berg Posted September 2, 2013 Share Posted September 2, 2013 Just had my car mapped on the turbo setup all has been well until saturday when i noticed the car is misfiring on cold start and sounds like a subaru! As soon as ive done a mile or so and it starts warming up the misfire goes and the car then drives perfectly from then on. Any ideas on the problem? I fitted new bkr7e plugs when we did the build but did not gap them they were fitted straight out of the box but it was fine for first few days so cant see it being that? Quote Link to comment Share on other sites More sharing options...
mellonman Posted September 2, 2013 Share Posted September 2, 2013 not totally sure if this same problem i found will be the same with a na/t but have a look over mate , also i would check the contition of the plugs as it could well be a bad plug from mapping ? is there any oil around the plugs at all crank cover gaskets leaking and cause an issue http://www.mkiv.co.uk/vbb/showthread.php?289482-cold-misfire-*updated*-HELP/page2&highlight=miss+fire Quote Link to comment Share on other sites More sharing options...
berg Posted September 2, 2013 Author Share Posted September 2, 2013 Ill check it over and report back Car is barely driveable until warm now as i just found out leaving work lol Wierd how as soon as it warms up a little bit it stops Quote Link to comment Share on other sites More sharing options...
berg Posted September 2, 2013 Author Share Posted September 2, 2013 Right, stripped it down and got the plugs out There was a tiny bit of oil around the thread on spark plug 1 although the rocker covers arent leaking ?? Any ideas on how these look, they have done 4 miles running ridiculously rich, then a mapping session and 200 further miles after that Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted September 2, 2013 Share Posted September 2, 2013 who mapped it? could be over fuling on the cold start map and bogging. Quote Link to comment Share on other sites More sharing options...
berg Posted September 2, 2013 Author Share Posted September 2, 2013 I thought that, or lean but aem gauge shows 14-15s on idle I noticed earlier it doesnt have to be a dead cold start, car was left only 3 hours today and it still did it for the first mile or so Noticed this white/yellow powdery stuff on the white ceramic part of 1 spark plug is this a bad thing At worst ill have to go back to Thor but if it was something simple that i could sort myself and not map related it could save labour cost of them finding the fault Quote Link to comment Share on other sites More sharing options...
Guest SupraV8 Posted September 2, 2013 Share Posted September 2, 2013 Those plugs look fine, did you pull them when it was warm and idling fine or when it was cold and spluttering? You should see AFR's of 13.2 ish for a cold start (coolant below 70 odd). 14.7 is stoichiometric for petrol at an engines ideal running temperature, ie hot, and not a cold start. It will need more fuel if this is the case. Quote Link to comment Share on other sites More sharing options...
berg Posted September 2, 2013 Author Share Posted September 2, 2013 Engine was warm as id just been out an hour before So not enough fuel can cause the problem? Quote Link to comment Share on other sites More sharing options...
Guest SupraV8 Posted September 2, 2013 Share Posted September 2, 2013 Engine was warm as id just been out an hour before So not enough fuel can cause the problem? That's correct. Missfires can be caused by fuel (too much, to little), incorrect ignition timing, compression issues etc. What are the afr's from cold? Bare in mind it will be based on coolant temperature, so note the gauge too (or if you have a stand alone ecu, connect to that). Quote Link to comment Share on other sites More sharing options...
berg Posted September 2, 2013 Author Share Posted September 2, 2013 All timing etc was set when it was mapped, afr's seem to be around 14-15 on idle cold start aswell, there was a reason it was set like this, i cant remember exactly what though but it didnt have the misfire fault for the first 2 days of me driving it after the mapping so guessed it werent related to that. Now the car only has to be left a couple of hours for it to do it Maybe i should refit the plugs and start the car and when it misfires switch it off and remove the plugs again to see what the plugs are like then? Someone mentioned that it could be a temperature sensor? Quote Link to comment Share on other sites More sharing options...
Guest SupraV8 Posted September 3, 2013 Share Posted September 3, 2013 An afr of 14>15 on a cold start will run like pig shiz. Two hours is enough for the coolant to drop right down, require enrichment on priming pulse, cranking pulse, ASE & WUE. I can't think of any reason not to give an engine more fuel from cold when it needs it the most. Quote Link to comment Share on other sites More sharing options...
mellonman Posted September 3, 2013 Share Posted September 3, 2013 agree a cold start of 14-15 is too lean it needs to be around low 13's i would say as a minimum Quote Link to comment Share on other sites More sharing options...
Noz Posted September 3, 2013 Share Posted September 3, 2013 (edited) Reset the stock ECU. Disconnect battery for 20-30 minutes. I had the same problem (just an idea). Edited September 3, 2013 by Noz (see edit history) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.