help please misfire is driving me mad

anybody got any ideas my 1990 gti cab has developed a misfire :?  the idle has become very rough and the cold start is sluggish it fires fine tries to start first time but does no idle for first twenty secounds or so if i do not press the gas it will stall it seems to build up pressure then the cold start valve comes in and it ticks over fine but ounce warmed up and the cold start goes off the misfire is really bad making the car almost undrivable
could it be the fuel pump filters
i have spent the morning replacing plugs and leads checked the timing everything is new and working properly any ideas were to go next would be really aprecated  :dontknow:

The cold start valve should only run for 8 secs from starting cranking so is probably not that.

Does it miss/run badly when warm?

Have you set the idel screw?

Check all air hoses are secure and no splits.  Check main inlet pipe is seated correctly.

Check auxuliary air valve operation.

Read the various knowledgebase posts

hi thanks for the help the misfire is more noticeable when the car is warmed up but is there when cold. when the car is started from cold it fires but does not start cleanly which it used to do it takes maybe five or six secounds before it will idle after reading the manual it talks about a clip under the sensor plate when i was looking for this clip i noticed that it appeared to be hanging loose could this be the problem? :dontknow:
main inlet pipe has all new clips and is properly fitted nice and tight no splits in the rubber parts

The clip should not be hanging loose I think - I'd have a closer look.

If not the above you might try disconnecting the cold start valve power by pulling the plug on it and see if this helps.

I had a similar problem with my Gti, turned out a breather had come disconnected which led to the inlet/plenum chamber, car would barely idle without it.

mine started this today only misfires below 2000 rpm feels fine above that, when starting its really lumpy going to investigate tomorrow. it seems a bit intermitent as well so hoping its moisture in the dizzy cap or somthing simple. :dontknow:

hi guys spent this morning going through the checks in the haynes manual for injection system faults
before i started the engine this morning i checked in this order
 cold start valve pressure check no leaks in one minute
 then operation check did fire but only very short time maybe two seconds max bearly enoungh time for the volt metre to notice spray pattern is fine though
then thermo time switch sending current to cold start
air aux working working fine passed all checks
begining to think it is a ignition fault not injection will try changing the coil
will let you know if it sorts things out
ps replaced the air flow sensor adjustment clip in the right place