air leak

[white]

Hi all
have admitted defeat over the fuel starvation problem (earlier thread) and called in an engine tuner whos usually pretty good. He's convinced its an airleak because the HCs rise to 1361ppm and O2 to 11%. Because it's intermittant he thought it was probably caused by something with a valve on the manifold, but I've tried clammping off the engine breather and extra air valve and other vacuum hoses I can find - doesnt make any difference. Any ideas would be appreciated because the car is undriveable.

[blaineuk]

try spraying wd 40 around hose joints and gaskets when engine is running, if revs rise you have got a leak and should be able to track it down

[2 sheds]

Sounds like faulty fuel pressure regulator, if it was an air leak you would normally see very high hyrocarbons but very low CO.
Tim

[white]

Hi Tim, CO was low at 0.14%. Fuel pressure seemed spot on. Annoying thing is that because it isn't a permanent leak you wouldn't expect it to be something like a gasket.

[Gerry Attrick]

Hello All
This could be similar to a problem I have been having for six months. I've tried to solve it without success and have taken it to TopCats, who have had difficulty in tracking down the problem.

In my case, I get misfire on a light or trailing throttle at low speeds. At higher speeds or under acceleration it's fine.

I've covered the following but without success:
extra air valve appears to operate OK
replace coolant temperature sender
fuel pressure is OK
no apparent air leaks
check throttle pot
air flap appears to move smoothly
electrical connections are all firm.

Just had the cooling system replumbed by TopCats, who say it is incorrectly designed and will not refill system from expansion bottle if there is an air leak. We considered the problem may be due to air getting into the system via the swans neck cap when the engine cools down. (There is no leak when hot and under pressure.) The air forms a bubble under the temperature sender causing it to give the wrong signal to the ECU.

Only got the car back on Sunday, so cannot confirm whether it is sorted or not. I will let you know.

Any comments on the work done so far would be appreciated.

Don