Help! - Messed around with metering head, now won;t start?

Hi All,

Some of you may have ready earlier post regarding my MOT failure emissions. I managed to pull a few strings and borrow a wide band exhaust analyser and strobe light.

First up was the timing, I follwed JSeaman's guide, and got it timed up and adjusted the idle to around 900rpm. I then fitted the wide band, and discovered it was running rich. I tried to adjust the mixture screw, but it made no difference what so ever. In fact,  it simply didn't feel like the allan key was engaging or adjusting anything. Tried 2.5mm and 4mm keys just in case, but nothing.

So….I took the metering head off the air box, and flipped it over. As suspected (using a small mirror), it was possible to see the allan key wasn't even fitting into the top of the ajustment screw head, let alone turning the mechanism. I Managed to use a small flat head screw driver and clear some dirt out, and get the thing free'd up. It was then possible to rotate freely.

Anyway, I then refitted the metering head started her up. Now she won't idle, and I can only get her to run if I hold the throttle open to around 2000rpm. Taking my foot off the accelerator it just stutters to a stall. Unfortunately it got too dark last night to do any more on it, so havent had a chance to have a play since.

Any ideas on this one? Is it likely that we have adjusted the mixture in the process of free'ing the screw up, hence the poor running?

Many Thaks in advance

Yes. All you can do is make guesses on the mixture screw to find out where the right spot is.

Thanks Paul, will give this a go and keep you posted.

Does turning the mixture screw have a serious impact on idle speed?

Cheers

Matt

Indirectly, yes, because mixture affects idle speed. But don't be tempted to use the mixture screw to adjust the idle speed!!!

Just to update, it ended up being a poor mixture setting. Adding a touch more fuel (about 1.5 turn clock wise) sorted it. Still want to check timing and  CO before MOT though to double check. I suspect its still a little lean.

You need to do a leak check before you attempt anything on these engines….normally injector seals perish or breather get little splits, spray easistart around the possible areas and check for engine note differences….if it changes you have a leak…

Timing next, then CO mixture setting, try to run it slightly rich about 1.7% is ideal IMHO.

Then Idle last….

Timed her up, idle at around 900rpm, and mixture setting adjusted. Ended up with 1% on the CO and 350ppm on the hydrocarbons.

MOT passed, well happy.

Matt

MattyB801 said

Timed her up, idle at around 900rpm, and mixture setting adjusted. Ended up with 1% on the CO and 350ppm on the hydrocarbons.

MOT passed, well happy.

Matt

high there how do u set the idle on these…. assumin this is 1.8 gti

set at idle with pipe up the exhaust, tweak it to 1.8% on a k-jet works well