Missfire

[dingle 0]

Hi all wonder if someone could maybe help me on this one. Ok well last week topped up the Corrado vr with antifreeze and noticed the temp sender dropping to 70 when fans kick in so just put it down too the antifreeze. Then car developed a popping from exhaust when easing off the pedal and then stoping at road ending and pulling away I also noticed a very slight missfire. So upto now I took the plugs out and cleaned them put them back in as weren't too bad but never solved the issue and then started getting worse to the point now it's very lumpy and then u set off it sounds like it's missing a cylinder for a few second then clears itself. I now put injector cleaner in and put new plugs in and to no avail it's still miss firing when u try to set off then clears. The temp gauge is still drops to 70 but goes up for a bit like it's intermittent so now I'm a little baffled as to what's going on. Unplugged the maf and it stalled straight away plugged back in and away it went,also pulled the plugs off the coil pack and they all sparking like a good one, so as of doing this post I'm stumped , thanks for any help PS no oil in water or vise versa so heagasket OK and runs spot on when traveling it' just seems to be at lower idle or setting off

Edited May 14, 2016 by dingle
Bad spelling

[seanl82 23]

Sounds like separate issues, with the idle problem likely to be the Isv, and the temp problem likely thermostat. If temp goes up when stationary, then drops down to around 70-80 when travelling at speed it's most likely thermostat.

[dingle 0]

I have had the isv off and cleaned it with carb cleaner and it made no difference and the temp only comes down when the fans kick in but it's been coming down lower than normal but while travelling it goes back up to normal and it's only done this since topping up with a small amount of antifreeze.

[seanl82 23]

The carb cleaner rarely works in my experience on the isv. Worth getting it checked on VCDS if you can. Thats a strange one with the temp then. I can't see how adding antifreeze to the system would do anything like that tbh, its probably just coincidence. The fans should be kicking in at around 98 degrees iirc, and they're pretty affective in bringing temp back down to around 90 where it should be. Unless you've got a bit of an airlock which is causing it to go higher, so maybe try bleeding the system.

[dingle 0]

I been out in it all day and ran fine while driving it's just the stopping and starting. It doesn't stall and starts up OK the rest doesn't concern me as much as the missfire when trying to set off.

[easypops 8]

Check all the leads are seated on the plugs correctly, I had an occasional misfire that turned out to be the back middle lead being on the plug but not quite home

[dingle 0]

I got some more leads on order as I don't no if the leads are seated properly as that tool u get is useles.

[dingle 0]

Update on missfire issue, went out and bought new coil pack with gritted teeth and hey presto no missfire revved and idled spot on. Changed the coolant temp sender after and seemed to be slightly lumpier with new sender in but once upto temp seemed spot, the old coil pack was split all over and could have been on there for its whole life so think I probly done well to get away with it as long as I have.

[dr_mat 0]

Yep, classic. When mine was going I found it got worse in damp weather ..

[dingle 0]

Mine was OK when u was above 1000 rpm ticking over was shocking kept firing on 5 cylinders and u had to try keep the revs up, been out in it today it's firing on all 6 now but still has a slight rough idle on occasion and sometimes a bit hesitant, still not cured my hot start issue as was hoping it would but been like that for 2 years so bit I'm more than happy I can go out and about in it.

[dingle 0]

Ok complete update on missfire issue,coilpack helped but didn't stop it striped mass flow and cleaned still had issue, stripped isv cleaned and still same issue, ordered some more plug with the 4 electode ones even tho I had just put some single electrode ones in and replaced the ht leads aswell fired it up and was worse than ever, so traced the ht leads again and see 6 and 4 were wrong swapped them and runs spot on so I only assume one of the leads had broken, even tho they weren't that old.

[fla 9]

Glad its sorted. Have a look at the old leads and see if the contacts at each end haven't opened out too much. Maybe bend them inwards slightly with a screwdriver. Also check for any corrosion and spray some contact cleaner on them. Worth checking with a multimeter - shake the lead around as well to see if thered6any change on the meter.