Skater Posted December 1, 2011 Report Share Posted December 1, 2011 Stump the chump. My SW8 runs strong and is a pleasure but, if I start it from cold and try to apply load like driving off slowly it bucks and the tach needle jumps around. A few minutes down the road and it just transforms to a dream ride. Great torque mild boost and smooth power.I had several 505 Turbos and never had a problem turning the key and driving off even at 20 below. This problem has developed recently. No hard starting. No problem starting cold. Idles fine. Will not show symptoms if slightly warm. NTC is correct. TPS is set to spec. Timing on the mark. Plenty of power when warm. Changed ignition box. Changed fuel box. Could it be: Bad coil? No misfires or problem when warm. Bad aux air device? Stuck shut? I have squeezed off the hose and it doe not change RPM. The fact that the tach jumps has got me. This would be ignition signal gone wild. Two different ignition boxes do the same. Skater Quote Link to comment Share on other sites More sharing options...
Bean Posted December 1, 2011 Report Share Posted December 1, 2011 How old and what kind of spark plugs? How old and what kind of spark plug wires? Distributor cap? rotor? Those are the basics when you have an issue like that. Jumping tach makes me think electrical for sure - so maybe try the coil or at least the connections to make sure. I'd also highly recommend an MSD 6AL ignition system on these - I found they make a really nice improvement in low speed engine smoothness. Rabin Quote Link to comment Share on other sites More sharing options...
N9TE Posted December 2, 2011 Report Share Posted December 2, 2011 I'm leaning towards the AAD. I fitted a new one to my 87 N9TE sedan and what I noticed the most was a big improvement cold drivability. I think the N9TEA part number is Bosch: 0 280 140 110 The N9T and N9TE part is: 0 280 140 174 I wasn't able to find the 110 part anywhere in North America. W-H only lists the 110 part (0345.30). Rock Auto has the 174 for $80. W-H has it for $100 more... <sigh> W-H sure makes it hard to support them sometimes... Quote Link to comment Share on other sites More sharing options...
Skater Posted December 2, 2011 Author Report Share Posted December 2, 2011 My confusion comes with the fact that after a slight warm up the problem disapears. The other is that the tach runs off the primary side of the coil. To my thinking it is spiking. Fitted BogiCord wires. Old but low miles. I have a spare coil and don't know what the plugs look like. I'll get to it this weekend. Stand by for full report. Rabin: What is your electronic ignition...I don't know the brand. Skater Sea Coast, NH Quote Link to comment Share on other sites More sharing options...
Bean Posted December 2, 2011 Report Share Posted December 2, 2011 Tach movement I've only seen a couple times, and one was when plugs wires were arcing spark to each other. It can also get a bit flakey with the ignition module / connection to the module - so check there too. Definitely check the plugs too as I've had crappy plugs (Bosch Platinums) arc to the head from between the ceramic and the base - really odd but odd misfire issues as well that just got worse and worse. The ignition is called "MSD" - just google it and you'll see what kind of system it is. I used the 6AL - but even the 6A would be fine (and I'm sure others). Search CL or whatever used site is popular in your area - usually you can pick up a whole set up for $100 - $150. (Ignition box and high output coil). Rabin Quote Link to comment Share on other sites More sharing options...
Skater Posted December 6, 2011 Author Report Share Posted December 6, 2011 Thanks Guys for steering me to the ignition. I made three changes at once, not good for learning what failed. Changed the coil, spark suppressor widget, and filed some peaks and pits off the rotor outside edge. The new old coil installed is Bosch. The old one was not. It has not been very cold this week but the symptoms have gone for now. The engine runs a bit tighter (nice) smooth idle. No hi way speed test yet. I will look for an electronic ignition. Changing plugs soon. Cheers, Skater Quote Link to comment Share on other sites More sharing options...
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