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240 Old Volvos hate hot Southern Summers...or the Nordic gods are laughing at you.

So I took the car out in the hot and humid afternoon weather, drove for a while to get temps up and parked in direct sunlight idling in a grocery store parking lot for 20 minutes...and it didn't cut out. Drove over to my buddy's house, let the car idle for another 30 minutes and no stalling. I think the power stage did the trick! I'll likely order a new one to replace the backup unit I threw in for testing.

Car did run a bit warmer than usual on the drive home (half way between mid-mark on gauge and red) but I was pushing it a bit. It does need a splash of coolant as the level is a bit over the min mark on the bottle.

Next up is PCV and throttle body cleanup. Might as well get a new set of wires, cap and rotor while we are at it.

Thanks all for helping me diagnose and solve this one!
 
Something else to consider is to clean and re-apply thermal paste between the powerstage and the heat sink. Under normal operation the powerstage generates some heat and it's important that it has good contact to the heat sink so it can do its job.

I've use some "Arctic Silver" brand from Amazon.
 
Well...victory was short lived. Car was pressed into duty for my wife to take to work this afternoon. Stalled on her just before she got there (about 20 minute drive in mixed traffic). I went and picked up car and it started acting up about 1/2 mile from home on the way back.

Guess I'll go ahead and tear into the PCV system since I now have the parts. Not bullish that will solve the issue.
 
When the power stage on my 88 765 was going out the tachometer went wacky. After swapping the power stage I had no more issues with the tach.
 
The power stage (ignition transistors) get so damn hot they will burn you...... yes, you need to "sink" the heat with the thermal paste.

Condition of the radiator? If you have access to an IR gun, you can check the inlet/outlet.... you should be getting a 10*C drop across a proper radiator. Check it, you may have a near dead unit with minimal heat transfer occurring.
 
rallydallas said:
Is there a hall-effect in there anywhere?
Click to expand...

No I don't believe 91 MY uses the hall sender.

DET17 said:
The power stage (ignition transistors) get so damn hot they will burn you...... yes, you need to "sink" the heat with the thermal paste.

Condition of the radiator? If you have access to an IR gun, you can check the inlet/outlet.... you should be getting a 10*C drop across a proper radiator. Check it, you may have a near dead unit with minimal heat transfer occurring.
Click to expand...

Good call...I'll see if I can find a buddy with a gun to measure temps.
 
Is this wagon a 5 speed? If so why not just sell it to me and let it be someone else's problem!

Ive been on the lookout for a southern car since I lost my '91 :(
 
HatredSerge said:
Is this wagon a 5 speed? If so why not just sell it to me and let it be someone else's problem!

Ive been on the lookout for a southern car since I lost my '91 :(
Click to expand...

I'll keep you in mind if I ever decide to sell my other wagon - '90 M47 that runs like a top (with some nice IPD stuff and Mille Miglia alloys). It's lack of A/C makes summers here in NC a chore (came from the factory without A/C, ABS, etc.). In Santa Cruz, CA where I bought the car, you didn't need no stinking A/C.
 
Had similar issue it was cracked solder joints in both relays
White one and the black one under the hood
Relays are built like a Volvo but solder goes bad after all the years
Check and if you need to repair cracks be sure to use a good flux
Solved my problem and it sounds same as yours
First post!
Daniel
 
Tbangin said:
You do NOT want electrically conductive type which is probably what Best Try will have
Click to expand...

The stuff I bought is labelled Thermal Compound with language like "helps prevent your CPU from overheating" and "provides high quality heat transfer from heat source to your heat sink", so I think I am okay.

Pulled the intake off and the PCV system was interesting and quite dirty. There was no flame trap at all, and the box that attaches to the block was quite packed and coked up (used an entire can of brake cleaner on it...not installed on the block obviously). The throttle body was pretty gummed up, too. One bright spot is that the intake valves look great.

Will reassemble everything tomorrow and see what happens.
 
That's what all thermal paste does but some does even more it conducts electrons because it has metal in it
Use whatever you like
 
The type that I have always used and is used on the ignition amps is a silicone heat sink compound. Commonly used on power transistors and stuff like ignition amps to transfer the heat. They used to sell it at radio shack in a tiny tube. Just enough for the unit on the car. It is white in color and is one of those things that gets everywhere and is messy if it does. lol.
 
Got the PCV system cleaned up, and the intake and rest of the stuff back on the car. Took it for a drive and it was fine, but eventually after about 40 minutes started to lose power (but didn't stall). I could floor the car and it wouldn't go past 50mph or so...felt like I hit a brick wall (LOL).

Picked up a coil at the j/y, and will get a cap and rotor as well. Seems like everything I am doing helps a bit more with each step, so at least getting somewhere.
 
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