EA81 rough idle - vacuum leak?

Silverbullet · Post by **Silverbullet** » Fri Mar 04, 2011 8:16 pm

Hi everyone, just started up the car for the first time in quite a few weeks (out of rego, out of petrol

) And boy did it sound rough, I think when it first started it must have been running on about 2 cylinders. Revved it up and it sounded a bit better, but still there was 1 cylinder out. I quickly threw the timing light on #1 and the flash was very intermittent and inconsistent and I've had this before so a new set of leads and plugs is first on the list. Oh and also the exhaust smelled like straight petrol and smoked out the driveway pretty well

Next issue; what kind of symptoms does a vacuum leak produce? if there was a major leak would there be no air flowing through the air filter? I only say this since the car is getting its air from somewhere that aint the filter! put your hand over the tube on the airbox and there is no suction, no change in engine note, nothing. Where could the engine be getting its air from then? Also if you tighten/loosen the wingnuts on the airbox the idle can change dramatically from great to terrible or vice versa.

It's dark now so I'm not going out to fiddle with it now, I'll have a look again in the morning for cracked/broken vacuum hoses.

-Cheers

RSR 555 · Post by **RSR 555** » Sat Mar 05, 2011 10:19 am

A set of leads and plugs will (IMO) fix your missing issue

Just remember that the airfilter draws air from many breather pipes around the engine and at low revs it doesn't require a lot of air to run.. also there is 2 little rubber breather flaps at the back (near where the spare wheel goes) of the airfilter that open whenever extra air is required.

But if you feel you still have an airleak.. it's a case of spraying some CRC/RP7 or similar around the manifold area whilst the engine is running and what you're looking for is change in engine revs.. when the engine makes a drop in revs then start looking for vacuum lines that are off or cracked.

Silverbullet · Post by **Silverbullet** » Sat Mar 05, 2011 10:34 am

Oh I see, I didn't know it took air from a few places. And I guess I should have figured the car wouldn't need much air at idle

Thanks I'll have a go with the RP7 once the new leads and plugs are in.

Cheers!

RSR 555 · Post by **RSR 555** » Sat Mar 05, 2011 10:38 am

Cool.. no probs dude

let us know how it turns out.

Silverbullet · Post by **Silverbullet** » Mon Mar 07, 2011 5:31 pm

Just thought I'd let you know what's happened, we traced the misfire to cylinders #1 and #4, #1 was constantly misfiring and 4 was intermittently misfiring. Turns out #1 has a sticky valve (bad spring, guide or stem? or crud buildup) so after the car has been sitting for a long time it gets stuck properly, need to put some moreys in the fuel. That coupled with the bad cable made it constantly bad. #4 just had a bad cable (wriggling it would make it fire then go out again).
We're getting new cables tomorrow but, for the time being we found a couple of old ones and put them on 1 and 4, and bingo! runs great!

Apart from the rocker/lifter tapping but thats nothing really. So new cables and plugs tomorrow should and she'll be fine.
Oh but I'll also check for vacuum leak since it has this incredibly weird symptom; if you tighten the center wingnut on the airbox the engine bogs down and almost stalls. Only if you properly tighten it, but loosen it half a turn and it revs up again

Even if you hold the rubber flaps at the back open it still does it and we have no idea what it could be haha.

Cheers!

Silverbullet · Post by **Silverbullet** » Fri Mar 11, 2011 9:53 pm

Last little bit, I found the vacuum leak! The vac hose going to the brake cylinder had a big split in it right above where it joins to the manifold. Also it seems the throttle return spring is in need of replacing, it doesn't pull the throttle lever back to 0 all the way. Got it re-registered this week and took it for a drive this evening, everything works and it ticks over very nicely now

creeps up over the speed limit so easily if you let it haha