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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22930
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Hi. Suzuki Jimny 1.3 16V DOHC Sept 2002. This car has been

Customer Question

Suzuki Jimny 1.3 16V DOHC Sept 2002.
This car has been to 3 garages now, one being a Suzuki dealer and still not solved problem of low vacuum and cutting out when taking foot off accelerator pedal. it seems to be low back vacuum, checked all vacuum pipes all OK.
I have a vacuum gauge fitted in the dash which is supposed to train your accelerator foot, this used to be in the green excellent position when starting engine and when engine ticking over, but this is now showing in the fair to good position and engine cuts out.
There are a lot of vacuum pipes going to something under the main fuses in the engine compartment down by the battery, with some wires going to it but can't tell what this is.

Valve clearances have been checked free and spinning, all valve tolerances are within specification, new spark plugs, new HT leads, throttle body cleaned. no misfires, all new sensors fitted.
Also I done a compresion test all cylinders read 12 bar or about 175 psi
That was on a dry teat on a wet test the readings were 14 bar or 200 psi on cylinders 1-2-3 but on number 4 cylinder it whent up to 16 bar or 230 psi.
Kind regards Roger
Submitted: 3 years ago.
Category: Car
Expert:  Matt replied 3 years ago.

I'd agree that this is vacuum leak

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

Customer: replied 3 years ago.


Hi. Thank you for replying, unfortunately I have already tried this with carb cleaner and gas, but did not find the leak, I thought it might be the inlet manifold gasket but no leak in, have check absolutely everything with a fine tooth comb, I have it booked in on Tuesday for a complete diagnostic check with a diagnostic expert, if he doesn’t find anything I don’t know what I'll do.


Kind regards Roger

Expert:  Matt replied 3 years ago.
Hello Roger

one other vacuum leak source thats possible is the brake booster

I've known the diaphragm to crack / split and then introduce a vacuum leak that is very difficult to find

if the brakes seem a bit heavy then this is a possible reason

which can be confirmed by clamping off the booster vacuum hose

if the idle speed is much steadier with the hose clamped this shows that the booster has a leak
Customer: replied 3 years ago.


I have already taken all of the vacuum pipes from off the bottom of the throttle and inlet manifold and blocked them all off this includes the one to the large brake reservoir, but still the same.


I think it must be the inlet manifold gasket, but it’s an hard leak to find there, the vacuum does improve a lot when the engine gets hot, probably expanding and sealing the leak somewhat, or it maybe a leak from one of the seals on the petrol injectors I haven’t checked them yet, I tried to see if I could get the seals ready first just in case it was that but can’t find any for this car yet so I haven't checked them.

It might even be the idler valve although I cleaned it and saw it was working.

This car also runs on LPG but it’s the same when running on either.


I know one thing it’s not coming out of that garage on Tuesday until they’ve fixed it.

I shall click the pay you button eventually.


Kind regards Roger.


Expert:  Matt replied 3 years ago.
Hello Roger

one other thing to try is cleaning out the throttle body as they can get all choked up with carbon which then stalls the throttle body