Hey all, I browsed through the forum but didn't find what I was looking for, perhaps someone on here can help solve my rabid squirrel electrical issue. For starters, I work on cars a lot but never came across an issue like this.

It started 2 weeks ago, it ran rough long after warming up and running around town. It threw a code P0245 Wastegate Solenoid low, P0268 Cylinder 3 Injector Circuit High, P0271 Cylinder 3 Injector Circuit High. I reset with my trusty ELM327 wireless OBDII module to my phone and it went away for 3 days. It came back for revenge, having no start situations where it seems to only attempt to start on one cylinder. Here's the timeline of sorts.....

Wife's car. She called me with a no start. I showed up and got it started but super rough and missing on 2-3 cylinders at idle. Occasionally there would would be a sound like a minigun which smelt of R143A which I think it either blew a high pressure line or a relief valve. Looking back, I think the relay or some other decision making in the electronics never cycled off the compressor, it ran all the time, thus high pressure. High pressure switch? Relay? I unplugged the control wire attached to the side of the compressor to prevent it from running because it was still spinning when the selector for A/C was off. Hmmm.

The injectors were audibly missing once the engine warmed up, causing the rough idle on cylinder 2,3,4 until either one of two conditions occurred: The cooling fan is running OR the cooling fan is disconnected, in which case the injectors fired without fault and the codes could be reset and the engine was smooth as silk. Completely odd. Of course, that would be too easy, with the cooling fan disconnected during a short drive, the injectors would stop firing under load again. It will eventually stop running all together. I have traced wires, looked for shorting, replaced the cooling fan relay and replaced all coil packs(When I went to disconnect #3 while troubleshooting, the top broke off, all were brittle so I replaced them for longevity). I printed all 130 pages of the Volvo electrical wiring book and spent 4 hours looking at it for answers. I believe there is a short but I am not familiar with Volvo electronics and no idea where to look. I also noticed I got the same smooth idle running when disconnecting the signal wire from the ECM to the cooling fan relay which can't be good.

I have a long 2 year history with this car, my first job researching and replacing the ETM through a Canadian company with magnetic Pot switches, rear door lift cylinders, normal maintenance. I really like this car and I'm too proud to take it to a real mechanic....today.

Has anyone run into this issue before? It's a long strange list of electronic things effecting each other, I almost think it's related to a ground switching wire getting 12 volts. I'm so frustrated. I need a good beer.

Thank you!!!

What fun! Cyl 3 and 4 only is strange and could be related to a wiring plug somewhere. While playing with the AC and other items, it seems there might be a bad ground wire/strap. Check all of the engine grounds first, then the battery ground, and there used to be a ground wire behind the passenger headlight on 1993-1998 which would get rusty and fail, not sure about 1999.

I am glad you replaced all of the coils, it is time due to the constant heat and plastic not liking heat.

Make sure you battery is fully charged. Once running take it to an autoparts store and have them check the alternator and battery. A running engine should put out 14.5V min at the battery.

Sources of info:
https://www.matthewsvolvosite.com/forums/viewtopic.php?t=50639
https://www.matthewsvolvosite.com/forums/viewtopic.php?t=43634
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Keeping it running is better than buying new

Thank your for that information. I am researching all avenues. I took it to a local Volvo Specialist that is super good and he said that he had never seen anything like it. After a few hundred dollars in diagnosing he said he couldn't find out the issue. The low speed fan would not engage but he could turn it on with his OBDII computer. I recently replaced the Relay. He suggested to replace the Thermostat and temp sensor which I did with Volvo parts. Same thing after it warmed up. Just changed the oil too. He said the ECM would have to be sent off and rebuilt if the other 2 parts didn't clear it which is nearly a grand. I don't think that's the issue and a really expensive hunch. He cleaned the ECM terminals and looked inside which looked visually good. A broken cable on the link you sent looks to be a plausible possibility. O2 sensor is another suspect.

I was having charging issues about 4 months ago and I replaced the Alternator, which solved the dying battery issue. I wonder if there is an issue there. I'll unplug the alternator while it's running to see if there's a change in running pattern.