Ok, first I will start with the fact that my wipers, and sunroof sometimes wouldnt work. Id have to jiggle the key a little then they would come online and work. Not that major of an issue for me, the car ran and everything else worked.

NOW, I had a jumping tach issue that started last weekend. Would bounce about 500-700 RPMS while sitting at idle, and it would bog down a little and miss while at about 3k RPMS. I checked the wiring several times for breaks, cracks, shorts ect ect and found none. I drove a little during the week, and it didnt bog or miss, but the tach would still jump UP a few hundred RPMS, but the engine wouldnt.

So, I go to take my class 3 inspection tactile yesterday and take the FC. It seemed ok on the way out. Well, about a mile front the place, at idle, the tach was jumping about 1k RPMS but the engine was idling. Wierd!!!

I changed out the CAS with a known GOOD one on the way home and she seemed fine. I Drive it today and WOW!!!!! Lights dim BAD as the RPMS kick up on the TACH, and the actual IDLE dips down. Wierd wierd wierd. Cranked a little slow when starting too.

Now, when I put this car back together, I cleaned and repaired ALL grounds. I Used all sealed and solder terminals, and put extra heat shrink around them.

I am leaning towards an Alt issue. Some input would rock espesially if you had a similar issue. I pulled the Alt and am taking it to work tomorrow to bench test.

 

well sounds like the ignition switch is failing from the wipers/sunroof issue.

Does sounds like a alt issue, I am assuming that this is a turbo without the voltmeter??? If so, grab a digital volt meter and start checking what the running voltage is... anything under 13.5 volts is bad and anything under 12.6 volts means the car is running on the battery.

 

Sorry, yea its an S4 TII. No volt gauge. I didnt get to take the Alt in to work to bench test it. I am still uber sick (walking Pneumonia) and I am not even THINKING of popping the hood lol.

I agree tho Ice, It does sound alot like an ALT issue. Hope thats all it is. Easy to Diagnose lol. If not, then she is just going into the garage again for an early start to a winter rebuild/refresh. She will be a top notch track FC come next spring.

 

I have the same wipers/sunroof issue. Once in a while have to jiggle the key for a sec to get them to turn on. Been doing this for 5+ years now.

 

I have been wondering if possibly resoldering the points on the ignition switch will help or do I need to replace it.

 

I have never had the problem, so I don't know what causes it (besides hanging 20 keys and a half dozen thinga-ma-bobs on the key chain- you should only have the key and maybe one other key).

 

So I got enuf energy to pull the alt off and get it test. Found the belt to be UBER loose and at the end of the adjustment. Frikin NAPA belt was too big. Got the ALT tested, its fine, got a new correct belt, went to take off my dual alt pulley (running YOOHOO BELT DUN NEED 2 ALT belts) and now the threads are fuxxord on the alt. Mite be what my issue was combined with the too biga belt. Gonna chase em @ work tomorrow and report back.

 

Well, the Alt was not the issue. Installed a BRAND NEW one because the threads were boogered up badly. I tested the coil and the T1 side was at 1.2 ohms. T2 side was 1.0 on the button. This was WITH the ignitor wires still hooked to the + and - of the coils. With them disconnected, they were both 1.0 ohms.

FSM, Alldata and mitchells on demand all say 1.0 ohm is the upper limit for resistance on the coils. Im seriously thinking that the magnetic field is breaking down when the coils get hot, or hte ignitor is acting up when hot. I cant test the ignitor because I dont have the right tester @ work.

I got a coil pack on the way, and will update after. I hope this clears it up because I am in no mood to chase wiring gremlins.

 

Pretty rare to see a coil pack fail

 

I have seen many GM packs fail. Then again, most of our cars have more idle time on them then actual driven miles.

 

UPDATE: So I wanted to install a new Throttle body/TPS and some other stuff. I was inspecting the grounds and found the ground at the tranny/engine (driver side) loose. I tightened it up, put her all together, with new coil and WHAM. Fired up!!

After running to temp, I made all my TPS/Timing/idle adjustments. (found a dead BAC so got my idle set with the set screw) I took er for a spin. No jumping tach, no missing, she ran STRONG!! Stronger then she did when I got er together earlier in the year. For ***** and giggles, I put the old coil back in, and after about 10 minutes of driving, I got the TACH jumping, and missing again. All tho no other elec issues. Put the new coil back in, and it cleared up. I tested the old coil right after this and have 1.9 ohms on the T1 coil!!!! I then tested it an hour later and she was at 1.2 ohms. Im guessing the windings were separating when hot.