Mk2 16V not running right- sorted 5/3/09

[Dirk Diggler]

Hi, in desperate need of help as I'm in the dog house with her indoors!

1988 MK2 16V on k-jet, standard car.

The car has for a while had some running problems, such as hunting at idle and you could smell it was rich as hell as it stank when ticking over, performance seemed OK though although a bit lacking in low end grunt especially if you just plant it rather than gradually opening the throttle.

Anyway, I got hold of some brand new injectors for it and also an inlet manifold gasket suspecting an air leak. I also got new injector seals.

Fitted this lot yesterday and now the car runs worse!!

The tickover is now steady and it doesn't appear to smell as rich, but it now has a misfire type symptom where when you put your foot on the throttle a bit, it kind of judders quickly like a misfire. If you floor it the performance is not there and it kind of makes it's mind up when it is going to give you a sudden burst and then hangs back again and then another shove in the back.

If you pull out from a junction with say 1/4 throttle and it has a bit of a splutter, if you back off slightly it catches and runs clean, but as soon as you open the throttle more it starts to stutter.

This is not what I would call kangaroo stutters where the car lurches etc, very much misfire type symptom. It also does it just revving it when stationary, so the engine doesn't need to be under load in normal driving conditons to do it.

I'm purely an amateur DIY mechanic, but her indoors is not too pleased that I have made it worse!

My train of thought is that it is a fuelling issue still but has anyone got any pearls of wisdom to help me out here?

Also, with the rubber boot off the metering head, so you can see the disc/flap, are you supposed to be able to push that open a fair way or just a couple of mm? there was a bit of oil/crud in there so I gave it a quick wipe over with a rag & carb cleaner, presumably this is crap coming from the crank case breather pipe?

I'm more interested in this misfire symptom though.

Help greatly appreciated.

Thanks

Lee

[mattkh]

Hi
What were you doing in the metreing head area when all you planned to do was to change the injectors ?
Anyway, just check the vacuum hoses. Also check the hose connections to the left of the airbox, as you stand near the drivers wing,
to what is called the overrun cut-off valve.

[Dirk Diggler]

I had the top (rubber boot) off the metering head when I had the inlet manifold off to replace the upper gasket. Also I changed some of the fuel hoses as some were very crusty at the joints on the braided lines.

I'm convinced it is a fuelling problem as you can bring the revs up steadily & it won't miss/fart, but if you stab it, then it just misses. But suppose it could be electrical. leads are less than 2 years old, dizzy cap new, rotor arm ok. Checked the wiring to the run off valve and seems OK. checked vacum hoses and can't see anything obvious.

I may just swallow and take it to someone who knows what they are doing with k-jet.

Been doing a lot of seaching on various forums and the 16v models seem to be synonymous with these type of problems.

[Conker]

Hi,

Seen as though its quite a serious problem, it should be easier to find the source if you know what I mean. I would check the following in my opinion...

> Distributor timing. It should be timed to 6 deg BTDC off the flywheel mark with a timing light.
> Faulty ignition system: Probably leads, but test the lot (cap, arm, hall sender, plugs etc.), no matter how new they are. I fittted brand new leads and they were faulty, giving me exactley the symptoms you describe.
> Fuel pressure too low, so check the two pumps are working and the fuel filter isn't blocked etc.
> Static timing i.e. cam belt - maybe's its jumped a tooth or two.
> CO2 setting is way out.
> Huge air leak as Matt said


Theres more possibilities, but all less likely.  Overall my £1 would be on timing or leads.


One question... Does it do it no matter if the engine is hot or cold?


Lastly... The air metering flap - Be careful with it, its delicate! It should spring downwards 10mm or so, but lift upwards cleanly and without much resistance.

[Conker]

These links might help too...

http://www.golfgtiforum.co.uk/index.php?topic=56707.0

http://www.golfgtiforum.co.uk/index.php?topic=99852.0

http://www.golfgtiforum.co.uk/index.php?topic=44784.0

http://www.golfgtiforum.co.uk/index.php?topic=22031.0

[Dirk Diggler]

Legend, thanks mate

Loads of useful links there which I have now bookmarked

[rubjonny]

I've had similar problems when the fuelling is way out, ideally you need to get the fuel pressure checked then have the CO reset to 2%.
You might get away with just a CO reset, it could be running mega rich now you have potentially cleared an air leak and also replaced partially clogged injectors

[Dirk Diggler]

Well the problem has been solved apparently, due to pick the car up tomorrow. Thought I would do the decent thing and post up so others can learn, although my problem may not be too common due to the cause (read above & below)

Took it to a local Bosch specialist who has been around for years and actually knows what K-Jet is.

After spending a fair bit of time on it checking fuel pressure & flow etc, the fuel pressure was running at about 8 bar so it was overfuelling horrendously, obviously a previous bodger overcoming an air leak and playing with the metering head and also the WUR.

It turns out it was my meddling that topped it off though as when I have replaced the 4 brand new Bosch injectors, the ones I bought off good old Ebay, allegedly for a MK2 16V actually are for a merc and Lamborghini. But they do work fine apparently. The cause of the misfire type symptoms has vanished when the guy removed some small silver end caps that go around the nozzles on the injectors. These came as standard on the original injectors and were absent on the new ones, so I just put the end caps off the old ones onto the new to replicate the same setup.

Apparently as soon as he took them off it sorted itself out straight away. Told me that it pulled clean from 20mph in 5th gear.

Just got the bill to look forward to tomorrow, probably gonna be somewhere in the £250-£300 region, but it has all been properly setup now and I hope it'll feel strong and pull clean from low revs as I have personally always felt it was lacking a bit low down, but put that down to the old 8V vs 16V debate.