It's been a long time since I've been here--learned a lot and was able to maintain the little S40 that could for all these years, mostly with this community's and Matthew's help. But now she's gotten really contrary--she starts OK, though a little rough, will idle, smooths out when revving over about 1800, but as soon as she reaches normal operating temp, she just dies and won't restart until cooled off to ambient (@60-70F) again.

All dash lights and the radio work and she will crank, but won't fire during the cool down period, so the issue doesn't appear to be electrical and I can hear the fuel pump priming each time the key is turned on.

I put a meter on the ECT sensor and got a good ohm reading for it cold, but haven't been able to check it while hot. Thinking it's almost got to be the ECT, but the fan isn't kicking on and running after the engine dies (fan ran @6 mins when I unplugged the ECT, I guess the ECU side is working as designed), so that has me a little mystified. Also temp gauge is behaving normally. Would appreciate anyone's experience/expertise on this before I throw more parts at her in the dark. Thanks in advance and happy holidays to all!

P.S., cleaned the MAF and that did seem to smooth her out a little, but no effect on the dying at operating temp issue.

People who use this board like to solve their own problems -

BUT -

Swapping parts, buying equipment, spending time, and losing the use of your beloved Volvo can add up!

Most Volvo dealers only charge a maximum of one hour's labor for trouble shooting.

My dealer has twice offered troubleshooting for free, with a written report.

I recommend taking your car to a dealer.

BTW - my son-in-law is a Subaru tech, and they only charge one hour as well.

One of his customers had a stalling problem in a new car, Frank drove his car for a week - when the car finally stalled, he evaluated the car while waiting for a tow truck - at the shop, the car started and ran fine.

Frank thought that it was the main fuse block - he found a broken connection on the back of it - the block and the main wiring harness had to be changed.

He won an award fro Subaru and a mention in their magazine.

The customer only paid one hour for troubleshooting - several cars with the same symptoms had to be repaired in the same manner.

PS - The dealer may even know what the problem is!

It is hard to believe that you get a shutdown without any codes. Could it be a loose ground wire that shorts when it gets warm?

Can you check a couple of spark plugs after shutdown and see if they are clean (no fuel) or very dirty (fouled)?
--
Keeping it running is better than buying new

Thanks very much for your response. I will follow up on the items you mentioned. I haven't been able to get codes read, b/c she would die before I could get to an autozone or shop. I've just gotten a code reader, so hopefully I'll also find out more with that and post back with developments.

No codes?
No "check engine" light?
Are you sure the "check engine" light works?
Does the CEL illuminate at key position II with the engine not running?
How does it die? Just runs fine and shuts off? Or a slow death?

Thanks very much for your response. I didn't mention codes, b/c I hadn't been able to get them read yet. That should happen this weekend--I've finally gotten a code reader. Also didn't mention CEL b/c this is an early '00 S40--she has never not had a lit CEL (at least not for more than a week). Maybe the most remarkable thing is that the CEL has lasted through 17 years of continuous operation.

Re: last question, she runs well, then when the temp gauge reaches its normal operating temp (slightly below middle of the guage), she dies immediately, almost as if the key were turned off, except all the electronics are still working. I guess that makes it most likely that fuel is being shut off in some way. Is that how the ECT sensor system shuts the engine down in an overheating situation?

To me, I'd think that an immediate shut down would point toward an electrical issue.

A loss of fuel pressure would also die after a few seconds, but I think it would kind of "chug" to a stop and not be as sudden. It sounds like you are losing spark to me, but could be wrong.
Can you hear the fuel pump cycle if you turn the key back and forth after it dies?

I'm wondering if it may be a MAF sensor or throttle position sensor related issue.

OK, after many family health and other issues, I've got codes:

P​0351 ignition coil a ​​primary /secondary circuit

​P​0352 coil b​ ​primary /secondary circuit ​

​P​0300​ ​
random multiple cylinder misfire detected ​

Following is the "freeze frame" information:

dtcffrzf ​P​0351

fuel system 1 OL
fuel system 2 N/A
LOAD_PCT 93.3
ETC 70
SHRTFT1 0
2 0
MAP 27.4

MIL STATUS ON
MISFIRE MON INC
FUEL SYS MON INC
COMP COMPONENT INC
CATALYST MON INC
HTD Cat n/a
evap symbol mon inc
sas n/a
a/c refrig mon n/a
oxygen sensor mon inc
oxygen htd n/a
egr system n/a

I replaced both coils, the coolant temp sensor, and MAF. I knew she needed one coil for a while, but went ahead and replaced both. Due to age and the shut-down at operating temp, I figured the MAF and ECT would not be wasted $/effort. She does run better for a few minutes, though there is a miss.

The connectors for the coils were in terrible condition, so I'm sure they need to be replaced. anyone got a part number or tip for where to get them? I'm OK with a soldering iron, so if I can get the components, I can get the wires attached.

I don't understand why a misfire or coil sorta working would cause the engine to just abruptly quit and refuse to restart at operating temp. As noted before, fuel pump continues to engage and engine will crank, but not fire during the cool down period after shutdown. She is responsive to throttle while running.

This is a real mystery to me. It's frustrating enough to make me look at engine swaps. Anyway, thanks again to all here for any and all help and best regards for an excellent spring to all!

Thanks, alschnertz. I think you're probably right re: it's electrical. I do hear the fuel pump cycle after she dies. Life and work got in the way for the last many days, but I'm hoping to have time to work on this this weekend. I'll reply with what I've found.

Thanks again. If not for this community, I'm certain I would have had to jettison "the little S40 that could" a long time ago.