RANDOM idle!!

Hi

I have a rather frustrating idle issue. When its cold it can either start on the button or not……when it does start it it can idle at 950 or 1400rpm. Once starting to warm it usually idles about 1400-1300 and varies around this figure once warm. If i stop and let the engine cool and restart it will idle at 950. then once warm and i push the accelerator it will go back to 1440-1300!

Its getting on my t*ts and im lost with it. I squeeze the tube at the back of the inlet manifold and it makes no difference when warm and is functioning perfectly on the warm up. The fith injector is not running as i have removed this whilst its warm and its not spraying.

Does anyone have any ideas? Thinking it could be the warm up reg but how do you check this? Air leak from some where but i have check it once.

Help or ideas much appreciated

Dan

This sounds a bit like my GTi. either starts first time or takes an age. Then when running cold it's very lumpy and idles between 500 and 1500, almost staling at times. Once warm it idles at 1200-1500.
It also has an issue when accelerating in which some times it seems as if it's being starved?
Anyone got any ideas what's going on?

best to start with checking the easy bits, give it full ign sewrvice new cap, arm, leads etc. then look for airleaks, especially for splits in the inlet boot folds. look for disconnected plugs, damaged wires or anything that looks dodgy.

next check the injector sopray patterns and delivery volume, pop all 4 out and sit in 4 containers of equal size. put a bridge wire across the 2 large terminals on pump rleay socket, then lift metering head flap by hand all the way up, then release back to idle. check spray patterns are nice cone shape with a fine mist, and measure volume sprayed by all 4.

wipe the tips and remove the bridge wire then watch for drips, shouldnt be any for at least 5 minutes.

if an injector has a problem swap it with another, if problem moves the injector is faulty, if not the line or metering head is faulty.  if 1 injector is faulty swap all 4 for new ones, can sometimes get brass merc ones for cheap off ebay.

Once thats all checked out only thing lef tis to have the fuel pressures checked using proper k-jet fuel pressure gauge setup.

Don't worry about 5 injector, it only fires for 4 seconds anyway. Had the same, got it down to 2 things. Auxilary Air Valve, stick Multimeter over the contacts, should be around 30ohms, also turn ignition key to posn 1 and get mirror in there beind manifold to see if gate is closing within valve (takes 5 mins.) This may explain the high revs as too much air getting through. Also take your distributor cap off, clean the 4 contacts in the cap with emery cloth and spray some WD40 in there and on the HT leads feeding the cap, did the trick for me.

Dont think it is the air valve as i can squeeze the tube and it makes no difference. Will look at it today and go through a few of your ideas.

Thanks for your help

warm up regulator maybee?

Yeah warm up regulator. Pull the green DC connector off and check with Mulitmeter, should be around 11.5V. If nothing check fuel pump fuse #5 (15A), if ok check fuel pump relay (pull it off fuseboard labelled #2) and use small piece of wire across the largest terminals on the relay plate. (they are the copper ones on the relay itself which plugs into) if you hear wiring noise, fuel pump ok, relay kaput.