mk2 16v rough idle

[mk2rolf16v]

hi,
could do with more help guys..... my car has also lately developed a cold start issue, when starting the engine from cold the engine cuts out and wont idle, its only when you hold on to accelerator pedal for 5-10mins and allow the engine to warm up that the car maintains idle.....  could the warmup regulator be on its way out??

[mk2bal]

It could be. Check the resistance across the wur terminals to see if the heater strip works, that speeds up the coming off choke process,if that's ok, (20-26 ohms) then the fuel pressure may need adjusting on the wur and system.. However, it could be the brown thermotime switch on the head not working, which won't enrich the fuel through the cold start valve. Also check the cold start works, when cold only, and for a short amount of time. Hence thermo-time..  It could be these things,if its purely a choke starting problem I'd say its wur/fuel pressures, however if the car is running like crap in general go through everything like isv, air leaks, injector flow and pattern,overrun valve holding open/air leaking,three head sensors, throttle switch and fully closing throttle, etc etc etc

[mk2rolf16v]

right, had a little success today  ........ my first suspicions were the wur was faulty, but did a test and it gave a reading of 23ohms, so think thats ok. was also gona test the thermo time switch as stated in haynes manual but didnt get round to it, hopefully next week now...
i did however replace all three temp senders on side of head, even crimped on new blade connectors and..... she fired up straight away and held idle!!!
one thing i did notice with the old senders was the very front sender of the three (top left sender when looking from side of head) had a different part number to the other two, it read 049 919 563A - which is a 180degrees oil temp sender white collar, while the other two are 049 919 501 - 125degrees black collar. my question is have i done it wrong by replacing all three with the same part number, or should that oil temp sender have not been there??

as for the idling, it does still fluctuate, but think ive tracked down whats causing it.. think theres an air leak in the joint between the overun cut off valve and the inlet suction pipe. theres a very short piece of union hose holding both components together, its only 20mm long, only just holding them together - its a very loose fit and it takes very little effort to pull out of position, and it definitely leaks air!!!!
what i had in mind was to buy a longer piece of silicone hose and jubilee clip both ends on. what do you reckon???

[rich1977]

just out of interest what would happen if the wur wasnt conected i,e wires broken so no circuit? only reason i ask is mines broken off at the plug with no way to open it up. just wondering if it will do any damage driving it like this while is get a plug from a scrapyard and join wires further back

[mk2bal]

Yeah that piece of over run pipe isn't too good is it.. I managed to get a 2nd jubilee on mine, but I'm gonna swap it for a longer bit of hose with a better join both ends.. The 3 black sensors off vwspares will do fine.for now you could put the yellow/red wire on the white collar sensor, your water temp gauge will be unaccurate, but the other two idle wires will at least be on the right sensorsand it may improve the running for now.. The wur terminals are only for the heater element, so that may work, but the fuel pressures themselves may need adjusting, that heater jus makes it come off choke on time...

[rubjonny]

yeah that white sensor is the wrong one, they should all be black collar ones. the white sensor is for the mfa, different rating to the black sensors.

driving with wur off wont really do much, it will get heated up by the engine anyway. only difference is it might run a little too rich for too long while the engine warms up

[mk2rolf16v]

suppose id better get measuring in the morning what hose size is needed and get ordering - before i go work....
also plan to order up a new viton o-ring seal for the idle screw, because any adjustments makes no difference..
dont suppose any of you guys know what dimensions the o-ring needs to be??
am i right in saying vw wont stock the o-ring on its own, in which case i have in mind to buy from a seals manufacturer.
oh - and i hate going to my local vw dealer, if i havent a part number i could be sat there for ages trying to locate the part im after, a bunch of unknowledgable twits!!

[rubjonny]

they dont sell the oring but you can get the idle screw complete with seal, but it'll cost ya 6 quid+VAT!

for mine i just had a big box full of o'rings bought off ebay, had a suitable seal in there

[mk2bal]

Yeah as rj says, a universal o ring set will have 1 with the right inner and outer dimension unlike some o ringswhich are a bit more specialist like injector seals etc.. I'm gonna look in my old coolant pipe pile for a bit of suitable overrun pipe and bash that on..

[mk2rolf16v]

before i start thinking about getting wur/fuel pressure tested, i decided today to get fuel emissions test done at my local mot station. the CO and HC levels are as follows:

CO Level: 2.29%(Actual)  -  3.5%(Max)
HC Level: 126ppm(Actual) - 1200ppm(Max)

My car was running a little rich before (over 3%).... but are the values 2.29% and 126ppm okay?? if not, whats the ideal setting??