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1994 Volvo 940 Dying

magna224

New member
Joined
Apr 17, 2013
Location
Mesa
TL;DR: Watch video links

I own a 1994 volvo 940. A few weeks back, it started giving me some issues. I first noticed something was wrong when I went to drive it and it wouldn't start. It would start normally if i turned the key on and off about 10 times. I assumed this was a fuel issue and that i had to prime the lines before it would start. I drove it for a day or two quite a bit(50+ miles), and, while it continued to give me trouble starting, it ran fine once it was going. I pulled into a parking lot and was idle/coasting to a spot when the car sputtered out and died. I restarted it, and it seemed only 1 or 2 cylinders were firing, it was running REALLY rough, under 100 rpms, and throwing the engine around. I parked the car for about a week before bothering with it again.

I went to pick it up and it started fine. I got it to the end of the parking lot before it died, and wouldn't restart. Went to try to get it again a few days later, and drove it about 3 miles home. While driving, the tach would sometimes drops to 0 and bounces back up, sometimes it dies(as seen in the videos below). When i start it back up, though, it turns over once or twice and whirrs right up, making me think it's not a fuel related issue at all, but electrical or a sensor.

It sat for a couple days at my house, when i went to mess with it i cleaned the battery terminals/cables, and found 2 loose plug wires. I popped em back on and drove the car about 10 miles with 0 issues. On the way home, it died multiple times and was idling weird.

Basically that brings us to now I took a couple videos of the instrument cluster with the car running.

https://www.youtube.com/watch?v=AWtopSUX6eI

In this first video(sorry for sideways), the car had run for a few minutes before I took it. It ran pretty fine until it warmed up. I decided to throw some random revs at it, and it died whenever I pushed the gas quickly.

https://www.youtube.com/watch?v=LSz3dv7UByA

Right after the first video and prior to this one, I ran the car a few times. It started off idling at a normal rpm, about 900. I pressed the gas pedal as quickly as I could(not depressed very far, just very quickly) and the car immediately died the first two times I did it. After this, however, a couple times I did the same thing again, only when I pressed the gas quickly, the rpms were going up and sticking for a second, then dropping back down. I did it again, and the tach was sitting right at 1.5k. I then restarted the car, and took this video.

There is no check engine light on and it's not throwing any codes, but she has given me some problems in the past. I haven't noticed it dying while not at idle, but the rpms have dropped to 0 and bounced back up about .5 seconds later while accelerating.

So for a while, especially during the cold months, I would be driving and either after accelerating or driving on the freeway for a couple minutes, it would run rough at idle or even die. Intermittently, for about 8 months(?) I will loose power while accelerating through turns or from red lights. I replaced plugs(which were pretty fouled), wires, cleaned throttle body, maf sensor, etc. This seemingly fixed the problem, but now I think the current issues may be related to what was happening before.

Thanks for reading. Please respond with any advice/experience/links/info you may have which would help!
 
Crank position sensor, or ignition power stage. Crank position sensor is located on top of the bell housing behind the head, inspect it's wiring as thats what causes it to fail usually. Power stage, not sure of it's location on your car but probably on left inner fender up front. Make sure you mount it with fresh heat sink compound to prevent it from over heating.
 
First job : replace your Crank Position Sensor which is located way back down over the flywheel/bellhousing in the dark depths behind your engine and is held in with one 10mm bolt. And syptom where the rev-counter drops or fluctuates is likely to involve a dying CPSensor.
It connects to the wiring loom above : black connector, (3 flat pins inside?).
Until you've unbolted one of these you may find it really awkward to do, you may also find it hard to buy the exact right part to so to a scrapyard and practice getting an old one out using your right hand and a short 10mm ring-spanner.
I can change mine in about two minutes, but I had to replace three on my last engine : it was cooking them to death.
 
Those are the two things at the top of my list of possible causes. I was thinking that if it were the CPS, the Check Engine Light would basically 100% be lit up and it would be throwing a code; is this true?

I have heard that just replacing the thermal paste on the ignition module can fix the problem people have with it, so I'm going to try that before i take a trip to the junk yard.

I'll check out the CPS wiring and the ignition module today. Money is a bit tight so just buying parts and replacing them without a pretty high level of confidence is off-putting.
 
The fact that it dies while trying to accelerate leads me to believe it's the CPS causing it. As the engine moves so does it's wiring. Try wiggling the CPS wiring with the engine running, if it dies you have found your problem. Replacing the thermal paste is also a good idea.
 
Yeah the issues while the RPMS change made me think it was CPS right away, it was just the CEL that really throws me off because it's basically a surefire thing that it lights up the CEL and throws a code. The fact that it also starts right back up almost every time and that it dies at idle makes me think it isnt the CPS also haha. But yeah, I'll definitely do all the cheap/free fixes/tests before i start buying stuff, CPS is on top of purchase list.
 
So moved wires around while running, nothing. The shrink tubing on the sensor wire is jacked up and the insulation is messed up too. Gonna run it til it dies again and then check again for codes. After that, I'm going to replace the thermal paste on the ignition power stage.
 
The fact that it dies while trying to accelerate leads me to believe it's the CPS causing it. As the engine moves so does it's wiring. Try wiggling the CPS wiring with the engine running, if it dies you have found your problem. Replacing the thermal paste is also a good idea.

This
 
Sorry for the long wait for a response. Replacing CPS did not work, and I have a (somewhat) new symptom. Whenever I slam on the gas, the car dies. No idea what to do next, as I was fairly sure it would be the CPS. Car also dies while idling, but when I depress the gas pedal rapidly, power cuts out completely and it just dies.
 
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Sorry for the long wait for a response. Replacing CPS did not work, and I have a (somewhat) new symptom. Whenever I slam on the gas, the car dies. No idea what to do next, as I was fairly sure it would be the CPS. Car also dies while idling, but when I depress the gas pedal rapidly, power cuts out completely and it just dies.

Check fuel pressure ,sounds like a weak/dead intank pump.
 
No codes, idle fuel pressure at a really steady 35 psi. Fuel pressure does go up to about 40 and holds at 39 when I turn the car off. Makes me think it's suddenly losing spark while the pump is still running for split second.
 
I think that pressure is a bit low. I recall a long time ago someone went through Everything for weeks, to find a clogged fuel filter that only allowed about 30 psi.
Also, is the car rusty at all? I also wonder about grounds, esp the little ground plates up behind the headlights.
 
It's an Arizona car so it's pretty rust free. I'll take a look at it closely and search for any rust. I was running it again with the fuel pressure gauge hooked up, and it was reading 22 PSI. I think there may have been some discrepancy in the gauge itself, because the needle on the gauge moved very slowly up to 22 and stopped, and dropped to zero when the car was turned off.

I cleaned the MAF sensor and it seemed to help a little bit. Going to mess with the fuel pressure gauge some more later today.
 
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