Electrical issues at idle

I'm having a weird issue that I need some help diagnosing, as I can't find any posts that are exactly the same as my problem. 1) I was driving for about 30 minutes when I noticed the sound from the stereo cutting out intermittently while I was at a stoplight. When I pulled away the sound was fine, every time I returned to idle after that the sound would cut out every few seconds. 2) I arrived at my destination and let the car sit for a few hours. When I started it up again, there was no power to the stereo. I turned the car on/off a few times, tried just turning on the ignition, but no luck. So I drove about 20 minutes to my second destination with no music and then let the car sit for for a few more hours. 3) When I started it again, still no power to the stereo. I started driving home, but when I hit the third stoplight, the engine just died. It started right back up with no problem, and the stereo was working properly again. I've driven it another 45 minutes the next day with no issues until the very end of the trip, when the stereo started cutting out at stoplights again. Some background: this car has a recently (about 4 weeks ago) professionally-installed rebuilt engine (factory short-block, rebuilt heads, and lots of new parts including coils). I also recently sorted out the wiring for the aftermarket stereo that the previous owner had wired incorrectly. I'm pretty sure the stereo wiring is all correct now, with crimp connectors on all connections. The volt meter on the dash reads close to 14 volts at idle and just a tick higher with some throttle. This behavior feels like short to me, but I'm not sure where to start looking. Any ideas where to check?

First thing I always do when it comes to these kinds of weird electrical issues is check the negative battery cable. Make sure it has a nice clean and tight connection to the chassis, as well is secured to the negative battery terminal.

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Maybe two separate problems. Sounds like power wire to radio intermittent; can you pull radio and tape or solder voltmeter lead to power wire to monitor whilst driving? If you had a short likely will pop a fuse or smell smoke. For engine stall start by checking codes...

Grounding is 90% of most electrical issues! I made the 90% up but do check your ground strap and obviously solder your stereo connections if you can.

Thanks, everybody. I did disconnect the ground cable from the battery when working on the stereo. Maybe I introduced a weak/flakey connection when I put it back on. I�m going to start by cleaning the terminal and cable lead and see if that does it. If not, I�ll look into the engine ground strap.

I would say there is a very good chance that the issues are not related. I don't know when you rewired the radio relative to the engine rebuild completion. I would remove the radio and check all the connections. Do a pull test on each of the crimped connections, if any pull out with little force, that needs to be corrected. I would also make sure everything is wired correctly and that the radio chassis is also grounded. The engine dying might or might not have anything in common with the radio. Seat of the pants says no, but anything is possible.

I've come to the conclusion that these were separate issues, but I'm still battling with intermittent sound from the stereo at idle. I've checked each connection in the back of of the stereo with a multimeter and they all check out OK. The ground connection was crimped by the previous owner, so for good measure I remove his connector and installed a new one myself to make sure it was connected correctly. I checked the ground strap on the engine and the batter terminal ground and all seem to be solidly connected and the cables look like they're in good shape. The stereo works fine with just the ignition on. It works fine at first at idle, but after driving for a few minutes it cuts out at idle. I can also make the stereo sound cut out when I'm on the throttle but activate the power windows. After bouts of intermittent sound at idle, the stereo will shut down completely and not come back on until it's disconnected/reconnected. Any ideas on where I should check next? Am I at the point where I should try to get another head unit and see if it works?

The stereo might be on its way out. Works good when the circuits are cold and then when they warm up something looses connection. As for the engine dying, I would concentrate first on that. Take it back to the mechanic that did the engine swap and let them look into it.

I've not had any further issues with the engine dying. After discussing with the mechanic, I think this was due to oil fouling the cat that had to be burned out after the previous block developed bore scoring. I had some codes from the after cat O2 sensor on that side and initially still saw some smoke at startup. I seem to have worked most of that through the cat now. The car is running well, I just need to be able to listen to some music. I'm suspicious of the way the stereo cuts out might indicate the car isn't feeding it enough power at idle or when competing with other electrical items like the windows. However, this aftermarket head unit was wired totally incorrectly by the previous owner before I straightened it out. Perhaps the head unit is fried. For $90 I can get a new one from Best Buy, and I might stop there this afternoon.

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This would be my suggestion swap out the radios and see if the issue persists. I have a radio you could try but I doubt I'm close enough to be worth it.

Just to throw out a completely random suggestion. The headlight and ignition switches do some really funky things to the electrical systems in these cars. Might be worth looking into if u hadnt already and want to throw some parts at it.

I have the pcm 2.0 stereo with the one with NAV screen. Had my stereo starting to do same thing ,it was my regulator , I bought new regulator and installed in OEM alternator , took a few hours ,part was 20 dollars. Try to save your OEM alternator , fixed my problem and my car only had 27k miles on it. Do a voltage check to see when stereo is fading out and see if voltage is low like 11 volts. Should be around 13.5 with little load

Did you wire brush or sand the ground strap to engine contact points?

So, I think I got it figured out without having to replace the head unit or anything else. I found the hardware reset switch on the head unit and that seems to have done it. I suspect that the faulty ground connection from the stereo to pigtail put it in a bad state. Once I fixed the ground it still needed a reset. I just took the car from Chicago to Great America and back (about 2 hours round trip) with no issues. I�m going to call it �fixed�.

Doh. That's what I get for bragging it's fixed. I just got back from running some errands and the issue is back, now with a check engine light. Everything was fine, but it started to rain and I got on the gas a bit coming around a corner, causing the traction control to kick in. When that happened, the radio started cutting out at idle, the check engine light came on, and the dash lights were pulsing slightly getting dimmer and brighter. After restarting the car, the dashboard calmed down and the voltage gauge came back to close to 14. Here is the volt gauge reading when it was pulsing. It still doesn't look that low, right? I'm going to go get the error code checked and probably take @808Bill 's advice to try cleaning up the ground contacts. However, from what I've been reading, I'm beginning to think this is the voltage regulator. What the most economical way to pull codes on these cars at home?

My gauge sits there or a needle with under that all the time. I have no issues with my car.

@FASTTRIP how did you diagnose the bad regulator? Did the volt gauge on the dash display strange readings? @De Jeeper thanks for the tip. I just found that the wiper delay **** seems to do nothing. I wonder if it�s bad and causing other problems. Also, I remembered that along with the major engine work I had a seatbelt buckle and sensor replaced to fix an airbag light. Need the shop to double check that installation for issues too.

I used multimeter with battery disconnected. Voltage regulators were know to go on these cars when new. Mine only had 27k miles but was like 11 years old. I had my dash light up like Christmas. Tree also. But first symptoms was my stereo not working.

I�ve had no sign of this issue for many months and then over the weekend it happened again. I�m starting to suspect the ignition switch. A quick on/off of the ignition stopped the issue, and one of the few records I have from a previous owner shows it was replaced in �13. For 30 dollars and the same number of minutes, I think I�m going to throw a part at it.

All of the current posts include everything that I can think of that could cause this issue. The grounds might all need to be checked again, a third time. It�s often not easy to spot. You could have a bad power cable (ground) strap somewhere. Just keep at it, you�ll find it. The only other thing it could be is the battery, but that�s unlikely if you can restart the car over and over again without issue. The fact that it�s fine when cold but then starts to go bad when warmed up is a hint of a failing component or a heat-related connection issue.

Diodes in the voltage regulator on the alternator. Let car sit overnight. In the morning place your hand on the alternator. If it is warm, or hot, much more than ambient temperature, the diodes are going bad. Not an expensive fix, however the alternator can be a bear to pull.

@Mike Murphy I�m going to just keep checking and reconnecting things. I do suspect it�s a ground issue and I suspect it�s something in the dash. I wanted to replace this head unit anyway and the ignition switch has a history of trouble on this car. So I�ll probably do both of those. @DBJoe996 thanks for the tip on diagnosing the alternator regulator diodes. I suspected those early on, but the battery charges and I don�t see any fluctuations on the colt gauge. I just checked the alternator and it�s as cold as my 60 degree garage after sitting for a day.

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Start checking any/all grounds that were disturbed/reconnected when doing the engine swap. Sounds like a classic intermittent ground symptoms... Good luck ** The reason the problems show up at idle is because there's less voltage, and depending on how rough your idle is, it could be jostling the connections (it's possible they've loosened up after heating/cooling or there could be oxidation on them).

@wsrgklt Did you find your problem? I have exactly the same. For me it looks like a ground problem I have already check and clean many ground cable. and just change the big ground wire at the rear of the engine. Thanks for the help.

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I think he is out of the country or something......he hasn't logged in in over 10 months...

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My problem went away after I replaced the very cheap and poorly installed head unit from the previous owner. I got a quality deck from Alpine along with the correct wiring pigtail from Crutchfield, and then made sure to wire everything according to factory specs with solid connections. After that, I never saw the issue again, so I'm assuming my problems were due to a faulty ground in the old radio installation. Hope that helps! @Porschetech3 I haven't been out of the country, but my car has been running well and hasn't required me to seek advice here in a while! Instead, I've been busy logging miles on group drives with other 996 owners and on road trips with my son. But happy to respond to a question when I get a notification in my email inbox. This community has helped me out a ton.

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@wsrgklt good to know all is well with you !!!!

Ok, Thanks for the answer. i have a cheap radio too, i will check that.