golf mark 4 engine running problem

[tyce]

hi,
my 2000 1.8 t gti runs poorly at tickover especially when cold, and when it is cold it is very jumpy but does seem to improve when warm.
i have fitted a new mass air flow sensor so it should not be that, any one have any ideas.
thanks in anticipation.

[adamss24]

Spray some carb cleaner into the throttle body few times to clean the oily residue inside but remember to spray after the MAF as not to damage it. Also you could run some injector cleaner trough your system but make shure is good for cars with catalysts and take it for a good trash on the motorway ! Also have the car scaned for fault codes as the Lambda sensor may be not within specs. How is your fuel consumption ?

[tyce]

thanks for that will try it, what do you think about ht leads is there a known problem with them

[adamss24]

You could substitute them with a known good set but i dont think that is the case as you says it improves when warm, HT leads will misfire all the time and give poor performance as well. To check them get a new spark plug and conect to HT lead and hold with insulate plyers 6mm of earth watch for bright blue light . You could also disconect the battery and switch lights onn and off to clear static and then reconect the battery and take it for a good trash including motorway and put the engine trough all loads to let the ecu learn the basic settings. It takes about 2 days for the ecu to adjust the fueling maps ...also is the temp gauge accurate, can you hear the fan kick in when hot ? you may wanna replace the coolant temp sensor as when fails it does give the same symptomps, 13 pounds from Euro Car Parts or GSF and take few min to fit. Have some spare G12 antifreeze(main dealer) to top up the spill. Also there are camshaft position sensor and a crankshaft sensor and if faulty will do similar simptoms and even non starting.

[tyce]

thanks again for that.
what do you think about it being an ignition coil, what are the symptoms of that

[adamss24]

It will throw a code as cylinder x (1,2,3,4) misfire- intermitent, meaning that the coil mai be defective, HT lead defective or ignition amplifier(integral within the coil pack) so it will need replacing. Sometimes the ECU Map sensor gives up so its new ECU time- big bucks to replace. Check crankshaft position sensor, camshaft sensor replace with a good known one or measure it as per AUTODATA instructions. Another cause for eratic idling could be defective fuel pressure regulator valve, bad injectors, idle speed actuator, idle speed sensor(electronically adjusted-no adjustment possible). Its difficult to asess you without scaning the codes or beeing able to measure the components voltages/resistances. Take the car to a good car electrician or audi specialist and see what they came up with. I had once a 98 A4 1.8t that misfired/run on 3 cyl. Had it diagozed by vag and had an estimate off 800 pounds without VAT. Scanned the car for faults and replaced the coil/amplifier and camshaft/crankshaft position sensor and since then he is a happy audi owner, cost 110 pounds all in.