Firing On Three In Low Revs

[Saveit 0]

Hi there

 

Eralier on I had a problem with my 1.9 gti (std). It kangeroo'd much more than 205's normally do. Sometimes i was even afraid that the engine would pop out. I gav it a quarter of a turn on the fuel mixture unbraco screw, fitted the vacume hose for the dizzy (which was missing for some reason), and turned down the idle (it was idleing at about 2500 rpm because otherwise as soon as i let go of the throttle the car would jump so much that i had to use the clutch to control it). And everything seemed a bit better now so i turned down the idle once again by turning in the air screw on the throttle body.

 

Now when the car is cold the idle sits at about 1800 rpm which is okay i think. But when it gets warm the idle drops to about 1000 rpm. The problem is that when its on those low revs it only fires on 3 cylinders for perhaps 25% of the time. This means that when i accelerate it pops and splutters since it changes between running on 3 and 4 cylinders. As soon as it gets over about 2100 rpm there is no problem at all. Car runs fine and doesnt seem to lack any power. But when i those low revs it really sounds and feels as though it is about to give up, and acceleration is of course terrible until it hits the 2100rpm mark.

 

Now the engine that i have put in it have been sitting in a garage for about 2 years without being started. I have not changed anything on this engine. Not even the spark plugs. Its only done 130.000 kilometers so it is nothing compared to the old engine which had done 270.000 kilometers. The engine came from a motronic car and was put in my jetronic car. Dont know if this should do anything?

 

My thoughts are:

Bad injectors

Bad spark plugs (but why does it run fine when over 2100 rpm)

Bad ignition timing

AFM adjusted wrong

Air screw on throttle body adjusted wrong (i have turned this almost fully in to lower the idle since the throttle cannot go any lower)

 

Someone has any idea of why it does this? It is really strange that it does this when it gets up to normal operation temperature.

 

Stefan

Edited January 23, 2009 by Saveit

[Richie-Van-GTi 72 2 Cars]

Do a cold and warm compression test. Sounds suspiciously like a worn valve seat to me.

[Saveit 0]

Ahhhh yea okay could be that.

 

But i just doenst understand why it runs fine when over 2100 rpm then?

[Richie-Van-GTi 72 2 Cars]

the extra engine speed and generated heat helps with combustion.

[Saveit 0]

Okay. Ill do a compression test when possible. Thanks!

 

But what about the injectors? Couldnt they be bad from just sitting in a garage for 2 years?