billathome65]

Ok finally found the source of the hissing which is down to the exhaust leaking at the middle box so when I get a moment.

 

[portland_bill]

Don't you just hate it when a hissing out, sounds like a hissing in.

 

[billathome65]

Not if a hissing out is a cheaper fix than a hissing in