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Model specific boards => Golf mk2 => Topic started by: MacBain on 30 May 2007, 15:19

Title: Engine runs smoother when cold
Post by: MacBain on 30 May 2007, 15:19

Seems like my engine runs better/smoother when it's cold, but after a few minutes it stutters/jerks more.
It's almost impossible to drive slowly without the car stuttering, it's so incredible sensitive when I lift off the throttle.

I don't have these problems when I start the car up in the morning.
It also idles better at about 1000rpm when cold, after it reaches the normal temprature it idles at about 850-900 rpm, but it seems to idle more roughly.

Any idea on what the problem could be?, would incresing the idle rpm help?


Ps. The car is a 1990 1.8 GL with a rp engine with a mono-jetronic carburator.

Title: Re: Engine runs smoother when cold
Post by: Simpson on 30 May 2007, 17:28

sounds like you need to check vacuum pipes, the reason it revs about 1000 is the choke is coming on when cold. It should be ideling about 850 to 950 revs as a rough guess. Have you checked simple things like leads, plugs etc?  :smiley:

Title: Re: Engine runs smoother when cold
Post by: MacBain on 30 May 2007, 18:33

I've changed all the plugs, wires and distributor cap. I also cleaned the carburator with some carb cleaner.
I don't think there's a vacum leak because I've tried spraying starter spray around all the pipes etc. and the rpm stayed the same.

Title: Re: Engine runs smoother when cold
Post by: mk2mark on 31 May 2007, 08:51

Sounds like the sensitive lift off is a slack throttle cable, you can tighten it on the throttle body.

Title: Re: Engine runs smoother when cold
Post by: rubjonny on 01 June 2007, 10:50

check out the blue temp sender then lambda probe next :)

Title: Re: Engine runs smoother when cold
Post by: MacBain on 01 June 2007, 12:52

I've changed the blue temp sensor.
Is changing the lambda probe difficult to do?

I know my catalysator has been gutted, could this cause anu problems?

Title: Re: Engine runs smoother when cold
Post by: rubjonny on 01 June 2007, 13:09

nah it wont be a problem. lambda isn't hard you unscrew it from the zaust & replace it.  Get a universal bosch one, bit cheaper than a gen vw one!

Quick test you can do is unplug it, if the car runs better then you have a faulty lambda :)

Title: Re: Engine runs smoother when cold
Post by: MacBain on 01 June 2007, 14:13

Where is the lambda plug located?

Title: Re: Engine runs smoother when cold
Post by: rubjonny on 01 June 2007, 14:32

its in the downpipe somewhere, if you follow the exhaust back you'll see the probe sticking out of it, then follow the wiring up to the plug :)

Title: Re: Engine runs smoother when cold
Post by: MacBain on 01 June 2007, 16:15

I think the plug is the one marked in red on the picture (according to the haynes manual).
Can I drive with the lambda unplugged?
Could it cause any harm?
(http://img359.imageshack.us/img359/3318/29042007296in2.jpg)

Title: Re: Engine runs smoother when cold
Post by: rubjonny on 01 June 2007, 16:18

doesnt look like the plug on my gfs 1.3 polo, but then i dunno what it should look like on a mk2 spi  :grin:
it wont do any harm driving with it unplugged, the ECU will switch to a base map., We had it unplugged for a week on our 1.3 polo, made a big difference to performance.

Title: Re: Engine runs smoother when cold
Post by: MacBain on 01 June 2007, 19:14

Tried driving with the plugg disconnected, but couldn't notice any difference.
The distributor cap I got isn't a vw original, maybe I should try a genuine part?
I'm really running out of things to check :smiley:

Title: Re: Engine runs smoother when cold
Post by: MacBain on 12 June 2007, 19:12

The guy at the genuine vw store said that changing the distributor cap probably woundn't fix my problem, told me to leave it as it is.
He said that most old vw engines don't run smooth att all, and to find the fault would be close to impossible  :laugh:.

Does anybody know how to increase the idle rpm on an rp mono-jetronic engine?
Is there a screw to I could adjust?