1988 Gti 16v Rough Running Issues - Found a couple of things - Need help!

The car didn't cut out during braking or hunt during tick over before I replaced the injectors and blanked the breather off.

 

So air shroud is only for better fuel economy? Why did you bland off breather pipe?

 

I'm not sure of the purpose of the air shroud, I was under the impression is affected the atomisation of the fuel? Not sure really.

I too blanked mine off after fitting the Mercedes injectors. With it connected, it wouldn't idle properly and low speed cruising (20-30 in 3rd or 4th) the engine struggled to run smoothly, the revs would wander up and down and the car felt like it was gently surging while it was driving along. As soon as I blanked off the breather to the manifold it drove better straight away but it would barely idle at all, it would hunt to the point of cutting out. Backing out the idle screw and leaning it out slightly on the metering head pretty much cured it. Before swapping the injectors, as you said is the case with yours, everything was fine. I swapped mine due to hot start issues rather than running issues.

I ended up capping off the breather port on the metering head and ran the breather hose into a catch tank. It needed another adjustment to the metering head and t/b screw after that but it ran 100 times better.

When you step on the brakes, the servo swallows a whole load of air from the manifold so that could cause problems if the mixture is already very rich (not enough air) especially as you say that there were no problems before. It's possible that the old injector seals would have been leaking air as well so swapping them for new would have sealed up a vac leak into the manifold reducing the afr even more.



Sent from my GT-N7100 using Tapatalk

 

When the car starts hunting when idling, if I press the brake pedal it affects the idling. I'll adjust the co screw and see what happens. Think I'll pop in to the local garage and have them set it properly over the next few days.

 

Adjusted the CO with an Allen key on the metering head and it's not cutting out under braking, but think I'll take it to the local garage anyway to get it set correctly.
It's still not perfect and hunting slightly but it's driveable at the minute.

 

Idle switch is the small button on the throttle body that CLICKS when you come off the throttle? If so, then it's working.

 

Thanks for the link to the CO / Idle guide.

 

Tried to set the Idle / CO according to rubjonny guide. Disconnected the spade connector on the coil. Started the engine, ticked over fine but as the car got warmer the car ticked over worse and worse. Wound out the Idle screw on the throttle body but it didn't seems to make any difference, then the car cut out all together. Started the car again and it just kept dying, and I couldn't get the idle screw in time before it cut out again. So plugged the connector on the coil back together and the car was as it was before: rough idle and cuts out under braking. Even with the coil connected back up, when you adjust the idle screw, it made no difference to the idle speed rpm - is this normal?

 

As stated in one of my previous posts, I've got a hole in the inlet manifold but have covered it with self amalgamating tape as a temp fix, so I've put a WANTED ad on here.
Just trying to cover any angle in trying to fix the problem.
Losing the will to live...

 

Thought I'd check the Idle screw as recommended. It's VERY dirty and the O-Ring looks very worn, to the point of being flat!

 

ISV is buzzing and vibrating. If I unplug the ISV, the car stalls. Idle switch clicks.

 

With the spade terminal near the coil connected, the idle screw shouldn't make much difference as the ISV (if working properly) will compensate for a lack of airflow passed the throttle body. Winding that screw out just allows air to pass by the butterfly. Winding it out let's more air through, winding it in reduces the amount of air getting into the manifold.

If winding the screw out makes it stall then I'd say you need to wind it back in to where you started plus another half turn and see how it behaves. It's a bit if trial and error lol

When I was having issues after swapping injectors, I screwed it all the way in, then backed it out 5 full turns. This gave a good starting point that's easy to get back to.

Did you work through the whole guide? Including the ignition etc?

How hard does the ISV buzz? May sound like a daft question lol but mine was buzzing gently so I figured it was all ok, after a bit of tinkering, I found a poor connection at one of the temp sensors was affecting the ISV, a new spade terminal and cleaning the temp sensor made it buzz like an angry bee

Sent from my GT-N7100 using Tapatalk

 

Just another quick thing gaz, give the ISV a decent clean with some petrol/carb cleaner/brake cleaner when you do the throttle body. it wont hurt it

 

Already done it!

 

Had the ignition timing checked by two different garages and they reckon it's spot on.

 

What about cleaning out the overrun cut off valve, next to the airbox? Would it make any difference?