Idle dropping

[Brenjacques]

Hi all

A new problem with the GTS has arisen over the last few days, whether its due to the cold humid weather and the weber not enjoying it or something more I'm not too sure yet.

As I drive I've noticed the idle is dropping whilst the car is still warming up. It'll start fine and 5 minutes into the commute when I hit stop start traffic the idle drops right down to approx 400rpm, jumping around and feeling like it will stall, sometimes I have to pull the choke out more in order to stop it from doing so but it then smells very rich. After its been running for a while and fully up to temp it usually levels out then runs fine after. It's been getting worse over the few days, usually I'll let it do its thing and it will clear up in less than a minute but on the drive home from work tonight it wanted to play up almost until I was back home.

I was thinking of adjusting the throttle/choke screw to allow for more throttle and less choke as I'm wondering if it's a bit too rich during this period and causing the engine to idle worse.

Any thoughts? It's the standard 1.8 8v weber setup.

[mark1gls]

Do you have the standard air box fitted?

[Brenjacques]

Yes I do, it's all standard really other than the weber fitted.

[james butler]

do not touch the settings!!!!!
check for air leaks and also blocked jets first!!

[Brenjacques]

Will do, I'll try and get a look in tomorrow. To be honest since the weather's got a bit better (before this storm) it pretty much returned back to normal. If I can't find anything obviously wrong there's a local(ish) chap who does mobile service and tuning on carbs so I'll call him out for a second opinion.

[mark1gls]

Check the rubber gasket between the carb and the inlet manifold, they are prone to cracks, wobble the carb when it’s running and see if the idle speed moves.

A tune up with someone who has a good CO tester to check the mixture and get the timing spot on could be worth it but as you said check for anything obvious.

[james butler]

evry time i ever get problems like this its usually down to as mark says the rubber flange or an assotiated air leak
or
fuel blockage in jets or the like
allways something simple

[RussGLAuto]

do not touch the settings!!!!!
check for air leaks and also blocked jets first!!

Agreed, contaminated fuel - blocked jet - air leak. In that order.

Don't fiddle with mixture settings.

[Brenjacques]

Thanks all for the advice, the rubber flange is relatively new (as of Sept. 2021) as the one fitted was cracking up at only two years old. I do wonder if the problem is likely to be with the vacuum system that operates the cold/warm air flap as the chap who last did the tuning said that they are often a problem, especially the vacuum switch on the air box. I'll see if I can find anything obvious.

[Brenjacques]

Well I had a quick look before it started throwing it down, I can't find any obvious air leaks although I can feel a weak cold air flow around the bottom of the vac hose for the distributor advance, this is the original type, plastic with rubber fabric coated ends, maybe the fault is with this causing the ignition to retard if more air gets pulled through. I did also notice if I remove the vacuum hose from the back of the carb then the idle instead rises and doesn't drop.

Another thing I found which is very recent (within the last 2 weeks) is this oil leak around cyl 4 of the head https://flic.kr/s/aHBqjzD4ed It has leaked all down around the distributor base too, all of this was clean and oil free just a few weeks back.

I have looked closely, initially thinking the worst (I had the HG replaced in Nov last year) but it seems there is an oil leak from the cam cover back corner as shown in the photos, is it likely that it's managing to travel all the way around to the front and drip down?

Back to the original cause of this thread, could it be possible that the air filter is just crappy, old and getting blocked or swollen from humidity? It's just a cheap paper one I fitted three years ago, the car has done 12000 mls since so maybe it is due a change, but I've never experienced a problem like this caused by an air filter.

[mark1gls]

The bits of rubber hose which connect the plastic vac hoses to what ever do need replacing every now and then, may be worth getting a bit of hose to cut down and replace all the old stuff. Could be a good excuse to swop them over to silicone hose?

Oil leak at the back of the head is the rocker cover gasket, try a nip it up a little bit but go mad or it will leak more…
Not sure about oil at the front of the head, could oil be tracking along the cambelt end of the engine?

[mark1gls]

Don’t seem to edit my post above… only replace the little bit of connecting rubber hose and keep the plastic pipe.

[Brenjacques]

Thanks, I'll swap those little ends over then. RE oil leak, it looks as though it's tracking from the cam cover leak around the head/block seam, all of that side of the engine seems to be wet with oil along the seam and its definitely started at the cam cover. I do remember when someone had it off last year they noted it was slightly warped and best replaced so I'll see if I can source a new replacement along with a new gasket and see how it goes.

[james butler]

i had oil leak out of the air box before now
went through load of rocker cover gaskets and whatnot chasing the leak and turned out to be the oil breather to the air box blocked and coughing up oil!

[Brenjacques]

Well the cover nuts weren't exactly tight, I don't do them up too tightly anyway but these were much looser than even I'd do them, so all tightened up and any oil cleaned away, I'll keep an eye out for any more leakage.

Re the revs rising with the vac hose removed (from the rear of the carb/inlet) would this indicate a rich fuel mixture? I'd have thought the revs would have dropped but it passed is emissions fine on the MOT only a few weeks ago too