Big_Al 10 Posted June 23, 2013 Hey guys. I am having a minor but irritating issue with my old girl. (2L 16v) On the first cold start she always seems to be a little lumpy for a minute or so until she is warmed up and then appears to be running fine after that. Been reading around on here and various other forums and it would appear that I may need to replace my 5th injector and or thermo time sensor. Has anyone got the part numbers for these items as I cant seem to find the relevant parts just by the names I have come across. Cheers. Al. Quote Share this post Link to post Share on other sites
fonzooorooo 10 Posted June 23, 2013 Thermo-time switches are DEAR! (£90 odd when I looked for our mk1) I'd go for the 5th injector 1st... You can always test it by whipping it out and popping it over a glass jar while an assistant cranks the engine. Have a look for "vw cold start" on ebay. Quote Share this post Link to post Share on other sites
tony_ack 0 Posted June 23, 2013 (edited) A faulty thermotime switch/5th injector usually causes problems on initial cold starting - after this the thermotime switch should close the 5th injector. The cold start valve (controlled by the thermotime switch) is only there to provide additional fuel into the injector rail on initial cranking when cold and the first 5 seconds of running. After this, the flow to the injectors is enriched until the engine is up to temp - either using the WUR on the 1.8 or the ECU on a 2.0. So if the rough running is longer than this, then the problem could be elsewhere. The only other problems with the cold start valve is if it is leaking, when it can cause problems and overfuelling when up to temp. If you're getting problems longer than this, it may be worth checking the ECU temp sensor (I think the 2l has one?). Note you should be able to check the temp sender and thermotime switch by checking the resistance across the terminals (though I don't know which pins or what the reading should be at ambient temp on a cold engine - sorry!) Edited June 23, 2013 by tony_ack Quote Share this post Link to post Share on other sites
easypops 8 Posted June 23, 2013 I had a faulty 5th injector(diagnosed by a vw specialist garage) and their advice, rather than waste money, just unplug it and you'll have no further issues with it. Which I did and they were correct. I ran it unplugged for 4ish years, no stress. Quote Share this post Link to post Share on other sites
Big_Al 10 Posted June 23, 2013 Ok, when first starting the engine from cold, which it does without issues, it sits and idles fine. If I rev the engine, I can only describe it as she is spluttering. If I hold the revs at say 2k, she will drop revs and build back up over and over again. After about a minute she is absolutely fine. On hot starts it can take 2 goes to get her to fire up as she seems to splutter a bit, but once started, all is fine. I have also noticed that when the day is very hot, she doesn't seem to suffer with the cold start problem. I have so far replaced the coil pack, the spark plugs and leads, the dizzy cap and arm and have no change. All the advice above is great and I will look further into each one. :) I could really use the part numbers if anyone can help with that though as I want to get the parts replaced as they have been on the car from new as far as I can tell and may warrant changing anyway. :) Any other ideas on the further information I have put here would also be fantastic. Many thanks guys. Cheers. Al. Quote Share this post Link to post Share on other sites
