Misfire & No brake servo at idle speed

jag.man5 · 12-6-07, 18:20

Hi all. Just a problem that started tonight. My 92 MX6 2.5 Manual was driving fine and has been since I've had it. Stopped at friends house no problem, but when I tried to start it after about 5 mins it had a bad misfire on 1 or 2 cylinders and at tisckover speeds stalled. Also at low speed there was no brake servo action and the pedal was hard at the top. At driving speed still had a misfire but less noticeable and I had brake servo action as normal. When I first strated it with the misfire as it idled it knocked a bit from the top end but soon stopped.
Does it sound like a valve dropped? or a leak in intake manifold? The spark plug lead to the central cylinder on the bulkhead side can be removed with no effect. On a picture of the manifold it looks like the feed to the servo is from the center of the manifold, does it feed just from the central cylinder or are all the vacuum channels connected throughout all the cylinders? Anyone any ideas please?????

**Einstein** · 12-7-07, 2:44

You definitely have an air leak,, and it is from the pipe that goes to the brake servo... if it's still connected, it may be cracked or split and needs replacing..

Check the loose plug lead, as the brass connector may have slipped up into the cap, and not clipping on the plug...

John

jag.man5 · 12-7-07, 16:56

Thanks John for your reply but further to my list of symptoms listed previously, today when I started the car to try it again there was a cloud of blue smoke form the exhaust (like when valve stem seals gone) so I suspect a dropped valve or even a timing belt slip on the inlet valve cam shaft?

**Einstein** · 12-7-07, 18:25

I can't see how a valve or belt problem will cause the blue smoke.... worn or damaged valve seals definitely will though... normally only on starting from cold, or stood a while.

The vacuum hose to the brake servo has a one way valve inside it... take it off, and check that you can only blow through one way..

John