1.9 gti: tries to stall after revving! Help!!!

Hi and thanks for looking

Does anyone have an idea of what could be causing this: The car starts a bit ruff but once warm settles down into a steady 900rpm (bit rough as it has a uprated cam). As soon as i touch the revs to any where above 1000rpm to the red line (which it does very cleanly) and let off it tries to die The revs drop to about 200rpm and some times hits so low the battery light comes on and then it goes to about 800rpm and sounds ruffer than when it warm after started. This will just continue untill i turn it off and the cycles happens again.

I have had this problem with the previous 1.8 engine which was checked over for compression and all was o.k. I have since uprated the engine as now it has a 1.9 with a uprated cam in.

I have replaced:
Fuel pump, distributor, injectors (all 4), Tank drained, new fuel accumilator, fuel filter. fuel neck pipe, plug, plug leads. It has been tested for compression, injectors double checked. All the pipes are straight with no kinks

Lastly there seems to be a oily/petrol liquid on the air filter and air flow plate. Could that be some thing to do with it?

Any suggestions would be great

Thanks

Too rich mixture.

did you mean you had the same problem in the same car but you  changed the engine  and still have the problem? i would suspect warm up reg or metering head but first  i'd be tempted to have a look at your metering head, give it and all breather pipes a really good clean . will it tick over ok when it's warm ? have you had you new engine tuned to make sure everything is set right ?

Hi Guys thanks for your time!

Just to clarify ihad the old engine rebuilt and it deveolped these symptoms (the rebuild was a hash by a unfriendly francise (can i name and shame?), i then bought a second hand uprated engine and the car still had the same problems. I had the mixture set up when i had the engine put in. It was a second hand engine but has had everything checked and its all healthy. Hadnt thought about the warm up regulator as i had that the fuel pressure checked and thought that would cover it! Will try a diffrent one though! The breather pipes are clean with a slight hint of oil. Only thing i thought of whether the filter inside the rocker cover could be blocked? What are the sympton of this happening (also what are the chances of both engines having the same issue)? It ticks over o.k when warm but is still a bit erratic at times but as soon as i rev it it tries to die! This is taking a lot of my head space and driving me insane so thanks again for your help!

Dan

To clarify what the problem is: I'm no expert but when you press the accelerator pedal, an engine's revs go up. And then when you release it, they come down again to idle speed.

What's happening in your case? Do they go down then up when you press the accelerator? Or do they rise ok, but then if you take your foot off, they fall and fall and the engine either stalls or dips below idle but then returns to idle?

When i rev the engine it revs freely and pulls well when driven, but as soon as i let off the accelerator, the revs drop (as expected) and it goes to about 300rpm and then just bounces around the 400-600rpm range and some times so low the battery light comes on to keep it ticking over. It just hunts all the time. If it does eventually settle either by itself (which is very rare) or i can if done gently get it to settle if i ease the revs up to 900rpm and come off the accelerator. But again if i jab the throttle to above 1000rpm it tries to stall. Its very very odd!

the oil in the inlet will be from the breather, the easy way round this is get a catch can and vent the breather to atmosphere… this will also make more power for you too, but the mixture will need resetting as this will cause the car to run rich.

but by the sound of it you need a tune anyway, as it sounds like the mixture maybe a smidge out.

shepp said

When i rev the engine it revs freely and pulls well when driven, but as soon as i let off the accelerator, the revs drop (as expected) and it goes to about 300rpm and then just bounces around the 400-600rpm range and some times so low the battery light comes on to keep it ticking over. It just hunts all the time. If it does eventually settle either by itself (which is very rare) or i can if done gently get it to settle if i ease the revs up to 900rpm and come off the accelerator. But again if i jab the throttle to above 1000rpm it tries to stall. Its very very odd!

Too rich mixture.